[acmikee]

what gear ratio should i run with a 408, 550-600hp, tko trans and an irs. the dif now has 273. the ford motorsport gears are out of stock in 373 so do i go 410 or 355. street use only and i never speed or drag race on the street.......

 

[Larry N. Johnson]

With that much torque, IMHO, you do not need gears.

My vote is to leave the 273's

 

[trevor]

You should take into account what type of cam is in your engine. Some long duration, high lift cams reduce the bottom end torque significantly. If you keep those gears - you probably will have to leave it in 4th on the highway and slip the clutch a lot to get it going. Your engine might have a lot of torque - but it's at 2500 RPM.
Hopefully someone has a similar engine/cam in their car and can give you advice on what gears to use.

I have a 302 with an X cam and I switched my 2:73's for 3:27's. But I am a long way from testing it out to give you some input on how well it works.

 

[Steve S.]

There are sources for gears other than FMS. Try Mike Forte. He's a forum advertiser, has a wealth of information, good advice, good pricing and is a nice guy too.

[email protected]

 

[Wayne Presley]

Uh Trevor, you probably have never driven an FFR with a stroker 351W. My buddies 408 w/450RWHP&480lb/ft of torque has 327's in the rear and any place that it is running in 1st gear, including idle, a stab of the throttle results in tire smoke from the 315/35/17 Yokohama A032R's. The FMS X303 cam is a big cam for the 302, I have it in my 342 and it works very well with the extra 40 CI. I would go with 3.27 gears because the motor will produce more than enough torque at freeway speeds (The above 408 made over 400 rear wheel lb/ft of torque from 2000-6000 rpm)

 

[Bart Carter]

The TKO has two choices on the final drive ratio. Which one do you have? Do you intend to track the car, and if so what kind of racing?