rob99SS

Bought the transmission used from my friend, it's a Performabuilt stage 2 with a 3000 stall converter, anyways it will shift perfect in 1st, 2nd and 3rd but will not go into OD. Reverse works fine. The transmission is a little over 2 years old and did the same thing while my friend had it.(he only drove it maybe once a month) Tried shifting it manually as well and it still won't go into OD. Otherwise from not having 4th, my transmission is functioning fine.
Could it be something as simple as a servo?

rob99SS

Anyone?

bbond105

Could be a shift solenoid.

lt1pwr1

iTrader: (1)

Is the check engine light on? Could be shift solenoid as mentioned, or servo assembly seal is bad as a couple things that come to mind. Do you have a scanner that can command 4th gear?

mrvedit

I've helped a bunch of people here with no 4th gear. Based on what they had to do to fix, starting with most common:
1. Band was worn. Sometimes lengthening the servo pin by welding a "glob" on it gave them more life.
2. Servo problem - a worn seal or cracked 4th servo piston.
3. Bad Valve body - (they never figured out exactly what, just replaced it.)

The first step is to determine the servo endplay. A crowbar can be used to press on the servo cover. Try to estimate how much it moves. The spec is .075 or a bit more than 1/16". 1/8" is about the working limit. At 3/16" the band will begin slipping in either 2nd or 4th gear or both.

performabuilt

iTrader: (25)

Remove the outer sonnax servo you will see a gold washer . Check that the gold washer is not colliding with the inner servo you will be able to see marks on the inner servo if it has. Sometimes over time the band will stretch or wear and the travel of the 4th servo become to great and it collides with the inner spacer servo. If this is true to correct this replace the gold washer with a factory black washer like you will find under the E clip on the servo pin. Not with that washer but one similar or from another trans. If this is the cause it will correct the issue permanently. The only other possible cause of a no 4th would the the 3-4 shift valve.
Frank at PerformaBuilt

jimmyblue

iTrader: (11)

Are you absolutely convinced this is failure to shift,
and not failure to lock the TCC?

performabuilt

iTrader: (25)

^good point^ would not be the first time I have had someone confuse lockup with 4th certainly with high stalls.

mrfister77

I'm having the same prob. w/ my 2002 4l60e. Rev. 1st 2nd 3rd and the TCC locks up (I set it to lock up in 3rd to check). Used HP Tuner to command 4th, nothing. No MIL, trans has all available upgrades minus the Sonnax Smart Tech Input Drum. 3-4 and intermediate servo is Superior/Fairbanks Max. Overdrive.
The torque converter is a Yank 3600 SST. Has the Trans-Go shift kit and VB plate.

Again, Sorry to Butt in.

mrfister77

Trans is very strong, you would never know it has prob. 'till it doesn't shift into 4th. It also won't do it by using the shifter manually. Also I can hear the solenoids when I manually turn them on & off w/Hp Tuners.

mrvedit

Start by checking the servo end play as I detailed in #5.
The Fairbanks servo might not be all that different from a Sonnax, so follow Frank's directions in #6. When you remove the servo, check that all the seals are in place and that the bore does not have excessive wear.
Since it sounds like your trans was recently rebuild with quality components, and the band is not worn, this sounds like a servo problem. I will add that in another thread the OPs problem turned out to be a bad valve body.

mrfister77

I'll do that now. Thank you very much.

mrfister77

The oring on the outer plate (the one @ the cover)was cut.
Replaced it and the prob was fixed. Thank YOU VERY much!

mrvedit

Glad you found and fixed it. That is the seal on the 4th servo piston I mentioned.

chumbini

I rebuilt the Sonnax billet superservo but it still would not engage OD. I also checked my solenoids and commanded all gears through my HPtuners. As a last ditch effort I reinstalled the factory servo. BINGO, it worked. Not sure why the billet servo worked for a few years and then no longer engaged OD. Maybe band wear? The trans fluid was clean as ever since my car is low mile since the trans was built. I'd like to reinstall the Sonnax servo but I'm not looking for extra issues. I have the Sonnax Super Billet second gear servo and that remains flawless. Any ideas?

PBA

Take the Sonnax 4th servo apart and see if there are any torn seals here. Sonnax has replacement seals if needed here. When installing the servo, do not forget the gold washer.

5.3_98s10

I just wanted to say thank you! I welded about 1/8” to my servo pin yesterday, and it tightened up my 2-3 shift, and also have 4th gear for the first time!

A little back story: I have a cobbled together V8 S10 with a 5.3 I bought for $350, and a $200 craigslist 4l60e...

I installed a corvette servo before driving the vehicle, and I’ve not had fourth gear since installing it in the truck. The 2-3 shift was starting to get a bit soft as well.

I measured the servo travel before welding it, and it was about 1/4”. After was about 1/8”.

Probably a temporary fix, but I really want a T56 anyways!

Thank you again for the help!

stockA4

I just used the thicker black washer from my old servo to fix my worn super servo that I used on my new rebuild thank you for this!

performabuilt

iTrader: (25)

Your welcome