fmx auto and 3.89 gear question

[sams66]

Guys, will I regret the 3.89 gear? looking at buying at 69 fastback, it has a FMX auto trans in it, and wondering if that 3.89 is going to be too much with just a 3 speed auto. overdrive out of question for now, looking for your advice?

Sam

 

[Ronstang]

Depends upon how much you drive it and how much of that driving is on the highway as you will be turning a little over 3000 RPM at 60 MPH with a 26" tall tire.

 

[WORTH]

If it's a 9" I'll trade you a set of 3.00's

 

[nosaj122081]

I ran 3.89's plus a FMX for about a year or so, til my motor popped. Loved it, I would never have it any other way from now on. Ronstang is right about the MPH, in WV the speed limit is 70, so at 75 I was doing 3500ish. But it was worth it, I love those gears. I'll be using them with my overdrive-less Toploader when the car gets back on the road.

 

[DarkBuddha]

Just be realistic about your driving habits/plans. If you intend to drive the car often on roads with speed limits over 50, then 3.89s are probably gonna get annoying pretty quick. However, if it's a weekend cruiser or around town street car, then they may work out fine. And if you're planning lots and lots of highway driving, then start saving now for an overdrive tranny...

Hope this helps.

 

[ForceFed70]

I have 3.73's and the FMX. Honestly, I wouldn't go ant steeper. Highway driveing is a PITA.. it's loud, it's hard to keep a constant speed, and the gas mileage is horrible. Luckily I don't do much highway driving and when I do, it's only for short periods...

With the 3.73's I run 60mph at almost exactly 3000rpm. With 3.89's, I think you'll be turning approx 3200rpm at 60mph.

It's not too bad, but doesn't leave you much room to play.. sometimes I like to pass cars.. and by the time I'd done passing I'm usually at the 80-90mph mark and the ole engine is just screaming...

 

[D.Hearne]

I run 3.70's in my 68 Merc, with 255/60/15 rubber. With a C-6 it's not too bad on the highway.

 

[grabberorange]

I went from 3.00 open to richmond 3.89 and a lockright locker about 2 months ago. It still makes me smile everytime i stomp on it. I even get 14.5mpg in the city. RPM's are up there, but this is only a weekend car and i never take in on the interstate.