I was wandering if anyone knows a modification to the turbo 400 trans that will improve 2nd to 3rd shift. Most "shift kits" I have installed in the past really wake up 1st to 2nd shifts but slightly improve 2nd to 3rd. Back in the 70's my buddy had a 71 buick gran sport stage 1 and it would spin the tires from 2nd to 3rd almost like 1st to 2nd. Thanks for any help, Tim
hello;i hear ya but i am not your guy. barneyformula or rowsley might know. they will likely see this.i think barneyfornula or pepsi 1 might remove the check balls.if you don't get an answer here, ask a local tranny shop. the good guys make their own mods.as far as kits go b and m is common and decent. they also have a kit called a transpak which allows for manual shifting too if you want.getting 3 - 3 to shift hard is a challenge with just a kit. you can also call b and m and yell them what you want and see what they say.i heard if you remove the spring from under the accumulator piston it will shift firmer from 2 - 3. if you already have a shift kit you can try this but i have no idea how this works.
its been too many years since i learned about this but the reason there is not the quick shift from second to third is to make the transmission live longer.. second gear is the forward clutch applied and the intermediate band applied.third gear releases the band and applies the direct clutch pack..if you apply the direct clutch before the band is partially released. you either rip the friction lining off or slow down the output shaft speed as you put the transmission into two gears at the same time.. if the band releases before the direct clutches apply the trans will slip or even seem to drop to first gear for a spit second.. 2/3 shift sequencing is critical google this term exactlyTH400 shift sequencingyou will find a power point presentation that talks about the simpson gear train designedit.. here is the power point presentation.http://tombirch.com/1/ppt/1.pptwhy can you get away with a tire ripping shift from first to second.. first is just the forward clutches applied and the rear sprag preventing the reverse section from spinning backwards.. yes. low gear has the sprag locked up tight and holding. when you apply the intermediate band.. the reverse section starts spinning so there is nothing to bind if you apply the intermediate band really fast.. other than pealing the tread off your rear tires to impress your friends..
If you know of any drag racers in your area, talk to them and find out the name of the local guy or guys who builds trannys for the racers. They will know exactly what to do. I'm not a tranny guy, but I have read that to get the hard shifts, sometimes requires stronger springs, increased hyd pressure to some parts, and aftermarket or modified drums that will allow more clutches in the clutch packs. Just one additional clutch in the pack can make a big difference in the shift.Auto trannys were designed to shift smoothly, not hard or harshly. Therefore, there are several basic mods that must be done to reverse this. The TH400 can be built to any level you could possibly need. You'll get harder shifts with a manual valve body. But, keep in mind, you'll need a ratchet or gate type shifter.http://www.transmissioncenter.com/Performance_TH400_TH350_Transmissions_and_Parts_from_PATC_TH350_TH400.htmhttp://www.superchevy.com/how-to/transmission/sucp-1006-th400-transmission-rebuild/http://www.atiracing.com/products/trans/400/index.htm?utm_source=PR_Blast&utm_medium=PR_Blast&utm_campaign=PR_Blasthttp://www.jakesperformance.com/TH400.htmlhttp://www.ckperformance.com/gm_th400stage.htmlhttp://www.crankshaftcoalition.com/wiki/TH400_rebuild_techhttp://fticonverters.com/Transmissions/GM400.aspxhttp://www.mikestransmission.com/catalogsite400trans.html
I'm not much help either, BUT... I did own a TH400 that would bark third like no other I have had. All I know about the shift kit is it was Fairbanks. Those are still available but its Superior now, I think. My experience was 25-30 years ago too. The TCI Trans-Scat kit I have now hits second like being rearended by a semi but third is no big bang.