So last week I told how I had decided that I “needed” a second vehicle. While I was still very pleased with my truck, and planned to keep it for a long long time, I felt that with all the driving I would be doing after graduating from high school and going off to college, I needed something a little newer and practical. Okay, so the truth is, I just wanted another car to play with! The need to have a choice of what I wanted to drive had set in and its something that I still feel to this day. I like having as many cars as I can, and like to keep the stock rotated pretty regular for freshness.
Now I was born and raised in a Ford family, and never really considered owning and driving anything but Fords. My mom still had her 1988 Ford Club Wagon that was like part of the family, and my dad always had FOMOCO vehicles as company cars. Crown Victoria’s and Grand Marquees for as far back as I could remember. Although once the Explorer was introduced, the switched to Explorers, much to my dad’s dismay.
My dad is from a small rural town in North Carolina. A part of the country that was deeply invested in tobacco and NASCAR racing. In places like that, and during the time my dad was growing up, there was a real divide between Ford guys and Chevy guys. My dad grew up listening to NASCAR races on the radio with his dad. His dad always drove Fords, most all of the other “MacBrides” drove Fords, and some of the hottest cars around his town were some “specialty built” Fords. He has told me great stories about being a little boy and being in his house or yard and being able to hear a particular car coming from a distance away. He would run out into the front yard to watch as this fella would come screaming past his house in his 1963 1/2 Fastback Ford. Rumor was that when this guy bought the car new, it was sent to Holman Moody to have the engine built. Not sure exactly what the car was used for, but you can take a pretty good guess.
My dad said it was the same color as this car and had a 427. Legend has it that he never let anyone look under hood and that nothing could touch this car including the law.
Now when my sister was turning 16, my family was trying to decided on a good car for her. Of course I was deeply interested in helping search, because I’ve always loved searching for cars. I remember finding a car that I thought was pretty cool and it fit the criteria of what we were looking for. There was only one problem, it wasn’t a Ford. No, it was a 1989 Buick Lesabre T Type. I still remember the exact words my dad said when I told him about the car. “I ain’t going to buy no Buick” My dad is a very well educated man, a graduate of Georgia Tech, an electrical engineer, and all around very smart guy, but mention the possibility of buying a GM product in those days, and I guess the old farm boy in him took over. She ended up with a ’89 Thunderbird LX.
So back to my car search. I guess you could say that I had a little automotive secret of my own that I wasn’t sure I was ready to share. While I was a Ford man myself, I also found myself attracted to a lot of other cars as well. One in particular being the Pontiac Grand Prix GTP. I was a bit hesitant to cross the line and buy a GM product but then I remembered that my dad had done the same thing in the past.
When he and my mom had got married he was still in school at Georgia Tech and they needed a vehicle badly. He actually bought a new Chevy Vega, price being the most determining factor of the purchase. I don’t need to go into to much detail explaining how that one turned out. Lets just say it suffered from every weakness that the Vega became known for and blew its engine within a couple years. But I really found the Grand Prix’s to have a great athletic look to them. The GTP with its plastic fantastic body cladding and lacy wheels looked great to my 18 year old eyes. I searched the local Auto Trader magazine for several weeks when I found an ad for a 1991 Grand Prix GTP.
This is exactly what mine looked like
It was a one owner car, with just under 100k miles. I called the number and the owner agreed to meet me in the parking lot of the local K-Mart that evening. I took one of my best friend with me to check it out. As soon as I saw the car, I knew I wanted it. It was blue, with the aluminum lacy wheels, not the gold ones and it didn’t have the spoiler on the trunk lid. That was my favorite look for these. It also had PONTIAC written out across the top of the windshield in bold white letters. I really liked that as soon as I saw that too. The owner seemed to me to be a nice clean cut business man, that’s what I remember thinking to myself anyway, and I thought “well good, its probably not been driven to hard”. Once I got in the car I was blown away by all “cool features and buttons and screens!”
Such advanced tech!
It was so different than my simple old truck. The seats had power adjustments for EVERYTHING! They must have been 15 way adjustable seats, It had a super cool compass that showed a graphic of the car and what direction it was going, and that steering wheel! It was filled with buttons for the radio controls.
