Axle width questions. Please help me with my math

[johnsonbz]

Ok, so i think I have convinced myself to go with 5.38 gears....only 500 RPM difference. LINK

Now it comes down to axels that can reliably support those 5.38 gears, and fit in my 04 LJ with a selectable locker.

Recently I am very intrigued by a 9.5 SF 14 bolt (67.5 WMS) that has popped up here on RME.... I have done my best first shot at the math:



(I had to do a screen shot as the formatting in this message was taking too much time.)

Please help validate my numbers.... I think I understand backspacing in this image, but I am very unclear on how setback plays into this picture.

Also, is 67.5" considered "full-size"? Should I be worried about finding 6 lug rims with ~5" backspacing?

What about narrowing the axel? is that an option on the 9.5 SF 14 bolt?

Front axle options are next. Seems like the dana 60 front and 14 bolt FF rears are the goto choices, but I really like the smaller lighter 14 bolt. Any thoughts?

 

[Tacoma]

67.5 is definitely full-width, full-size, whatever. Since SF 14's were only available on fullsize GM products, there is no debate on that.

Stock GM rims are pretty close to a 5" backspacing if I recall-- maybe not quite 5, but close. Toyota, Nissan, etc also used 6-lug rims and there are several interchange lists online for what rims used whatever bolt pattern.

Narrowing an SF 14 would be more cost than it's worth, IMHO, and require custom shafts.

I wouldn't put a 14 bolt into a JK, personally. Twin 60s, with a FF in the back, would probably be enough unless you're killing it on the trail. 14 bolts are great but large, and if you don't need the strength there's no reason to run it, same with the front 60.

Evaluate your driving style and planned future upgrades to this Jeep. An upgraded 44 may suffice, and weighs less. If not, balljoint 60's are out there for not a lot of money and there are a TON of upgrades.

 

[bobdog]

What width axle do you want? For full width FF I don't see a more cost effective rear than a 14 bolt. I would not be looking at FF 60s as they are going to be 30 spline. SF 60s may be perfect for you as most are 35 spline. If running 5.38s I would want to run the 10.5 inch 14 bolt not the smaller SF 14. The larger the pinion gear the better. Ford 9" may be worth looking into.

 

[leorn]

I believe the tacoma 5-spoke aluminum wheels are 5" bs. FJ cruiser should be as well. Going off memory, so double check me. I run the 5 spoke on my 85 4runner and they have taken a beating with 39 iroks on them.

 

[thenag]

What width axle do you want? For full width FF I don't see a more cost effective rear than a 14 bolt. I would not be looking at FF 60s as they are going to be 30 spline. SF 60s may be perfect for you as most are 35 spline. If running 5.38s I would want to run the 10.5 inch 14 bolt not the smaller SF 14. The larger the pinion gear the better. Ford 9" may be worth looking into.

I totally agree, I don't see any reason to run a gm SF 9.5 axle on anything.

Remember that the only cons on the FF 14 bolt is the size of diff, and weight. Every other category it is great, or fantastic.

The typical single rear wheel FF 14 bolt is 67.5 and can be narrowed to 63.5 by using the hubs from a dully axle.

I think you have a more difficult time figuring out what to do with the front axle, then decide on the rear.

Nathan