73-77 Rear end width

[oldsmobiledave]

Can someone give me the width (backing plate to backing plate) of the differential for the 73-77 A body cars. I have a 3.42 posi from a 73 442 on my shop floor at home but am away working & do not want to wait 3 weeks to measure it.

Also does anyone know if the 73-77 El Camino used a wider rear end than the regular 2 & 4 door cars. I know the wagons use an odd ball 12 bolt. I may have a buyer for the 3.42 posi but the El Camino owner wants to know the width to be sure it will fit in his car.

Thanks in advance.

[birdseye]

The rear from my 73 (also sitting on the shop floor) measures up pretty much right at 56" backing plate to backing plate.

Barry

[first car]

The 10 bolt that came from my 74 442 measured at 55"

[aretubj]

The rearend in mine is from a '73 El Camino.
No issues

Joe

[zodiacblue442]

Wagons and El Camino supposedly use a 8.75 or 8.875 inch ring gear. The 2 drs and 4 drs use an 8.5 inch ring gear so I would think there would be differences in the housing. 72 and earlier cars also used different (bigger) rear brakes and drums. I don't know if GM carried it over into the 73-77's. I wish I had my shop manuals with me now to look stuff up. I did browse around on the Internet and was finding posts that El Camino used an 8.5 inch ring gear. Now I'm confused. If the ring gear is the same diameter, no worries and the rear end from the 442 will fit just fine. If the wagon / El Camino gear was orignially larger, even if it would fit I'd not use the smaller one - GM engineers felt they would be too light duty.

[oldsmobiledave]

Wagons and El Camino supposedly use a 8.75 or 8.875 inch ring gear. The 2 drs and 4 drs use an 8.5 inch ring gear so I would think there would be differences in the housing. 72 and earlier cars also used different (bigger) rear brakes and drums. I don't know if GM carried it over into the 73-77's. I wish I had my shop manuals with me now to look stuff up. I did browse around on the Internet and was finding posts that El Camino used an 8.5 inch ring gear. Now I'm confused. If the ring gear is the same diameter, no worries and the rear end from the 442 will fit just fine. If the wagon / El Camino gear was orignially larger, even if it would fit I'd not use the smaller one - GM engineers felt they would be too light duty.

Thanks for this info but I am only concerned about swapping the entire diff not doing a carrier, crown & pinion swap.

Looking above someone posted 55" BP to BP while someone else posted 56" BP to BP. Which is it?

[W451973]

I don't have one in front of me to measure but I know for a fact that they WILL interchange. Some 73-77 El Caminos come with an 8.5 while others had the 8.875. Some had the 9 inch drums like the earlier models and some had the 11 inch drums. I guess it depended on the year and if it had the tow option. And even some of the Grand Am's, Grand Prix's and Lemans's were the same way.

[74hurstolds]

Dave, when I get home in a few hours I'll crawl under one of my cars and measure for you.