Rear End Swap Question and Help Needed!

[James G.]

Hey guys, I am looking to swap in a posi rear end into my 1972 Monte Carlo. I currently have a 10 bolt open rear end with 2.56 gears (original rear end, ID #L K B 1 5 2 2). I have a guy who would be willing to sell me a rear end from a 1969 Pontiac LeMans which is a posi unit, 10 bolt. My questions are:

 

1) Would I be able to bolt the 1969 LeMans posi rear end up to my 1972 Monte Carlo without much modification?

 

2) If it would bolt up pretty easily, would it be worth the $400 price tag since the unit appears to be in very good shape, gears look good and no rust on it at all?

 

Any help would be greatly appreciated, thanks!

 

-James

[714024SPEED]

Yes James the rear end will bolt in with no problem.You may need to change you ujoint on your drive shaft.I put a 12 bolt from a 70 MC into my 69 Lemans convert.with no problem i needed to change the ujoint.

[Sam (Bones)]

I agree, the u-joint should be the only issue

[MGD72Monte]

2.56 gears!!! I thought 2.73 were the lowest gears available in the Monte.

 

Was that a special high mileage or top speed option?

[Big Jim]

That's what I've been told. I changed mine to 3.08 limited slip.

[Montemedic]

My 70 SS came with a 2.56 12 bolt posi in it. It's also on the build sheet.

[MGD72Monte]

My 70 SS came with a 2.56 12 bolt posi in it. It's also on the build sheet.

 

Must be on big block cars only then.

[Sam (Bones)]

2.56 were stock gears in 1970 for the SS454

[James G.]

Ok, so it seems the u-joint would be the only issue. What kind of u-joint would I need for this swap to work? Sorry for all the questions, but I have never swapped rear ends before, so this is new to me. Thanks!

[speedfreak71]

Seems a little high priced for a 10 bolt. There are plenty of chevelle and monte 12 bolts still around. They are stronger and help the value of the car. The last 2 I've bought for $250 a piece. I found a aftermarket posi on the net for $235 shipped and found some used 3.31 gears for $50 and have been very happy with it. And the 12 bolt just looks MEAN Just my 2 cents worth

[714024SPEED]

You have to look at your u-joint it might bolt right in.I had to get what is called a "trick joint" it has the small caps on one side and the large caps on the other.I got it at my local NAPA auto parts.Also look to see if your joint has inner or outer clips,or if it is org.to the car it may still have the nylon in it.