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

[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.

[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.

[WarrenG]

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

Sorry, three types. I have the 0.64 and don't regret it a bit! Also no problems or issues with shifting or getting stuck in 3rd or any other gear.

[patrickt]

Originally Posted by WarrenG

Sorry, three types.

Jim's brilliant analysis is close, but needs a tweak... there are indeed only two types of people -- those who categorize all people in to two categories, and those who do not.