I just finished my first 4l60e (2000 model year Fbody) rebuild and found that the trans is binding in manual first gear. It feels as if something else is applying only in manual low causing the binding. There are no DTC codes and data display is showing correct gear when selected. All electrical connections are in tact. All up shifts and down shifts in all other shifter positions work as normal and feel great. I do have compression braking when downshifting to manual 3rd and 2nd (first locks up). In D4, D, 3 and 2 I have all gears including first and reverse as well as proper TCC lockup and release but when downshifting to manual first or when trying to start out in manual first, the tranny locks up and the car wont move similar to how a trans brake behaves. I did not use a shift kit but have disassembled valve body to clean it out, I'm wondering if I may have botched that up. I checked all clutch clearances when assembling and all were within specs. I have installed a Yank3600SS converter, wide 2-4 band red friction material, new reverse input drum, .500 boost valve, Zpack 3-4 clutches and new GM clutches for the rest, Transgo thick separator plate, Corvette servo, and a beast sunshell, both sprags were working when checked. Just looking for ideas on possible causes on the binding, I have trouble pinpointing what is different in manual first as compared to 1st gear in D4. Seems it would have to be either the 2-4 band, reverse clutch, or 3-4 coming on in manual 1st when its not supposed to. Thanks for any help / advice!

Jay

 

There only difference between manual first and first in the other positions is the low/reverse clutch comes on if theres a bind up then another clutch set if likley on, I would think missing or misplaces check ball or torn valve body gasket.

 

Thanks for the response. I pulled down the valve body today and double and tripple checked the checkballs and verified they are in the correct positions. I checked the valve body gaskets were intact and in good condition. I swapped the valve body out for another unit and the manual first lockup condition is still there. I have noticed that when the vehicle is first started cold, the lockup isn't as bad but gets worse as the vehicle is driven for a bit. I was suspecting a crossleak at the low reverse piston between the low apply circuit and the reverse apply circuit but after looking at the hydraulic circuit schematics, it looks like that is not possible. Something is definatly applying that is the cause. Oh well, looks like I'm going to tear into it once again, I'll let y'all know what I find. Its definatly an odd ball issue, none of the trans guys here at my dealership have ever seen this before, we're all sctatching our heads on this one. Thanks for the help.

Jay

 

No doubt that based on your desription of the symptom there is an element applied when it shoud not be. I would focus on the Reverse Input clutch and related circuits.

If it feels like a brake, then it's probably reverse. Have you tried to stall it up just to see? Point is, go with your instincts on this one.

There is a possibility that a cross leak that is allowing pressure to bring the Reverse Input Clutches on. I can't put my hands on my Hydramatic book... John has it corn holed somewhere... so I cannot verify that statement.

But if all of the other ranges / functions operate normally then that is where I would focus my intital efforts at finding it when it comes out.

g

 

Hey JAY4SPEED, hate to breath life into an old post, but did you figure this one out?

 

Nah, I never did find the root cause of the binding. I just started from another core and was successful. I still have the problematic trans sitting under my bench for when I have time to go over it more thoroughly.

Jay

 

Cool, if you do ever figure it out, please post it here. I have had an identical issue and also was unable to find a cause, just built a different core as you did.

 

any updates on this issue yet, just installed a tranny in a 04 suburban that is identical, thought it was electical, but didn't help it at all

 

I think I know what I did wrong on that build I had problems with. I did another build identical to the one posted above when I had those issues and it jarred my memory of something that I know I did wrong in that first build.

The GM rebuild kit comes with two different valve body gaskets. An early style ('93 to 2000) and late style (2001 and up). I know I installed the late model valve body gaskets on that 2000 model year transmission and that was incorrect, I should have used the early style gasket set. I suspect that could have caused the cross bleed issues I was having causing the binding.

It would kind of make sense since when I was trying to get that particular unit to work, I had the trans in and out of the car 4 times. I tried a different valve body, different separator plate, different pump assembly etc. I know that each time I installed the wrong "late style" valve body gaskets every time. So that was the common link between everything I had tried to swap out to fix it.

I don't know if that was 100% of the problem I was having but it is something I know that I didn't do correctly. Now, I pay very close attention to which style gaskets I'm pulling off duing the teardown to be sure I put the same style back in.

Hope that helps some...

Jay