Narrowing 12-bolt Rear

[2fast4u]

Just finished mini-tubbing my 67 Firebird and need to shorten a 12 bolt rear to accommodate 335/30/18 tires on a 18x12 rim. Do I need to shorten and re-spline the axles or BUY SHORTER housing axles???

Who sells them and how much do they cost???

How much should I expect to pay a shop to do this???

Thanks, chris

[diffdude]

It should cost about 150-200 to shorten the housing. You should get the housing narowed before you order axles so you get the correct length. Call moser or dutchman for custom length axles.

[rkw1969]

whats involved when shortening the tubes? can a guy do this at home?

[diffdude]

You need a jig so the axle bearing to the carrier bore is perfectly straight.

[diffdude]

Something like this.

http://www.markwilliams.com/esell/prodinfo.asp?prodid=1683

[chicane67]

Now why is it that you have to shorten the housing and axles ??? You dont have to do anything except purchase your rims with the correct wheel backspacing. But then again, if you have already purchased your wheels.... I guess you'll use this as a learning experience.

If you have to shorten the housing, you may as well do the conversion to a 'press on style' axle bearing and housing ends. What is envolved in this is that you will have to purchase the axle kit, have the housing narrowed and then have the ends installed.....and then have the housing straightened once all of that is done.

The associated costs are about 200.00 for the housing being narrowed, the ends installed and then having the housing straightened. The axle kits will vary somewhere between 450.00 to 600. But do you home work on these as there are many with different attributes to choose from. My recommendation is to Mark Williams (http://www.markwilliams.com/pdfcat/pg9.pdf) . Now, this is pretty much the best your money can buy, by as you see by the associasted prices and what you are getting..... its pretty much a no brainer. That and nobody else but Sommers Brothers and the higher end Strange axles have near the quaility of Mark Williams for the price.

Can you do this at home ?? Well, unless you do this work often, I wouldnt recommend it unless you have a housing straightening fixture and the associated tooling for it stuffed in your garage somewhere and that you know how to use it.

The reason I dont recommend most of the others that people will tell you about, mainly company "M" and compnay "C". The axles you will be getting with their associated kits have axles that 'single point cut' splines. Which, is the weakest design in all concering spline cutting. Which is what company "M" and company "C" use specifically....... not to mention other reasons that will not be discussed in a forum as it would be better for PM at that point. If your gonna spend your money, and considering that the prices are going to be within a few dollars of each other, you may as well spend your money the best way you can. Differential work isnt cheap and you dont want to do it over and over again. The differential world and knowing what to use comes from years of experience and hands on work will all associated products on the market.

Depending on where you live Chris, I might be able to point you to someone in your neck of the woods that is reputable and can preform the associated work. The higher end differential world is close knit and we pretty much know who is capable of what.

But by all means, do your home work on this one. Your money is worth just that........

[BirdDrop]

Thanks for the responses. I basically knew the look, stance and wheel dish I wanted and chose to accomodate that by narrowing the rear-end, rather than choosing wheel backspacing to accomodate the rear end length. I knew that going into this.

[chicane67]

Having a shallow offset does look nice.......... no doubt about that.

[diffdude]

Your best bet is to sell your 12 bolt and buy a new one from moser. People pay alot of money for factory 12 bolts.

http://www.moserengineering.com/moser_interior/products.asp?CatID=28
The shop i work at we have seen all axle brands and for the money moser in the best.

[2fast4u]

How much would a posi 12 bolt rear with 3.73 and drum brakes go for??

DO you recommend a Moser 12-bolt rear over a Currie 9" rear-end for street/strip use???

Thanks, Chris

[MrQuick]

Is it an original Firebird set up or a Camaro unit that was transplanted. Do you know if the axles are non c clip? Please let me know. I agree Moser is the best bang for the buck.