Which is better for my Cobra: Tremec .62 or .82 OD?

[Jim Norris]

I have the TKO with .64 and 3.73 rear gears. I don't like it. I'm constantly hunting for the right gear on the freeway. Fifth gear drops the rpms so much that I'm always on the verge of lugging.
I'm thinking about either changing the overdrive gears in the existing trans or swapping the trans out altogether.

[mikeforte]

Hi Jim,
I stock the .82 gearset for your TKO-600. You could also sell the TKO you have and purchase the TKO-600 .82. One other option would be to install a camshaft that doesn't lug at low rpms.

[WarrenG]

I had my cobra in SoCal for a while and used the 0.64 on the highway all the time with no problems or issues.

[mikeforte]

Hi Jim,
I sold a guy a TKO years ago to install in his 428 Shelby Mustang. It had 3.89 gears, 2 4 bbl Holleys & a nice Crower cam. The problem was the cam wanted to go 80-90 mph to run clean and not buck. We installed a much more docile camshaft and he then loved to drive his car at normal speeds. The cam we used lost a tiny at redline and gained total driveability....

[Jim Vander Wal]

OK, I'll go against the grain.

I have the .64 with 3.27 gears. I like it on the highway as I cruise at 2,200 @ 80mph with 315/35/17 tires.

Where I don't like the .64 is 55-75 cruising backroads, the RPMs are too low and 4th forces the RPM range too high for just cruising.

My use may be different than yours. I run lots of highway (hours/days at a time) and find that 2,200 is at the bottom of my usable RPM range. I also play on the track and find that I can run to 157 in 4th if needed so I don’t shift to 5th on the track.

I've looked at the .82 and run the numbers and just don't like the higher RPMs for long distance highway cruising.

There has been a new post about putting the T56 into a SPF. This really interests me as it offers the best of both worlds.

Jim

[twobjshelbys]

Mine is a 3.54 rear end with a .82 5th. It works very well on the freeway - 2500-3000 RPM at 75-85MPH. The engine starts to lug down at about 2200 RPM at these speeds.

[patrickt]

... with the .64 OD. But, I do like the fact that I redline 5th at 225MPH for those quick trips to the Salt Flats.

[twobjshelbys]

Originally Posted by patrickt

... with the .64 OD. But, I do like the fact that I redline 5th at 225MPH for those quick trips to the Salt Flats.

I never thought of it that way. Hmmm...

Heck I haven't even hit the red line at 4th gear yet. Working.... I did in 3rd though. I think it was about 95 but I wasn't watching speedo only the tach.

[jwd]

You'll find there are 2 types of people. Ones that have the .82 5th gear and those that regret not having it. I have it with a 3.27 rear and it is PERFECT.

Jim

[patrickt]

Originally Posted by jwd

You'll find there are 2 types of people. Ones that have the .82 5th gear and those that regret not having it. I have it with a 3.27 rear and it is PERFECT.

Jim, cruising at 80 mph with your set up is 2700RPM. That's kind of high, but maybe doable (probably not, though). Move your rear down to a 3.54 though and the revs climb to 3000RPM. That's just too high for pleasant cruising and chatting.

[jhv48]

It all boils down to your engine. Will it be comfortable cruising in fifth gear at 2000-2200 RPM?

If not, go with the .82 ratio.

Mine is.

[Ralphy]

I am new to the Cobra World and I am considering the same thing. Looked at the T 56 Magnum. After getting familiar with my car I agree with most posts here. The .62 would be fun. however the .82 will be used more often in my opinion. I am running a 428 plus 03. 4 speed top loader with 3.36 gears. Someone mentioned going with the same gears as the top loader, yes to that also. If you want the .62's go with the T 56 Magnum if you can.

[jwd]

Originally Posted by patrickt

Jim, cruising at 80 mph with your set up is 2700RPM. That's kind of high, but maybe doable (probably not, though). Move your rear down to a 3.54 though and the revs climb to 3000RPM. That's just too high for pleasant cruising and chatting.

I suppose if you live in "Moose Butt, Wyoming", you're correct. There is no place you can cruise at 80 MPH in my area.

My Corvette has 4.11's and 60 MPH is 3000RPM. I avoid driving on the freeways.

[eschaider]

Originally Posted by timsullivan

I'm building a Superformance with most likely a 351W stroker of around 418 or 420 CI that I'm shooting for 450 to 500HP. I will be running 15 inch BFG's or Goodyear GT2's. My rear end ratio is 3.46:1 I am unable to afford changes to the wheel size or tires and don't want to change the rear end ratio. I will be doing occasional freeway driving here in SoCal and occasional longer trips on the freeway but the vast majority of my driving being simply around town.

Which TKO 600 should I get .62 or .82 OD and why in your judgment? Thank you in advance for any input you can give me on this.

-Tim

Tim,

You ought to do some searches on here and other places about TKO shifting problems going into third gear. Another good search is TKOs that have locked up in gear forcing you to drive home in whatever gear you parked it in.

Both are real problems and take a lot of the driving fun and turn it into maintenance fun. Driving fun is preferable.

Tremec has a very good transmission in the T56 that does none of the above and if you are after brute strength then check out their new T56 Magnum that they rate at 700 ft/lbs of TQ.

Although you can change once the trans is in, if it is not in yet the T56 might just be the better choice ...

Ed

[Rwillia4]

CA highway crusing is at 80. Go with the T56 and don't worry about it. It cost more but it comes with a bellhousing which will cover the cost and has a great feel.

I got mine for $2100 and love it. I just moved from CA and cruised comfortably in 6th most of the time.