Ive heard it only works for a couple of gears. Would anyone recommend it And what are the positive and negatives.

 

Right: only affects 2nd & 4th. 2nd more than 4th.

Yes it is probably THE most recommended part for a 700 or 4L60E. Next most recommended is a larger boost valve. Those 2 things typically REVOLUTIONIZE yerbasic slushbox. (assuming of course it's not already wore out)

No negatives I can think of, with the possible exception of rear tire wear, if your driver lacks self-discipline.

 

Here's a real good informative thread from a Truck forum with a lot of pics. Should be all the info you need to get the Vette servo installed and what to expect. ( Again; it's from a truck forum, so some of the info isn't relevant - but the pics are great ! )

http://www.performancetrucks.net/for...476223/page10/

 

That servo is the best thing I ever did to the auto. Firmed up the 1-2 shift big time. Still drives nice and smooth at low throttle too.

After doing it, I've never driven an auto I liked more, and I work on cars for a living.

 

I agree about it being a must have item in the 700r4.

I changed mine before I installed a shift kit.
The Corvette Servo is all I need.
Very nice, especially with the 3.42 gears and posi. I had installed.
I did the install by myself after studding this.

Link = http://sethirdgen.org/servo.htm

 

I've been debating this mod to my car for a month now. Tranny is empty and the car is already on jackstands so getting to it will be easy. Are these servos all the same, quality wise?

 

"Quality", probably so.

There are variations and add-ons though; such as the Sonnax "super hold" for a similar effect on 4th gear.

 

Im just looking for the OEM Corvette servo kit.

I found this on Amazon. Looks very complete to me. Would it work?

 

Yes get it. Ive had Corvette Servos in 4 Third Gens ive owned I liked them so much.

 

The corvette (Or any intermediate servo for that matter) does not affect 4th apply at all. The two things a larger intermediate servo will do is #1, firm up the 1-2 shift by applying the 2-4 band faster and harder with more holding power in second gear. Second of all, it will actually firm up the 2-3 shift as well because it is allowing the band to disengage and the 3-4 clutches to apply quicker.

As far as fourth gear, the band DOES apply, but is operated by a different servo. When you first take the servo assembly out of the transmission, you will see a smaller disc directly behind the cover and in front of the intermediate servo. That is the servo that applies the band in 4th gear. As you can plainly see, it is considerably puny.

I have the sonnax servo & pin set, 4th return spring, and the cushion spring shimmed in mine. Shifts like a bat out of hell.

I used to have a long, slow 3-4 shift at WOT. I upgraded to the sonnax dual piston overdrive servo and it made a night/day difference. I also ran the corvette servo on my old combo with good results for quite some time. After the new motor, the 1-2 Got noticeably softer so I upgraded to the sonnax billet intermediate servo to bring my firm shifting back.

 

I did the Corvette servo thing when I rebuilt the 4L60E in my GMC Safari. It came with the kit I got from Pro-Built automatics.

I don't know what effect just the servo had on the 1-2 shift because there were a few more things that I did to the trans during the rebuild, but it changed the 1-2 shift from a release-delay-engage kind of feel to a release-engage type of shift. So yes, I'd do the swap.

I don't know what other parts come with the servos supplied by other places, but mine came with a spring kit and some grinding instructions.

 

The original idea behind the Corvette servo (according to GM) was to eliminate the 2-3 shift flare when GM started to raise horsepower/torque. The 1-2 shift also got quicker at WOT. Yes, the Sonnax 4th apply servo does make it possible to do 3-4 WOT shifts and have the band live. You still need to open the 4th feed hole on the separator plate, (.155" - .204") and you should block or flip over the piston and spring in the 4th accumulator.