I've got that high gear rear end in my 89 GT
273 i would imagine from my rpms.

anyway, i'm rebuilding the rear end due to a bent axle and was going to throw in another gear. I dont want it to be a track car but i do want to give it a little more pep. My uncle told me 355's would kill my mileage.

How much gas mileage would i be sacrificing for a set of 355's? Its an AOD if that's any help.

 

Well, I have 3.73's with my 5 speed and I still pull 20+ easy. If I had an auto, I would put in 4.10's for sure! I have been think of doing that now....

 

Go with the 3.27's (optional on the AOD's) or 3.55's....

Door code, Axle M= 2.73 E= 3.27 on the AOD's

 

ive got 3.73's in mine and i love them, my car is a 5 speed though. 3.55's would be a big improvement, and 3.73's would really wake it up. as far as mileage goes it will make a difference but it shouldnt be too dramatic.

 

your uncle is flat wrong and if you want any noticable gain 3.73's or 4.10's as the aod has a tall first gear = 2.40 vs a t-5's 3.35

 

how much higher would my rpms be at with a 355?

 

I'm not usually one to suggest a low gear but unless you're planning some high boost go with at least 3.73s. I have 3.55s in my Cobra and if I had an auto it probably wouldn't be enough for the price unless you have a hook up for the gear install.

 

NOT MUCH WITH AN AUTO

 

I'd go with 4.10's. You have OD so it should bog down nice on the highway. Mine turns 3250 at 60MPH with a 3 speed and 245/60/14's on the back. Swapping my gears (2.73 to 4.10) was the best cash spent besides the engine itself. Get at er'!!

 

I think those of you suggesting 4.10's for this guy is too much. From what he is saying he doesn't want a track car, just wants some more pep and driveability and gas mileage are a concern, either 3:55 or 3:73 and you will get what you want with little or no negative aspects. Just my 2 cents