I would appreciate any ideas or help with this issue! Thank you in advance!
1999 Buick Lesabre Custom transmission "Jumping / Shuttering" when starting from stop with load on tranny (Usually starting on an upgrade) while in 1st gear. These symtoms were non existent until after I changed the transmission fluid / filter the first time. After fluid change, symptoms appeared immediately.
Transmission: 4T65E (GM Service Part Code MN3)
1. Vehicle at operating temps.
2. When starting on a uphill grade with moderate throttle, transmission jumps/shutters the car while still in 1st. If you take your foot off throttle "jumping" will stop and a normal shift into 2nd will usually occur.
3. If you manually put shift lever into 1st gear, and accelerate, jumping will not occur, however if you manually put the tranny shift lever in OD, 2nd or 3rd jumping will return.
4. Jumping does not occur when vehicle is cold, only when warm.
5. Tranny seems to shift fine/smoothly into all other gears. This just happens from a stop when tranny is still in 1st. Shifts to 2nd fine.
Actions that I have taken: Checked...double and triple checked fluid levels!
1. Hooked up Snap-On Scanner and went into transmission settings and manually increased line pressure by going into PC Solenoid and increasing duty cycle (Pressure) to 10%. When I do this jumping / shutter goes away and shifting is fine. If I disconnect scanner or lower duty cycle back to 0% the symptoms return return. Repeated this step several times with same results.
2. Changed tranny filter / fluid. Fluid was pink, smelled good and the pan / magnet were normal with only slight / normal "Clutch mud" in the pan. Thermal element was fine. There was not other debris in the pan. Disassembled the filter and found no unusual debris.
3. All engine and tranny mounts were replaced (New)
4. Replace Throttle Position Sensor (New)
5. Replaced I.A.C.
6. All vacuum lines were checked with no leaks / issues.
7. Checked all History Codes with scanner. There were no codes set or in history on the engine or tranny side of system. Repeated this step several times...several times after duplicating symptoms...still no codes.
8. Cleared TAP Values and reset ECM / PCM by disconnecting battery overnight. Symptoms returned after a short time of driving.
9. Checked drive line / half shafts...no issues.
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If the condition of the fluid that came out originally were good (not burnt, not full of friction material or grits, etc.), some debris and sediments might have shifted inside the valve body. If you feel up to it, try disassembling and cleaning the valve body.
I can manually adjust the line pressure and make the shutter go away, so this tells me it is most likely a pressure issue. I realize that debris may be in there..but I am thinking its a PC Solenoid or manifold press switch. Your thoughts?
You stated that "symtoms were non existent until after I changed the transmission fluid / filter the first time." I don't see why the fresh fluid would affect electrical components and thus I'm rather ambivalent about replacing the PC solenoid. This "manifold press switch," are you referring to the MAP sensor? If so, my position on it is the same.
On a vehicle that old, usually the friction material suspended in the fluid makes up for the worn-out friction surfaces and thus it's better to leave it alone if the fluid sample looks like it's about had it. So, how was the condition of the fluid the first time?
Thank you for your suggestion. This is a very intelligent answer...which is what I am looking for! To answer your questions... These symptoms started as soon as I changed the fluid...and I mean immediately. This makes me think that perhaps I have sediment in the solenoids or Manifold Press. Switch. No the manifold Press switch is a component under the side cover which comes with the solenoid switch...you will see what I mean if you Google it. However, I did replace the MAP Sensor also in and unrelated issue..that was way before the tranny issue though. I also agree that friction material could be suspended in the fluid, however the fluid was almost immaculate. It did have a little mud in the pan and on the magnet, however I dont think that is was abnormal. Also the were NO symptoms before the fluid change. GM has a Service Bulletin with my exact symptoms listed and they cite the PC Solenoid. If I drop the tranny I am going to replace it all. The whole kit is 70.00...might as well. I just dont want to drop it for nothing which is why I am here...to learn. Thank you sir!
BTW, the mileage on the car is 85,000 and the car is clean and was well taken care of..(I am told, of course) The fluid tells the story....it was either changed recently or was driven very lightly. I have only owned it for a few weeks.
I see, what you're calling "Manifold Pressure switch," I'm used to hearing Transmission Fluid Pressure (TFP) switch which shouldn't have anything to do with your problem. Based on the vehicle history or the lack thereof, the most likely scenario is, the previous owner noticed the problem, tried the fluid change (thus the fresh-looking fluid) first, and then used some sort of an additive to make the problem less noticeable. You then came along, changed the fluid, and then got the problem right back. I'm sorry to say but I think you have a worn-out transaxle.
I happen to know the previous owner, and he was older and believe me he isn't this smart. He took care of the car...but I dont know when the last time he had the tranny fluid changed. I can tell you he changed the engine oil every 3000 miles LOL. As stated in my original post...I am able to increase the PC Solenoid using a scanner. I increase it only by 10% and the shutter goes away. Also, when I manually put the tranny in 1st gear with the gear shift, it also goes away. Also, it only happens under an uphill load and under moderate to hard acceleration. There was no additive in the fluid as I'm sure you know, you can tell when there is an additive such as Lucas in the fluid. Everyone wants to tell me that its a rebuild job...and that is an easy answer. I refuse to swallow this with my symptoms...obviously GM thinks this also. If i had the obvious symptoms of a worn trans axle and it wasn't so sudden, with great fluid and no symptoms before the change I could buy a rebuild as a fix. I will do a rebuild if needed, I did have a trannny expert (23 Years take it for a drive. He even said that the symtoms didnt point to a clutch problem. However I had a bad mount and he said that he couldnt do a proper diagnosis with a bad mount. SO I changed all the mounts and the TPS and the symptoms improved but they are still there. It is eay to say rebuild. I prefer to think out of the bax. Perhaps someone else, if not me , will benefit. There are A LOT of posts concerning this same probelm on MR. Google and I didn't see one that didnt at least mention the GM Service Bulletin on the solenoids which is a known problem. Your thoughts are appreciated. I am not discounting your diagnosis, I just respectfully disagree at this point. Thanks for your time and help!