[68 Firebird]

I am debating whether to attempt to install a transgo shift kit in my 68 Firebird.
I have searche and read countless posts and like the transgo 1-2 kit.

Just leary on installing it as my trans has never been gone thru since I have owned
the car(10 years) and for all I know its never been goen thru. My car has 73,000
miles and trans is coded correct to car. It has has a light blue torque converter which
I also believe is original(stall is low). Currently no issues with slipping, upshift or downshifts.

Just feel shifts are a little slow&soft. Trans modulator has been adj, and does raise rpm
but still soft shifts. I changed the fluid and filter a few days ago and pan was clean and trans internals appear spotless.
Have any of you had issues once trans was placed back in svc, like the kit pushed an
old trans to far?

Would you be cautious to install a kit with a trans of unknown age????
Also would money be better spent on a converter upgrade??

Current gearing is 3.08 posi and running a 25" tire.

thanks

Gerry C

[Squidward]

I did the transgo kit in my TH350 based on research and recommendations. I didn't go the full out setup because I wanted to keep some streetability and longevity. I haven't tested it fully, tho, since my engine just got fired up last week and all I could do was cycle through the gears and verify it went forward and reverse in all the appropriate gears.

I say this because the TH400 I rebuilt in another car got a B&M kit with the "strip" level mod - no accumulator spring, drilling separator plate hole, etc. It shifted TOO hard on the 1-2, and jolted my dental work every time. I went through a couple sets of u-joints on that car.

[chiphead]

The Transgo kit won't hurt the tranny. Leaving the accumulators functional has a huge affect on the shift harshness, especially the 1-2 shift. Raising line pressure, changing the shift springs and opening the transfer holes in the plate help reduce overlap and shift time. The Transgo seperator plate is a very good one, it dual-feeds the 3rd gear clutch and increases 3rd gear holding power by 50-75% in TH350s. I'd assume it'd do the same in a TH400.

The main causes of shift-kit related failures is rolled (broken) intermediate sprags. This is caused by a too harsh/sudden 1-2 shift that forces the sprag race to stop the direct drum instantly. The B&M style kit will cause this harsh "chirp" type shift. It tells you to drill out the 1-2 feed hole and remove the 1-2 accumulator spring. The result is a fluid dump into the 1-2 piston that causes instant sprag lockup.

I find that transgo 1-2 shift is very good, actually just a tad slow for my liking at the dragstrip. I've taken to enlarging the 1-2 feed hole in the seperator plate to speed it up just a bit. It's still not too harsh, because the accumulators are functional.

Installing the kit in the car isn't much fun. The main trick is getting the check balls to go back in their passages. Just take your time and keep it clean. I suggest getting a Haynes service book, as it really comes in handy as a reference.

[68 Firebird]

Thanks for the info guys. I agree to get a manual for the T400 and will
hopefully get everything together to do this in summer.

Agreed I don't want to shake my teeth when it shifts, just firmer, crisper shifts.

Thanks Again

Gerry C

[Half-Inch Stud]

Me thinks you can skip the Transgo Kit, in favor of a proper program setup that avoids any shifter-to-upshift delay(latency), and also get shift firmness that is related to pedal demand.

The baby blue color converter is not GM original. I'd be glad to remove your TH400, go through it, update the internals for 34 element sprag, fresh seals (the old seals are brittle and 1 seal may have cracking or a tear by now), perform my proven "Recipe II", and reinstall your TH400. All within the day, and you drive home. PM if interested. HIS

[Cliff R]

FWIW, I'd hold off till the trans needs to come out for some work. Installing shift kits in well "aged" units can produce less than desireable results, and you really need to have it out to install the good sprag, "Jack Armstrong" retainer for the intermediate pack, and direct clutch springs supplied in the better Transgo kit.

Nothing at all wrong with "home-brew" shift kits, IF the trans is our for rebuilding, and the installer has extensive experience with these units. I have my own shift kit in my new TH400, with some parts from the Transgo kit added in. Got a few items from Jake as well, and couldn't be happier with the shift performance......Cliff