What rear end did the factory put in the 78 El Camino ?? Gears ??? Any info would be great.

You'll need the Axel Codes to determine the rear end your Elky got. Look on the top of the Driverside axel and it is stamped there. Collect all the numbers just like they are stamped and post them here we'll be able to determine the gears from that. Or if you know the Option code.

For the fifth generation the performance gears were 3.08:1 but that is just one of the options.

I have been studying this question. It looks like most 75-80's El Caminos came with 7.5 inch rear end, and most were "open" meaning no posi traction. Yours probably has the 26 spline tapered axles. They are considered OK for street, but definately marginal for performance [and I NEVER pull out in front of people from a right turn!!!] Rebuild and performance parts are available, but a nice set-up would cost about a grand, and aftermarket stuff is not than much more [$1600-2000 for a 12 bolt or 9"]. One alternative is the Powertrax locker, about $300 for parts. Noisy, but very effective traction control.

7.5 has a square oval rear cover, and a small nipple at 5 and 7 o'clock positionson the case. Rear TA covers are same as F-body all the way to 2002 [which also had the 7.5 from 1983 forward], so some parts are cheap.

I am trying to find an 8.5" from the Grand National, but those are rare. Found out steel prices have recently increased, and the rear drive cars are heavier than FWD, so are being scrapped in droves. Exceptions would be Monte Carlo SS, GN's and 442's. Malibus and Monte Carlos are going away as spare parts doners...78 models were on the much heavier chassis, so have even less chance of survival.

V6 - 2.56 (standard) or 2.73 (performance)
V8 - 2.41 (standard) or 3.08 (performance)

These were the only four rear ends offered in 5th gen El Caminos, with one exception. In 83-84 the 105 horsepower LF9 5.7L diesel engine came with the 2.29 rear end.

I am trying to find an 8.5" from the Grand National, but those are rare.

All 4th generation Elkys and station Wagons came with the 8.5" 10 bolts unless they had a BB in them. Use one of those. The Buic/Olds/Ponitac rear ends were not as strong as the GM Corporate 10 Bolts, they are not the same.

to stray off-topic for a sec. so if a 4th gen elky has an 8.5 rear, would a 2nd gen ( 73-77 ) monte carlo have one.

It is completely possible that is true.

If you are looking to change your 5th gen for a 4th rear then it will probably need to be cut down. The 4th generation Elkys are about 3/4 or so wider could be as much as 1.5" oveall. I use to know the differences but forgot.

They say the first thing to go when you get old is the memory, I can't remember the second thing! :D

It is completely possible that is true.

If you are looking to change your 5th gen for a 4th rear then it will probably need to be cut down. The 4th generation Elkys are about 3/4 or so wider could be as much as 1.5" oveall. I use to know the differences but forgot.

They say the first thing to go when you get old is the memory, I can't remember the second thing! :D

Got that right! I'm seeling a rear from a Buick GS (I think '72 was the last year for them) because it's 1.5" too wide. That's a 3rd gen. though. 3.42 posi 8.5" if you're interested. :lol: