1999 Pontiac Grand Prix 3800 Transmission Problems

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Jan 10, 2005
Went for a trip with my dad the other day and his 1999 grand prix 3800 v6 and the transmission is acting wierd. Here are the symptoms when it gets hot it "bangs into gear" when upshifting, shifts very hard. Downshifts seems smooth and fine. Also there is a whinning noise when starting out, not terribly loud of anything kinda sounds like a supercharger if I had to explain it. I asked him how long it has been doing this and he said a couple years. I was thinking adding a B&M supercooler, magnefine filter and a few pan drop fluid changes. Well, one then adding a drain plug to change fluid. Anyone know any known problems with these transmissions or cars? Thanks for any input.
If it were an older rear drive car, I'd suggest a new modulator. These cars have it all inside. How many miles?? Fluid and filter change is the first thing; you might try a synthetic fluid. You'll only get about 4 quarts of new fluid in and much is in the convertor. If all else fails, talk to a transmission shop. They'll maybe try to sell you a new transmission, but some will suggest a quick fix. A busy shop maybe less interested in selling and more generous with advise. My 2¢
Bingo. A autotrans mechanic once told me 70-80 percent of autotrans. problems are because people never change the fluid. 25-35 thou. fluid change intervals is/was the suggestion. The first change is the most important.
Sounds like the clutches are going in it if the fluid is ok. However Im sure new fluid would make something better. 80,000 on OE fluid is not good. If its a normal 3800, thats 220ftlbs of torque put on that FWD tranny for the life of it, and it takes a beating. The 4T60E was never strong to begin with.
I told him about changing fluid long ago, he just didn't listen. Personally I change my fluid every 20,000mi. Except on my 2000 blazer it has a motorguard bypass filter on the transmission line. Amazing what the filter looked like the first few times I installed a new one. It was a dark grey color, now it comes out bright red. My 92 blazer has a magnefine filter and a drainplug to make fluid changes easier. I am going to change the fluid and filter for him later on. I was hoping someone would say it was something like "ya, it's a TCC solenoid and it was a common prob." I'll give him the bad news.
Iceberg, don't count on the fluid change helping this issue. Adding a trans cooler and magnefine filter won't help it, either. I've been there. You're dealing with a design problem here. These transmissions are well known for solenoid issues. There are four of them under the side cover. One each for pressure control and torque converter clutch application and two for shifting gears. These tend to get bad and start to stick. There's nothing you can do but to replace them. The good news about this is that it's only $100 for all four solenoids. The bad news is that the side cover removal is very involved and requires an engine lift. It's an all day job for the average DIY'er. (Been there, too). A mechanic would charge $1000 or more in labor. It would be worth getting the whole thing rebuilt if you can't fix it yourself. On my car, I wasn't getting the hard shifts, but it was sort of banging into gear every time I left a stop light. I replaced all four solenoids and cured the problem.
Ditto on the fluid change. I would change out the fluid and filter and refill with a good synthetic. Drive it for 1000-2000 miles and see if the problem persists. The P.O. of my one car followed the factory specs of lifetime fill and did zero transmiission services on it. I had a hesitation and sloppy shifts at 66K. Exchanged the nasty looking old fluid with Redline synthetic and put in a new filter. At 80K it shifts like a brand new transmission.
Lack of maintenance kills another transmission. Throw in a bottle of gunk transmedic(black bottle) now. Drive 500 miles. Drop the pan and change the filter. Refill pan and then do a cooler line flush or get a machine flush. Use the cheapest dexronIII. Now is NOT the time to upgrade cooling, fluid type, or filtration. Save tho$e mods for the rebuilt unit that you'll soon need. Cross your fingers. Failed modulator valve, accumulator spring breakage, and numerous electronic gremlins could also cause issues. Make sure engine is in a good state of tune, no vacuum leaks, that there are no stored or active ECU errors, that throttle position and vehicle speed sensors are good, and all grounds and wiring harness connections should be cleaned and corrosion free.
My 4T65E suffered from a sticky pressure control solenoid causing a jerking when accelerating. After a run of AutoRX it has completely cleared up. So don't count it out yet. The problem is more maintenance then anything. The first fix on an auto tranny is always a fluid change.
Those of you criticizing this person for lack of maintance should take into consideration that as early as 2000, possibly sooner, GM was advertising 100k mile trans fluid changes for this transmission. This is not a neglect issue. It's a design problem with the solenoids. BTW, I did several fluid changes and an AutoRX with flush on my trans when it exhibited the problem I described above. None of it made a lick of difference.
Just because GM recomends 100,000 doesn't mean it's not a maintenance issue. Solenoids are hard to "design" to withstand crud and build up. The issue is the fluid being in their too long, whether or not GM says it's OK. BTW I think that is the "normal" interval, severe is much sooner.
I forgot to mention, the car shifts absolutely fine until it warms up. Well, I got what I was hoping for I guess it is a solenoid problem but it sounds like a PITA to swap them. Is this a 4t65E tranny in this car then? What is the procedure for swapping the solenoids? I have an Cherry picker, engine support bar, and a Kwiklift in my garage.
I forgot to mention, the car shifts absolutely fine until it warms up. Well, I got what I was hoping for I guess it is a solenoid problem but it sounds like a PITA to swap them. Is this a 4t65E tranny in this car then? What is the procedure for swapping the solenoids? I have an Cherry picker, engine support bar, and a Kwiklift in my garage.
That's exactly what happens when the solenoids start to stick. It's fine until they get hot, they they start showing problems. To get the side cover off, you have to remove the driver's side axle shaft from the trans, which involves disconnecting the lower A-arm, supporting the engine, then dropping the engine support subframe. At that point the side cover should be accessible. Once that's off, the solenoids are right in front of you. They're held in with clips, some easier to find that others. I HIGHLY, HIGHLY, HIGHLY recommend you replace all four if you're going to do this. They're about $100 - $150 for all of them. If you're serious, PM me your e-mail. I can send you some excerpts from the factory service manual that will help. There are a lot of pre-steps involved and the side cover bolts have to come off in a certain sequence.
Update: I did the rear brakes for him last week and added a bottle of lubeguard red in the tranny. I asked him today about the tranny and he said it has been shifting fine ever since and no longer does the banging into gears. We are keeping our fingers crossed. Thanks everyone for the information about the sensors and such. If the problems return it will be going to the shop for repair.
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