So i rebuilt this trans but didnt know the history off it, by the way i got it i would assume it had a shift kit in it. it had a beast sunshell and corvette servo in it. Everything went together great.

I have all the gear and it shifts great except when i got WOT then it flares on the 2-3 shift about 500 rpm. once its into 3rd its fine and holds great.


the one thread i read said something about if it has a shift kit, it will flare due to the difference between the 2nd release hole and the third apply.

 

Its sorta wierd because it only happens from a complete stop, if i go WOT on the highway and it downshifts to 2nd then it wont flare on the 2-3.

 

You may only need to drill bigger the 3rd apply hole in the separator plate.
Better yet, I would suggest this $12 part:

http://www.sonnax.com/system/announcement/77701-076.pdf

Installing it includes drilling the 3rd apply hole to a whopping 0.128 which ensures there is enough apply fluid available.

Other than that, I would suggest checking the line pressure; with the trans in Park, you will see the base pressure, with it in Reverse you will see close to the max pressure. If necessary, bumping up to 200 lbs should reduce the flair.

BTW - The 3-2 shift is controlled by the 3-2 shift solenoid and I have no idea what that does, especially knowing that 2008+ transmission no longer have it.

 

The 3-2 control solenoid (it is not a shift solenoid) controls the rate exhaust of 3rd accumulator fluid during the 3->2 downshift;

it does not trigger a shift like the 1-2 and 2-3 SS's do;

see page 41 in the HMTG;

the trans will still downshift 3->2 without this solenoid.

 

Joecar, Thanks for the additional info on the 3-2 control solenoid. I read page 41 in the HMTG (Hydramatic 4L60E Technicians Guide) and that was helpful too. (Don't want to hijack this thread, but still curious why GM decided to eliminate it in 2008+.)

 

mrvedit, you're welcome;

the PCM uses the 3-2 control solenoid to slow down the apply of the band when vehicle speed is high (what HMTG said)... my guess is GM removed this solenoid from 2008+ because the various 4L65E-specific components (band, drum) were now being made from better materials...?

also see HMTG page 64B.

(op, yes sorry to hijack)

 

Installed a new seperater plate today and when i took it down i found it had that sonnax thing in it all ready so i drilled the hole it wanted to around .130" and the flare is still there if not worse......

Im looking in my ATSG and cant seem to find the 3rd gear accumulator.

What other possiblities could it be?

Im def tearing up those 3-4 clutches by testing it each time and im sure if i dont fix this flare the clutches will have to be replaced again... and the trans is not easy to get out in my car with the SLP headers

 

Interesting (and too bad) that the Sonnax valve doesn't work for you.

The 3rd gear accumulator is "the space" between the body and the servos. As it fills up, it pushes against the 2nd gear servo to release the band. It is this area:



Notice the check ball; it is important that this ball seals the area. The purpose for some check ***** is to let air in/out, but seal up tight with fluid pressure.

A "detail" which is not obvious/intuitive is that as the 3rd gear apply fluid fills the 3rd accumulator, the 2nd gear apply fluid is still ON the servo. However the "back" side surface area of the 2nd gear servo is much larger than the 2nd gear apply area and therefore the servo is pushed back and the band releases. In fact the 2nd gear apply fluid is on for 2nd, 3rd and 4th gears.
I suspect that switching from the plain to the Corvette servo therefore affects 3rd gear apply in some way, but I don't know how yet.

The reason I mention this is if your 2nd Servo apply is not very strong, the 3rd gear apply would slam the servo back and release the band before pressure had built up for the 3/4 clutch, giving you a flare. I would think the Corvette servo would give enough apply, but if it is leaking OR you don't have the 2nd fluid hole drilled big enough, that might be your problem. I know its a pain to open up again (and I'm no expert here),but if the 2nd fluid hole in the separator plate is smaller than .093, I would personally start there.

Also, do you have any idea what your line pressure is? Talking to a local trans mechanic recently, he mentioned solving a 4L60E flare by removing pressure regulator spring, stretching it by hand and reinstalling it. (He didn't have an official stiffer spring available.) Since this is easier than dropping the valve body, you might try that too. Or get the stiffer Sonnax pressure regulator spring.
Again, I'm no trans expert, but I know the theory and hydraulics pretty well.

 

I have been studying My atsg manual and the hole they tell you to drill in the sonnax instructions is called the "2nd". My ATSG manual says the 3-4 clutch apply hole is a completly different hole. So im gonna drill out my 3-4 feed hole tomorrow.

 

I was discussing your problem with my very experienced local trans builder and after reading this thread and thinking about it, he emailed me this:

==================
The 2-3 flair complaint may possibly be an incorrect servo pin length (adjustment).
Too short of a pin will allow release of the band before the 3-4 clutch has
engaged. Thus causing a 2-1-3 shift.(flair). The GM tool for checking this pin length is somewhat pricey.
The 1-2 shift may seem fine due to only one element being applied to achieve the shift.
The 2-3 shift involves one element release and one element apply making timing more critical.
Seems as though I remember an alternate procedure for checking this clearance. Maybe in one of the shift kits.
===================

I think he is referring to the Transgo HD shift kit which has you install shims on the servo cover to get the band clearance correct.

So there you have some more ideas to consider and check.
I have a few questions too:
* Do you remember the 3/4 clutch clearance?
* Did you install any/some/all of the 3/4 clutch return cage springs that come with the Transgo HD kit?
* Did you install or leave out the 3/4 clutch "load release springs".

 

WRONG! The ATSG manual pages 26-28 label lots of holes "22" and are all mixed up.

Here is the correct hole ID:



The Sonnax "Servo Release Check Valve" definitely has you drill the 3rd feed hole (very close to middle of plate) to .128. (They say .130, but the closest drill size is .128.) The Sonnax directions only show part of the plate, adding to the confusion. If you can pull the Sonnax valve out, make sure the orifice in it was drilled out to .120 as in the directions, which say that too large can cause a flair.

Your 2nd feed hole should be around .093. If you got them mixed up, your local trans shop should have the universal Transgo plate for $20.

If you like, PM me and I'll give you my cell phone #; I have extras of all these parts to experiment with. You can also email me at
ted -at- vedit -dot- com.

 

Swapped out the trans for another one i rebuilt. When i took it apart it had a a lot of 3-4 clutch pack clearance compared to the one that went back in the car. Im going to assume that was my problem.

 

Also the new one seems to be working great. sorry for double post

 

Great to hear that your 2nd rebuild solved it.
Congrats!