Winter Project - Rear End Conversion

SCrazy

SCCoA Member
So after breaking yet another half shaft at the Shootout I am now convinced that I need to convert the IRS to solid axle. My problem is I have never done this before and have so many questions I'm not even sure where to begin.

What size tire to run? Currently running 28"x10" is there any need to think about 11" or 12" wide tires or is that simply too much tire. Can an 11" or 12" tire fit in the stock wheel well with the shock mount removed. Also most 11 or 12" tires are 29" tall not 28"

What size wheel to run. I'm thinking 15"x10" unless I go to 12" tire then I might need to go wider also going to run 5x4.5" bolt pattern. No clue on backspace, I guess I'll need to mock something up and do some measuring.

What size breaks will fit under a 15" wheel? Seems like 12.5" rotors is pretty standard but I can't really tell what size wheels they fit.

Axle housings...do I buy new made to order or get an Explorer rear end and modify it? Housing ends would need to be replaced with 9" ends for oversized bearings...but lot of measuring to figure out the overall width. 3" tube diameter seems to be pretty standards.

Axles......How many splines makes sense 28, 31, 33, 35 how the hell do I know. Gun drilled, lightened flanges, stud diameter, hardened, etc, etc.

Springs & Shocks.....absolutely no clue here

Ladder bars.....is the Jegs special ladder bar kit OK or should I be looking at something like Chris Alston stuff.

Which cross member to use....2"x3" box or tubular.

Heck these are just questions about components never mind setting up and installing all of this crap. Sure would be nice if there was a list of "this stuff works well together" to use as at least a baseline to start from.

My head hurts..................

Edit:

I am going to update this first post with the products I decide to go with and their associated costs.

Wheels: Weld Alumastar 2 15x10 with 5" backspace and 5x4.5" bolt pattern (Jegs $933.95 including lugs and stems)
Tires: Hoosier Drag Slick 28"x10.5" stiff sidewall (Summit $438.94)
8.8" Rear End Housing: Currie 53.5" with Big Ford housing ends (Currie $650 + shipping)
Axles & Spool: Moser 35-spline, gun drilled, star flange with bearings (Moser $812.00)
Differential Support Cover: LPW (Summit $150)
Disc Break Kit & Break Lines: Wilwood 140-0261-BD (Summit $506.89 + $59.95)
3.73 Gears, Pinion Yoke, Bearing and Misc stuff to set up Rear end including pinion depth gauge: (Summit $543.70)
QuarterMax Ladder Bar Rear Suspension Kit Incl Strange Double Adj Shocks, Strings and 2x3 Cross Member: (RJ Race Cars $1270.98)
Billet Pinion Yoke & Transmission Yoke: (Mark Williams $618.00)
4" Aluminum Driveshaft: (Precision Shaft Technologies $400.00)
Assorted Crap estimated $1,000.00
 
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I don't know the answers (or even want to!), but I think Kevin Leitem may be a good person to ask. He has been running a solid axle for quite a while now, if I remember correctly.
 
Sounds like you are over thinking alot of stuff.

I can give you my experiences with the marauder.

4200 lb car 31 spline axles stock studs 28x10x16 hoosier drag on 9.5 rim best of 1.41 60's launching at 2200 rpm and 10lbs of boost. Not breaking anything here.
 
We all know that 3 people on this board have done it, Kevin, Casey and Mike Siska, I'd consult one of them.
 
Here are some pics I swiped years ago from here with the intent of performing this upgrade as well. I think most are from Kevin's car. I'd love to see more pics and gather more info if anyone has any...
 

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I've spent the last couple of weeks trying to make some initial decisions.

It seemed to make the most sense to start with Wheels/Tires then once I had those in hand I could make actual measurements for rear end width.

I'm going to order a set of 15x10 5"bs 5x4.5" bolt pattern Weld Alumastar 2 wheels and mount 28"x10.5" stiff sidewall Hoosier slicks on them.

The stock rear end width from the faces of the hub flanges is 62.5", my initial thought is that the new rear will be in the neighborhood of 6" narrower than that but I'll make that determination once I'm able to set the wheels in place.

Currie builds 8.8" axle housings to order so I am going to go that route with 35-spine axles and 3.25" axle tubes.

Not much else to do but strip out the old stuff until the wheels show up.
 

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try Art Morrison

They used to have a back half kit for the birds at one time. I did one and was happy till the rest of the car twisted up.. Their setup came with a 9" rear and 35 spline axles. They also had a disc brake set up as well.
The nice thing about the kit is that everything is pre set and you don't have to go crazy marking and cutting for weeks and have to use a dozen bottles of Advil to kill the pain.. Give them a hit and see if they still will put one together for you.....Rich
 
New wheels and tires are in and mounted.

Now I can make some rear width measurements and get the housing and axles ordered.
 

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Rear end width measurement

I set the tires so that the tire bulge was 1/2" inside the inner fender lip and came up with a measurement of 55-1/2" from wheel to wheel.

I'm going to allow 1/2" each side for rotor thickness and 1/2" each side for a wheel spacer which will allow me some fudge factor for potential future wider tires.

I wind up with a final rear end width from axle flange to axle flange of 53-1/2".

Does that make sense??
 
Rear end width measurement

I set the tires so that the tire bulge was 1/2" inside the inner fender lip and came up with a measurement of 55-1/2" from wheel to wheel.

I'm going to allow 1/2" each side for rotor thickness and 1/2" each side for a wheel spacer which will allow me some fudge factor for potential future wider tires.

I wind up with a final rear end width from axle flange to axle flange of 53-1/2".

Does that make sense??


Your making it awful hard to keep up with you. Always feel you and Neibert are miles ahead of me performance wise. Going to have to look into a booster rocket.

Ken
 
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