GM Drivetrain & Suspension Chassis | Transmission| Driveshaft | Gears/Rear End/Differential | Traction Aids

2-4 Servo Pin ??

Old Jan 16, 2008 | 08:18 PM
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Default 2-4 Servo Pin ??

Guys,
I'm having transmission problems with my built unit and have bought a salvage yard tranny to put in temporarily and keep as a spare.

Anyway before I put the spare tranny in I'm installing an TG HD2 shift kit, aluminum accumulator pistons, TG spacer plate, Corvette 2nd servo, and Sonnax Super Hold 4th servo. I have also bought and installed the long GM servo pin. The stock pin had 2 rings and the servo travel was at least .250". With the long GM servo pin the servo travel is now about right at .150". That is a figure I found in an install write up for the Sonnax Billet 2nd servo kit. Is that a good number for the servo combo I have? I have also confirmed that I can slide the band up and down on the drum about an 1/8" per the Transgo kit instructions.

Next question.... Part of the Transgo kit is adjusting the band using 1 or 2 large shims in the servo bore. I am pretty certain that is what I did by using the longer servo pin and I don't need to add any of the transgo shims. What say ye?
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Old Jan 16, 2008 | 09:17 PM
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i would think that the longer pin and puting in shims/spacers is the same thing. i would call finish line and ask them. i think either one or the other, i put in one shim and it is fine. 2 was too tight. as long as you can move the band like you said and rotate the drive shaft.
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Old Jan 16, 2008 | 09:39 PM
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D All of the above. Get that band as tight as you can get it and still be able to turn the output shaft in both directions.
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Old Jan 16, 2008 | 11:15 PM
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Agreed however do a test with the OD servo only also if it like a sonnax servo/and pin only ,The 4th gear clearance is not allways the same as the 2nd servo clearance
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Old Jan 17, 2008 | 02:24 PM
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Thanks for the input guys. Maybe I think things over to much... but I've drawn everything out trying to understand everything and can see depending on what method used, pin length or shims, may affect how much force each servo piston applies at rest and how far they have to travel to apply it when under fluid pressure.

Generally though you want the band as tight to the drum as you can get it at rest without it dragging and the pin travel at short as possible for each servo to get quick shifts. Right?
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