tko-600... .082 or .064

patrickt · #1 (**permalink**) 09-16-2008, 08:12 AM

Quote:

Originally Posted by Ron61

Pacrickt,

You are right for most people, but my engine was built for racing and then when I got to old and sick, it just didn't work out well for cruising with that ratio and a .6 split. My cam came in at around 3600 RPM and with the .6 split it effectively raised my rear end ratio to 2.10 with the street tires I used. So at the 1900 RPM at 70 MPH I was lugging the engine and a .8 would have been better for that use. I would say that 80% of my cruising was done in 4th gear as the traffic and speed limits stopped me from getting the engine up to where it ran well.

Ron

Perfect example of a need for a .82 and not a .64 gear. If you have a rear numerically lower than 3.5, or an engine that isn't at least awake below 2500rpm, I wouldn't go with the .64 trans. It can be a tricky call, and if in doubt, I'd go with the .82 gear.

maxum_101 · #2 (**permalink**) 09-16-2008, 08:27 AM

ok this is a bit complicated... lets say i have a spf cobra with a 3.46 rear 17 inch tires and a roush 427r engine what would be a good 5th gear to have? i want to be able to drive hwy at a comfortable rpm and still be able to hammer it around town . anyone out there have this set up that can give their comments on this?

Slick61 · #3 (**permalink**) 09-16-2008, 10:00 AM

Quote:

Originally Posted by maxum_101

ok this is a bit complicated... lets say i have a spf cobra with a 3.46 rear 17 inch tires and a roush 427r engine what would be a good 5th gear to have? i want to be able to drive hwy at a comfortable rpm and still be able to hammer it around town . anyone out there have this set up that can give their comments on this?

I'm running a KCR 427W in my Backdraft with 3.73 rear & the 0.82 overdrive. At first I wished it had the 0.64, but with my cam, it would be completely useless at anything below 80 mph.

2600-3000 rpm on the freeway is PERFECT for my engine... the engine sounds fantastic, is running in the sweet spot for the cam, it's not too loud, and I still have good, tractable power on-tap for quick maneuvers. 3000 rpm puts me right around 75 mph, with 80 mph coming at ~ 3200 rpm. It's great. Above that, the wind buffeting is too uncomfortable for long-distance cruising. I know several people with the 0.64 overdrive who practically never get to use 5th, as the engine lugs too badly. Believe me... 3000 rpm on the highway sounds FABULOUS! It's not as fatiguing as it would be around town. If you want mileage, slow it down to 65 mph... it's mostly aerodynamics (or lack thereof).

... and you can still hammer it around town...

DC COBRA · #4 (**permalink**) 09-16-2008, 04:12 PM

Quote:

Originally Posted by Slick61

I'm running a KCR 427W in my Backdraft with 3.73 rear & the 0.82 overdrive. At first I wished it had the 0.64, but with my cam, it would be completely useless at anything below 80 mph.

2600-3000 rpm on the freeway is PERFECT for my engine... the engine sounds fantastic, is running in the sweet spot for the cam, it's not too loud, and I still have good, tractable power on-tap for quick maneuvers. 3000 rpm puts me right around 75 mph, with 80 mph coming at ~ 3200 rpm. It's great. Above that, the wind buffeting is too uncomfortable for long-distance cruising. I know several people with the 0.64 overdrive who practically never get to use 5th, as the engine lugs too badly. Believe me... 3000 rpm on the highway sounds FABULOUS! It's not as fatiguing as it would be around town. If you want mileage, slow it down to 65 mph... it's mostly aerodynamics (or lack thereof).

... and you can still hammer it around town...

I agree with ya Slick, the .68 just plain sucked when I had the cobra. When I put the .82 in her that was the hot ticket. You should have heard her with my exhaust on her now that was sweeeeeeett!!

DON

Slick61 · #5 (**permalink**) 09-16-2008, 04:47 PM

Quote:

Originally Posted by DC COBRA

I agree with ya Slick, the .68 just plain sucked when I had the cobra. When I put the .82 in her that was the hot ticket. You should have heard her with my exhaust on her now that was sweeeeeeett!!

DON

oy vey... I can only imagine... It's still a little too loud for my ears when cruising around town... most of the curbs are about 6-8 inches high & reflect everything right back to me... gets fatiguing around town, but sounds awesome on the freeway at 80 mph.

DC COBRA · #6 (**permalink**) 09-16-2008, 05:14 PM

Quote:

Originally Posted by Slick61

oy vey... I can only imagine... It's still a little too loud for my ears when cruising around town... most of the curbs are about 6-8 inches high & reflect everything right back to me... gets fatiguing around town, but sounds awesome on the freeway at 80 mph.

Dude it can never be too loud, that means you just getting old and need to stay on the porch HA!HA! But you know BILL said the same thing, it was way too loud.

DON

ng8264723 · #7 (**permalink**) 09-16-2008, 05:36 PM

My Terminator has a 6 speed in it and I cruise all the time in 6th. It's very comfortable the engine is cruising at 1700RPM and is nice and quite. My 70 SCJ with a 428 and stock tires with 3:91's use to cruise (60mph) at 3000RPM. Boy was it loud!! I think a lower RPM at 60MPH would be more comfortable. Having never done autocross I have to ask what is your ave speed?
chris