Finally got around to installing my corvette servo in the escalade. Only sat around in the garage for like a year.
Everyone should do this. Shifts are more positive, but not jarring. Trans temps stay a little lower and it reduces wear/increases service life thanks to less slipping
My issue isn't with the 1-2 shift. The 3-4 shift on my truck is really sketchy, espc the way I drive it. When I was putting together items for the 1st trans service, I had an old trans guy talk me out of replacing any hard parts so I figured next best scenario was have the parameters changed in the programming. I haven't gotten with a tuner yet but I'd still like to get 1st hand testimonials from a number of folks running a vette servo and more on the orig trans, attesting to any experience with component failure or degradation of useful service life.
This is (below) is what the old guy from the trans garage told me over the phone; about increasing pressure on parts that are 120,000 miles/15-years old. I wouldn't hesitate w a newly rebuilt/reman unit but you never know how long old shit is going to hold-up to performance mods. I'm not saying the servo is some 'wild mod' but these 4L6 trans aren't the most robust piece of equipment. as discussed below, the Sonnax piece is better designed to hold both 1st & 4th. From what I've read and experienced, that 4th apply is a much better target.
Michael Dose
The servo applies pressure on the band, not the clutches. The band is a weak point and the extra pressure is achieved by making the center section smaller, giving the apply piston more surface area. The band applies in 2nd and O.D. or 4th. Notice that the center section of the servo moves independently from the outer piston. The outer piston is located inside the cap that you see from the exterior of the trans. The outer piston applies pressure on the band when in fourth gear. When the user installed this set up he would be increasing pressure on second gear band apply only. Sonnax has a larger outer piston to increase pressure in fourth gear as well. I mention that because the band is a weak link and it can slip in fourth as well as second. Given the fluid color of this transmission I would say you may very well have some band slipping going on. Obviously it is best to make this mode before that begins to happen.
2 months ago•1
Furthermore, about that pin sometimes included with the servo setup, I couldn't get a straight answer on that in the time I had to put this together, which also gave me pause. I would certainly buy the kit with the pin, but everyone should do his own research instead of taking Joe-Blow advice. I had read mention of filing the new pin to fit, which means it may be needed to for clearance purposes in at least some cases depending on your own, specific unit. Unless you have extra 2k just burning a hole in your pocket, I suggest saving the trial & error for something less-critical, and much less expensive. The consequences of a mistake may not be immediately noticeable "DOHH!" Moment, but neglecting to utilize a replacement pin could very well be creating some adverse condition within the operation leading to an overall decrease of the orig unit service life which is my biggest hangup on this.
Upon further investigation, the Sonnax version of this 2nd gear upgrade (corvette) servo comes standard with a replacement pin, which they make to seem somewhat important. I think a lot of you guys installing the piston only without the new pin are neglecting necessary procedure, espc if working on high-mileage/orig trans.
https://www.sonnax.com/parts/2486-2nd-gear-super-hold-servo-kit
https://d2q1ebiag300ih.cloudfront.net/uploads/part/instructions/2486/77911-03K-IN.pdf?v=1495651615
I can't speak for everybody else but Sonnax has built an incredible rep in the world of aftermarket trans replace parts & upgrades. If their 2nd Servo comes with a pin, then by God you need to be getting a pin with your GM vette servo, as well. Has to be a reason for it.
The only reason I would have for replacing the servos is extending the service life of the orig trans that came in my truck from the factory. Wether or not the trans tech with 30-yr experience is correct about the advice given to me, it is still wise to expand on his theory, nonetheless. If anybody reads this and would like to comment on their experience with upgraded servo/s on the original transmission, I would certainly appreciate you dropping a line on the subject and helping build a case for any pros/cons in the long-term affects of this mod.
