I’m going to try list as much info as possible without making this longer then it needs to be.

- Tranny: ’87 Formula 350, 700r4, 80k miles, shifted fine before I messed with it.
- Just installed Transgo 700 Performanc Shift Kit, came with Vette servo and larger boost bushing
- Tested it up in the air like transgo video, shifted through all 4 gears
- Test drive, shifted the same as it did before (firmness) for a couple of miles but would not shift into 4th. Immediately responded to shift lever changes (didn’t do that before). I was a little disappointed. All of a sudden it started working correctly, much more positive shifts in all gears including 3-4. Figured maybe something was hung up from the install and finally loosened up
- Drove it 3 times today: when it’s cold 4th won’t engage, but shifts well otherwise (nice and firm, responsive). After a couple of miles I get a nice firm 4th gear upshift if I let off the throttle a little over 2000rmp in 3rd. Shifts into 4th at part throttle (normal acceleration) without letting off between 2500-3000rpm, seems a little high but livable.

What it does when it doesn’t upshift: if I have it in D just cruising at light throttle, shift into OD, rpm’s drop like it upshifted into 4th, but if I give it a little gas it acts like 4th isn’t engaged and revs back up to where it was when it was in D, if I pull the shifter back into D at this point the RPM’s stay the same.

If the car has been driven a little when I push the lever from D to OD I get a nice firm shift, and it won’t downshift again until I’m going pretty slow, or if I give it more then about ½ or ¾ throttle.

Any ideas what’s wrong?

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Mark
'87 Formula 350
’83 Crossfire TA
'97 WS6 TA (for sale)

 

Sounds like one of the teflon seals is missing or damaged in the servo. I would take it back apart and check them over. If I remember correctly there's 2 large split teflon seals, one small one and the red rubber o-ring and the blue cover o-ring.

If it's not this, did you install the last piece that goes in before the cover goes on backwards? The nub should face out into the cover. If all else fails, did the kit come with a new apply pin? Possibly the length is off. To check for proper servo clearence, istall everything without the seals and less the large spring and pull the cover out against the snapring and zero an indicator. Then push the cover in and it should be berween .060" to .125" with the tighter side being more preferable.

 

Make sure that the outer piston in the Servo assembly is OK. With the spring that goes onto the servo it is easy to damage that seal. Use some Vaseline to keep it together.