I thought all this stuff was so cool, and it all worked as well. But the coolest, part about the whole package was the heads up display on the windshield. We are talking real Top Gun, advanced technology here people. Not only would it display the speed, it would shown the turn signal indicators, and other cool stuff like the check engine light! Wait, I’m getting ahead of myself here. The owner told me that the tires were about 3 weeks old, “very good, they are awfully wide, I’m sure those were expensive, all the more reason to buy it”
Once we took it for a test drive, he told me that NASCAR driver Rusty Wallace had driven this very car around Atlanta Motor Speedway when it was brand new as part of some promotion and that the PONTIAC lettering on the windshield was put on at that time. Well Rusty Wallace was one of my favorite drivers at this time, so if I wasn’t already planning on buying this car before, I really was now. I agreed to meet him at his house the next Friday when he got home from work to buy the car. I had my mom take me over there and the deal was done in about 30 minutes. The car was running good, and I had the windows down and sunroof open, just enjoying the experience of driving it home for the first time.
My mom was following me in her van, and informed me that it had blown some black smoke from the tail pipes a couple of times. No matter I thought, probably just blowing out the catalytic converters! I really cant recall how soon it was after I bought it, a day, 2 days, maybe 4 at the most, before the car started to run poorly and the check engine light came on. Both on the dash and displayed on the windshield by the oh so cool HUD. The guy I bought it from had told me the shop he used for all his repairs and it was pretty close to my parents house.
I took it by there one day after school to ask them about the car, and see how much it would be to diagnose the problem. When the shop owner saw the car, he immediately recognized it and informed me that he was very well acquainted with it. Not what you want to hear when your 18 and just spent all your money on a new car! I didn’t know much about this engine at the time, the GM 3.4 double over head cam 24 valve V6.
What a pain in the butt to try and work on.
I soon learned that this was a very problematic engine and that this car had spent a LOT of time in the shop. I honestly don’t remember what was wrong with it that first time, but I remember had something to do with the timing being off. My new ride was in the shop within days of buying it and I didn’t get it back for a good 2 weeks. It was close to $1000 to fix the thing and I was feeling cheated. I called the guy I had bought it from and told him about the situation and surprisingly, before I could even bring it up, he offered to pay 75% of the bill. I was very thankful and gracious for his kindness, and was happy to get the car back.
When I got it back it ran better than ever and seemed pretty quick to me. Granted it was an automatic and not a 5 speed, but it was fun, and looked good! I had a solid week of it running well, and then boom, it started running like crap again and that dang check engine light came back on. Both on the dash, and staring back at me on the windshield through my kind of cool HUD. I pulled it into the shop of my auto mechanics class that pretty much majored in all 4 years of high school and discovered the problem to be some leaking vacuum lines. Not a huge deal right? Yeah except on this car they were VERY had to get to.
The car was back out of service for a week while I worked on trying to replace the vacuum lines that were buried way down deep in the belly of the beast. But once that was done, it was back in action! Oh happy days are here again! I got it all put back together and running on a Friday, and picked up my new girlfriend from her house in it. I had owned the car now for probably 4 weeks at this point and she hadn’t even gotten to see it yet because it was always in the shop. We got in and were getting ready to go to the high school basketball ball game, and then on to some other planned activities and I remember feeling excited for her to experience my cool ride. I cranked the car up and BOOM! Something went boom under the hood, very loudly and the car was now running poorly and sounded different under the hood.
I opened the hood and discovered that apparently the boom was a backfire through the intake which in turn blew apart the air cleaner cover. While the car was running crappy again, and the check engine light was back on, both on the dash, and on the confounded wind shield through the $@#&% HUD, it did sound really cool with the open intake! It really growled and was misfiring, so it sounded like it had a big cam in it and so I played it off for the night.
Unfortunately I don’t think my girlfriend was overly impressed with it and after I drover her car one time I could see why. She had a 1992 Acura Legend coupe and that car was far superior to my Pontiac in every way. “Hmm, maybe there is something to these imports after all.” Funny how different these two cars were and yet the same on paper. Both were front wheel drive coups, both produced 200 hp, both were their respected manufactures top offerings, but they were so vastly different to drive. Her car was also a good second faster than mine in a 0-60 drag race.
her car was also like mine in the fact that it did not have the optional rear spoiler. At least my car was a better color than hers!
And so the cycle went on for a couple of months, fix the car and drive it for about a week, then either put it in the shop or fix it myself again for about a week. The thing started to behave and run good for more than a week at a time towards the end of my senior year of high school and I actually drove me and a few of my closest friends to Spring Break in Panama City Florida in that car. On the way down, the car started making a funny noise when I would apply the brakes.
