'40 Ford rear housing assembly

[Bill]

A friend of mine is restoring my old '40 wagon and noticed one of the rear radius rods is bowed. Looks like someone tried to jack the car up on it. He wants to know if the bend will affect the alignment of the rear end. I told him I thought it would not. I'm relatively sure there is no adjustment on these rods they merely provide the geometry to keep the torque tube/ rear end ridged. He has it off the car so I told him to bend it straight and put it back on. Good advise or am I missing something? Bill

[Kube]

Originally Posted by Bill

A friend of mine is restoring my old '40 wagon and noticed one of the rear radius rods is bowed. Looks like someone tried to jack the car up on it. He wants to know if the bend will affect the alignment of the rear end. I told him I thought it would not. I'm relatively sure there is no adjustment on these rods they merely provide the geometry to keep the torque tube/ rear end ridged. He has it off the car so I told him to bend it straight and put it back on. Good advise or am I missing something? Bill

Bill, In my opinion it will effect the alignment of the rear. How much? That depends on the significance of the bend.
Think of it this way:
Three points (triangle) are made between the outer ends of each axle housing and the point where the radius rods attach.
By bending one of the rods, the length of that side of the "triangle" has been shortened (changed). That definitely changes the geometry.
My advice is to straighten that rod as best possible or get a replacement that has not been bent.

[Marvin/TN]

I agree with Kube.

[deuce_roadster]

What Kube says x3. The word Geometry says it all.

[drolston]

Let's do the math. If the radius rod were bent badly at mid length, like 2" out of line, that would only shorten the radius rod by .055". The radius rods are part of an iron triangle with the rear axel as the base and the torque tube as the center post. The reaction to that bend shortening one leg is contained entirely within the triangle, exerting no force to the frame that could cause a change in alignment with the frame. What you have is some stress within components of the triangle. When it comes time to take the rear end apart, you may have a bit of a problem getting the bolts out of the radius rods, because they are under some tension. Until then, drive on!

Bent radius rod on the front is another story, because the radius rods are hooked to the frame.

[JM 35 Sedan]

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I also agree that a bent/bowed radius rod will affect rear end alignment. Hold a piece of string taunt between your fingers of both hands. Have someone pull up on the center of the string and see if your hands remain the same distance apart.
I have a bent/bowed 35-36 rear radius rod on a 35 rear I'm putting back together. I'm planning to straighten it using my hydraulic press.

[ford38v8]

Tire wear and gas mileage will remain the same. Tracking will be slightly different, meaning that the rear tire tracks will not ride in the path of the front tires. Just think of watching a dog trotting along, rear end to one side or the other!

[V8COOPMAN]

Actually, the Pythagorean theorem is the mathematical equation that will tell the real story.....A²+B²=C². DD

[Kube]

Originally Posted by drolston

Let's do the math. If the radius rod were bent badly at mid length, like 2" out of line, that would only shorten the radius rod by .055". The radius rods are part of an iron triangle with the rear axel as the base and the torque tube as the center post. The reaction to that bend shortening one leg is contained entirely within the triangle, exerting no force to the frame that could cause a change in alignment with the frame. What you have is some stress within components of the triangle. When it comes time to take the rear end apart, you may have a bit of a problem getting the bolts out of the radius rods, because they are under some tension. Until then, drive on!

Bent radius rod on the front is another story, because the radius rods are hooked to the frame.

I tend to agree that the bent rod won't make too much difference but according to the initial post the rod is currently out of the car.
Probably an opportune time to correct the issue.
Me? I tend to prefer to do things correctly. It typically doesn't take a lot longer than rigging something together and making it "okay".

[40 Deluxe]

The torque tube is what aligns the rear end to the frame, not the radius rods. For a radius rod to affect alignment it would have to be bent so much that it would bend the axle housing (bell) on that side of the car. This would put the axle shaft out of alignment also and would likely eat itself up. In theory, it could maybe bend the torque tube and destroy the driveshaft bearing but the radius rod is the weak link in this 'triangle'. So, just drive on!

[Mart]

While not ideal, the bend should not really cause major rear end alignment and the car to "crab" down the road. the rear axle/torque tube is pretty strong and will hold good alignment, all centred around the torque tube being attached to the transmission on the car centreline.

The advise to remove the rod, straighten it, and refit it is (in my mind at least) good advice.

It's an early Ford, not a Lamborghini. The axle is pretty strong, the radius rods don't position it, they just protect the torque tube/axle connection from road shocks, for example when one wheel hits a pothole or obstruction.

Take it off, straighten it, or fit another one, and keep on trucking.

Mart.

Edit: Similar replies above added while I was typing.

[PeteVS]

One could possibly elongate the hole at the front of the bent radius rod to allow it to bolt onto the front of the torque tube without pulling things out of line. The bent radius rod would, however, lose a little bit of strength under a severe compression load. If that happened however, there would be a lot more damage elsewhere.

[cas3]

mart says it all, fix or replace, not rocket science

[rotorwrench]

The radius rods are basic braces triangulated to get most effective bracing. If they weren't there the torque tube and rear axle bells can flex more. How much they would flex I don't know but flex they will. A bent rod puts a pull on one side that shouldn't be there because it would force a little flex to the one side, A person wants those components to remain as straight and true as Ford intended them to be. It would mean less wear on parts and therefore longer life with better reliability.

A rear end out of alignment by even a little bit looks funny going down the road. Following from the rear, it looks like it is crabbing into the wind for those that fly. For those that don't, it just plain goes down the road crooked.

[Bill]

Thanks to all who replied. To be honest I didn't expect that much interest. As the radius rod has a long sweep rather than a kink we are going to straighten it. I'll take some pics of the event which should take place in the near future. Bill

[JM 35 Sedan]

Originally Posted by Bill

Thanks to all who replied. To be honest I didn't expect that much interest. As the radius rod has a long sweep rather than a kink we are going to straighten it. I'll take some pics of the event which should take place in the near future. Bill

Will be interested in seeing some pics of how you go about the straightening operation. I have been pondering ideas on how I will straighten mine, which also has a long sweeping bent over the full length of the radius rod. I believe this was also bent by someone jacking up the car from underneath the radius rod, or maybe they placed a jack stand uner the radius rod, and the weight of the car bent the rod.

[rotorwrench]

A person could start the job utilizing a fairly long piece of I-beam, several lengths of chain, and a jack. The same basic tools used to straighten a frame rail with some wood blocks or purpose made mandrels to keep from making marks on things..

[JM 35 Sedan]

Originally Posted by Bill

Thanks to all who replied. To be honest I didn't expect that much interest. As the radius rod has a long sweep rather than a kink we are going to straighten it. I'll take some pics of the event which should take place in the near future. Bill

Bill, did you ever straighten that rear radius rod and take some pictures to post here??

[V8COOPMAN]

Originally Posted by JM 35 Sedan

Bill, did you ever straighten that rear radius rod and take some pictures to post here??

JM....On 1-22-18, Bill posted that he and a bud straightened the radius rod by use of a floor jack and some chain. He said the event was over with in three minutes, and that the camera batteries were dead anyway! All supposedly went well. DD

[JM 35 Sedan]

Originally Posted by V8COOPMAN

JM....On 1-22-18, Bill posted that he and a bud straightened the radius rod by use of a floor jack and some chain. He said the event was over with in three minutes, and that the camera batteries were dead anyway! All supposedly went well. DD

Got it, thanks DD