Corvette servo ?'s

QIKSILVR · June 2, 2003

I'm thinking of installing a Corvette servo in my 99 Silverado. Who's done this mod? Opinions? Will it work well with my HPP? Thanks for the info!!

MoJo · June 2, 2003

All a larger (Corvette) 3-4 servo will do is give more holding power in 4th and reduce drag on the 4-3 downshift. I doubt you programming would be effected.

Is that the results you had in mind for the change?

QIKSILVR · June 3, 2003

I was under the impression that this servo will firm up ALL shifts. I see that others have done this mod and says that there shift firmness was improved. Purhaps I'm wrong. Anyone have the low down on this?

RoadrunnerRod · June 4, 2003

I hear a lot of people recommend the billet servo, but I decided to go with the vette servo (it was cheaper and I didn't want to have to adjust stuff.) The install went simple enough and really did firm up the shifts on my 99 Z71, it now easily spins the tires all the way through 1st, and gets big chirps on the 2nd and 3rd shifts. I definitely recommend it, it is also supposed to help with the life of the transmission. I guess on some of the newer Silverado's the vette servo came stock, but our 99's didn't.

MountaineerTom · June 4, 2003

I've always wondered what those did.

What if you did that mod, then used a Programmer, such as the Predator, would that make your sifts even firmer? To firm?

MoJo · June 17, 2003

The line pressure in the trans is controlled by the EPC solenoid, aka 'force motor'. The computer sends a "%" message to the force motor, usually 100% @ WOT. Your programmer can reset the computer to send a 100% signal at less than WOT.

Now, here is the stickler. 100% of what? The force motor may only be putting out 175 psi @WOT. Factory max is 189psi @WOT. Good news is that the EPC is adjustable. Over all, you can turn the adjuster screw 1/6 of a turn without hurting the tranny. 1/6 turn = about 15 psi. Thus, inproving all shifts under any condition.

I'm sure there is a write-up on how to adjust the EPC somewhere here on the board. Since you have to remove the 1-2 accumulator to get to the EPC to adjust it, replace the standard outer accumulator spring with a purple T350 1-2 accumulator spring.

These 2 mods, along with the servo mod, will make a good shifting trans without getting into the valve body or having to buy a programmer.

If you want harder shifts yet, there are other servos available that are bigger than the Corvette.

As with all mods, do this at your own risk.

Lots'a'luck!