Now the route we chose to take, put us mostly on small state highways out in rural Alabama. This route was chosen because we wanted to avoid the State Troopers as best as we could, no need to explain why. It was out on one of these sparsely populated areas that the “funny noise” the brakes had been making, presented the actual issue. I was slowing down for a stop sign when a loud metal on metal sound occurred. I pulled off the road and jacked up the front passenger wheel and removed it. There I found the top bolt that holds the caliper to it bracket had come out and the caliper was now riding the inside of the wheel. Thank goodness the bottom part of the caliper was still on the rotor or I would have pushed the piston right out of the caliper and had a much bigger issue to deal with.
I got very lucky and was able to find the bolt lying on the road about 30 yards behind the car. The only problem was that it was some kind of hex head and I sure didn’t have anything like that in the car. One of my friends, flagged down one of the few cars that actually came up on us and got a ride into the closest town and took the bolt with him to find a tool to tighten it back up. Meanwhile, the rest of us hung out on the side of the road and actually had a grand time as pretty much the only people that passed us were other kids on their way to the beach also. We were given food, beer, phone numbers, and for once I wasn’t mad at the car for breaking on me!
This became a regular issue on this car. The passenger front caliper would loosen itself up and the drivers side would tighten its self. I got to where I would just tighten it up every two weeks or so as preventive maintence. I once broke 2 ratchets trying to loosen the drivers side caliper bolts though. That summer before leaving for college, I did a few things to it. I had the windows all tinted 5%, and had some glass pack mufflers put on. I typically don’t like loud exhaust on anything but a V8, but it actually sounded pretty good on this car. It wasn’t the angry bee buzz of a 4 cylinder and just gave it a bit more character.
I did do one thing that I thought was rather clever at the time, but seems stupid now. The hood had those cool vents running down both sides, and I honestly can’t remember if they were functional or if I made them functional by putting vent holes in them, (I want to say they were actually functional heat extractors) but at any rate, I disconnected the windshield washer fluid tube from the hood, and aimed it to spray on the exhaust manifold so that when I hit the washer button, it would blow steam out of those hood vents. I thought it looked cool and mean, everybody else just thought it was overheating…
Heading off to high school graduation. This is the only picture I have of my actual car.
In the fall of 1998 I headed off college in the Pontiac just as I had planned. I was living in a dorm room with one of my friends from back home. Being confined to a small room that had to be shared with someone else meant there was very little space for anything other than your essential items, thus no tools or car care products. What was I going to do when the car messed up again as I knew it inevitably would? I decided that the first weekend that one of my friends was going to go back home, I would go along with them and drive my trusty 87 F-150 back down.
So here I was living in a dorm and having 2 cars, well at least I was back to having a choice again about what to drive! One day while driving to a friends house who lived out in the country about 10 miles off campus I happened to drive past a very interesting vehicle with a for sale sign in the window. This vehicle soon took over my every waking thought and I had to make it mine. I quickly lost all interest in the troubled GTP and decided to dump it quick while it was still running. I drove it back home and took it to a Car Max dealership and sold it to them for whatever poor cash offer they made me. It was enough however to buy this next glorious thing that I had found and fallen in love with.
So I guess you could say my first experience owning a GM car was about like my dad’s. He says the Vega was fun to drive when it was actually running, as was the Pontiac. But those times were to few and all the other problems both of these cars had did nothing more than push the both of us deeper into the Ford camp.
One of the Deadly Sins of GM. Baaaad decision.
I’m not so sure it qualifies as a Deadly Sin. Granted it sounds as the subject car was a bit of a lemon (and the early 3.4 cars were far from trouble free) but overall I think it must be acknowledged that the GM10 (W) cars were mostly successful efforts. Each division had their own distinct flavor /styling, powertrains were mostly good (again, leaving aside early 3.4 flaws), and my recollection is that build quality was pretty good as well. I liked the Grand Prix (especially with the updated front fascia as this car had) but the Olds Cutlass Supreme was always my favorite.
