4l60e problems after rebuild

[CaptainSpalding]

I just finished rebuilding my 4l60e trans and am having issues. The truck is a 1996 K1500 and I am the original owner. A little history of the trans; this is the 3rd rebuild. First rebuild was due to 3/4 clutch burn up was rebuilt by a local shop with a good reputation rebuild during pandemic cost me $3200 took 6 weeks and never seemed right had a convertor shutter from time to time and shifting into 3rd was not crisp then a lost 3/4 again and got a P1870 code at the same time. Lasted a little over 8000 miles, warranty was 12months/12,0000. Took it back to them and they rebuilt the trans again under warranty (4 weeks this time) lasted a hair over 12,000 miles and 3/4 went out again. So this time I decided to rebuild it myself.

Installed did a full rebuild along with adding in 3/4 ZPak, Smartshell, Sonnax performance pack, line pressure boost kit, Transgo 7-CS spring kit, Kevlar extra wide band, 2 and 4 super hold servos, rebuilt 13 vane pump, all new solenoids, new pressure switch manifold and harness.

Pump pressure is good, fluid level is full

with harness hooked up: I have reverse and normal power, when I shift it to drive there is no movement it is like it's in neutral, shift to manual 3 - nothing, shift to manual 2 - moves but it is like the emergency brake is on, manual 1 - same as 2. The movement in manual 1 and 2 is a crawl with the engine at 2000 rpm.

Disconnect the harness: Full reverse normal power, shift to drive slight movement (like the e brake is on), shift to manual 3 - moves but it is like the emergency brake is on, manual 2 - same as 3 and manual 2 with harness, manual 1 - same as manual 2 and manual 1 with harness. Again it is at crawl with the rpms up.

I figure it is an electrical issue at this point but what has me stumped is the crawl under power in forward gears. Any help and guidance is appreciated.

 

[tayto]

how can it be an electrical issue, when the harness is unplugged and it doesn't move? should default to 3rd gear. it will seem sluggish but still move. have you hooked a pressure gauge up yet?i'd probably start by dropping the pan and check basics, manual valve hooked up correctly, valve body bolts in the correct location (too long of bolt in certain location will pin the gear train), etc.

don't take this the wrong way, but it seems you got "got" by all the gimmick parts out there. some of them are definitely nice, but most are not needed at all. all those parts won't save the trans if you didn't address the hydraulics.

 

[NickTransmissions]

I just finished rebuilding my 4l60e trans and am having issues. The truck is a 1996 K1500 and I am the original owner. A little history of the trans; this is the 3rd rebuild. First rebuild was due to 3/4 clutch burn up was rebuilt by a local shop with a good reputation rebuild during pandemic cost me $3200 took 6 weeks and never seemed right had a convertor shutter from time to time and shifting into 3rd was not crisp then a lost 3/4 again and got a P1870 code at the same time. Lasted a little over 8000 miles, warranty was 12months/12,0000. Took it back to them and they rebuilt the trans again under warranty (4 weeks this time) lasted a hair over 12,000 miles and 3/4 went out again. So this time I decided to rebuild it myself.

Installed did a full rebuild along with adding in 3/4 ZPak, Smartshell, Sonnax performance pack, line pressure boost kit, Transgo 7-CS spring kit, Kevlar extra wide band, 2 and 4 super hold servos, rebuilt 13 vane pump, all new solenoids, new pressure switch manifold and harness.

Pump pressure is good, fluid level is full

with harness hooked up: I have reverse and normal power, when I shift it to drive there is no movement it is like it's in neutral, shift to manual 3 - nothing, shift to manual 2 - moves but it is like the emergency brake is on, manual 1 - same as 2. The movement in manual 1 and 2 is a crawl with the engine at 2000 rpm.

Disconnect the harness: Full reverse normal power, shift to drive slight movement (like the e brake is on), shift to manual 3 - moves but it is like the emergency brake is on, manual 2 - same as 3 and manual 2 with harness, manual 1 - same as manual 2 and manual 1 with harness. Again it is at crawl with the rpms up.

I figure it is an electrical issue at this point but what has me stumped is the crawl under power in forward gears. Any help and guidance is appreciated.

Did you:

- inspect your front and rear planets for wear to the splines or gear teeth, pinion side play and excessive vertical travel (same for other shafts gear components)?
- replace the forward sprag with a new BW 29-element unit and if so, confirm proper sprag rotation?
- replace the low roller clutch assembly with a BW low roller unit and confirm proper roller clutch rotation?
- replace those aluminum pistons in the forward drum with late model 97+ bonded steel/rubber pistons and corresponding return spring assembly?
- air check all applied elements?
- pressure test your forward drum for leaks at the input shaft?
- set proper band clearance?
- set proper clutch clearance in all clutch packs where its possible to measure for and adjust clearance?
- properly adjust end play?
- properly drill the clutch feed orifices in your separator plate based on everything else you've installed?
- put all non captured checkballs back in their correct locations?

That's just a small list of things to add to your list for when you pull the trans back out and go through it again.

As an aside, im not a fan of the Z pack and will run an 8 or 9 clutch stack with regular frictions and steels in the 3-4 for performance builds.

Based on your description of the symptoms, something is either broken or there's a bind up...

 

[Dropped88]

Did you:

- inspect your front and rear planets for wear to the splines or gear teeth, pinion side play and excessive vertical travel (same for other shafts gear components)?
- replace the forward sprag with a new BW 29-element unit and if so, confirm proper sprag rotation?
- replace the low roller clutch assembly with a BW low roller unit and confirm proper roller clutch rotation?
- replace those aluminum pistons in the forward drum with late model 97+ bonded steel/rubber pistons and corresponding return spring assembly?
- air check all applied elements?
- pressure test your forward drum for leaks at the input shaft?
- set proper band clearance?
- set proper clutch clearance in all clutch packs where its possible to measure for and adjust clearance?
- properly adjust end play?
- properly drill the clutch feed orifices in your separator plate based on everything else you've installed?
- put all non captured checkballs back in their correct locations?

That's just a small list of things to add to your list for when you pull the trans back out and go through it again.

As an aside, im not a fan of the Z pack and will run an 8 or 9 clutch stack with regular frictions and steels in the 3-4 for performance builds.

Based on your description of the symptoms, something is either broken or there's a bind up...

What about the 1 bolt put back wrong in the valve body that binds it up?

 

[NickTransmissions]

What about the 1 bolt put back wrong in the valve body that binds it up?

If he misplaced those bolts and locked up the sun shell, he woudnt have reverse, which appears to be working normally so the sun shell and reverse input drum appear to be unincumberer. It is entirely possible he put one or more 8mm bolts in another incorrect location that's binding the forward drum. Very easy to check for once pan is off.

I didnt mention it in my above as Tayto already had it covered.