Mutt Broke Down Today

[Lou]

Well after 14,000 miles and 17 years our M151A2 “Mutt” broke down just before exiting the woods today. We were doing about 10 MPH, transfer case was already disengaged when BLAM! All hell broke loose at the back of the mutt and she “no drive no more”, lol.

Turns out the mutt gave us the shaft today, but in all actually it really broke the shaft! Meg looked at me and I see the look in her eyes WTF was that! Turns out rear drivers side, wheel side axle shaft decided it was time to part ways with the wheel. You would have to experience this yourself to truly understand the racket this made as the now free end of the drive shaft was banging against the suspension arm, exhaust, and spring. Glad it did not happen earlier in the day while doing 50 MPH on the street!

At first I thought it was a blown U joint, but no the actual knuckle that holds the U joint shattered. Looking closely at the shaft, rust on one side shows it was cracked for a while. Do not know why I did not see this while greasing the U joints.

Anyway lucky for us the mutt is 4 wheel drive but could not drive it with that shaft trying to destroy everything in it’s path. Was very concerned that it would take out the brake line. So get out the tools we keep in the mutt and darn, wouldn't you know the freaking 1/2 open end wrench is missing! Luckily the adjustable wrench just barely fit between the U joint and diff yoke.

So pulled off the shaft and drove home in 4 wheel drive. The mutt was not happy driving on the asphalt in 4 wheel drive. It was letting us know by wagging the steering wheel left and right 3 inches on every turn. But it got us home and glad it was not one of the drive shafts that let go. Always concerned about those because if you pull out one of those shafts there is nothing to hold the yoke in on the transfer case and the yoke will fall out and puke oil all over the place.

Among the many spares we keep on board are U joints for both drive and axle shafts. But to carry an actual half shaft on board, don’t think so! Of course after this Meg, thinks we should! Have any of you folks seen this occur before?

IMG_2666.JPG

IMG_2667.JPG

IMG_2668.JPG

[rickf]

I know Fil had a similar thing happen years ago on the road where a u-joint went on a rear axle and it took out the brake line. This is something I tell everyone all the time is to always be aware that if this happen you will have zero brakes and the e-brake will be useless because it only stops the driveshafts, so unless you are in 4 wheel drive the e-brake will not stop you with a broken axle. The only possible chance you have is to try to match engine speed to road speed and jam it into 4 wheel drive while moving down the road, all the while trying to stay calm with no way of stopping. You probably never would have seen that cracked yoke since you do always keep it clean and greased, because of that the rust line would not have been prominent. And since it was hopping on turns in front wheel drive you might want to give the front axles a very close exam. It should not have been doing that since there was no bind from the rear.

[m3a1]

Carrying a spare is not the problem you might believe it to be. Wrap it up and strap it to the bottom or top half of the rear seat where it will be out of the way. Easy.

Cheers,
TJ

[lpcoating]

I take a pretty good amount of spare parts on trips. My thought on a half shaft has been that I could pull a front if a back one ever failed. Also agree with TJ's post.

Guy

[Mark]

A long time ago I decided to check my drive shafts, the nuts on the u joints were loose, I caught it just in time.So I took the drive shafts to a driveshaft place, had them balance my driveshafts as they were out of balance.Which I think is beneficially to the drive train to lessen wear as well reduce vibration

[svramselaar]

hi

for yeas this happend to me

at my drive way



george

[rickf]

George, you REALLY need to stop doing burnouts with the mutt!!!

[m3a1]

Looks more like he was doing wheelies...

[Mark]

Don't that look like junk metal?

[Lou]

Thanks for all your replies and information. Mutt is back on the road and now carrying a complete spare shaft.

Rick must have ESP, because we found LH front diff side u joint had like 2/16 lateral play. This make sense since when in 4 wheel drive this shaft and the right rear are doing most of the work. Always tested u joints by twisting the shaft looking for play. This one was found by testing the joint laterally, up and down then left and right. Once a year every u joint gets tested then greased as well as all other zerks. Since the tire has to be off the ground, good time to check wheel bearings and ball joints.

Good thoughts on swapping front and rear shafts. Gave up on that thought when reinstalling the front driveshaft. Cap came off with the little frigging needles going everywhere, found them under the bottle jack!

Thoughts of laying on the cold winter dirt swapping a shaft twice made us realize carrying a spare shaft, ready to go in is not so bad. And yes, after moving my spares around, stored it under the rear seat.

This shaft was purchased from TNJ years ago. The replacement NOS shaft looks different. The one from TNJ does not have the part number in raised letters and the yoke is shaped slightly different. My belief is that this shaft was some cheap import, not one manufactured here. Believe poor metallurgy caused the failure. As a kid had a 67 T-Bird with close to 400 HP doing neutral drops every day and never blew apart a U joint or drive shaft. Rear ends do not count, blew a couple of those, lol! So to see a shaft with a good U joint explode with the mutts paltry horsepower is a big surprise.

