Swapping rearends

[CamaroAdam73]

I got an opportunity to swap the rear in my Monte with an 8.5", right now i've got a 7.5" stock rear with 3.73's

My friend wants to trade me my rear for one of his. He's got about 20, no sh*t. I want to lower my rear gears so that's one reason i want to do this swap. Like i said i've got 3.73's but i would like closer to a 3.0 in the rear, maybe even one of the HIGH two sets ( aren't they like 2.73's or something similar?)

So my question is, is it worth it? Are the 8.5"s that much stronger/better than the 7.5" rear ends?

 

[Blue86Monte]

Simple answer, Yes.

 

[-83MONTESS-]

The going rate for the 8.5s compared to the 7.5s alone would make me wanna do the swap other than the fact it's a direct swap. Plus if you had to sell the car someday the 8.5 is a definate plus to a GM or Gbody enthusiast that knows what an 8.5 is.

 

[timo22]

This is a slam dunk.. You will have to get your driveshaft shortened, but it is a major upgrade! Lucky dog!

 

[CamaroAdam73]

Sweet! I just hope one of them is a posi. I'm getting the chassis up on stands today to get it ready for a full teardown, i'll hopefully be dropping the rear end out. I've got two driveshafts, one from the 79 Trans am that the 403 came from, and the other was in the Monte carlo when i had a 700R4 in it, how much do you have to cut the shaft down?

 

[CamaroAdam73]

So the deal gets even better, bout time karma cut me some slack.... So the rear end i'm getting is a posi 8.5" geared at 2.70 something and it originally came out of a 78 buick regal with the 3.8L turbocharged motor. He's still got the motor/trans but the car was demo-ed.

Just got off the phone with comp cams, it's a no go. Going from 3.73 down to 2.73 will bog the motor too hard. I figured as much, this isn't a deal breaker though, Where can i hunt down a set of 3.73 gears for the 8.5" ? I mean, other than that the upgrade is essentially free....

 

[jrm81bu]

So the deal gets even better, bout time karma cut me some slack.... So the rear end i'm getting is a posi 8.5" geared at 2.70 something and it originally came out of a 78 buick regal with the 3.8L turbocharged motor. He's still got the motor/trans but the car was demo-ed.
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I'd be absolutely sure it's an 8.5 and from a g-body not a-body before you do anything. The car you listed did not come with an 8.5. And with those gears i'd be more inclined to think it came from a 77 and earlier a-body.

 

[CamaroAdam73]

Yeah i'm only going by his word on that, i'll deff run numbers and what not before i pick it up. We're pulling the cover back off again to check everything. It is for certain a posi rear end though, whenever my buddy gets ahold of good parts like this he doesn't run them in the demo. He would rather get a 7 1/2" rear posi, or weld the gears than trash a sought after part.

And that's the reason why he has a literall PILE of big blocks lol.

Anyhow, gotta hunt down a set of 3.73's for an 8.5 because i'm not passing up this opportunity.

 

[CamaroAdam73]

Alright got the rear, still havn't torn it down to count splines and what not.

I'm looking at gear sets on summit, they arn't as bad in price as i thought so i don't know why i was even looking for a used set 😛 , Anybody on here ever use the SUMMIT brand gears?? I know they're a pretty trustworthy brand with other parts.

 

[ham1974]

You will need a ring gear spacer to go up to a lower gear. I am not an expert but someone else should know1