I am a do it yourselfer so to speak and I love building my own transmissions. I find that minor modifications are adequate for lighter vehicles but thinking of building one for a 3500 pound Nova with a 406 running 12.6 with a th350 and 3.73's. I'm pretty well set about what size boost valves, servos, 3-4 clutch stack and apply plate and other things that I would consider common modifications like shift kits, etc. My questions are about the strength of the planetaries and a 28 element forward sprag. I estimate my horsepower and torque to be 380 hp and 420ft lbs. Will the sprag hold up and what is the horsepower limit of a stock 28 element sprag and the planetary sets? The car is not driven much because of fuel consumption and excessive rpms at cuise. I am also looking for a lock up converter that stalls approx 3000rpm that will hold up and costs under $350, what do you offer for converters? Any other advice is welcome and all is appreciated. My best core is coded 9YPM and was told it's either an F-body trans or older vette. I have other cores as well and many spare parts. Thanks for comments.

 

Here is what I found to work best in street/strip transmissions. Starting in the front, (1) install teflon bushing in pump. (2) If you are going over 5,500 rpm, install Hi Rev No-Yo-Yo steel rings & spring from Trans-Go. (3) Get the clearence on the new 10-vane rotor to .001-.0015, slide should be about .002-.0025. (4) Check out stator support (must be in very good condition). (5) Install .500 main boost, .296 intermediate/reverse boost valve, and the new updated pressure regulator valve. (6) Install Turbulator (low drag) steels in the reverse input drum. (7) Restrict hole in reverse input piston to .065, and install the front pump teflon bushing in the reverse input drum also. (8) Install Viton seal (input/output shaft) in the input drum, this seal guarantees oil to the rear planets. (9) Install Borg Warner Hi-Energy .080 thick 3-4 clutches, aling with the correct steels (.060-.080 in thickness) & pressure plate to get .040-.055 clearence. The stock late planetaries work fine. (10) Replace the sun shell with the latest updated version from GM. (11) Flat sand the new bronze thrust washer that resides in the sun shell till it is perfectly flat,(it has in stock form 4 intentional high spots) it now has 3 times the surface area to more evenly distribute the load. (12) Use Turbulator (low drag) steels in the low/reverse pack. (13) Install the bronze case bushing, instead of the babbit bushing. (14) Install the teflon extension housing bushing instead of bronze/babbit bushing. (15) Use the Trans-Go 700-2-3 Performance Shift Kit, make sure that you install (ALL) the new 3-4 & forward clutch springs from the Trans-Go kit. Use the Sealed Power Filter (OEM) only. (Do you want full automatic shifts at near 5,800 rpm, when in the drive position? Then if you have a Corvette trans core, then you will want the valve body, valve body plate & governor. Install these items in a 1988-1992 non-Corvette transmission. Corvette transmissions have a apx.1" shorter tail housing & shaft, and there aren't any trans mount holes in the case like the non-Corvette transmission. Use the latest from Borg Waner on the input/low/reverse sprags. Almost forgot, install the Corvette servo along with a Borg Warner Hi-Energy 2-4 band. I am sure there are other things that I have missed, but this should give a good start. Best synthetic Amsoil, or Redline. Non-synthetic the best is Mobil Dexron III (not MobilOne). The lowest in price for a lockup that will give you the best in torque multiplication, 60 foot times, and the least concerns when it comes to parts breakage, is the ACT 9.5" lock-up. With 3,000 rpm stall the price on this is $525.00 (one year warranty, and a free stall change). Stay away from the 12" lockups they very hard on parts.
Hope This Helps!!!

 

Thanks for sharing that information, I'll put it to use during the build up.