68oldscutlass

Hey guys,
So without looking under the car yet for castings or anything, I am fairly certain I have the 2:56 gears in my posi. 68 Cutlass with 2 speed jetaway. Im pretty good mechanically but have never touched a rear. What would be needed to possible go up a step or 2 in gears. Looking for my off idle umph. I know I dont have race car but gears cant hurt. I have a 4bbl quadrajet, headers and true dual exhaust. Doing h-pipe soon to balance it out. Is this a huge costly project? Thanks in advance for any help!

monzaz

Well first off ZI would can the balance pipe...Usually only needed to help the motor breath better at top end. AND since you have a 2.56 gear you would want the low end. BIG exhaust pipes and big header and big heads and big cams ALL lead to big mistake...LOL Smaller header pipes lead to better savaging and will help bring in the new charge. Your car is not a race car and top end screamer which all that stuff is built to do.

YES it build HP...BUT the HP power is a sacrifice in low end drive ability, ALWAYS... This bigger is better stuff is the reason why we need big converters and steep gears etc. ALL band aids for a bad pick of a can or too large of carb intake etc.

Anyway on to the subject - rear work is not all that. You need to find the pattern and get all the specs in correct.
You will need TIME first most important- If you think your gonna wipe this rear together in a night DO NOT START!
Tools
Magnetic base dial indicator
shim packs for the carrier and pinion
(good rebuild kit will be a huge help if you need the bearing and stuff as it will have EVERYTHING needed to do the job and all the parts.)
Brass drift -
normal hammer socket set - basic tools
Torque wrench
GM or other specs book.

Jim
JD

Eddie Hansen

You may also need a bigger carrier or special gears if your looking for say a 3:42? I am not certain and Jim or Brian would know best, I rebuilt my Posi and the service manual will be invaluable, bearings will need to be pressed on the axles etc, and you might want to get a digital micrometer to measure shims etc. You will also need a BIG extension bar for your breaker bar when tightening your crush sleeve to set your back lash.


Take your time and be careful it should be fine, Jim makes it sound easy but he does this stuff in his sleep LOL...

J-(Chicago)

You can get the shim kits right from Jim (monzaz) He is a helpful guy when it comes to differentials.

Best tip I have for you is to avoid making a big stack of thin shims to get to your desired spec. They go everywhere when you pull the carrier in and out, and you will waste a lot of time monkeying around with them. Use factory thick shims and use the thin ones for fine adjustment when possible.

Other than that, use your mic to double check shim thickness, and don't put a ton of pattern paint on the gears. A little goes a long way. I bolted the wheels and tires on when checking the final pattern to make it easy to apply extra drag.

507OLDS

Just a note: The Richmond gears are already backordered,with an unkown availability date.There are plenty of places that have the 3:90's in-stock,but no 3:42's.Good thing I got more last month.They might not be available again until 2013,but hopefully sooner.

Eddie Hansen

Brian can you use a 2 series carrier with 3 series gears? Or are these specially made gears?

507OLDS

The 2-series #673 posi carrier can be used with the 3-series gears,if you use a spacer.The ring gear journal on the carrier is wide enough,to take the spacer,and still have enough journal for the ring gear itself to press onto.I have made ring gear spacer kits in the past,but you can also take a Mr Gasket 908A spacer,for the 71-up 8.5" 10-bolt,and modify it by elongating the bolt holes,and enlarging the inner diameter.

Eddie Hansen

Thanks for the clarification Brian, trying to learn all I can

monzaz

Yah I did the same thing... lol. I even have some on back order at the lower price...They better not can that deal or I will be mad. lol. Jim

507OLDS

They might magicly say not available,then reoffer them for the higher price.It's their way of saying "We can't sell them to you at that price."

z11375ss

Put a gear in that thing. It will wake it up big time. I went a little overboard with 3.73s. I had 2.73s or something around there. I couldn't let the clutch out without it almost stalling. It's great for around town but I hate them on the highway. I take the Caddy in that case. It has like a 2.73, perfect. The 3.73s are a blast though, I must admit.