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Discussion Starter · #1 ·
Hi everyone, I building a 8.5 inch 10-bolt. I'm planning the following:

73 Nova Axle - $100
Rebuild Kit from Richmond Gear (their "mega kit") - $130
30-spline cone type posi from 1993 Buick Roadmaster in junk yard - $50
Keeping original 2.73 gears since I'm planning on 6L80E in future - $0
Moser 30-spline 8.5 axles www.summitracing.com/parts/MSR-A103002/ - $250
Hotchkis 3" drop springs - already installed

I'm hoping to have 400-450 horsepower someday. : )

I've heard the u-joint is different, is there an easy fix? And I know Ill need to shorten the driveshaft. I already have U-bolts for the leaf springs. I'm doing the rebuild with a buddy who's done a few. Plan to use existing shims from the pinion. What about the moser axles, has anyone had a bad experience with them?

Oh, and I should mention, Im saving money to buy a house so Im a cheap a$$ right now! : ) And as you may know from y other posts Im not a big fan of aftermarket stuff, I avoid it when there is an OEM option.

Looking for tips from anyone who may have done this swap already?

Thanks
 

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That trans is an overdrive unit and with a high rear gear that you are planning on it just isn't going to work real well imo. Not in overdrive anyway.

You may want to look into a 3.42 or 3.55 rear gear with that trans, in overdrive it will effectively be similar to the 2.73 final drive tou have now.
 

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Discussion Starter · #3 ·
I'm using the 2006 Corvette as my ratio target. See the chart below. DUe to the ultra low 4:1 first gear in the 6L80E running a 3.42 would be like having a 5.47 rear axle ratio with my TH350. I'd rather have a useless 6th gear than a useless 1st gear!

But seriously tho, if you look at the corvette and what Im planning its almost exactly the same. The 2006 corvette has the same trans and actually uses a 2.56 rear axle ratio!! With an optional 2.73 in the performance package.

 

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Wow, that is a heavy trans.

You will need to have a good torque converter, probably a lock up unit I would guess, and an engine that makes some good low end torque. Probably on EFI too.
 

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Look in the latest issue of Car Craft, March?
The issue with a '72 Chevelle on the cover
They show how to re-gear a 8.5 axle.
 

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I've built more of the 8.5 rear ends that I can count. Don't use the Richmond kit. The shims are junk and some of the other parts also may not be as good as they should be. DTS, Randy's Ring & Pinion and Tom's Differentials have much better kits. Don't use the Auburn from the Road Master. A new Auburn is junk and a used one is just scrap metal. Get a Eaton Posi or Duragrip. The Moser axles are a good choice. The 2.73 gears are not a good choice. Use a 3.42 with over drive. I know that you are looking at Vette ratios, but if your engine doesn't have the same torque curve as the Vette engine then you will ne very unhappy with it. Use a 200 4R or 700R4 transmission. They are much better choices for what you are building. The '73 Nova would have the 1310 u joint, same as what you already have. The drive shaft may need to be shortened about an inch, but if you use the transmission that you are looking at then the drive shaft is going to be completely wrong. I recommend the 200 4R for the size, ease of installation and gear ratios.
 

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Listen to Freddie :yes:

He helped me with 2 over the internet (pics and e-mails) he knows his sheet ;)

Both turned out great :D
 

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X2 ^^^

I used an Eaton posi, 30 spline, the Moser axles but for the weld on Moser ford bearing ends to eliminate the C clip axles, and I forget who's install kit, Strange maybe. It had decent parts.

I used and 8.5 from a 73 Nova in mine too, and the 1310 U joint yoke (what should be like your stock one) and the driveline fit right in. The 3R yoke for the newer 8.5 is different and seems like it requires the driveshaft to be shortened. Either way the only way you'll know for sure is by checking, too many variables.
 

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General advice -- listen to Freddie :)

Auburn posi is junk -- not rebuildable, used one likely worn out. I also think a 2.73 with any kind of overdrive will keep your revs so low that the engine won't like it. Given the time/$ it would take to set up the 2.73 with a new posi, I'd just keep the 2.73 open rear in there until you get the trans and sort out if that's what you REALLY want, but I hate doing things twice...

Eaton or detroit TrueTrac get my vote for limited slip diffs.

'73 Nova rear should have a 1310 U-joint (same as your 8.2"). I think they changed to the 3R in '76 or so, but not completely sure. As you mentioned, you will need to shorten driveshaft. If it IS a 3R, you can use a conversion U-joint (1310 on one end, 3R on the other). I think you'd be better off converting the driveshaft to the 3R, but maybe you want to wait until after you swap out the trans too.

You'll need "something" to use as a spacer between the Hotchkis leafs and the multi-leaf spring perch. I think Hotchkis may supply you with some steel plates if you talk to them OR you can use lowering blocks to take up the space.

Stock mono-leaf lower spring/shock plates will fit, but you may have shock/wheel clearance issues. If you do, you'll need to get the multi-leaf plates -- Detroit Speed plates are recommended (fit better than the repros)

Are the "aftermarket" 30-spline axles and "stock" Auburn posi the same size/profile?
 

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Are the "aftermarket" 30-spline axles and "stock" Auburn posi the same size/profile?
Moser makes 30 spline 8.5 axles that don't have to be modified. All of the others must be modified to get the c clips to fit.
 

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Something else... take a good look at the trans yoke before having the driveshaft shortened. If there are grooves worn in it, even a new seal won't keep fluid from leaking out of the transmission tail shaft.
Ask me how I know.
;)
 

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Discussion Starter · #12 ·
Thanks everyone.

I'm using the used posi from the Roadmaster cause it was $50 bucks at the junkyard. Like I said, I'm doing this on the ultra cheap. And if its good enough for Buick!! ; )

The whole axle gonna cost around $500 when said and done. So if its got a crappy posi thats fine, my camaro is not a racecar, or a drag car. Ive got a modern sports car in the Boxster S and a 2007 CBR600RR for racing and track days. Camaro is my cruiser, that's why it has an automatic. I would never ever buy an auto anything normally, but I bought the camaro when I was 15 and didn't know any better.

Im planning at modern L92 with the trans down the road so the 2.73 should be ok. And Im running small diameter tires so that will help too. I just cant put a 4-speed auto in the car. Its so 1980! : )
 

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I think you are going to be sorry that you used the Auburn, but if that's your only option then go for it. Sometimes something cheap ends up costing more in the long run. When you have to disassemlbe the whole rear end to clean out all of the powdered metal from the Auburn and replace all of the bearings you may wish that you had used something else.
 

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I think you are going to be sorry that you used the Auburn, but if that's your only option then go for it. Sometimes something cheap ends up costing more in the long run. When you have to disassemlbe the whole rear end to clean out all of the powdered metal from the Auburn and replace all of the bearings you may wish that you had used something else.
Listen to Freddie! :D:thumbsup:

Mike
 
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