I have a 69 Skylark, I think it has the 2.73 gear, I'm wanting to put something like a 3.43 or 3.64 posi gear in it. What is the best way to do this. can I buy the differental? How do you know if it is the 8.5 rear. and I have a chevy 12 bolt rear,but what do I do about the drive shaft. Thanks alot guys
To go from 2:73 to a ratio over 3:08, you'll need a 3-series carrier, and yes, they are available. If you switch rearends, I think your driveshaft will still work, but you may need to change the rear universal joint. 'Combination' joints are available that have 2 different sizes on them to do this conversion.
3:23 is a nice gear. I use a 12 bolt and it was not a big deal to switch, you have to get the correct u joints but you should change them anyway.
The chevy 12 bolt rear is a 6 lug. It came out of a 70 c 10 3 speed 6 cly, Not shur of the ratio. But I was thunking it would proably be cheaper just to change the differential in what I got. But I was wondering if I do change how would I make it a posi, doesn't the posi have some type of cluch assembly and if so can you buy it? I dont know anything about rear end if you can tell. Thanks again
James, I believe I would take Mike up on his offer if I were you. You can't make a non-posi into a posi (well, you can, but it's more expensive and definitely not stock). A lower gear ratio (higher numerically) will be a good idea. You can buy every thing you need brand new, but you're going to spend in the $700 range. If you buy Mike's posi differential, just find a good automotive machine shop near you and ask them if they can do the swap for you. It will be much easier with the rear out of the car, but it can be done in the car. You need some specialized tools for this; namely a dial indicator and stand. You'll also need pinion and side carrier shims of various thicknesses to set the backlash and pinion depth correctly, plus a crush sleeve, rear cover gasket, new pinion lock nut, pinion seal, gear lube, a small tube of gear marking compound, and possibly bearings and races. It takes some time to get it right, but it's not a job you can rush. Get it wrong, and the gears will eat themselves for lunch. A factory shop manual should show & explain the entire procedure. You might take a look at one of those and see if it's a job you feel comfortable tackling yourself.
