I'm parting out a '78 lesabre with a posi rearend. I haven't had time to check for serial numbers or pull the cover yet. What gear ratio would this most likely have? What other models would this fit? We have an '85 lesabre and an '86 monte carlo, both with open rearends. If these interchange, would it be worth the trouble of swapping performance wise? The '85 has an olds 307, and the monte's got a tired 305, but eventually the monte's getting a 350 and the 307 might be replaced with a 403 if our neighbor will sell it cheap enough. It also looks like the posi rearend is bigger and I think the brake drums are bigger as well. I once had an '85 caprice wagon with the big rearend, and it looked similar to the 1978 lesabre rearend.
nevermind, it says the gear ratio right on the tag, 2.41, which wouldn't be any kind of performance improvement whatsoever
Well, if the LeSabre is getting parted, it's prob worth yanking the posi. On B series cars of this vintage, one could get one of the following corporate rears... all were avail in 2.41 gearing 7.5 8.5 '77+ style 8.875 MP series rear. -7.5's are easily spotted as the axle tubes are 2.6" in diameter. Only reason to pull their high ratio cone type posi's is there are THICK aftermarket gears that will mate to them. -8.5 corporate rears will have ten 3/4" headed ring gear bolts holding ring gear AND the high ratio (2.41-2.56) posi carrier will have #9's cast in pass side end. This style factory posi will have an S spring for preload. IF, bolt-in axle version, def worth pullling. If c-clip style 8.5 rear, Id check the axles for pitting or chew in the bearing lands. Nice used 4 3/4 bolt pattern 8.5 28 spline c-clip axles are easy sell for this style rear. - 8 7/8 MP version will have 12 bolts holding the ring gear & will have plates & coil preload springs in the window of the posi. IMHO, really not worth pulling in the high ratio version. IF it was a low ratio MP, definitely worth pulling. Hope this helps. Got Posi? :3gears: Roger
