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Topic: transmission jerking on light throttle decel in overdrive (Read 1762 times) previous topic - next topic

transmission jerking on light throttle decel in overdrive

Hey all,
  I believe I have a pretty bad problem with the aod in the 88birdsc. When I first got my vehicle back running after a couple of years down, I noticed a slight buck on decel in high gear. I thought it might be egr since it felt like a lean miss. The transmission also had some soft shifts and may have slipping some. I installed a tci shift kit, which firmed up the shifts and allowed it to stay in gear longer. I still thought I had a lean miss do to some type of vaccuum leak; however, the problem got worse and I didn't seem to notice much in the lower gears. Engine runs pretty strong at wot and it's definately not lean. It blows black smoke even at part throttle. The fmu is forcing alot of fuel through the injectors; nevertheless, the map worries me a little if the supercharger hosed it up. I was wondering if anyone could give me some advise on how to isolate this bucking and jerking to the engine or transmission. In addtion, some advise on how to set the tv pressure since I heard that you could adjust all the slack out of the cable and it would be good to go. The transmission has 90k on it and I could possibly get a junk yard aod for $200.00. As a result, if the problem is still present that $200.00 would obviously not be well spent. Thanks to everyone for their input.;)

Mike
[SIGPIC][/SIGPIC]88 t-bird: 5.0ho, gt40y, crane 2031, fms 1.7, paxton@5#, aod wide ratio, tci stall, performer rpm upper, 70mm bbk, pro m 60, 42#s, 3.73 7.5" posi, jba shorties, borla, upr x. 13.4 @ 104mph. cbaza, moates, tuned by decipha

transmission jerking on light throttle decel in overdrive

Reply #1 –
When i first got my 87 5.0 bird, everytime i came to a stop it'd stall.  then after changing all the usual tune up parts and adjusting back into spec just about everything in the engine bay (the person before me let the egr start sticking, didnt know about an egr and played around with everything in the enginebay, leaving me with a very sick car) i got it to run alright...  i then started getting this VIOLENT bucking issue, i thought for sure something washiznitting the underside of the car.  i mean it sounded that horrific.  not to mention it actually only really happend in OD decelling at around 55+mph.  i thought about trying to figure some enginious way to spy on the drivetrain while this happend.. for some time i couldnt figure it out, oilchanges, sparkplugs, you name it, i threw it at it.  it came down to replacing a bunch of vacspoogee fittings and hoses.  not only was i having this serious bucking problem but the idle was up and down up and down up and down... pulsating.  well after the vacspoogee leak was eliminated by the new hoses and fittings the idle smoothed out, and i didnt have the bucking problem.  it sounds strange, but the car was trying to STALL!!! while letting off the gas at 55+mph.  to be honest i threw so much at the car all at once i cant for sure if it was my tune or just a vacspoogee leak, but in hindsight, i can tell it was the car wanting to stall.  try new hoses and fittings everywhere, different oil and filters throughout, a whole new tune up, flush all fluids, go to the parts store and get some maf cleaner (dont be dumb and spray it down with anything else like carb cleaner or parts cleaner) basically do everything you can lol b/c thats basically what i did and it solved the problem...  the only problem i have after that stall problem, the backlash in the rearend is so out of wack, you can actually feel the rearend change directions (accel deccel).  after the car had been down for a couple years a vacspoogee leak sounds about right though, rubber stuff like that likes to dry-rott.

transmission jerking on light throttle decel in overdrive

Reply #2 –
I would NOT spend money on tranny parts...I've dealt with the exact same problem and it was the TPS sensor....9 out of 10 times, that's what will cause such a problem.  Make sure you set it to the proper voltage at idle and that the sensor is not out of range.
Project 3G: Grandpa Grocery Getter-'85 Crown Vic LTD 2-door, 351W with heavily ported/polished GT40 heads, heavily ported/polished Typhoon Power Plus upper & lower intake, Comp Cams 265DEH retarded 1*, FAST EZ-EFI, HD T5, 8.8" 3.73 trac lock with extra clutches, 3G alt. swap, '99 CVPI front brakes, '09 CVPI rear disc brakes, '00 CVPI booster&m/c + wilwood adj prop valve.

