Mlunsford33

Okay guys I got this car and the previous owner said the rear end in it was a posi 373 gear out of a 85 monte I have a 10 bolt ready too pull out 0f a 69 chevelle my ? Is what's the difference between the rear ends I'm pretty sure the monte rear is more narrow would I be beat to go with the rear end out of the chevelle thanks for any guidance

brownbomber77

The Monte rear axle is 58.5" whereas the Chevelle is 60.5". The Monte axle is more likely than not a 7.5" rear and is generally weaker than the one from the Chevelle. Short answer, yes, swap it but be sure the ratio from the Chevelle is desirable.

joe_padavano

A 1985 Monte would have had a weak 7.5" axle. The angle of the ears for the upper control arms on that G-body housing also are not correct for an A-body and require the upper control arms to be forced into place with binding unless aftermarket spherical bearings are used. Whoever did that has no clue about axle swapping if it is true. The 69 Chevelle housing is a bolt-in for a Cutlass and avoids these problems. It is also stronger than the Monte axle.

Mlunsford33

Okay thanks guys I'll have it swapped this week yes it had looked like that cut and shortened the upper arms on the rearend too make it fit but I have the rearend from the chevelle ready too pull on another hand could you help me with this ? Will a 4 speed say out of a Buick skylark bolt right too my 350 or is there any later model vehicles that's a direct bolt on trans

svnt442

You might run into driveshaft issues as well. Keep that in mind when doing the swap.

joe_padavano

Any GM-compatible four speed with a Muncie bolt pattern bolts right in. Of course, that primarily limits you to a Saginaw (weak), a Muncie, or a BW T10 or Super T10. Frankly, the Super T10 with the 2.88 first gear is a good choice. They were used in late 70s F-body cars.

Your bigger problem is that Olds did not drill the crank for the pilot bushing if the car came from the factory with an AT. The crank needs to come out to do this right. There is an aftermarket pilot bushing that fits in the AT crank but the hole is not deep enough for the trans input shaft. You either need to cut 3/4" off the tip of the input shaft or drill a non-critical clearance hole in the end of the crank.

Mlunsford33

Thanks alot for the advice guys

Mlunsford33

So what vehicles did the muncie 4 speed mt come factory