[Scott Stoneburg]

Thanks for all the replies guys. Looks like i may lean towards the TKX 5 speed with 2.87 1st and .64. 5th. Gear and leave the rear gear alone. Thanks

[chuckies76ta]

Scott: Gotta watch that od gear at .64 with 3.23's rear gear. 80 mph at 2000 rpm. The .72 is a lot nice with 3.23. 2000 rpm 72 mph or Even the .82 2000 at 63 mph. Depends what engine likes. Just my .02

[Formulajones]

It should actually be more like 75 mph with a 26 inch tire and the .64 overdrive at 2000 rpm.

That's about perfect.

I ran that setup with 3.27 gears and loved it. Excellent for long trips on the 75 mph highways around here and knocked down 26 mpg with that car.

That's what you want with an overdrive, that's the whole attraction for it. Get your moneys worth.

I'm currently running 3.55's with a 27" tire and the .64 overdrive and it's again, about perfect. Just a little 302 chevy and it lugs just fine. 2000 is 70 mph and even with a big fat 780 holley on it I'm getting just over 21 mpg with that one. It's an excellent long distance car.

[Tom Vaught]

Originally Posted by chuckies76ta

Depends what engine likes. Just my .02

Have to agree with that.
My "not light weight" 4 door truck with the 10 speed trans just loves cruising at 75 mph at 1700 rpm
with the turbo set-up on it. I could run all day long at 80 mph with a increase in rpm but our State Boys
(and Girls) are just looking for the 80+ mph guys to hand a ticket.

Not sure what is magic about 2000 rpm though but it beats the heck out of 3400 rpm at 57 mph.

Tom V.

[chuckies76ta]

Not sure what is magic about 2000 rpm though but it beats the heck out of 3400 rpm at 57 mph.

lol, Was just for demonstration purpose. Same with rear tires. I used 28"in formula.

[tom s]

1900-200 is my target RPM for final gear highway cruising in all 3 of my cars.My 63 Lemans with 3.90s and the TKO falls a little short.Swapping in 3.64s will get me there.FWIW,Tom

[Formulajones]

Yes, from my experience with various size engines and brands, that's a nice place to be that returns good mileage, less noise, and still enough grunt with any engine to pull any grade without the need to look for another gear.

I like to shoot for 70-ish mph at that rpm range in overdrive. That way on the long trips where speed limits are 75 and I want to cruise 80 I'm still not pushing the engine very hard at 2200 or so, and it still gives me respectable mileage at those speeds.

The problem I have with the new TKX now is they are starting to creep up the OD gear to .68 which is causing me to readjust and rethink the final gear ratio to keep my MPH and RPM where I want it to be. If they are going to do that then I want the 1st gear ratio a little steeper so I can knock some rear gear out of it. They would have been better served to play with the 2-3 gear ratio and leave the overdrive alone. However the .68 overdrive would work well for those that run 3.23 gears like the OP, this trans will fall right in your wheel house. I start to not like it as much with 3.73's or more.

That's one reason that now really has me leaning towards the muscle car trans (McCloud) which is T-5 based with stronger gears and case. I went with a Promotion version of this trans, (good for 600hp) and absolutely love the gear ratios.

[Scott Stoneburg]

So to make the swap to the TKX 5 speed, what is all necessary to change?
*Shifter
*Driveshaft
*Clutch?
*Will it bolt to the existing bell housing?
*Trans crossmember?

[Formulajones]

Already a 4 speed correct?

Shifter body for the TKX (will accept any bolt on hurst stick) So if the car has an aftermarket Hurst in it already, the stick will transfer over.

You'll at minimum need the yoke, which then can be used if you want to shorten the existing driveshaft. That's the cheapest route, if you have a driveline shop nearby to do the work. Otherwise buy a new driveshaft with correct yoke. I tend to like a new driveshaft anyway, something stronger.

For the clutch, if running a 10 spline now, you can get away with just replacing the disc to a 26 spline. Again, cheapest way to go, I find most clutches on these classics that don't get driven much are in really good usable shape and just swap out the disc and go with it. If already running a fine spline muncie, nothing needs to be changed.

Yes bolts to existing bellhousing

Trans crossmember is optional. Usually I fab up the existing cross member. If you have the ability to do that it saves money. If that's not an option and you want to save time, and not monkeying around with driveline angles, then there are several on the market made for this swap.

Another piece I like to buy is the short speedo cable adapter that extends your current cable and has the Ford style speedo end on it. All these Tremecs still use the Ford style speedo adapter and gears..

One other little piece I like to have is the pigtail for the backup lights. A harness can be made yourself to run the wires but I find it's much nicer to buy the short pigtail that already has the correct weather tight rubber seal to fit the Tremec at the connector, and they don't cost enough to squabble about.

That pretty much covers a swap for a car that is already a 4 speed. Pretty straight forward.

[napster]

Again, late to the party. Look at this thread of the T-56 install in my "73.

https://forums.maxperformanceinc.com...d.php?t=839167

Not much to cut in post #15. Look at post #14 where a lot of surgery was done because the engine was an inch back from stock in a 1970 Formula.

I have the T-56 in my 1970 T/A. Same deal not much cutting. It was already cut for a four speed, but the T-56 was put in without any further cutting. Same amount of cutting as my '73 was previously was done as it was an auto to stick conversion.

I have another T-56 going into my 1970 GTO which was a factory four speed. I don't expect any cutting. Will update once it is in.