9" axle shaft flexing? what now

So I have a big bearing 9" presumably from an early 60's truck. Wanted to run the old 1946 20" fire truck wheels I had on it so I modified them to fit a ford center. Wheels ended up having to have alot of negative back spacing (mounting surface is behind the wheel, they stick way out). Tires are 9 20's about 40" tall 8" wide, wheels rather heavy. When the weight of the truck is on the suspension the wheels show negative camber ( a lot). Jack it up and they are parallel. Bearings are good, no end play or up and down movement of any kind. They are sealed bearings not the tapered kind. I have a spartan locker, splines seem good, can't hear anything sloppy moving in the 3rd member as i let weight of the truck down and the wheels tilt in.

I confirmed it is the axle flange moving, not the Drum, rim, tire or combo of those things. Also if I mount the wheels backwards the problem is revers (wheels show positive camber).

Question is: are the axles so week they flex in the tube between the bearing and splines, can the heavily offset wheels and 40" tires actually be enough to flex them? I thought these were supposed to be tough!

Disappointed as the truck is about ready to drive. Never thought the 9" would be a problem like this so everything is measured up to look right with this rear end....poop.

 

Sounds to me like your modified wheel are flexing in the center. Can you post some pics of the wheels showing how they were modified?

 

The truck is in my avatar, here are some photos of the wheels on backwards for comparison. I got to tired to flip them back around tonight. Tough to see at these short distances but the bottom of the wheels are much close together than the tops. To make it tougher the floor is sloped to the left and the dam file keeps uploading upside down.

 

Easier on the brain right side up. I don't know how the axle could flex just sitting there. Think of the abuse 9" axles go through on off road trucks.

 

Wow that was fast. I will get more photos when I get the wheels off again. The ford centers are welded on the 20" wheels bud wheels. They have pretty heavy gussets from 5/16 plate. I can actually measure the flange moving in relation to the backing plate, heck you can see it with your eye and feel it by hand.

Believe me, I was hoping it was the wheels, or bent drums, something not seating right, or bearings but I am sure it's not those things.

Hoping someone has tried something like this and can tell me first hand if I just have to much leverage on axle flange or if certain 9" axles will flex in the tube.

 

Sure sounds to me like the bearing is loose in the housing. Seems like the axles couldn't flex inside the housing unless the bearing was able to twist slightly in the housing end?

I think it's that, or the wheels flexing.

 

Man, that's some traction!

If you jack it up by the center of the diff, then lightly touch the tires to the ground, mark a like at the outside of the tread, and let it down all the way, if the tires move out you should see it at the line. Then roll it forward. Like when you jack up an independent suspension car and let it down, the wheels are still tucked in until it rolls.

 

What kind of suspension set up you running?

 

Have you looked, closely, at the welds where the axle tubes go into the center housing? Any sign of things moving around there?

 

Well to begin with the 9 inch u have is a lite duty. What spline are the axles? I will bet they are 28 spline and very spinley, unlike the 31 spline also u need a heavy duty housing. Looks like your truck is HEAVY!

 

A ford 9" in a pu will handle around 3500# loaded to the max...I know there can be [should be] some camber change but the amount you are getting especially when you turn the wheels around is not normal...

 

I think you will have to find a full-floating axle rear that was made for dual wheels.

 

There are several 9" housings with different axle tubes. You have the weakest of the bunch. The best fix would be to get a heavy duty unit with the thick tubes. Next and probably easiest would be to get the girdle or brace made to be welded on to your housing that ties both sides together and really stiffens it up. Currie and others sell them ready to weld but you can make your own with a cardboard template. Take your time and weld short sections at a time or the housing will twist like a pretzel.

 

40" is a lot of tire for a stock 9". Especially with the odd offset. Big tires tend to break the factory axles just outside the wheel bearing. Step up to chromoly 31 spline shafts. With aftermarket shafts and a trussed housing, the center section becomes the weak point, and it's time to upgrade to a nodular center.

 

Well the original thought was to use a medium duty axle but my neighbor gave me this one cheap and I thought all 9's were pretty stout.

