Here's the situation:
My '88 Iroc has basically a stock motor, and from what I can tell has a 9-bolt with 3.70 gears. I don't plan on doing too much work to the car at all, so are these gears too much?
The gas mileage sucks, and it's like the motor revs itself out and chokes too quick, and I have no top end power. Would it make sense to swap rears with my friend who wants to do work to his car and has a new 2.77 rear? Keep in mind I have my '80 to make into a monster.
Any advice?

------------------
1980 Camaro, '88 Police 350 engine, Headers, full exhaust, completely redone, my baby!
1988 Iroc-Z L98, MSD 6a, Accel coil, K+N's, Airfoil, Coolant Bypass, Flowmaster, Gears, Late model Bose, I like the 80 better

 

Steve,

If I were greedy, I'd say to get a 9-bolt 2.77 rear end and throw the other one away (as long as you throw it MY way).

The 3.70 is a precious commodity. If you do replace the rear end with a different unit, save the gears, carrier, etc. as they can be valuable. The 2.77 Borg axles are a lot more common, and you should be able to find a good used one in a recycler yard. Your's is probably worth two of them, so don't get suckered into a trade. The Borg axles are very stout, and even with mileage they can be reliable, so don't be afraid of a used one. They were available starting in 1986, so they should be easy to find. You'll certainly get more top end and fuel mileage on the highway, but accelration will suffer unless you change to a higher stall-speed torque converter.

------------------
Later,
Vader
------------------
"Fear is how I fall, Confusing what is real..."
Adobe Acrobat Reader

 

How can I go about getting better mileage with the 3.70's?
I'm at about 2200 RPM's at 60mph. My uncle told me that even if I get it down 400 RPM's, it won't make much of a difference at all. Is this true? Right now I get about 18mpg highway. How can I get it to like 23 or 24?

------------------
1980 Camaro, '88 Police 350 engine, Headers, full exhaust, completely redone, my baby!
1988 Iroc-Z L98, MSD 6a, Accel coil, K+N's, Airfoil, Coolant Bypass, Flowmaster, Gears, Late model Bose, I like the 80 better

 

I have a 700R4 and 3.42 gears and on trips I get about 25 - 27 MPG. I think you have to keep your foot out of it if you want to increase mileage. I found I get this milage if I run about 75-80MPH

------------------
91 Z28 Camaro
305 TPI
Flowmaster 3" exhaust
700R4 with 2000 Stall and shift kit 3.42 rearend
One sweet sounding system

 

i'm getting about 24 on the highway. Thats between 70 and 80, revs are at about 2000 at 70mph. This is with a 3.23 rear and t-5 with a 350 TPI (stock for now) up front.


------------------
------
82 T/A, 86 T/A interior, 350 TPI/ T-5