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Rear end swap (gbody)

11K views 71 replies 10 participants last post by  64nailhead 
#1 · (Edited)
Hello all
I' have a 79 Monte that I'm wanting a little more fun with. It's an all stock 305 with th350 and 2.73 gears (7.5) rear. I have a few other upgrades in mind but this I kinda want to do this first. It'll be a kinda mild build for now. Anyway I recently pulled a 3 series carrier from an 84 s10 to replace my 2 series. I couldn't get the damn pinion gear out though. It would have been a 3.73 ring and pinion set. I was thinking the 3.73 might be a little to much anyway for my 3 speed trans. I don't really do any highway driving at all though so I'm not totally against it. So what would be a good ratio? If not the 3.73 i was thinking 3.42 maybe. I'm looking to smell some burnt rubber and have some better off the line performance.

Other upgrades so far will be:

Eddy intake
Headers with 2.5 exhaust
Transgo shift kit
Carb
 
#2 ·
The 3.42 gear makes a real nice all-around gear for street performance driving.

I ran 3.31 in my Nova for several years of cruising and car shows and it was a real comfortable gear, not too much on the highway at 70 mph and still able to burn rubber when I felt like it.....Only reason I took it out is I got hooked on racing it.
 
#4 ·
The S10 had to differentials, the standard differential and the Eaton Governor Lock. Neither one is any good for a performance car. The standard differential will just spin one wheel and the Governor Lock is weak and will break if abused. If I were you I would invest in a Yukon Dura Grip, a set of 3.42 gears and a USA Standard installation kit from Quick Performance. You can get the whole package for about $550 and you will be avoiding all of the headaches from trying to set up a used set of gears, finding shims that will work, getting all of the small parts needed for the gear instalation and the problems that will come from the S10 differential.
 
#5 ·
There are special thick gears for the 7.5 rear end that fit the 2 series differential. They only cost slightly more than the standard gears. Using a ring gear spacer is a very bad idea in the 7.5 rear end. It's not a good idea in any rear end, but it's even worse in the 7.5. As for the F body differentials, they were all Auburns from '82 to '97. A used Auburn is also a bad idea. The Auburn isn't good when new, and used it a total waste of time and money. 35 years in the rear end business has taught me a few things, and with the 7.5 rear end you are better off to avoid any of the factory installed differentials except the '98 to '02 Torsen. It's the only one worth messing with, and they are all for 28 spline axles only. All of the G body 7.5 rear ends had 26 spline axles, so you would have to get a new set of after market 28 spline axles to work with the 28 spline Torsen.
 
#10 ·
Thanks for all the advice guys, I appreciate it. The quick performance set up seems great but I still can't really afford it at the moment. I might save for it and go back to the junk yard for that Pinon. I don't mind 1 tire fire for now. At least I'll have a series 3 over a 2. But man going to the 28 spline torsen sounds OK too. Seen 1 on ebay for 300 and I think jegs has 28 spline axes for about 250. So either way it's about the same price.
 
#15 ·
There is a part that some people call a paddle that goes between the axles and holds them in place after the c clips are installed. Somehow this gets lost in a lot of JYs when they pull these out. I've seen several people on different web sights that were trying to find a replacement to go in a Torsen that they had bought on ebay.
 
#17 ·
What's your location? My son's old MCSS has been rusting away in my yard for over 10 years now and he may be willing to part out the 8.5" GN rear axle from it. It was an open rear, but now has a LockRite locker installed with the factory 3.42 gears. It would have to be picked up from SETX...

Russ
 
#26 ·
Well I went through with the purchase. Hopefully it's not a big regret. Should be shipping out tomorrow. I talked to the guy a few different times and everything seems good to go. it just seems like a steal of a deal, so that worries me. Someone tell me it's going to be ok. Haha
 
#27 ·
My rule of thumb for buying used performance parts on EBAY, Craigslist, etc is 1/2 to 1/3 of new cost.
If they want more than that, forget it, it's too big a risk.
I don't care if it was new yesterday, if you used it, price drops.....I'm not paying top price for a used item and not getting warrantee and customer support.....If seller wants too much I'll just go ahead and buy new.

I'd say you got it right on the expected used cost, 1/3 of new :thumbup:
 
#31 ·
I'm thinking so. Don't really care for the idea of 3.23. And there's a chip or 2 on the pinion head. 3.42 or 3.73. Just got it today. Please, let me know what you guys think. From what I looked up I think it's actually a 98 not an 01.
 

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#32 ·
The chipping on the pinion gear won't be any issue as long as it isn't into the contact pattern of the gear set.

Not sure why they sent you the main caps off the rear housing the parts were out of....main caps stay with the housing, just like engine main caps stay with the engine block. You won't need the ones they sent you.

You might try the 3.23 gears, they are still a big improvement from anything in the 2's and you might find you like them.....they are tight there in front of you, won't cost much to give them a shot.
 
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