Bluelightening717

I have a 4l60e in a silverado with 2600 hundred stall. I broke the input sprag a while back so I had it rebuilt by a shop, 2 year warranty. After a while it started to flare from second to third gear?? I took it back he said he would fix it after a whole bunch of drama going back an forth cause he didn't want to have to do warranty work, got it back and it still flared just a tighter flare, it didn't drag out so long. Any suggestions on what it could be? I'm gonna build it myself, I just want to kinda have a idea what to go in looking for.

mrvedit

A serious flare on the 2-3 shift indicates that the 3/4 clutch may be slipping, which is the achilles heel of the 4l60E. When the trans was rebuilt, a 6-friction 3/4 clutch was used, likely of cheap quality.
If the shop recently did not remove the trans to really fix the flare, then they likely just increased the line pressure (by stretching a spring) which reduced the flare, but didn't solve the underlying problem.

The solution is to rebuild the trans with performance parts. This would include at least a 4l65E rebuild kit (which has a better 7-friction 3/4 clutch), a Borg Warner sprag, a stronger SunShell and a 0.500 boost valve. Options would include 5 gear planetaries, input drum reinforcement and the Transgo HD2 shift kit.

Check out this similar recent thread:
https://ls1tech.com/forums/automatic...i-rebuild.html

As mentioned there, ebay seller TrueTechTrans sells very complete kits with all the parts I mentioned. Sure, you could save money by buying individual parts from Amazon, the dealer and online stores, but buying a kit with matching parts is a safer bet.

Even then, you might want to find a local builder with some experience building a performance 4L60E with such parts. Based on reading many threads here and helping a bunch of people myself, I estimate that fewer than 50% of people get their first trans rebuild to work. Any mistake, mismatched part or overlooked problem will mean removing the trans and rebuilding it again, which quickly increases cost and aggravation.

Bluelightening717

Thanks. I've also been told that it could be clearances in the clutches, maybe not be to the T. Is that true? Or could it be something to look at?..but either way the problem lies at the 3/4 clutches?

mrvedit

I don't have the experience to answer whether excessive clearance could cause a flare. The factory value is .060 to .075 clearance, but most performance builders go much tighter in the .040 range.

I would start by installing a 0.500 boost valve, which only requires dropping the pan.
Second, I would install the Sonnax Servo Check valve:
http://www.sonnax.com/system/announcement/77701-076.pdf
However this requires dropping the valve body and also drilling the separator plate. Without this valve, I would still drill out the 3rd feed hole on the separator plate to make sure it is at least .082.

It would also be good to know whether you have the standard or the Corvette servo. In fact you need to know this when installing the Sonnax Servo Check valve. If you pull out the servo, which is hard in some cars and easy in others, also replace the seals as any leak here will cause various 2/3 shift problems.

If none of this solves the problem, then a trans rebuild may be needed. Go with a 7 or 8 friction 3/4 clutch and a tighter-than-stock clearance.
I'm no expert, so get other advice too.