Need some opinion's on 3:90's...


Founding Member
Apr 9, 2002
New Jersey
I'm lookin for a coprimise between 3:73's and 4:10's. I want the acceleration of the 4:10's but don't want to be at 2500 goin 60 down the highway. Soooo what do u guys think about 3:90's? I know they're pretty new, and my buddy got them when they first came out and they f*ed up his rear end and tranny. Are OK now, like do they whine? and do they have almost as good pick-up as 4:10's? thanks :flag: :flag:
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SLiM JiM 156 said:
if its your daily driver, definatley go with 3.73's, you end up shifting so much around town. 4th gear going 40 sucks..

Hmmm.....I always go 40 in 4th with stock gears. Its at like 1800 rpms too. What do you cruise at? Just curious because I haven't driven a stick really long and I always shift at like 2000-2400 when cruisin'. :shrug:
IMO, don't fear the gear. If you want 4.10 accellerating, get them.

Thinking about it mathematically, deciding between 3.73's and 4.10's is similar to 2.73's to 3.08's -- not much difference. Now you're thinking about 3.90's -- that's splitting that little difference in half. Not worth it if you ask me.
:banana: I got 3.55's and I shift into 5th at 40. fixing to get rid of them for some 4.10's unless my buddies 3.90's feel better he is getting his car back tom. with them in. If i like them i might get them instead. Either way I'm still gonna get a crazy ride in his tom. :banana:
I went with 3.89s. Wanted to be sure I'd be in the right rpm band at the track, but still wanted to keep them as high as I could for on the street. Don't have the setup all done yet, so I can't tell you how it worked out. It really depends on your motor and the rpms you plan on using. Do the 3.90s cost any more than the other 2? If not, put them in and try it out.

I ran 3.73s with a 3550 behind a mostly stock 5.0. I don't believe I would've wanted them any lower for a car that's mostly used on the street and only sees the track on occasion.
davs5.0 said:
if the 3.90's messed up his rearend and trans, they must have been installed wrong. I've had mine for over a year and i love them. Nice compromise behind my aod. And picked up 2 tenths at the track going from 3.55 to 3.90.

How much should I expect to p/u going from 3.08's to 3.73?
I really don't understand why so many people approve of 3.73's for a 5-speed daily driver, but when it comes to 3.90's... WHOA thats just way too low!!

The difference is what... 100 RPM? A small price to pay at the pump for better performance, if you ask me. I plan on switching to 3.90's as soon as I get some other stuff out of the way. Not too many people have them in their car, but those that do have nothing bad to say about them.

Yes, 3.90's are a little more costly than 3.73's because FMS doesn't make them. I think the only company that does is Pro 5.0. They go for about $189, whereas FMS 3.73's can be found for as low as $139.
I got my 3.90's from Motive Gear, They are a little steep for town driving but They are not that bad only runs 2,100 at 60 on the highway. I'm just running a stock T-5 Also got the 23 tooth speedo gear it runs about 4 mph fast, accoding to the Iowa state patrol. :) I'd recommend them to anyone, Mine cost $189 from national drivetrain and the install kit with axel bearings was $75. small price to pay for the performance over 2.73's.
a gear swap does not put your car at 100rpm difference, or, 4mph off.
it is a ratio, aka a percentage... thus, the higher you spin it up, the greater the differential will be.