It must also be acknowledged that GM was the only American brand at the time even attempting a modern 24 valve V6 while Chrysler had only the Mitsubishi 3.0 or their homebrew 3.3 boat anchor, and Ford had either the Vulcan 3.0 or Essex 3.8, none of which were great by any measure. And, as always, GM learned lessons: the 3.4 begat the 3.6 family which was and remains a clear success for GM. So do consider the context, eh? 🤔
Anyone ever played with one of these with the 3.1 Turbo? They made them…
Ford had the 3.0L DOHC V6 in the Taurus SHO starting in 1989.
That was a Yamaha designed valvetrain above the tired old Vulcan block. I love SHO like the next guy, but it doesn’t count as a real Ford engine, sweet as it was – particularly as it was never offered in ANY other vehicle.
Good try though 😉😁
It was indeed a combo of Ford shortblock and Yamaha engineering, but the 3.4 DOHC was hardly a clean sheet design itself given that it was based on the old 2.8/3.1 X-engine V6 that powered everything from Citations to Celebrities to S-10 pickups. The Vulcan was at least six years newer in design than the X and replaced the old 2.8-2.9 Cologne (amusingly the 4.0 Cologne variant eventually sprouted overhead cams in later life).
Remember that the LQ1 was also introduced 2 years after the SHO, using a longblock that dated to 1980. That seems a bit more “tired” to me. 😉
Taurus SHO, 3.0l and 3.2l engines in collaboration with Yamaha.
“’I’m not so sure it qualifies as a Deadly Sin. Granted it sounds as the subject car was a bit of a lemon (and the early 3.4 cars were far from trouble free) but overall I think it must be acknowledged that the GM10 (W) cars were mostly successful efforts. ”
I’d argue that the GM10 cars (W-cars) were the biggest of all of GM’s deadly sins. Not only did GM spend nearly 7 billion on development, but they were immediate sales flops out of the gate. At one point in the early in the program GM was losing almost $5000 per car! GM took way too long to get the car to market (started in 1982) and when it did release them, they only released 2-door models. Ford had enough sense with the Taurus to know 4-doors were the future, GM should have too.
Cardy Davis was assigned to the W-car program, in the early 1990’s to help turn it around. At that time, he was quoted in saying “The W-platform is losing more than any car in history, in any company.” GM had the means and opportunity to create a competitive midsized sedan during this time, but instead it developed a poorly built mediocre cars, that were uncompetitive and cost way too much money. There was a chance they could have turned things around had they released a decent car.
As for the 3.4 DOHC engines, they may have had the content on paper, like much of GM’s products at this time, but they were far from well executed. Who cares that they “attempted” a DOHC when the end result was so bad. There is a reason they didn’t stay around very long. Then lets not mention the huge other variety of mediocore to awful engines, such as the Quad 4, the turbo 3.1, the Iron Duke.
7 billion!!??! I heard it was $21 billion when all was said and done! The GM-10/W-body project was the costliest in GM history. ‘Automobile’ magazine boldly stated on its cover in 1987, about them being ‘The Cars That Can Save GM’. They reviewed all three, the Pontiac, Olds and Buick, and did praise them for the three division’s W-body offerings not looking alike on the outside, but the fit & finish in many areas was sub-par, even compared to other older GM products already on the market at the time. Someone I worked with at the time did buy a 1989 Grand Prix, and he commented how it was less refined it was in ride and poorer fit & finish over a 1986 Camry sedan he traded in for it.
Adam, I wonder how much real experience you have with W Bodies. Speaking as a GM service advisor, these cars were junk. They did not have good quality materials in them. After 140,000 km, the cars self destruct. It is amazing that the cats on the featured car didn’t need replacing every year. Strut mounts, brake calipers, ABS sensors, electrical problems plagued these cars and this is only a few of the list.
The “Twin Dual Cam V-6” was an aberration of heavy new twin cam heads bolted on an existing block, using the camshaft location of the old engine to drive all the cams. It was rushed into production and caused no end of problems with overheating, backfiring and general bad running. The also leaked like crazy.
These cars killed GM’s lucrative family sedan business. They were an unmitigated disaster and to top off, GM lost money on every one they sold.
The Mitsubishi 3.0 V6 was the engine along with the earlier 2.6 that kept our resident local Chrysler dealer rich from constant oil burning and head issues along with constant check engine lights and running behavior issues. Combine it with the wonderful Ultra-Drive transmission and my high school friend that worked there at the time was swapping them out 3-4 per day 5 days a week! And these things always happened right out of warranty so the dealer was racking in profits from repair work. I used t pick him up for lunch and would see 3 new engine or transmission cores sitting in wooden crates and the joke was “how many did you swap today” Chad? A Deadly Sin for sure.
