Heres a questions that has bothered me for sometime now about the good ol' 9 incher. Here it is: What is the biggest possible tire that can be ran on a 9 inch rearend? I don't mean tire size limited by a weak front end but just the 9 incher alone.

 

Cody,
Do you guys get "Street Rodder" on the Speed Channel on TV up there? Reason I ask: I've seen hundreds of mild-to-wild hot rods (trucks, cars) with Ford 9" rear ends (it's kind of the "gotta have" rear end, especially for muscle cars). They run everything from OEM tires/rims to full-blown race slicks. Basically, when it comes to the Ford 9" rearend.... if it fits on the hub and under the car, with the right gears, the Ford 9" will turn it.
Daryl
'59 F100/"bully" 302/AOD/9" with 3.50 gears..

 

Yes we do get hot rodder and all of those showsup here. I was just wondering cause in offroading i've never seen really anything all that big for tire sizes (37" is the biggest i've really ever seen) and i was just wondering cause i always see people swap something else in for the 9 inch in offroading.

 

Fine nine problems are usually too much weight, or two high of gears.

After market parts are cheap to. (expect 3rd members)

 

The 9" is not incredibly strong but is very good for a half ton. There are different models but if you're referring to the standard 1/2 ton 4x4 31 spline 9 inch then you should be ok with 35 or 36 inch tires under pretty tough conditions. You can run any tire you want if it's not hard wheeling.

I've torn up a couple with 38's.

 

35s - four wheeler recommended up to 38s, but, I think that is too big. 35s with an axle truss should handle about anything you throw at the 9 inch. You can run huge tires on the street because there is not much axle shaft deflection, the wheels are on the ground all the time.

 

My question is, how much can a nodular 9" withstand? Nodular 9" as in nodular iron bearing caps with reinforced carrier ribbing, thicker pinion shaft, w/31 spline axles. I've heard these carriers withstand up to 1000hp on drag cars without a problem. I sure paid a pretty penny for it.

 

That Nodular 9" is a powerful beast. Those are great rearends. The limiting factor with that setup will probably be the axles. Buy good aftermarket axles and it should hold up to 38 or 40" tires without much trouble. Just don't go super low with the gears or the ring and pinion will be your weak spot.

 

Are richmond 4.10's to low? The axles are ford 31 spline with no tapers. Are they known for weak spots? So far the 9" has seen ~400hp, and seems to be doing quite well. The clutch pack is still pretty tight.

 

> The limiting factor with that setup

imo

Axle case deflection with a wheel in the air is the limiting factor, not the 3rd member. Get a five to six foot straight edge (aluminum like they use for roofing) and tape it to one side of the axle so it lines up even with the bottom of the opposite tube.

Now jack up your truck near the center section (right on the edge) and see how much the housing droops downward. The extra weight of 38s, plus spinning them hard, plus the droop is what will kill the 9 inch and is the limiting factor. Not the 3rd member. There is a BIG difference in weight and spinning a tire with a wheel in the air between 35s and 38s.