Switching from 3.89 to 3.00 gears...
 

My car is a 67 Mustang with a 9" rear, TKO-600 with .84 5th gear, tires are 26.1, and 3.89 gears. Currently I max out at around 75mph at 3100rpms. Kinda rough on the FE 428/7.0L that I have in it, especially after doing a few 1500+ mile round trips across the USA in it. I just moved to Germany and the cars here are crushing me on the highways here. The average speed, when the speed cap is lifted, is about 180kph/120mph. I have coil suspension all around and dropped it to the ground already but my rear gears are whats holding me back...It handles great at 135mph, it's just that I can't sustain that speed for hours at a time (if you're doing the math, that's 5500rpm). I have disc brakes x4 already, so stopping isn't a problem. I hate BMWs, Audi's and Merc's non-stop passing me...my poor American pride :'(

Does anyone here run a big motor with low low gears, like 3.10, 3.00 or 2.90...how much take off speed will I be giving up?

Thanks,

James

Booger...finish your Fastback.

What is the 1st gear ratio on your tko?
.84 OD is not much either.

1st gear is 2.87.

Just this last weekend I FINALLY got off my cheap ass and upgraded the 8" pumpkin from the factory 2.80 peg leg to a 3.25 trac loc. I didn't go higher because I still have the C-6 and didn't want ungodly RPM's on the highway. I figured the 3.25 would be a good compromise and I have to say that I'm pretty tickled with it. It has, obviously, more oomph off the line while keeping the revs at an acceptable level on the open road.

I have always run a small block and even with the 2.80 in it I had plenty of pull off the line for any driving condition Hell, even with my 2.80 and a small block I was able to do great one-wheel squeals with minimal effort so with a big, healthy FE, you'll be just fine and be able to scald the hell out of your tires.

Yeah, big block torque should have no problem with a rear ratio change. But your OD may still prevent easy cruising at high speeds, the math is easy enough.

Damned you!! And your big block!! I picked up a engine stand this past weekend, and started collecting my Post 911 MGIB for college.. Soon, my friend, soon!!

Would it be easier to change the gear set in the trans to something like a .64 like the AOD? I know nothing about the TKO, but it would probably be worth looking into.. ?

https://www.gearvendors.com/

You could add this, seen these on a few classics