gmtech97

hey guys what things should I be looking for during my teardown tonight, the tranny lost 3rd and 4th...guessing the 3-4 clutches smoked but there should be a reason why... any input would be great I plan on going over it with a fine tooth comb anyway but just some helpful tips to look for.

Dynamic396

There are several things to look for in the hydraulics for the 3-4 clutch, but the clutch is just a weak design, so you may not find anything amiss hydraulically. The 3-4 clutch is the #1 area in the 4L60E that needs to be upgraded.

A few things to take a close look at:
-where the stator seals to the input shaft (sealing rings, stator sleeve condition, bushings, etc.
-reverse abuse valve bore plug (in valve body)
-make sure the 3-4 air bleed cup plug hasn't popped out of the input drum
-3rd accumulator bleed check ball in the case (this should be replaced regardless)
-anything along the way from the valve body, through the pump and into the input drum

mrvedit

In addition to what Dynamic396 listed, I would suggest performing an air test on the input drum before you disassemble it. With a rubber tipped blow gun apply air pressure (50 lbs or so) to the hole closest to the drum which is the 3-4 clutch hole. It should apply the clutch. You will hear some air leaking out of a bleed hole in the drum very close to the input shaft. You should be able to plug that with your finger and should then not hear any more bleeding. If it still leaks there is likely a problem with the 3-4 clutch piston seal.

An even better test is an air test with the complete input drum inserted into the pump. I use the outside of a thick 8"x8"x8" cardboard box to support the entire assembly with the input shaft down. Then air test the holes in the pump. There will be a bit more air leakage from between the pump halves and the previously mentioned bleed hole, but the clutch should still apply.

If nothing else, it is good to learn this procedure for when you air test the completed rebuild.

I recently bought a 4L60E off CL for $50 which had a blown 3-4 clutch. The clearance had gone up to .105 and simply started to slip. Nothing else was wrong with the trans.
So, I would suggest measuring the clearance too. Anything close to that indicates the frictions simply wore out.
(Use 3 or 4 angled feeler bladed together to measure it.)

Good luck and keep us posted. And welcome to ask more questions.

gmtech97

Thanks guys for your suggestions, tore it down at work so we have a tranny table and all the special tools so I wont need the 8x8x8 cardboard box ...I rebuilt the tranny about 10,000 miles ago the clearance of the 3/4 clutch pack was WAY to much, idk how I missed that....still going to go through it and check everything over see what else needs to be replaced, prolly not going to be much since the build was less than two oil changes ago...is there a thread on here for some good upgrades for the 3/4 clutches

mrvedit

Here is my suggestion for the 3-4 clutch using either 7 or 8 frictions:

https://ls1tech.com/forums/automatic...some-info.html

Also see my post #10 in this thread for suggested clearance depending upon the type of friction material.

https://ls1tech.com/forums/automatic...n-problem.html

These setups use .067 frictions and then one or two thicker .080 ones of the same brand&type to reach the desired clearance. It also helps to have different apply and backing plates for reaching the desired clearance.

I think that Dynamic396 has a slightly different formula with 7x thicker frictions and thinner steels with specific apply and backing plates to reach a .025 to .030 clearance. There is no consensus on whether 7 or 8 frictions is better, but in any case don't use just 6.

I also suggest at least a .093 hole size for the 3rd feed in the separator plate. I know that some builder go with .125 (1/8"). Personally I go that large but also use the Sonnax Servo release check valve ($15).

Dynamic396

I use a new OEM .225" apply plate, seven .080" high energy frictions (Borg or Raybestos), six .076" steels (700R4 steels), a new OEM .192" backing plate and a .093" snap ring. This will stack at .025-.030" pretty much every time. Leave the load release springs out.

This setup, in my experience, has outlasted any other combo that I have used. I have found .076" steels to be plenty thick as long as you get the 3-4 on reasonably quick during the 2-3 shift. Pretty much every 4L60E that leaves my shop has this setup with either regular steels (truck applications) or kolenes (quick shifting high performance builds).

A .093" orifice will give you a nice, firm 2-3 shift with the 3-4 clutch setup listed above and a Corvette (or better) 2nd servo set up at about .070-.080" servo travel. I use a .110" in many street rod setups. A .125" orifice will work well with a very loose converter, but would be pretty abusive in a truck application.