Calling all experts ... Rear End Swap... Need help??

[Anonymous]

OK,
I have been coming the local pick and pull to see what i can find for my project (81 El Camino). I have come accross a few possible (Jackpot) finds. there are about 5 78-79 Monte Carlos with the 5.0 and what looks like the the 8.5 Rear end. all but one have the whole drive train intact... that being said, does anyone know what came stock for trans and rearends on these MC's? another note, all of them have the rear swaybars still intact (may grab one of those too) I will open the diff cover to check them out (gonna bring my Brake cleaner to hose them down and get a good idea of the gear condition), but is there another way to determine a better canidate than the next?

Now, the good news..... i can pick one of these complete rear ends up for $100 bucks (any idea what the stock gear was in these?), and the trany for $125(still need to determine what trans in them). once i determine what trans... rear... ect is there would i be able to just swap over the rear and (im guessing they are 350 trans) trans without any modification aside form the cross member? for now this would be going behind my 3.8 V6 but in prep for when i can locate a solid 350 to refresh. then would be behind a mild 350 (looking to have around 350hp as a base goal).

to sum up, my questions are;
1. what gear came in these rear ends?
2. What trans came behind the 5.0?
3. are the rears the same width as my 81 Meano?
4. are they a direct swap? (the upper and lower Control arms look the same)
5. what should i look for to determin the wear/life left for these parts?



Sorry, i forgot my camera and dont have any pics yet. Ill try to get back out there to get some.

any help appreciated. Thanks!

 

[kevind]

1. They are probably 7.5" not 8.5"
2. I'm not sure on the trans.
3. The width is the same.
4. Should be a bolt in.
5. They gears shouldn't be worn sharp the pin shouldn't have slop and the gear oil should be clean not full of metal shavings.

 

[Anonymous]

that is a start... if these turn out to all be the 7.5 what vehicle should i look for to find a suitable 8.5 rear?

also, what (visually) is the difference between the 7.5 and the 8.5 so i can identify them easily?

 

[t5montecarlo]

The rear gear is likley 2.29:1 or 2.41:1. If you are really lucky, you may find 2.14:1. The El Camino likely came with 2.56:1. Manual trans G bodies came with 2.73:1.

 

[kevind]

Grand Nationals have 8.5" the 8.5" have "ears on the bottom" someone probably has a pic of one.

 

[bigbadbu]

do they have overdrive? maybe 2004r the 8.5 has triangles on the bottom of the pumpkin, the 7.5 has hooks.

 

[Anonymous]

I have determined the difference between the 7.5 and 8.5 after a little searching. Ill have to check the donor cars im looking at. though it doesnt sound good for getting anything other than a 7.5".

Now, with my plans for a mild 350 and used for some spirited street driving. will the 7.5 hold up till i get some funds built up for something that can handle the power?

I will deffinately be finding a 350 trans to replace my 200 boat anchor in the car now.

 

[Anonymous]

Normally a non-SS monte will come with a 273 open rear in the 7.5 size. A SS monte will have the 7.5 also but with the limited slip (tag will be on one of the rear diff cover bolts) and will sport the 373 gear. I have run a 7.5 in my 88 LS alky motor door car and was able to do so for almost 2 years running flat 11.00. Granted I am not whacking it with a brake just foot brake only. Now the rear did grenade at the track but I abused the bologna out of it. Prior to that is was in a 11.40 Bu and had over 100 passes on it then. I would not have a problem using it in a mild 350 car as long as you had no real serious power adders. As far as the 8.5 goes that is what I have now with Moser internals. Super strong rear and can handle alot of abuse. Hope this helps.

 

[Anonymous]

You should look for the Monte SS rear spoken of. 1984-1987 I believe.

You won't find anything decent in the year range you are speaking of.

And if you are going to run the 3:73 gear that is in that posi rear, you might as well pick up the 2004R transmission that should be in it as well. It won't work out well with a 350T if you want to cruise above 55 mph and not turn the sh*t out of the motor. You'll need the OD.

The way I came about mine (for elcamino) was to purchase an SS some boy tried to wrapped around a tree. Took the entire drivetrain (including a 350 crate engine) and suspension as a donor.

 

[lilbowtie]

"81"
Where are you located - I have a 3:73 Posi I might part with. (7.5)