Thread: Strange Trans. problem...help!

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.

swap your axles first. then see whats up with it. the axles are most likely your problem as broken transmission parts dont cause vibrations.

I would lean towards the axles as well........for what its worth.

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 =)

Originally Posted by lastonemade02

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.

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?

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.

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

Originally Posted by wickedintent79

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

TCC stuck on.. ick.

Delay in shift or "Long Shift" ??

Sounds like you got 4t65E Blues...