While under there did check all the u bolts and they were ok, thanks for the tip. Pretty much since 2004 every u joint has been changed at least once. Use to ford a creek routinely and got tired of changing u joints and diffs. And now with parts 3 times the price they were in 2004, and living on retirement income, treating the mutt a little more kindly.

[rickf]

2/16? That is 1/8 in mechanics terms and that is a lot of play in a U-joint! What makes you think the right rear and left front are doing all the work? The diffs are open differentials so the force is split evenly between the two wheels. That is why when you lose traction on on wheel you have no drive on the other one either, evenly split between both sides. Basically the wheel with the least traction determines the force on both axles. I never understood why the military did not put a locker or limited slip at least in the rear axle. In the front they tend to do very strange things to the steering, sort of like what you felt with the bad joint but on steroids. LOL.

[svramselaar]

Hi

I know i drive a lot with my mutt
Every year i have one or two rear outer U joints go bad
They get all the grease they want
For me this is normal now there are eight or ten at stock

george

[rickf]

George, where are you finding them? The military ones are getting scarce around here and so far I have not seen a civilian joint that is a correct match. There is one people are using but it is a little too short side to side and that allows play in the joint and vibration that will eventually take out either the joint or the bearings it is attached to.

[lpcoating]

Army Jeep parts has them listed on sale for $29 each. Rapco has them as well, $24.50 each. I don't think there getting hard to find, they're just not cheap.

Guy

[Lou]

Rick,
Maybe 1/8 of inch is an exaggeration, but it had enough play to hear a knocking noise when the joint was moved up and down.

Had to rethink my statement about the right rear and left front doing most of the work. This was based on years of doing burnouts with the before mentioned T-Bird (non posi rear). Even while demonstrating this to Meg last week, 4 wheel drive is a misnomer. Even the Mutt, if taking off quickly on the dirt, causes the right rear and left front tires to spin. Meg verified this while standing outside the vehicle watching. What I did not understand was why this occurred with an open diff.

Google being my friend had this to say:
On solid axle cars it's very unlikely to spin both tires at once, reason for this is the applied torque from the driveshaft effectively tries to turn the entire rear axle about the axis of the driveshaft.. of course it can't, but it will apply more downward force to one tire while lifting the other... the tire that's getting 'lifted' will of course have less friction between it and the road, and will be the first to start spinning. In most cases it's the right side tire, because most driveshafts (and engines) are clockwise rotation when viewed from the front.. so when viewing from the front, it 'plants' the car's left tire, and unweights the right, which is why it spins first

Source https://www.physicsforums.com/threads/o ... te.869028/

Agree with the locker limited slip statement, 99% of the time having either of those would have gotten us unstuck. Ordered my 1994 explorer with a limited slip rear axle. Took it and my old CJ-5 on the same sugar sand trail. With both vehicles out of 4-wheel drive the explorer could negotiate the trail, the jeep just spun 1 tire and could not start out from a stand still. With that said since you were into dune buggy’s at one time so were we. Remember the kit bugpack had to separate both rear cables on the emergency brake with 2 levers? That was awesome, as soon as one wheel started to spin, used the lever to brake the spinning wheel, and 99% of the time it would get us unstuck.

In fact, modern traction control systems (like our 2015 Explorer has) kinda simulates a locking diff by braking the wheel that starts to spin. It works remarkably well as we see this in action on the Brigantine beach. Hmmm, what would it take to make this happen manually with the mutt? 4 separate brake lines with electrically operated solenoids and switches to select the spinning wheel, something to think about.

George,

Early on we were going through U-joints often. Found out the U-joints we were purchasing from a famous supplier were poor quality. Most of those were in the female part of the axle sleeve. We purchased the axle sleeve with the u-joints and those u-joints did not hold up. The u-joints came with a clear grease inside that looked like synthetic, but really think it was Vaseline! Started buying the u-joints in the military box that has the u-joint, clips and new ubolt and nuts. Those have held up very well. Glad we still have a few of those left. Like I said before we grease them all every year and do about 1,200 miles a year and have not changed one in about 10 years. We use a marine grease by Pennzoil and it seems to work well.

And Rick, I see on fleabay the joints you speak of. Folks are selling them for the mutt and they are clearly not the right ones as they come with the spring clips that are used on a car driveshaft, buyer beware!

Below is parts from one of our failed diff’s. Do not know why they do not use radial torrington thrust bearings. You sure get lots of play when those washers go south, never found the 4th one, lol!

DCP_0727.JPG