Return of the 4L60E with no reverse....

[entodad]

Tony,
I finally got back to that tranny that was giving me fits.
A 1997 4L60E 4wd in a s-10 blazer.
Pulled it down, and didn't find any slipped retaining rings, However the clutches in the reverse input drum showed slippage on the steels.  the clutch pack clearance is 0.075", right on the outside edge of the book's clearance recommendations.  Could the problem be in the teflon seals on the back of the pump? They look fine, but?  No burrs were found in the rev drum either.  Reverse piston was still seated correctly and I could engage it using air with no leaks.

Any ideas?
Thanks
Doug

[Crosley.In.AZ]

too much clearance in the clutch pack.

As I recall you had very poor ( if any) engine braking in manual low gear?

what do the low / reverse clutches & steels  look like?

Tony,
I finally got back to that tranny that was giving me fits.
A 1997 4L60E 4wd in a s-10 blazer.
Pulled it down, and didn't find any slipped retaining rings, However the clutches in the reverse input drum showed slippage on the steels.  the clutch pack clearance is 0.075", right on the outside edge of the book's clearance recommendations.  Could the problem be in the teflon seals on the back of the pump? They look fine, but?  No burrs were found in the rev drum either.  Reverse piston was still seated correctly and I could engage it using air with no leaks.

Any ideas?
Thanks
Doug

[entodad]

The low / reverse clutches and steels look almost like they just came out of the box, no scuffing like the reverse clutch pack

Ok, the book says to replace the top plate with a thicker one to change the clearances, could this be done also by adding a steel at the bottom of the stack?

BTW, Thanks very much for the aid!

Doug

[Crosley.In.AZ]

A steel plate is usually too thick to use for a spacer , unless you have a thin one on hand.

Check the sealing rings on the pump stator and the grooves.

IF the grooves for the sealing rings have an "edge" on them, that will grab the teflon sealing ring and NOT let the ring seal correctly

[entodad]

Yep, yer right the steel is too thick by about 0.040, so it is a new top plate

The teflon seal groves are chamfered on each edge so that may not be a proablem, however I noticed what might be a nick (very small though) in one of the seals, so off they came and are being replaced by some new ones.

I guess the big question here is ... is the clutch clearance of about 0.075 enough to cause the slipping reverse?  I would have expected more slop in the engagement piston travel.  But I have been wrong many many times before (just ask my wife).

Unless you have any other things to check, I plan to reduce the clutch clearance to about 0.040-0.050, put new teflon rings on the stator and put the goofy thing back together and into the truck.  this time with a small bomb in the pan to detonate if it doesn't work.

Doug

[Crosley.In.AZ]

did you reduce the size of the * hole in the aluminum piston of the reverse input drum?

Did you air check the low/reverse piston clutch pack?

Yep, yer right the steel is too thick by about 0.040, so it is a new top plate

The teflon seal groves are chamfered on each edge so that may not be a proablem, however I noticed what might be a nick (very small though) in one of the seals, so off they came and are being replaced by some new ones.

I guess the big question here is ... is the clutch clearance of about 0.075 enough to cause the slipping reverse?  I would have expected more slop in the engagement piston travel.  But I have been wrong many many times before (just ask my wife).

Unless you have any other things to check, I plan to reduce the clutch clearance to about 0.040-0.050, put new teflon rings on the stator and put the goofy thing back together and into the truck.  this time with a small bomb in the pan to detonate if it doesn't work.

Doug

[entodad]

did you reduce the size of the * hole in the aluminum piston of the reverse input drum?

Did you air check the low/reverse piston clutch pack?

The * hole is being reduced as soon as I get a 0.60 drill bit, probably tomorrow or Wednesday.

As to the low/reverse clutch pack, since it is currently out of the tranny, I can't check it.
But, just to be sure, it is checked by putting air in the hole at the back of the valve body to enagage the large piston in the rear of the case?  If so, I checked it before I tore the tranny back down and it worked fine.
 
In checking the piston in the reverse input drum, I had difficulty getting the piston to engage until I put a long hose on the end of the blow hard and held it firmly against the hole inside of the drum.

If the teflon seals were leaking on the stator, could it have caused the clutches to not engage completly?  they are now replaced with new seals and I was very careful to not nick either of them.

Thanks
Doug