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

[Brian F.]

I have had two T5 transmissions in my roadster. One had approximately a .8 5th gear, the other slightly less, .6 about. With my setup, 351w, 400 hp/tq, 3.55 rear, I like the .6 a lot better. I didn't like the high rmps with the .8. At 75 mph, the .8 was around 2,700 and the .6 is about 2,100 rpm. It doesn't lug, though.

[BeasleyRB]

351W .82 3.25 rearend. 5 great gears.

[Mooch]

I was having the same decision making trouble and made some rpm calculations for the ERA 3.54 and 3.31 rear ends. See pages 2 and 3 of this thread:

ERA #783 - with questions

I've decided to go with the 3.31 rear and the 0.82 5th for the better shift and balance, and I'll deal with the higher rpms and noise at higher speeds - which can be frequent on Florida freeways.

I'll let you know how it turns out.

[Boostedsnake]

Thank you very much. My plan whas the 0.64. I hate when it rews to much on the highway. But after reading this i have been comfused?

I have 3.54 in the back and driving a kind chevy 350 turbo engine. Do you know how much different its in on the fourth gear in tremec against the munice?
Its perfect in any places but not on the highway.
My idea whas a pure overdrivegear for highways. Not a performencegear.

What do you tryout experts think?

[Slick61]

I've got an aluminum 427W with a fairly snotty cam... aluminum flywheel too. I'm running a 3.73 rear end & the TKO-600 with the 0.82 overdrive. When I first got it, I thought I wanted the 0.64 as well- but as I drove it more, I discovered it was set up perfectly. My engine doesn't come on-cam til about 2400 rpm, so the 0.82 is ideal- especially for freeway cruising. 2700-3000 rpm is an uncomfortable cruising range??? For my engine, it's the sweet spot... sounds amazing without being too loud. My engine could never handle cruising a 1900-2200 rpm... it would buck like crazy. As others have said... it's the combination of engine setup/cam profile and rear end that will dictate the best overdrive for you. Good luck with your build!

[Boostedsnake]

My engine runs very smothly even at very low rpm. And probobly capable to produce around 1000nm+.

Sounds like 0.64 would be good? Or? Its a hard choise!?