Rear End Gear Advice

[WallaceMFG]

Recently my drive train has been changed and I would like some input from other people. Here's some info on the car:

1969 Chevelle. I'm going to use the small block 350 that came with the car for now since its already done. Its a mild engine with 4 bolt mains, a upgraded cam and track baffled oil pan, but that's it. I got two Muncie 4 speeds with the car, an M20 wide ratio and an M21 close ratio. The car has a 12 bolt rear end I put in but it has 2.73 gears.

The other day my dad called me and told me he got a Richmond 6 speed from a friend for a smoking deal! :seizure:


I've been searching for months for a T56 that was in my price range but with no luck. I have a Richmond 5 speed in my Torino and love it, so I'll be even happier with a 6 speed.

I'm looking for some advice on what rear gears to run in the car, and while I'm at it, what posi units should I look at that don't have a price tag on the moon. The car will be autocrossed, but it will spend more time on the street going to car shows and cruises. The gear ratios for the trans are: 3.28/2.14/1.57/1.24/1.00/0.76.

Thanks for the help!

Nelson

[Schwartz Performance]

We put truetracs in a lot of the cars we build. For your application that'd be fine!

What's your rear tire size?

[WallaceMFG]

Oops I knew I was forgetting something, the tires are 26" tall.

[Schwartz Performance]

I'd go with about a 3.42 gear which would be spinning 2000rpm at 60mph. You could go a little taller for a quicker accelleration, but I wouldn't go taller than 3.73 with that small of a tire.

You could play around with the ratios at WallaceRacing.com/gear-speed.php

[WallaceMFG]

Thanks! It looks like a 3.42 or 3.55 would work best for me, and that shouldn't have to change when I eventually get turbos like I want.

Could you shed some light on the different carriers for a 12 bolt? I was looking on jegs just to see and I saw ring gears in the same ratio, but one said it was for 3 series carrier and one said it was for 4 series. I've heard that with a 12 bolt some carriers only do ratios up to a certain number and then you'd have to get a new one. Not really sure where to start.

Thanks!