Just finished an engine/tranny swap on my 95 Z with an all-forged 355 and a 4L60E built by a shop with kevlar bands, corvette servo, 2400 stall converter, etc. Did the assembly work myself, and made a slight mistake overfilling the trans w/ fluid (read pts for qts ). Realized that when fluid started dripping out of the little drain hole in the torque converter shield, so I dropped the pan and drained the extra fluid. According to the dipstick, my level is still slightly high, but not excessively so.

THE PROBLEM: The trans seems to be slipping at all times, getting much much worse when hot, to the point that the car will barely move on flat ground. It still will leak a little bit from the converter cover hole, but just a little and mostly in reverse gear (!?!?)

Any ideas?? My freshly rebuilt Z is slower than a Civic!! Help me please! Any sort of input or brainstorming could help...

 

if you drained the fluid back out, then its nothing to do with the fluid, i've over filled tons of trannys and drained a lil back out to make it right.


the reason why your tranny isnt moving is because 90% of all transmission problems will begin at start up on a fresh tranny.

check your build, or have a professional do it, if there are any

or swap to a 6 speed

 

Any manual I have ever seen has "don't overfill" emphasized for an auto transmission. I think it is very likely you screwed something up (especially if you put twice as much fluid in it [quarts for pints]).

 

I wouldn't be too worried about overfilling it, hell, it has a vent that it can come out if you do. Shouldn't hurt anything since you drained it. I'm curious to find out what this problem is, as my 4l60e that was rebuilt 27,000 miles ago has this problem...once it gets hot, it does nothing but slip. Once it sits for a few hours, it drives fine...has a little rumble on the 1-2 shift...but it goes.

 

Check for a pressure control solenoid problem. It has a very sensitive adjusting screw. It's pre-set and shouldn't have been mess with, but if you or the rebuilder adjusted the screw, it might not have enough pressure to shift. If it was adjusted, might just be better to by a new one that's already set than to keep having to pull the pan and adjust. Approx. $140 from the dealer

 

Welcome to my world. 26k on my "performance rebuild" and I lost 3rd and 4th.
In the process of fixing the problem for good........TH400 swap.

 

I think I'm just gonna throw a six-speed in her. 3 tranny's in 2 years is just rediculous. Never, ever EVER go to Metro Transmission in Waterloo, Iowa. They will not stand behind their work. 18,000 mile warranty on this tranny, took it in 3 days after I got it back and twice more before the warranty telling him it was going, and he said nothing was wrong with it...guess that must be why my car doesn't move...

 

"1994TransAm"
Well, I'm not expert, but that depends on how long and hard it was run overfilled {and I'm not talking months or days or hours}.
I know an overfilled tranny causes the moving hard parts in the geartrain to churn air into the fluid in the pan, therefore the pump pick-up, which causes the pump to cavitate therefore reducing line pressure. Since the line pressure will be reduced and erratic, the piston / band apply pressure / time will be retarded, the friction / steel contact pressure will not be enough to hold on initial engagement, and if the frictions / steels don't hold the torque for a very short time, {split seconds}, major damage to the clutch pack is the result. Automatic transmission clutches will not hold up to slippage like manual tranny clutches will.
I'm not saying this is the problem. Not 'now' anyway. But running an automatic tranny overfilled is not a good idea.

"BTM"
If you have been driving your car with the tranny slipping, the friction / steel damage is already done. Although there may be another problem, they will need replacing. JMO