Parted & Gone-'88 T-bird Sport, 351W swap, ported GT40 heads

transmission jerking on light throttle decel in overdrive

Reply #3 –
got bad news.  my AOD just popped... first a U-joint, now the trans...  that problem is terminal.

transmission jerking on light throttle decel in overdrive

Reply #4 –
i agree,, after chasing down what was causing my bucking, it ended up being the tps.

however, on the CFI setup i also seem to remember the idle control motor assembly swap improving this issues as well.


autocat, sorry to hear bout that, but it takes a lot of damage to call it terminal, especially when a decent AOD can be had fo less than a hunderd.
look for the most grease caked, dirty tranny you can find on the LTD's, LInc, Mark, ect.  If they are dirty as hell, they aint been screwed with and if you find that plastic lolly pop in the tranny pan, you probably scored a good one for sure.
:D

transmission jerking on light throttle decel in overdrive

Reply #5 –
Sry for the hijack but

Those who had tps problems... did your car chug around 30 mph? or is that a timing problem?


/end hi-jack

transmission jerking on light throttle decel in overdrive

Reply #6 –
my bucking or "roll over" was usually experienced while the car was in overdrive.  it wasnt really speed specific although i thought it was early in the game, it turned out that backroad driving produced the same buck.

what i really need to do is pick me up one of those really cheap buttstuffog meters so i can test variable resistors and pinpoint the microscopic open's.

all ya'll aught to take a hammer to an old tps and see how it works,, then you'll see what i mean by the green wire and what it does.

transmission jerking on light throttle decel in overdrive

Reply #7 –
my tps is prolly all outta wack.

.98 right? ill have to check it tomorow.

transmission jerking on light throttle decel in overdrive

Reply #8 –
The ol' TPS buck is usually most noticable in direct/overdrive because the trans is locked up at that point.
Project 3G: Grandpa Grocery Getter-'85 Crown Vic LTD 2-door, 351W with heavily ported/polished GT40 heads, heavily ported/polished Typhoon Power Plus upper & lower intake, Comp Cams 265DEH retarded 1*, FAST EZ-EFI, HD T5, 8.8" 3.73 trac lock with extra clutches, 3G alt. swap, '99 CVPI front brakes, '09 CVPI rear disc brakes, '00 CVPI booster&m/c + wilwood adj prop valve.

Parted & Gone-'88 T-bird Sport, 351W swap, ported GT40 heads

transmission jerking on light throttle decel in overdrive

Reply #9 –
i just remembered what my car had goin wrong that cuased my buck.  the reason it was stalling was b/c the throttle body AND spacer was cracked.  i think it got brittle and then popped very very soon after it was driven more than 50 miles after sitting for about 8 or so years?  not sure how long it sat (garaged cept for the last 2) i belive it was on the bottom near a screw or fastener.  but yeh NO tps will also cause bad idle problems.


oh yeh, and my transmission is getting replaced.  i know, its cheaper to install a 5spd myself, but my dad doesnt think i can do it (i have done it in school.  not all in one job, we put a tranny on an engine and bolted in, then on another similar car setup we hooked up the linkage and for braggin points tried to get it perfect (groups) and then even did some wiring (it looked alien since all i've really worked on that deep has been the bird, hell it was mopar) but im sure i could do it myself in a parkinglot, and for the price of the new tranny, the labor, etc.  i could have a new trans and rearend, which sucks.  i cant wait to get out of school and make money!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

sorry for the hyjack.

transmission jerking on light throttle decel in overdrive

Reply #10 –
This is a kinda old thread but my car kinda jerks in OD if I'm going up a hill and I'm lightly on the accelerator.  Once she downshifts, everythings fine.  But if I'm goin up a hill and either slowing down or barely speeding up, she seems to be 'indecisive' about downshifting or not, and the car kinda shakes.  Is this the same problem?  The car runs perfectly otherwise.

transmission jerking on light throttle decel in overdrive

Reply #11 –
nah my old neighbor used to work at a ford dealership and when i pulled my car over to his garage to get some air he was tellin me how the most common thing for our auto birds to come in for was exactly what your describing.  "indecisivness" is the best way to describe it.  i think what we're talkin about here is a full out problem, not just the tranny bein confused (i think its a factory vac problem)
 

transmission jerking on light throttle decel in overdrive

Reply #12 –
Quote from: kingcars;131495
This is a kinda old thread but my car kinda jerks in OD if I'm going up a hill and I'm lightly on the accelerator.  Once she downshifts, everythings fine.  But if I'm goin up a hill and either slowing down or barely speeding up, she seems to be 'indecisive' about downshifting or not, and the car kinda shakes.  Is this the same problem?  The car runs perfectly otherwise.


Mine did that when I first got it. I changed the TPS and the problem went away.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.