Hello,
I have a 94 Z28 with the 4l60e. I have been having issues with it for the past few months. The car shifts harsh into reverse and drive, only shifts at 3k rpm in all gears, will shift ok at WOT, and will not downshift when cruising. I have already replaced the TPS and just recently had a shift kit and all new solenoids (EPC as well) replaced. Those were the things that I read about could cause the issues. The car has right under 130k miles and I am unsure of any modifications done before I purchased the car. It did not have this problem at purchase as well. It also has an intermittent check engine light. Any help would be greatly appreciated. I'm about to burn this thing to the ground. Thanks

 

what did the fluid look like? Also check line pressures for every gear and when then trans shifts. A stall test may be helpful too, to see if the clutches are slipping when engaging. ... It sounds like some kind of hydraulic issue with the valve body leaking or something. Does it engage harshly when it upshifts? The 4l60's are known to have valve body issues there is a TSB on it.

 

Fluid is brand new. Yes it engages harshly when it upshifts. How would I go about testing the stall and line pressures? thanks

 

Take a look at this TSB and maybe take a copy of it with you to a good reputable trans shop... 4L60E GM Bulletin TSB # 01-07-30-023A DTC P1870 - Trutechtrans.com

My dads astro had this problem and his would slip and then bang the next gear. The CEL was intermittent and the repair described in the tsb fixed it. Have heard that the same about the earlier ones too not just the ones in the link. it may be a good idea to have a good trans tech look at it though, because im no trans genius and diagnosis of a computer controlled trans can get really complicated lol. just hoping the tsb would be of some help.

 

Thanks for the response. I'll check into that, but right now it doesn't even shift normal at WOT. With the pedal to the floor is still shifts at 3k rpm in every gear...

 

did you see this one 4l60e only shifting at 3200 rpms - LS1TECH

 

Yep I just recently tried adjusting it. It worked for a couple of test drives, but I will have to see if it really fixed the problem. Thanks

 

Still no dice. It will have one good test drive, but the first time you go WOT and let off the Check Engine light will come back on and it will go back to the same problem. Is it possible that driving on a new TPS with the throttle plate being wrong could have messed the TPS up?

 

at wot it may be going to far and off the scale in the tps. do you have a way to see what volts are coming out of the tps at wot.

 

Not too sure. What would be the best way of testing it?