So my new ride has a zz385 motor, turbo 350 trans and 12 bolt rear end. On the freeway it sounds really hi-rev at 70mph. Matter of fact, I didnt' want to go any faster than that (I have no tach so I was playing it safe).

It's a newly rebuilt turbo350 trans (previous owner just sunk $2200 into it) but he should've went with the 700R4 I think, same price.

Anyway, a shop told me the cheaper way to make it freeway friendly is change the gear ratio in the rear end. I'll lose power at lower speeds but won't be at 3500rpm going 75mph. I'm more of a cruiser and will be taking freeways to the beach now and then.

Is this method advisable? Not advisable?
Do you have a recommended gear ratio? Not sure what I run now or how I would find out.

 

Jack both rear tires off the ground and turn one wheel. If the other wheel turns the same direction, you have a posi rearend. If that, then count how many times the driveshaft spins to the wheels one spin. For instance, if it's about 4:1, you have 4.10's.
However, if your initial spin test has the wheels turning in opposite directions, you have an open diff rear. There you want one tire in the air and the other on the ground. Spin the tire 2 revolutions (not one), and count the number of driveshaft spins.
For a combination town/highway driven car, I probably wouldn't go lower than 3.55's.

 

Awesome thanks!!