• The site migration is complete! Hopefully everything transferred properly from the multiple decades old software we were using before. If you notice any issues please let me know, thanks! Also, I'm still working on things like chatbox, etc so hopefully those will be working in the next week or two.

Strange Trans. problem...help!

lastonemade02

lastonemade02

New member
I have a 98 bonneville, and if I step on the gas hard from a DEAD STOP the whole front end shakes violently. Took to a trans. shop and of course they wanted to rebuild it for $2500 saying the prob. was a bad gears design and the gears were not meshing correctly or some bs to that effect. He claimed the trans would completely fail in the very near future. Since then I just babied it off the line and have had no issues at all. 2 years later I'm still driving it(only if I hit the gas too hard from a dead stop) Anybody have a clue to what this problem is? I love this car but cannot afford a new tranny.. Thanks!
 


My dad has a 99 LeSabre and it's been doing the same thing for years. Drives fine, and runs perfect, even WOT downshift into 1st at 20mph. But mashing it more than half throttle from a stop, and the car shakes hard and shimmies, like the tires have broken loose and are wheel hopping, until you let off the gas. It'll do it hot or cold, and consistently.

I'm thinking it's caused by the input clutches cycling in and out rapidly, caused by low initial trans oil pressure, because it never slips or shakes after it has had RPM's on it, i.e. the WOT downshift into 1 doesn't slip.

There is an idea I'm going to try. Like a brake stall test. Hold the brakes down hard, then give it maybe 1/4 throttle for a few seconds, let the pressure in the trans build, then mash it and let off the brakes.. If it doesn't shake on the mash, I'm thinking that would kind of verify the low pressure..

I'm guessing there is a partially blown out gasket somewhere on the Valve body or Channel plate. Input piston seals from the factory are weak on 4t65e's also. That makes sense because the issue is "static", not getting worse over years.

Fixing any of that basically requires pulling the tranny out, and if ya got the damn thing out, might as well at least do a light rebuild (gaskets, seals, frictions etc) That's what anyone who has done it before, is thinking. Unless you are just going after a known bad solenoid on a low mile trans..., well I'd be close to suicidal if I went thru to time and hassle to pull the trans to replace a single part, and have something else give out 500 miles later. Drive it till it dies.
 
Last edited:
swap your axles first. then see whats up with it. the axles are most likely your problem as broken transmission parts dont cause vibrations.
 
when you say "Swap" the axles, do you mean replace them? ...and how much would that cost? I'll be paying a mech. to do the work.
 


def look into the axles or 1 axle as being the problem, i have also seen bad inner tie rod do some things under extreme pull. still i would lean towards axle =)
 
lastonemade02 said:
when you say "Swap" the axles, do you mean replace them? ...and how much would that cost? I'll be paying a mech. to do the work.
Click to expand...
it depends......do you mean gm parts or aftermarket.......the shafts themselves can be anywhere from $90 to $955 list price from gm each...plus labor... so are you taking it to aftermarket mech. shop or the gm stealership?
 
Hmm, I was never thinking tranny either. I am leaning towards axel as well, maybe even a bit of chassis and suspension as well.
 
you can get the "stage 1" axles from ZZP that have grease ports on them. if you have the money i would go with those. they are only $90 each for them.
 
OK Two different guys have told me that it's not the trans. at all! They say it's the MOTOR MOUNTS. Makes sense. I'm gonna have them looked at here at the local Goodyear.
 


I'm having the same issues. only in 1st and only once it is warmed up. if it's cold there's no slippage. when it's warm it's like having a 4000 stall "strip" torque converter in it, unless you baby it OR if i pull it into 1st gear and shift manually it won't slip.
this problem is not the axles. if the problem was shudder only, I would side with y'all. :th_scratchhead:
 
my 98 gtp sorta did something like that this am but it was torque converter lockup suck on and delay in shift codes that came up
 
I have a 4t65e in a 07 GP GT. When I slow down to make a turn, and I notice it more on right turns, as I begin to accellerate out of the turn the shifting feels sticky thats the only way I can describe it. It seems to shift hard. I would'nt say its really slipping though cause my RPMs aren't flying up, or maybe its so slight I don't feel it. Anyway anyone ever experience this? Is this an example of factory shift characteristics or is something lurking for the future with this tranny.
 
Well, I took it to Goodyear, and they said NOT motor mounts. They said if it were that, it wouldn't shake and shimmy, it would just "clunk" and stay in that position until the torque was released. Makes sense. I'm about to give up trying to find the problem because it sounds like its gonna be expensive to fix, and I'm not gonna dump 2500.00 bucks into a car thats worth.... you guessed it. 2500.00 bucks.... :(
 


You must log in or register to reply here.
Back
Top