Yes i own 2 1990 ASC MCLAREN TURBO GRAND PRIXS and they run quite good. They make 205hp stock and I’ve chipped mine along with a catback exhaust system, larger injectors and underdrive pulleys has it making about 270hp at the tires (which is a fuzz over 300 at the crank gross horse power) not bad for a v6. The downfall is the DM PMIII integral abs brake system. GM no longer carries parts or services them as of 2006 so i did some research and found a couple factory service manuals for the setup and with some digging managed to find a parts supplier.. i completely rebuilt mine, picked up a tech 1 scan tool and now have perfect brakes.. The main problem with the system is due to the integral part, contaminated fluid really causes havoc on the internal seals.. if driven daily flush your fluid and add new 1 time per year.. if an occasional driver once every 2 yrs.. if you do this you’ll keep perfect brakes for years to come aside from the occasional de-pressurizing of the accumulator and taking the bleeder screws out and pushing the pistons on the calipers back in during a brake pad swap.. * another issue people cause themself when not taking the bleeder out since when u push the piston in and don’t remove the bleeder you push contaminated fluid thats inside the caliper out into master cyl.. which messes up the seals and causes the problems to begin with so just remove ur bleeder and push out the nasty stuff and simply tighten the bleeder back up. Just be sure once you have done each wheel top off the master with clean fresh dot 3 brake fluid
The thing about the GM10s was, it wasn’t only the ‘performance’ versions that had issues. If you were unlucky, even the most basic ones were basket cases. My parents bought a bog-standard Olds Cutlass Supreme in 1994, and it became my daily driver for a year in college. Its 160hp 3.1 was burning a quart of oil a week by then–on one trip to Mono Lake through the central California mountains, I was feeding it a quart every two hours. And when coming back down the mountains, the disc/drum brakes had faded so badly we had to stop every half-hour to cool them down. It was almost as though the Olds looked like a ’90s car, but with ’60s limitations underneath. That said, a friend of mine at the same time drove a ’91 Lumina that was an absolute tank, so it seemed GM quality then still depended on the day of the week your car was built and the shift workers assigned to its assembly.
140 or 145hp.
The naturally aspirated 3.1 never produced 160 bhp.
I had a 1991 Pontiac Grand Prix GTP and never had any issues. I drove it for years. Loved that car.
I find it strange that General Motors would call its LQ1 V6 engine “Twin Dual Cam 24″ when the definitions of twin and dual are about the same.
I think it meant four camshafts. Think twin cylinder banks, dual camshafts per bank.
All right, wouldn’t be simpler and clearer to say “Quad Cam 24” on account of having four camshafts?
It would probably confuse people with Oldsmobile “Quad 4” engines…
My friend and I liked to call them “4+1” cam motors, since the original OHV cam is still in there, driven by the crankshaft. It in turn drives the 4 overhead cams.
He had a 92 Lumina Euro 3.4 sedan that he put 200k mostly trouble free miles on. That car ran strong, sounded amazing with a K&N cone filter, and handled quite well. Definitely a tight engine bay, though! I’d love to drive one with a stick sometime.
Beautiful car, sorry you had so many problems with it. I had a 1993 Lumina Z34 coupe, the Chevy version of yours, and it was a reliable, comfortable car. I ran it for six or seven years, then sold it to my brother. It had well over 100,000 miles on it without any engine problems.
Wow, isn’t it terrible when the automotive love of your life morphs into a serial abuser? I tried the 2 car thing for a year in college. It proved to be a financial disaster.
The one thing you left out was your father’s reaction to this Pontiac coming to live with you. I’ll bet the phrase “I told you so” was in his mind if not coming from his mouth. And I laughed at the irony of a true blue Ford guy getting a Vega when he decided to try a Chevy.
Your comments about your GP and your girlfriends Acura ring so true. I was a Pontiac guy through and through, buying five new Pontiacs during my lifetime – a ’73 Firebird, ’78 Grand Am, ’84 6000 and ’89 and ’96 Bonnevilles. I would describe every one as “OK”, but none really ever hit the sweet spot for me. Fit and finish was so-so and all became increasingly more unreliable as the miles piled up. It got to the point where I figured this was just the way it was. I never considered a foreign product, until a friend let me drive his new Acura TL in 2000. I was blown away by the high level of quality throughout and smooth, refined engine. It was just better than my Pontiacs on so many levels. My next car was a 2001 Acura TL, a car that required ZERO repairs in the eight years I owned it. Two later MDX’s were equally reliable.
