Gearbox change out - T/Loader, T5 or TKO 500 ?

KiwiGT · Jan 29, 2007

My car is a '66 GT Fastback, automatic, nice condition, only non easily reversible mod so far is subframe connectors. I'm just installing a new 342 crate engine - 450hp, 420ft ft lb torque and am going to change the car out to a manual gearbox at the same time.

I live in New Zealand and we have very few freeways here, mostly twisty winding canyon type roads. Most of my driving is under 1 hour in duration, very little long distance driving. My car is well set up in suspension and braking, and my driving is mostly 'canyon blasting' for weekend fun. The car is not a daily driver.

By the time I import a manual gearbox changeover kit from the U.S., the cost of a Top Loader, T5, or TKO 500 kit ends up being close enough to each other that cost isn't the deciding factor. All options have benefits and drawbacks:
Top Loader - will handle the hp, originality-no mods to car, but no 5 speed
T5 - marginal for hp if not G Force, minor car mods, offers 5 spd
TKO 500 - will handle hp, involves trans tunnel bracing cutting mods, 5 speed

Which gearbox would you use ?

ForceFed70 · Jan 29, 2007

If your not going to use the overdrive, might as well get a 4speed.
Toploader gets my vote.

Pbum5 · Jan 29, 2007

What is your rear gear ratio?

KiwiGT · Jan 29, 2007

Pbum5 said:
What is your rear gear ratio?

3.0:1 limited slip

Pbum5 · Jan 29, 2007

If you plan on keeping that 3.0 ratio then go with a 4spd Top Loader.

SoCalCruising · Jan 29, 2007

Yeah, the toploader would be good choice. If money isn't a big factor, though, you might consider a Richmond 5- or 6-speed. It doesn't require cutting up the tunnel and will handle that crate engine handily. With either, you can specify much of the gear ratio and find something that will work fine with your 3.00 gears.

If you don't plan on tires much bigger than 245/50-16s, or equivalent, and don't powershift it, the T-5 will hold up well. It's hard shifting coupled with lots of grip that kills 'em. Mine is holding up fine.

If those 3.00 gears are stuffed into an 8", you might have problems there quicker than with the gear box.

KiwiGT · Jan 29, 2007

SoCalCruising said:
Yeah, the toploader would be good choice. If money isn't a big factor, though, you might consider a Richmond 5- or 6-speed. It doesn't require cutting up the tunnel and will handle that crate engine handily. With either, you can specify much of the gear ratio and find something that will work fine with your 3.00 gears.

If you don't plan on tires much bigger than 245/50-16s, or equivalent, and don't powershift it, the T-5 will hold up well. It's hard shifting coupled with lots of grip that kills 'em. Mine is holding up fine.

If those 3.00 gears are stuffed into an 8", you might have problems there quicker than with the gear box.

Yep, the rear end is an 8". Its the old increased horsepower story isn't it ...let the drivetrain problems begin !

I don't know anything about the Richmond 5 or 6 speed, and hadn't considered that. Thanks, it will be worth looking into

D.Hearne · Jan 29, 2007

I think considering you're going to keep the 3.00's, and though I too favor a Toploader, the TKO's first gear would be a plus over the Toploader's (wide ratio) 2.78 1st. But that's the only plus I can see. Now if you're planning on a hydraulic clutch setup then that would be another plus for the TKO (Notice I haven't referenced the T-5? ) Also consider what bell housing, the TKO and Toploader use the same bolt pattern, but the TKO requires a deeper bell for it's longer input shaft. The stock Toploader bells will work with it using a 1" spacer.

SoCalCruising · Jan 30, 2007

D.Hearne's point about the toploader's first gear is spot on. The TKO is much deeper, at 3.35, or so. The problem, then is the spread between the other gears. This is where the Richmond really shines. With the 5-speed, 1st can be had quite low, but 5th is 1:1, so you have an extra gear to narrow the spread and lessen RPM drop as you're bangin' gears through the canyons.

KiwiGT · Jan 30, 2007

D.Hearne said:
I think considering you're going to keep the 3.00's, and though I too favor a Toploader, the TKO's first gear would be a plus over the Toploader's (wide ratio) 2.78 1st. But that's the only plus I can see. Now if you're planning on a hydraulic clutch setup then that would be another plus for the TKO (Notice I haven't referenced the T-5? ) Also consider what bell housing, the TKO and Toploader use the same bolt pattern, but the TKO requires a deeper bell for it's longer input shaft. The stock Toploader bells will work with it using a 1" spacer.

My clutch setup is compounded by the fact that I am running a power brake booster, which I want to retain. It looks to me like the JMC hydraulic clutch setup won't fit, because of interference with the brake booster, so it seems to limit me to a cable clutch arrangement if its T5, or Z bar for the T/Loader.

Keisler's TKO system appears to have the clutch pedal push a small master cylinder located lower down through the base of the firewall area, rather than being located around the traditional brake master cylinder area. Any suggestions for overcoming the brake booster issue ?

SoCal Cruising, what cable clutch setup are you running; and does it have acceptable pedal effort ?

Thanks for the reply's

SoCalCruising · Jan 30, 2007

I'm using the Modern Driveline setup. Clutch effort with diaphragm clutch is smooth and much less than with stock. The only issue I had was with the headers - one tube had to be moved and I use a simple bracket to hold the cable so that it cannot contact the header tubes. I'm running Doug's Tri-Ys; this problem may not exist with other types or brands. I've heard that Ford Powertrain Applications in Payullup, WA has headers compatible with a cable clutch; maybe others do, too. Shorties or stock manifolds are not a problem.

KiwiGT · Jan 30, 2007

SoCalCruising said:
I'm using the Modern Driveline setup. Clutch effort with diaphragm clutch is smooth and much less than with stock. The only issue I had was with the headers - one tube had to be moved and I use a simple bracket to hold the cable so that it cannot contact the header tubes. I'm running Doug's Tri-Ys; this problem may not exist with other types or brands. I've heard that Ford Powertrain Applications in Payullup, WA has headers compatible with a cable clutch; maybe others do, too. Shorties or stock manifolds are not a problem.

Thanks. The Modern Driveline kit looks to be quite well specified and sorted out. What gearlever are you running, and are you happy with comfort in regards to the throw/reach of the gearlever ?. I have a factory console and want to retain that.

SoCalCruising · Jan 31, 2007

I use a Pro5.0 shifter with the Hurst lever sold by Modern Driveline. Very smooth and the reach is okay. Increasing the bend in the lever would make it a little better, though. I haven't done that, yet.

I don't think there is anything special about the lever and it can probably be had cheaper elsewhere, but I got it from them because it was the easiest thing to do. Now, the threaded holes in the Pro5.0 are metric and smaller than the holes in the Hurst shifter. I had a brass bushing made and pressed into the lever holes to fit the metric bolts. Nice fit and the lever fits snug.

67 Evil Eleanor · Feb 1, 2007

TKO with .82 final, centerforce duel, modern driveline cable. makes me happy.

Gearbox change out - T/Loader, T5 or TKO 500 ?

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