Help diag'ng 4l60e reverse issue.
 

1995 4l60e. Everything was working tip top. My wife went to leave and no reverse. I've read up on possible causes but was hoping someone could pinpoint a little bit. I disconnected linkage and went through gears by hand underneath, reverse seems to engage, drop in idle, but nothing. Drove vehicle, shifts all forward gears perfectly with proper braking at throttle "let off". I pulled the pan, fluid is like new and no burnt smell whatsoever. The internal linkage seems to be sloppy(side to side play while out of park). Is this normal? I've read up on the "sunshell" issues, but was lead to believe there would be problems with other gears as well. Can anyone help? Is this enough info? Vehicle is 1995 Tahoe. Thanks.

From what you are saying it sounds like its the sunshell.Usually when it goes bad you lose rev,2nd,4th but i have seen where it works fine foward and have no reverse. IMO its the sunshell.

I had read that also, that's why I mentioned that I still had all forward gears.. I was seeing if there were any other possibilities before I pull the trans..

I guess that's the issue for sure?! Or, are there any other places to look first?

If the shell is stripped it shouldn't have second or fourth , but I have seen a few times when they would break and still try to engage second . Are you sure all the forward gears are ok ? A stripped shell can give you a 1-3 upshift if you wind it up in first and let off at the right time , skipping second .
There are no solenoids that effect reverse directly . It is all hydralic from the manual valve . You can lose the reverse input clutch ans still have all forwards but you should have signs of it in the pan
Even if you un-plug the case connector and have no power to the trans it will have reverse if the mechanical components are good .

Yes, all forward gears function 100%.. I put a new exhaust on, the truck was in park, had my wife rev a little bit to hear the exhaust. The truck seemed to lunge and I didn't think it was anything, although it was in park. Next day, no reverse. I pulled it out using my Expedition(lol, I know) and drove to my garage, runs like new in forward gears. The truck had been having column to trans linkage problems prior. Seeing as I completely disconnected linkage and did by hand underneath, didn't want to dive into linkage 'til after I figure out reverse issue.

The center could have broken in the low/reverse piston this will cause no reverse and nothing in pan wit sudden loss of reverse. also i have seen the reverse input drum do the same with the aluminum piston

I guess pulling it out and apart is inevitable. Damn. Such a shame with everything else being so perfectly functioning. Good ole' GM.

when my 700r lost reverse.....i had all 4 forward......tore it down...clutches were toast

Disassembled trans about 10 mins ago. Everything inside looks brand new.(clutches, shell, etc). Where next? lol

did you by chance check to see if the boost valve had came out like the snap ring came unclipped if this happens you will ose reverse also

It wouldn't move if the boost valve blew out of the pump.

Forward sprag ok? not locked up?
It would bind up in 4th if it was but it wouldn't have reverse either, it freewheels in rev and 4th. Only difference might be that 4th gets a running start and it ends up looking like this.

Boost valve was in place and good to go. I pulled out the guts except for the rear most(lo/reverse I believe)(I'm an r&r guy, first time diving this far in)... I spun the gearset connected (inner) and it spins one way and not the other. Tomorrow, I'll pull that also, to inspect further. Thanks for the the help/patience. I'll have more info tomorrow.

Taking the "guts" to tranny shop tomorrow. By eye, everything looks perfect, no wear, heat marks, anything. They should be able to pinpoint it.

Forward clutches attained moisture(possible cooler problem) and seized up, essentially locking it in forward motion. Nothing wrong with reverse at all, just couldn't engage as the forward clutches were seized. Just filling in the blanks, incase anyone encounters similar issue. Time to fix and throw 'er back in. Thanks for the help guys.

my problem is similar. it was jerking in revese and then would go fine for a while. so dacking up initially it would jerk funny then smooth. today it would back up at all. reved it to 4k and it moved. fluid isnt low, doesnt smell good or bad, maybe a lil burnt. drive perfect in forward gears. its a 94 z28 with 106k any ideas. im also trying to figure out if a older more common auto like a 700r4 or turbo 400 or 350 will fit in my car. thanks in advance