jwags01

I am building a GTO and the engine is a 421 with about 600 hp. It came with a 4 speed Muncie, but it will not handle the horsepower. What manual transmission do you recommend? What will I need to mount it to the engine.

Jimbo1367

T56.Magnum

Michael Yount

iTrader: (1)

How is the car being used?

ForceFedC5

iTrader: (1)

OK, first I just wanted to say AWESOME CAR & ENGINE!! Please post pics!

Must be a "Transmission" day. This is the 2nd time today I'm recommending RPM Transmissions (765) 640-5411.

I've used them for 15 years for both manual and automatic and they've been beyond great.

Make sure to speak with Jeremy, he's always getting me the best bang for the buck, is honest and is actually an old school Pontiac enthusiast.

jwags01

First, thanks for the response. Car is being used for some street driving, show car, but I want to be able to take to track. I have seen the T56 as option. Will it bolt to the bellhousing used for the 4 speed muncie? Any other recommendations?

Michael Yount

iTrader: (1)

Do you have highway rpm limitations/desires? Define "track" - autocross, road racing, 1/4 mile? You're gonna have a ton of torque -- so 6 gears aren't strictly necessary and the T56/6060 series is a big/heavy tranny with lots of parasitic loss (rotating weight). There are 5 speed options out there too -- might be a better "fit" -- unless of course you want 1300 rpm on the highway at 70 mph.

jwags01

If I bring to track, would only do 1/4 mile. A 5 speed sounds good to me!

CattleAc

iTrader: (7)

Ok, so are we talking about a "421" cubic inch LS based engine...or, an original Pontiac 421...???

jwags01

Original Pontiac 421 - sorry, I know this is an LS forum.

CattleAc

iTrader: (7)

Ok, I see. I think McLeod makes a "direct fit" 5-speed for old muscle cars that I think requires no cutting for install, and I think it will bolt up to your bellhousing...


Link

pdxmotorhead

DOnt see them talked about much on here,,, but,,
Reman Jerico, they come up on the Oval track for sale pages.. and at Oval/dirt track swap meets, the big teams run them for a season and trade them in each winter.. There are 2/3/4/5 speed variants.. Not "cheap" but very rebuildable and they handle some serious power.

Michael Yount

iTrader: (1)

Sounds like you're going about it the right way -- I'd pony up for a TKO600 with the gear ratios you want and add the "shifts like it should" option that many perform with this. Much smaller/lighter/more efficient than the 6 speed and should hold up to your demands. Pretty sure I've seen a bell for this application - BB Poncho to TKO.

Jericho, Nash and Richmond options - but they're gonna be noisy.

pdxmotorhead

Use smaller mufflers,, then the tranny noise won't matter.. LOL

joyridin'

iTrader: (1)

As stated, go with the TKO with the .82 OD. I think it is considered the close ratio version. There is another option with the .64 OD, but it is a huge drop between 4th and 5th and unless you have EFI, your car will not like the .64 OD.