Hey guys,
Just got a 1998 SS with 4L60E trans. When driving and at WOT it works perfectly besides a bit of a smell which, I am told, will go away after I get it flushed or at least put a new filter/fluid in.

The real question that I'm here is that my car tends to shift very violently into drive and reverse. Going into reverse isn't so bad but going into drive is. Idle RPM is about 900 at time of shift.

Lets say I start my car up and let her warm up for a minute. Shift into reverse to back out of driveway, no noise or "clunk" feeling. If there is, it's not very bad. I back out, shift into drive, RPM sorta rises as it goes past N and then there's this...unfavorable sound coming from the trans and there's a bit of a clunk feeling. It's not as bad if I have my foot off the brake because then there is less resistance on the trans and what not.

It was especially bad as today I got home and decided to see how bad it was with my foot on the brake. I shifted into park in my driveway, stood on the brake, and shifted into drive. I can only describe the sound as something trying to escape the transmission. It wasn't just a clunk noise but it sounded...sloppy...or...loose? inside. There was a decent clunk feeling, but the sound it made as the RPM went from 900 to like 700 was not good.

I had a 1996 Z28 ("had" as in literally just sold it today) and it had a bit of the same thing but not to this extent. I am taking it to my local shop to have them flush it or maybe just replace the fluid and filter for me. The car drives fine and is quite fast and shifts well at WOT. It tends to hesitate to go out of overdrive when I'm going about 70 or so, so I have to push the gas down a bit more for her to shift into 3rd if I wanna accelerate (compared to the 1996 where it would downshift to third after pressing the throttle just a little) but I've heard from some friends that theirs do the same thing.

I'm more worried about my shifting into D problem though. I've read some places where it can be the EPC solenoid in which case this will be an easy fix, but I just want to hear from other owners what my diagnosis might be.

Sorry if this is incoherent, I am super tired but just wanted to post this.

thanks,
nick

 

What is the condition of the fluid now? If it looks good, then leave it alone. If you could make a video of this and try to get the sound as clear as possible without the exhaust sound getting in the way, it might help out if we can hear this. I or someone that knows these units might be able to point you in the right direction. Does it do this as bad when the idle speed is less? Say 750 rpm. 900 rpm sounds like a high idle, but it still should be softer. Do you have a big cam in this? I have heard way too many horror stories on the flush machines and would avoid them, it's your choice on this. If you need to make a complete trans oil change, there is a better way of doing it and you can do it yourself for apx. 1/4 to 1/3 the cost. If you have access to a 0-300psi gauge I would use it here to get some readings, as from what you say the pressure sounds high or someone has modified the transmission here but not is a good way. It could possibly be a stuck forward accumulator piston or broken accumulator spring here. If you trust the transmission guy, have him do the pressure check if he cannot tell you what it is right away. Don't let him talk you into anything without coming back here to say what his plans are and to verify he is actually helping you out. I hope this helps some.

 

This sounds like a combination of high line pressure with a moderately worn trans and perhaps a broken "anti clunk spring" (which is insignificant).
Like PBA (a trans expert with 35 years experience) says, hooking up a pressure gauge would be very helpful. Combine this with a scanner that indicates how much current the PCM is commanding to the PCS and you could confirm if and why there is high line pressure. The PCM can command max line pressure due to an engine sensor problem or detecting transmission slippage. The first step is always to scan for codes.

I would skip the fluid and filter flush; it won't help with this. Have a good trans shop check the pressure and run the scanner and come back with the results and their recommendation.