[CantedValve]

I am going to be doing a transmission swap this winter. I am still fighting with which one to use.

I will end up with a 351C that pops about 400-450 ft-lbs of torque. I currently have a Toploader that is probably ready to go. I want to keep some gas mileage in my car, so I have opted for 3.00 gears out back. This gives me good 1st gear (8.34), while also a fairly decent (3.00) final drive.

I have recently began donsidering a TKO II, which will handle 475 ft-lbs of torque (so says Tremec). This transmission will also have a .83 5th, which would allow me to run almost 3.73 rear gear and still retain the highway driveability (plus 1st would be a whopping 12.20, enough to REALLY fry them at CF3).

Money aside, if you had that kind of power in a 351C and both a Toploader and TKO II side-by-side, which would you snag?

Also, if the TKO II is not a direct bolt in (save new crossmember), let me know... that has a large impact on my decision.

 

[Billgear]

Overdrive is very nice to have!!!!

 

[Bucket Lister]

The toploader can take a lot of abuse. More than a T5 or a C4 auto. The tremec TKO is just about as strong, so, no advantage to either one there. We all like horsepower, acceleration, and gas mileage. I'd say, money not withstanding, get the TKO. Your car with the TKO and 3.73's will out run the toploader AND get better gas mileage.

 

[kketell]

The TKO is the better choice, if for no other reason than the overdrive 5th gear.

The TKO is an easy swap. You will need a toploader bell from a Cleveland block though. You can get one from a truck.

The guys at the shop I use have recently done just what you are talking about. You might give them a call and pick their brains. They are at

Mustang Fever
(408) 748-1337

Talk to Mitch or Scott. Mitch did the work, but Scott would know as well.

 

[bullit]

definatly TKO.regards javed

 

[abn]

Overdrive!!! Seriously, I put a lot of real world miles on my Mustang and the overdrive makes the car so much more enjoyable. Of course my commute is mainly open freeway...but I think the same would hold especially if you ever wanted to drive on a long distance tour or to a car event. With my 3550 and a 3.0 rear I still feel that 1st is just a little too low. With a 3.73 you could probably start in 2nd...effectively making the Tremec a 4 speed overdrive with an anti-Camaro gear (or anti-traction gear).

 

[CantedValve]

Yeah, Allen had that problem. His wife woudnt drive the car because she couldnt keep traction in 1st, so I told him to have her start in second... in second, he had more gear than I do in first!!

Okay, now i gotta sell my wife on the $1300 extra I need for it.

 

[abn]

I was replacing a three speed with a bad second gear synchro...so the choice was relatively easy for me. I forgot to consider that you already have a good toploader...I guess that would have a big effect on my decision. $1300 is a hefty chunk of change. The overdrive is still more comfortable on the street...but life is more comfortable all around with $$$ in the bank! Toploaders are generally in demand maybe you could get the "right" price for it.

 

[BossBill]

CV,

A Tremec is one inch longer because the input shaft is one inch longer (approx). If you use the std Tremec you will have to get a bellhousing spacer (to make up for the input shaft length) and shorten your driveshaft the same amount.
As noted you need a crossmember.
You can order the Tremec with a short input. It bolts right up to your existing bellhousing and uses the std drive shaft.
It's about $125 option.
The Tremec shifter is biased to the passenger side.
Actually the std Mustang is biased left because the std shifter hangs off the left side of the extension housing. You may have to trim the floor because the Tremec is dead middle.
The Tremec's .82 od is nice and either a 3.5 or 3.73 works. You may find the 12.20 in first a bit much. You will find yourself short shifting first -- often.

The biggest problem with the Tremec is gear spacing.
If you intend to drag race or want a close ratio gear box, this ain't it.
In fact, the wide-ratio T/L at 2.78 ain't it either.

Here's some numbers. If you shift 1,2, and 3 at 6000 with 26 inch tires and a 3.73 rear here are the rpm drop numbers
(6000 - rpm drop=rpm in next higher gear after you shift. Too big a drop or big differences between gears equals a bog when you shift):
rpm drop from 1 to 2:
Close Ratio 1640
Wide Ratio 1840
TKO 2360

rpm drop 2 to 3
Close Ratio 1430
Wide Ratio 1790
TKO 1940

rpm drop 3 to 4
Close Ratio 1350
Wide Ratio 1600
TKO 1530

As you can see the Close ratio has decent spacing (the wide ratio has better spacing, but the rpm drop is too much) and keeps the rpms up.
The Tremec falls flat on its face in second...look at that rpm drop.
I was ready to buy a Tremec, but it does not fit properly in the 65-66 without surgery or a bad rear tilt (over 6 deg).
The later tunnels are bigger, and I understand they fit.
Personally I like the spacing of the T-5Z, with a 2.95 first and 1.94 second, but you have too much hp.

Just some more stuff to consider.

BossBill

 

[CantedValve]

thanks!

This isnt a drag race car by any means. I want a nice brute daily driver /forums/images/icons/smile.gif I will maybe take it tracking a few times a year, but it will not be a competition car.

My only use for 1st gear is going to be at CF burnout contests /forums/images/icons/smile.gif

I understand the wide vs. close arguement. I agree.. the longer you can keep your car in your powerband, the better.

I am probably going to start with the wide ratio gearbox, and as money provides, maybe I can get into the TKO II later.

 

[dmcq]

Have you considered a Gear Vendors overdrive unit and then you'll have an 8 speed? <grin> Seriously though I believe they warrant their unit at those HP levels...
D