I purchased a 2000 4l60e out of a Tahoe, 4x4.
Owner said he rebuilt it just 10k miles prior.
My issue is It shifts HARD from Park to R or from N to D.
I have been troubleshooting this for 2 weeks now, research online etc...
I've replaced the electronic pressure control solenoid (which would be n my first guess) in fact, I did a master solenoid kit with wiring harness.
I've replaced the 1-2 accumulater piston with sonnax pinless (1-2 was shifting hard, this helped a good bit with that.)
I've changed the TPS.
It shifts fine when driving... Mostly
And yes, the fluid levels are good. No leaks.
AND IT STILL SHIFTS HARD OUT OF P OR N...

Any ideas?

Thanks in advance...
John

 

Any trouble codes? Harsh shifting, specifically 1-2 could be a sign of the computer commanding max line pressure.

 

No, no codes.
I spoke with the guy who did my pcm, he said he didn't touch the shift pressure.

 

It's a non shifting clutch problem. Most likely reverse input clutch clearance or leaving the belville or waved plate out, or modifying the feed size.

 

Does it shift hard into R and into 1?
in your 2 weeks of troubleshooting I'm going to go out on a limb and assume you haven't bought a $30 pressure gauge and hooked it up to your transmission? You know...prettymuch the first test any forum google search will tell you to try.

 

Im not certain what any of that means. Is it about the PCM tune or something mechanical?

 

It shifts hard from P-R and from N-D
All other shifts are nml.

And yes, I read about installing the pressure Guage but for this specific problem some said it's useless as we KNOW there is high pressure if it is making my tires chirp from P-R Etc....

 

Thank you guys for brainstorming with me.
I appreciate the replies.

 

you KNOW it has high pressure...well shoot...why are you asking for help then?
sounds like you've got 'er licked!
Just go ahead and get it fixed up bub

 

When I researched my specific problem, hard shift from Park to reverse Etc, people would recommend putting a pressure line in there but others notoriously would say there is no need because you already know there's high pressure which is what's causing the hard shift. I'm not saying I know anything, I came on here to learn. If you have some useful information I'm happy to hear it, otherwise if I want smart alec I have three boys for that.

 

What things might cause the PCM to command higher pressure?

 

You need to confirm that it has high line pressure. There are things that the builder could have done when the trans was assembled that would cause a hard engagement other than high line pressure. @Jays_SSZ28 touched on a few of them in post #4.

 

OK, I see, what I thought was that the hard shifting was from high line pressure but it was just a matter of finding out what was causing the high line pressure.

I replied to Jay's post, I have no earthly idea or any of those things mean. So that means this is out of my pay grade, I've got a great transmission place here in town I just hate conceding defeat. Thanks for the input

 

I've read enough to learn that this has defeated you already. No offense intended, by saying this I'm trying to motivate you to stop throwing parts at this and just take it to a shop. It will probably save you money.

You're already too focused on the pressure being too high. Did you forget to mention it idles at 1300 rpm? Thats another possibility.
I find that a lot of people misdiagnose things because they're too focused on the most common problem. It's not always a common problem.

 

Thanks Jay's,

I have zero Knoledge of 4l60es other that what I have read over the last 2 weeks.
It seems like the troubleshooting list is a bit out of my range of inexpertise. I'm going to take it to the shop on Wednesday.

 

The forward feed hole on the separator plate, could be too large. Should be .086". A larger feed hole on the separator plate can do this.

 

asks for help...calls the person offering help a smart alec...ok?

I told you some useful information...check the line pressure. make sure the pressure is too high. Otherwise there could be other things that cause hard shifting.
You chose to sidestep and ignore that information. So...since you know it all...do whatever you want.

Like others have stated...this appears to be above your pay grade. Take it to a shop and have it diagnosed.
The diagnosis may very likely be high line pressure...but they will confirm that, then take the necessary steps to determine the solution.
Cheers

 

OK.
I've try to get ahold of the mechanic I bought it from a year ago to see what modifications he has done but haven't heard back from him.
Thanks for the input.

 

This wouldn't affect the reverse engagement being harsh.
A broken fwd accum spring, a stuck abuse valve, etc...all of these would make sense but I find it pretty unlikely that both the fwd and reverse abuse valves are having issues. And reverse/fwd engagement firmness shouldn't depend on one another.

BUT I agree...I always keep fwd feed hole at .078 or smaller