This is a 28 spline axle. I posted some pictures using a yellow pencil line on the backing plate as a ref. the drum is tight and again no end play at all. Both sides are the same.

After the last few posts (thanks everyone) I was convinced the axles are to weak but wanted to finish with the pics in case someone else need the info.

So I'm looking for a full floating rear with posi, anyone need a wimpy 9 with spartain locker.

 

Here it is with the weight off the wheel

 

And a pick of the wheel modification.

 

curious.....how much does this thing weight?

 

Not sure of the weight, I would guess 5800 or so (judging by feel on my flat bed). Distributed close to 50/50. Little more on the front axle.

 

heres the 9'' i built for my henry j. heavy housing with the back brace.. with the tire height and weight combined with the leverage caused by the offset ,a much larger axle should be used..

 

I'd surely be looking for a full floater, and the dually axle should be shorter.
That will put you into 8 lugs. Most of those are at least 373 lockers and plenty of 4.10s out there.

There's some math involved but that big offset on a huge tire is increasing the leverage quite a bit and that is what's bending the axle. Those wheels and tires need at least a one ton suspension theory, and that includes the front if you are running the same wt combo up there.

 

Those small, thin tube 9" housings will flex without being braced. You really need a floater rearend.

 

I find it really hard to believe that the axle/housing is flexing. I do find it easy to believe that the wheel assembly contraption is flexing.

 

What's going on in the center of those wheels?

 

The first picture that Relic Stew posted is what you can expect with your set up. You need a floater.
An 8 lug set up out of a 3/4 or 1 ton truck is an option.
If you want to stick with a 9" look for a used floater from a stock car. They often have allot of offset so you might need to change one tube and axle. The market got flooded with 9" floaters a few years ago when the UMP modifieds switched to QC.

 

I'm thinking that when it is sitting on the ground the rearend has no clue as to what tire combo is bolted to it nor does it know how much the tire weighs...the tires are sitting on the ground and the axle is supporting just the chassis - just like every other 9" rear. It has no clue as to what is bolted to it.
Now, if you raise the car off the ground and then the tires go into weird camber then the problem is rear end flex because the rear is supporting the weight of the tires etc.

 

Take a 28 spine axle and mount to a bench, supported at the bearing surface and splined end. Put a dial indicator on the center of the shaft and another parallel to the axle on the flange.

Now bolt a offset bar on the flange, it should be 20" past center and same offset looks like 8" or so. Put a 1450# load 90* thru the axle and see if it flexes on the indicators . (5800/2) /2 = 1450.

In the pic with yellow pencil line,(post 15&16) looks like the movement is just over the thickness of the line at 5" past center. Multiply that x 4 to see the movement at 20" past center or the 40" OD tire.

Not that it couldn't be in the bearings because those are the littlest 9" bearings out there, but its the leverage of the offset . Try some zero offset rims and watch it be greatly diminished. Or mount them up dually style and the load will be even and no camber change. ( also a zero offset) I also think that the particular housing is overloaded at nearly 3000 lbs

 

Is that a Sterling cab?

 

Wow two pages on a RR without being hated into submission, ARE YOU GUYS AWAKE?

 

Well, I have a couple of observations........

1. My first thought was Rat Rod and I am amazed no one has raised that issue here, given the usual reactions to "non-conventional", non-Traditional Builds

2. Since #1 didnt negate the thread......I also athought that this needs a heavier housing, i.e. full floater

3. Even if the axles/housing were up to the loads, the grafted in wheel center is most certainly not. I would expect that welded in center to fracture very soon in regular use.

4. This is one of the most poorly engineered contraptions to show up on the HAMB in some time....... sprung to unsprung weight ratio being absurd, brakes wholly inadequate for the wheel size and total weight of the ahhh, errrr, "vehicle", just to name two that scream out from the pics.

Putting a HD fullfloater may solve the axle/housing issue, and improve the REAR brakes some, but at the expense of even worse sprung/unsprung ratio.

5. edit: Rotten Leonard is more succinct than I am and/or types faster


Ray