What will happen to my T5?

[goaztecs]

..If I bolt it up to a 392W? It would be so much easier to preserve my existing tranny after I swap engines for the obvious reasons - Driveshaft length, input shaft length, bellhousing, etc. Not to mention $$. But what's going to happen to a tranny built to handle 265 lb ft of torque when it meets a the output of this engine? Am I asking for trouble? Or will it just mean a replacement down the line?

[G.R.]

It might last for awhile as long as you are easy on it--Hi-torque burnouts won't make it happy--How heavy is your "leadfoot"

[goaztecs]

It can be pretty heavy.

What can preserved if I go to a Tremec? Can I reuse my bellhousing? Is the case length the same as a t-5, or will I need a new driveshaft too? Shifter location isn't that important, can always modify the hole in the tunnel, but it would be nice if I didn't have to.

Any ideas? help?

[Jim Werth]

Just a word of caution. My first t-5 lasted 760 miles behind a 351w. Jim

[goaztecs]

Jim,

Great - this is the kind of feedback I was looking for. What exactly happened? Did it begin to bounce out of gear, refuse to shift, completely disintegrate? Or were you able to limp home and replace it? What did you replace it with?

/Chris

[Dirty Harry]

I got a 100,000 mile T5 for $200 when I built my car, I thought I'd use it as long as it would last and replace it when and if it broke. I run a 351, bored .030 over, balanced and with Edelbrock Performer cam and intake with a 600 carb. and '69 heads, mildly ported. I don't know what the HP is, but I do know that the 295/50's go up in smoke easily and often. While I haven't raced the car, I also have not "babied" it either. In 6000 miles I've only replaced the input shaft bearing and retainer-more of a wear issue than a breakage issue. They should have been refreshed before I put the tranny in. So, a T5 can live in a judiciously-driven, 2400 pound car with a mild 351, but I don't have any experience with one behind a stroker motor.

[G.R.]

The Tremac should bolt right up to your bell housing, the driveshaft length "might" be an issue as I think the Tremac is slightly longer than the T-5--?not sure though?

[wickedmach1]

Rebuild the T-5 using G-Force internals. That way you know it fits.

[Jack21]

I'll make a case for the T-5.

First off, don't confuse the early T-5's (rated for 260 f/p tq) with the late T-5Z (rated for 330 f/p tq).

Second, close ratio T-5Z's were not installed by Ford in any Mustangs so upgrading or new purchase is necessary.

So far, 15,000 miles on T-5Z filled with Moble 1 synthetic ATF behind stout 351W, and no problems. I love the way this trans shifts.

A lightweight Cobra will spin the tires before putting enough torque through the drivetrain to damage the trans. The one problem with the T-5 is the shifter forks. The shifter MUST be a positive stop design which the stock one isn't, and aftermarket ones (Hurst, etc.) are.

[goaztecs]

Jack21,

This is exactly the advice I got from Will and Bruce from Modern Driveline. Their entire business is swapping T-5's and Tremecs into Mustangs. They carry a full line of trannies and conversion kits. They have a 486hp Mustang that has run a z-spec T5 on the track for 6000 miles without incident. Their opinion is that the z-spec T5 is seirously inderrated, and is just the ticket in application like mine. Everything will fit, and it will last. With a Tremec of any variety, I'm looking at replacing a lot, and I'm not sure how it will fit. I am sold on a new Z-spec. Also, they are right here in San Jose.

Check out their site, it provides a thorough history on the T5 and Tremec trannies. Modern Driveline

[Jack21]

This is the discussion I had with Liberty Racing Transmissions also. They said I would be happier with one of their blueprinted 'Z's than a Tremec on the street. They were right.

Another Tremec vs T5 issue is gearing. The T-5Z offers a close ratio gearset (2.95:1 1st), Tremec doesn't. For a Mustang with 2.73 rear gearing, this works fine. Stock T5 has same 1st. For a 3.55 rear geared Cobra, winding out in 1st is akin to an old VW Beetle. Most Tremec equipped Cobras short shift 1st for this reason.

Tremec only has a .62:1 OD. In the 'Z, there are optional OD gears that any trans shop can install. I put the .73 in mine.

A stock EFI 5.0 will happily cruise at 75, with the engine ticking over around 1700 - 1900 RPM in .62 5th. Cams in a Cobra engine like cruising RPM's over 2000 so the shorter OD is useable. (My 75 mph cruise is 2300 rpm.)

I like having 5 useable gears in the trans rather than 3.