I know quite a few people who, like me, were loyal to Detroit iron for years, then something happened to get them to buy a foreign (usually Japanese) brand. Few ever bought a domestic product again.
Ford guy here checking in, but kinda the opposite of you in growing up. My Dad mostly had GM cars until passing down the one Ford he bought to me as a teen turning me into a Ford guy….
….but then I was bit by the GTP bug myself and traded my last Thunderbird in on the one pictured below. Fortunately, mine was the next generation with the 3800 Series II Supercharged engine. Drivetrain wise, I never experienced the issues of the 3400, although my stepson experienced a few with his ‘99 Grand Am GT with that engine.
But then my wife at the time was a tech at a Pontiac dealer, so whenever it needed anything, she just took it to work and fixed it, so it may’ve had more problems than I realized. I do recall a front coil spring just breaking going slowly over a speed hump one day; a leather seat started to fail and she somehow got it replaced under the extended warranty I reluctantly and uncharacteristicly got talked into purchasing.
When she and I were about to split up, and she was also no longer working in a situation where she could just take my car to fix it, the float for the fuel indicator went up on me. I decided to fix it myself. That didn’t go so well. The car smelled like gasoline for 2 weeks while I looked for a new car. I went back to Ford with the purchase of my 2007 Mustang. Of course that brand loyalty has since waned. I like lots of different cars, and currently have a turbocharged Civic Coupe for the DD. It’s a blast to drive and gets killer gas mileage. But I still have my Mustang. 😉
FWIW, even owning a Pontiac, and at the time they were running in NASCAR, my favorite driver was still Mark Martin, who drove the No. 6 T-Bird (and then Taurus), so that loyalty did not change. He’s retired now, and I no longer watch NASCAR races.
3400 in grand am was different than 3.4 in grand prix
I feel your pain. I recently ended an abusive realtionship with a 2001 Audi A4 1.8T Quattro. Loved the thing when it wasn’t in the shop. Will never buy another VW product again.
I suspect this is the attitude of many former VW/Audi owners: they’re terrific…when they’re not in the shop…
The local VW dealer is advertising 2016 TDI automatic Jettas for $7,000 with an unlimited mileage 2 year warranty including maintenance. They must have been the ones that were recalled and reprogrammed after the VW diesel emissions debacle. Be afraid, be very afraid…
My brother had a 1995 cutlass supreme with that engine. Was purchased new by my uncle. I do remember we had to do alternate and plugs and wires around 100k miles. That was a pain. Had to loosen motormounts I beleve maby part of the cradle.
I hate to hear but definitely understand. Lesson learned to never trust the gadget and toy overdose, dual exhaust, and tire size on that X-Motor equipped type of car.
Wow this brings back memories of my 1996 Monte Carlo Z34 that I bought in ’99 with just 45k miles. Yes…to a 21 year old thats landed a good paying job at the time what else could go wrong??
3 alternators, a transmission, and plug wires in 10 months of ownership not including the famous “Service Engine Soon” light that illuminated everyday payday week. I shudder at the warranty cost and finally traded it 2k miles before extended warranty was up. But, when it ran on on non-payday weeks it was a gem.
I have a poster of one of these on my wall, it was on the other side of a 1988 Pontiac brochure I bought on eBay. I’ve always liked the way these look.
Great story about a total turd – GM strikes again!
I had 3 W-body cars equipped with the 3.4 and never had an ounce of trouble with any of them. I’m thinking this was either a lemon or the first year blues with a new engine design. They were not easy to work on, especially the alternator and thankfully none of mine needed one even with over 100K. I did have the 94 and 95 Cutlass timing belts replaced by a good crack mechanic and he told me there was a specific way to do them right.
I remember the transmissions in these cars. The 3.4 was a high revving engine. If you were going say 35 MPH and floored the throttle the transmission would do this thing were it felt like it slipped and would catch and then catapult forward. The mechanic said it was programmed that way as to not stress the output shaft. That was one of the weird things with all 4 cars with this engine. Otherwise those 4T60’s seemed to hold up well even after the torture my right foot gave them. But I always keep things well serviced so that might explains it.