Low power, tire-spinning 1-2 shift... HELP!

[NickTransmissions]

"Did they install the Corvette Servo? I have the same behavior in my LS swapped truck. The WOT 1-2 shift will spin the tires like crazy. Even at light throttle it's a very firm shift."

Yes, I'm pretty sure he installed the Corvette servo.

Purely fyi: a corvette second gear servo by itself isnt going to spin the tires or generate a super firm 1-2 shift. It can potentially generate such shifts in combo with mods done to the separator plate, valve body's 1-2 acc valve and 1-2 accumulator housing. Would be curious to see what was done with those other three things...if its too firm at light / part throttle the 1-2 feed orifice is likely drilled too big and accumulator housing shimmed too much for the TC's stall speed.

For street driven vehicles set up for performance, part throttle shifts shouldnt feel too different than stock while WOT shifts should be crisp/quick with no lag.

 

[GoToGuy]

Does the sway bar mount on top of axle using the pads that are already there? Like Tahoe?

 

[L31MaxExpress]

Does the sway bar mount on top of axle using the pads that are already there? Like Tahoe?

Suburban and Tahoe rear axles have the same sway bar mounting points. My 99 Tahoe actually had a 4x4 TBI era Suburban rear end in it.

 

[bfcg30518]

It shifts perfectly normal at part throttle and regular use. Its only at WOT that it will burn tires from 1-2 shift.

Purely fyi: a corvette second gear servo by itself isnt going to spin the tires or generate a super firm 1-2 shift. It can potentially generate such shifts in combo with mods done to the separator plate, valve body's 1-2 acc valve and 1-2 accumulator housing. Would be curious to see what was done with those other three things...if its too firm at light / part throttle the 1-2 feed orifice is likely drilled too big and accumulator housing shimmed too much for the TC's stall speed.

For street driven vehicles set up for performance, part throttle shifts shouldnt feel too different than stock while WOT shifts should be crisp/quick with no lag.

 

[bfcg30518]

Suburban and Tahoe rear axles have the same sway bar mounting points. My 99 Tahoe actually had a 4x4 TBI era Suburban rear end in it.

I had to cut the pads off the Suburban rear and welded them under the pickup rear. They align with the shock mounts and were welded/blended into those when I installed them.
The pickup frame is shaped differently, so i had to extend the end links about 4" longer than stock.
Autozone sells unassembled replacements that unclude poly bushings. I just cut the round ends off and added my own steel rod that measured 7.5" long.
Center to center they ended up being 9" long and worked perfectly.

 

[NickTransmissions]

It shifts perfectly normal at part throttle and regular use. Its only at WOT that it will burn tires from 1-2 shift.

Then its set up correctly

 

[GmcGreenmachine97]

Fuel pressure was 55-60psi... so I left fuel pump alone and replaced all 3 O2 sensors with new Bosch units since it had multiple O2 sensor codes and CEL.
It seems to be running much better but still feels like its laying over pretty bad when I wring-out 1st gear. Theres still something "not right" going on here.
The cat was gutted, but still no check engine light.
Maybe the new MAF sensor is bad.

I’ve been having the same issue in my 97 suburban for almost a year and 2 transmissions*. The truck bogs in first and when you try to take off but when you get it shifting and moving and you give it some beans it goes like a freight train. I’ve tried cleaning out the throttle body replacing sensors, putting on a less restrictive muffler but it’s still a slouch to get goin. the transmissions that I have had rebuilt have both failed and did the same thing. When I took the second one for a test drive first gear felt firm and it took off perfect but then it slowly got worse over a few hundred miles and I was in the same boat. Im pretty sure now after thinking about it for months on end that the trans wasn’t rebuilt correctly.