MTFCA Forum

Bill Robinson posted recently that on his 1921, the axle was not centered in the torque tube. He later discovered by adjusting the radius rod, he could alter the position of the axle center, where as it had been previously not centered. This caused wear on the Hyatt cages and actual cut grooves in the axle shafts. This was after several years of service.
My issue was the same off centered axle, making it difficult to get the Hyatt installed without having to pound the bearing in position, something I have never had to do before on any axle rebuild.
I checked the axle housing to make certain it was straight. This is on a 27 rear end with a Ruckstell. The rear end was rebuilt about a year ago and had developed a noise while on tour in October, after ;less than 1,000 miles service.
This car has disc brakes and inspection of the rotor clearance was made to make sure the noise was not coming for the brake rotor rubbing the caliper mounting bracket. While there was clearance, one side was closer than the other, but not rubbing.
I took the Hyatt our with some difficulty, being tight to the race. Bearing inspected OK, with the rolls being slightly undersize, just the way I had put them in. But the axle was off center to the tube .075".
Buy loosening the radius rod anchor nut, allowing the radius rod to go back toward the rear end, the axle went nearly to center. After this adjustment, the bearing was a little tight going in, but could be pushed in with my thumbs. Before it required a mallet.
I used a washer I had split to take up the clearance generated by the loosening of the anchor nut at the 4th main and then tightened the nut up. This time, basically the radius rod was neither pushing or pulling.
I put everything back together, thinking that I would need to adjust the disc brake alignment to the rotor. Not so.. The alignment was pretty much centered, much more so than when I took it apart.
I am in the process of building another Ruckstell for our 23 touring car. This experience will make me look closer at the radius and the position axle in the tube. So if you have a difficult time sliding the Hyatt over an axle and the axle is not centered in the tube, you might want to look at the radius rod if all else is good. While I have not taken the car out due to snow and cold, I fully expect the rear end noise to be gone. I'm just glad my co-pilot noticed the noise on the tour. No damage was done to the axle or bearing like Bill had experienced.
Also thanks to previous posters to the forum from years back in discussing radius rod concerns. That was a great resource!
Thanks much to Bill for making me look at other reasons for assembly irregularities. I'd have never thought to look at the radius rod as a contributor.

Tom

Very good discovery, and method of checking the axle to housing alignment. Normally I run the upper nut down to get the cotter in place, then tighten the lock nut against the lock washer, checking each axle end to be centered with the housing, if not, adjust the lock nuts. Then again that assumes the radius rods aren't bent! If the Hyatt won't go in fairly easy, with just slight tapping, time to recheck the alignment, and adjust the rods.

Service Bulletin 1919 discusses this issue.

Thanks Dan. I guess I've been lucky on previous rebuilds where this has been a non issue. Good Ole Bill was the one who found it, not me! Learn something new everyday!

The position of the driveshaft tube to the rear axle tubes should be checked with a framing square. It should be square. The distance between the bolts at each backing plate and the driveshaft ball joint should be measured and be the same. With those measurements correct, the alignment of the axles, driveshaft, and bearings should be correct.
Another very important thing which is missed, is the alignment of the ball joint could be affected by the straightness of the frame and the crankcase. If the frame is crooked, it must be straightened and the crankcase must be straight with the ears correctly aligned for the rear of the transmission to be centered.
Anyway, all those things must be accounted for.
Norm

Here's the Service Bulletin article from a PDF.

Thanks Steve!

It makes me wonder why the 26-7 radius rods were made non adjustable. Does this indicate that if adjustment is needed to correct some misalignment of the axles, there is a problem somewhere?
The procedure outlined in the service manual replicates what happens with the fixed length 26-7 rods. The castle nuts are wound on and the split pins fitted, then the lock nuts are wound forward to lock it all up. If one castle nut winds on much more than the other before it registers on the ears at the ball, something is wrong. Using the radius rod to make corrections is not something I would contemplate. Fortunately, I have never had to contemplate it.

Allan from down under.

Once I have the diff housings cleaned and Hyatt Bearing Sleeves removed I check the straightness of the assembly.
I install install 4 sleeves in the location of the Hyatt bearings and then offer up a matching shaft that should slide right
through the left housing, across the centre and exit the right housing just by pushing it with the palm of your hand.
The Thrust Plate landings are checked to confirm that they are at right angles to the shaft. Once installed back in the vehicle
the adjusting lock nuts and adjusted and tightened to hold the assembly where it is with no loading either pushing or pulling.
Like Allan, the two I have done on the 26/27 were perfect and the single nut tightened up nicely
Alan in Western Australia