No reverse after Overhaul

SG2nite · #1 (**permalink**) 10-17-2004, 07:11 PM

Hello everybody ! I am a injury retired heavy equipment mech. I have been restoring and rebuilding motors fro everyone else except my self for the last 15 yrs.
I have never tried my hand a the 4L60E tranny. I have rebuilt TH 350 and 400's . I thought I could handle this one. . . .

I am working on a 1995 Tahoe 5.7 4x4 . The rear U-joint had flew apart. It was the main reason the rear of the tranny housing was cracked up. After locating a used transmission I set out to rebuild it. Purshased the needed and required items for the rebuild. Everything went just fine. No excessive wear, or cracks. The pistons looked fine. The used tranny was in very good condition. After completing the rebuild, and the bench tests. I put the tranny back into the vehicle. I have all of the forward gears but no reverse. I have full range of the forward gears 1,2,3,OD. Manually as well as automatic. Just no reverse. You can hear the direction change in the tranny when shifting. Once in a while it will hit in reverse and let out. I have taken out the tranny and checked to make sure I got the lip seals back in the right direction. They were all in the right direction. The clutch pack dimensions all checked out.
I have looked threw alot of posts reguarding the 4L60e tranny. Alot of different ideas on what could have possible went wrong but now I come to this. Any Ideas anyone? I need help. . . .

**poncho62** · #2 (**permalink**) 10-17-2004, 08:00 PM

welcome................moving post to "Tranny" section.

sbchevfreak · #3 (**permalink**) 10-17-2004, 08:42 PM

I'd take it to a trans shop (if you don't have access to a scan tool) and have it scanned and find out if all the shift solenolds are energizing.

Also, did you make sure the MLP sensor was centered when you put it back on? There is a small hole in it that you slide a wire into to centralize it before you put it on, and pull the wire out after it is installed. I'm not sure if this could cause your problem, though.

Crosley · #4 (**permalink**) 10-17-2004, 08:56 PM

Shift solenoids and shift lever sensor have nothing to do with reverse engagement. You can un plug all of them and reverse will still function.

Two clutch packs function for reverse. the Low / reverse and the reverse input.

Did you down size the relief hole in the aluminum piston in the reverse input drum?

Are the sealing rings on the stator support for the reverse input drum?

have you air checked each clutch for application or leaks?

Did you check the clutch pack clearance in both packs ?

Did you replace any steel plates in these packs?

Did you check the surfaces of the case and valve body for flatness?

sbchevfreak · #5 (**permalink**) 10-17-2004, 08:58 PM

Thanks, Crosley. I wasn't sure if that stuff was relevent, but thought I'd throw it out, figuring if I was wrong, someone would pick it up. I was going to suggest that he scroll down the board a little farther..... another 4L60E thread on the same type of problem....

Crosley · #6 (**permalink**) 10-18-2004, 09:56 PM

Actually not the same problem, similar but sifferent.

this unit appears to have all 4 forward gears.

A stripped out or broken drive shell , you will not have reverse , 2 gear or 4th gear (OD)

The drive train update kit mentioned in the other post works OK at best. Not too many options to use though.

The drive shell spline area is still a problem that GM has not fully adressed in my opinion

Quote:

Originally posted by sbchevfreak
Thanks, Crosley. I wasn't sure if that stuff was relevent, but thought I'd throw it out, figuring if I was wrong, someone would pick it up. I was going to suggest that he scroll down the board a little farther..... another 4L60E thread on the same type of problem....

sbchevfreak · #7 (**permalink**) 10-18-2004, 11:01 PM

Thanks again, man. Looks like I'll have to bone up on my auto trans theory, it's been a while since I was inside one. Seems to be unless you are in the trans rebuild indusry, you don't get much chance to pull 'em down, unless it's your own. To tell the truth, I haven't had a lot of time lately to wrench on any of my own rides, I think I'm somewhere around 3600 miles over my oil change! (I know, I know, bad, bad, Freak!!

)

SG2nite · #8 (**permalink**) 10-19-2004, 05:38 AM

Sbchevfreak: Thank you for your advice. I did check this aspect with a scan tool. and all of the forward gears work fine.
As far as the MLP Sensor; I thought I had alinged it right. But something to double check when I get it back out and tore apart.

Crosley : Thank you for you informative questions.
Did you down size the relief hole in the aluminum piston in the reverse input drum?
No I didn't do this because this was the second time I have heard about it. I had read the thread for which you had mentioned. It will be something I will closely look at.

Are the sealing rings on the stator support for the reverse input drum?
Yes they are the correct ones for and in the right direction.

have you air checked each clutch for application or leaks?

I did air check it while it was still on the bench

Did you check the clutch pack clearance in both packs ?
I checked the clearance on both packs and only had to change one ring out. both well within nominal tolerances.

Did you replace any steel plates in these packs?
Yes all steel plates were replaced.

Did you check the surfaces of the case and valve body for flatness?
Yes the valve body and case were checked for flatness.

I have herd threw chatting, that there is a different Pump for the 1995 4l60e trannys. An eerier and a late. Could this possible be part of the problem? I have noticed a year stamp on the transmission pump housing from the original tranny that was taken out 95. Now the pump that came with used tranny that was purchased for the shell has a stamp 96. ? ? ?

About the drive shell cracked or broken It was inspected closely and no cracks were evident even after the 2nd time out and reinsertion of .

I am going to go out now and pressure test it and log the readings.

Once again I would like to thank you both for your help. It has directed me where I was just spinning my wheels.

SG2nite · #9 (**permalink**) 10-31-2004, 08:07 AM

Well I would like to thank the ppeople that helped me, SBCHEVFREAK and Crosley.

Well after I had taken the Tranny back out and Dissassembled it and tested all of the clutch packs Using Air presure. The reverse input clutch pack would hold air for a few seconds then would all dump. My error was that I didn't leave the presure on long enough to make a good descision on if it was good or not. The housing was cracked. Missed on initial inspection. Thank god it was a relative and not a paying customer.
I ran oout and got new parts and put it back in and it runs like a charm !

ps. THANK YOU ALL !

stu · #10 (**permalink**) 10-31-2004, 03:52 PM

Way to go. A guy has to get lucky sometime.

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