My recently purchased 2004 Mustang GT has the Tremec 3650 5-speed manual transmission and 3.27:1 rear end ratio. I don't plan on doing extensive engine modifications to add BIG horsepower --- only basic intake/exhaust mods and tuning to maximize the stock engine.

I will definitely be changing the final gearing --- the 3.27 gears have GOT to go!! From the research I've done, it seems like the 3.73 gears would be OK and the 4.10 gears might be a bit too much?? I'm thinking that 3.90 gears would be the "perfect" compromise.

So.... just curious ---- is anyone running 3.90 gears on a car like mine? Looking for any info I can get from those that have "been there, done that" before I spend $$$ on a set of gears/installation.

 

Oops! Read my own post and realized that you'll need more info.

I am not trying to optimize the car for 1/4 mile drag racing (or ANY kind of racing). And, the car isn't a "daily driver" --- it is just a car to have fun driving on the streets and highways on nice weather days. Just looking for a performance combination that will give me a strong running Mustang from 0- 115/120mph (gears 1-4) and put a smile on my face!

 

I'm interested inn 3.90 gears too. Same car, mild mods and driving profile as 04Blue281 except mine is an auto. Also, if I get a tuner which would firm up shifts, would a shift kit make much of a difference, or would I be better off spending my money on a TB/Plenum upgrade?

 

Just go 4.10s especially if auto

 

crusing rpms between 4.10s and 3.73s is only a 300rpm difference if youre worried about cruising on the highway or anything like that.

If you dont daily it, then i say 4.10s, but I've never had 3.73s so I be someone else will chime in that has had both

 

I have 3.73's with the t-3650 (supposedly... there when I bought the car) and I am redlining 4th right at 120.

 

I have 3.90 gears and loved them when i was N/A. Not so much now being boosted. Its too much gear for a boosted car i believe. 1st gear was pointless even @ 400RW...
Again, when i was N/A i loved them. I wasn't making a lot of HP so they performed great and 1st wasn't so short. As soon as i tear into the rear end I'm swapping them out for 3.55's

 

I have 4.10s in my automatic 03 GT. It's fun at lower speeds but it kills top speed acceleration.

 

I have 4.10s and im boosted, seems fine to me wish I did 4.30s