Unhappy Dogbone thingy

So I have been chasing a horrible "bag of marbles in a steel bowl" sound for lack of a better term. It all started after I played with my transfer case for the first time, so I ASSUMED the problem was in the transfer case. The scenario: Get up to speed, start coasting down from about 40-45, no problem....hit the brakes and THERE IT IS, that sound. Slower speed, no problem. Slept on it, talked to a few folks, thought maybe the air switch for the front axle engage was stuck, so I tested that and it worked perfect. Checked every fluid in the drive line, can not find a problem. So I was laying on my back, looking at it hoping that the solution would just "materialize" to me.......and so it did. Looked up at the forward upward dogbone and here is what I see. So what was happening was when I hit the brakes, without the upper dogbone in place at all, the axle was rotating forward and the gears in the diff were screaming at me to STOP doing that! So, its now time to find some parts and get to work on this...at least it seems to be a fairly (relatively) easy repair. Gonna have to wait until I get back from NC next week to even start on it.

Good catch , that could have got REAL ugly , I would check all of ends at this point . Not a bad job , just big , once you get the DB off , press out the old joint press in a new one . Some disassembly required .

So after reading the TM, it says that these uppers have to be "pre-stressed". Has anyone done this? If not has the install survived OK? I guess I just can't understand what this is doing. Any thoughts?

So help me out here. (Good catch by the way), but how are the diff gears feeling any effect from the rolling of the axle? I suggest that you look VERY hard at the primary and intermediate propeller shafts for joint and spline damage while you enact the repair.

Lucky you. I had a dogbone come off a M35A3 shortly after I bought it in my back yard. While I was backing it into the pole barn my wife noticed a trail of fluid. The middle axle dogbone on the drivers side had come off and crushed the brake line. I replaced them all and it was a bitch. I still think it's a poor design though I got flack complaining about it.

Squirt-Truck said:

So help me out here. (Good catch by the way), but how are the diff gears feeling any effect from the rolling of the axle? I suggest that you look VERY hard at the primary and intermediate propeller shafts for joint and spline damage while you enact the repair.

Click to expand...

Yeah they are definately on the list, I have a complete set of serviceable driveshafts, as well as two axle assemblies, so no matter what at least I have the parts to fix. I was thinking the diffs because there is a lot of oil on the seal and that was always dry, so thinking there was some undo stress there, but thanks for the reminder!

Wheelspinner,
With respect to your upper torque-rod (TR) bushing pre-load question, imagine that you have put your trunion axle on jack stands high enough for all your rear tires to be 12-18" off the floor and you could oscillate the axles (if you were strong enough) completely through their full range of motion. The upper TR angle to mount brackets would put the rubber in the bushings in a "relaxed/neutral" state when the axles are level...when you either raise the forward axle or raise the rear you can picture the torque/torsion being put on the respective front upper and rear upper bushings at the axle mount brackets.

If you tighten the new TR bushing into the axle bracket at too extreme of an angle... and then managed to get the TR and bracket bolted back onto the axle, then when your axles would do their full oscillations on the trunion, in effect the rubber bushings at the brackets would be twisted even more when the angle between TR and mount bracket rotate with each other. This is wordy explanation I realize..I would otherwise just say that if you tighten the rod bushing nut with the bracket to rod angle too far off, it will twist the rubber in the bushing too much and will fail prematurely. Also, the preload specified in the TM will help reduce "wheel hop" when set correctly causing the axles/wheels to "push" towards the road (not so sure this point is as critical as the previous).

And I am sure you already know, the repair will be much easier if you burn and wire brush the (5) coats of CARC paint from the bracket bolt threads before removal first.
Regards, Bob

Ok, so today I made a very ugly temporary repair, while I am still waiting on parts to come....It seems to be holding on a test drive, hopefully it will make the 50 mile trip to a friend's house so we can replace the bushings. Good news is, ALL of the offending noise is gone, so I am sure this repair will close the issue once the parts arrive from Eric's.

Right out of the Battlefield Damage Assessment and Repair manual. Good job!

Al Jones
'84 M923

Now you can clearly see why I always say, "just because you own a welder, does not make you a welder".

doghead said:

Now you can clearly see why I always say, "just because you own a welder, does not make you a welder".

Click to expand...

HA Ha! If you can't weld well, weld a lot!

wheelspinner said:

HA Ha! If you can't weld well, weld a lot!

Click to expand...

that is awesome!

Well its been a little while, and I had to drag Doghead off of his deathbed with a 117 deg temp or something....hot flashes, menopause....IDK, but he was a great help none the less. The job on these uppers was a little more difficult, really alot more difficult than the bottoms. But we got it done. I took a bunch of pics, including the Doghead Dogbone Press Tool ( a modified Haun Welding Supply gas cylinder cap ) that we modified. It worked perfect for the task and has been marked and saved as a very useful tool. I tried to number the pics but it didn't work well

1) Getting started at DH's house, 2&3)DH hard at work despite a life threatening fever 4) The DH DB Press tool

l

And after we got done we took a cruise out on Lake Ontario and check out what we found......

BTW, it took about 7.25 tons of force to break them free in the press.

And, I opted to torch cut the nut on the trunnion mount because the cotter pin was rusted stuck. We had a couple extra nuts for the task.

Always good to have a couple extra nuts around. Need to slip next door at work and get a tank cap to cut down I guess.

Hey, is that a UFO?

Kinda looks like a sea gull to me. But I don't have Elvis glasses on.

doghead said:

Hey, is that a UFO?

Click to expand...

Shhhh remember we weren't going to mention that?????