U joint Failure

[1986Blazerk5]

I have a M1009 and when i bought the vehicle i had the U joints replaced and they were just replaced again today, 6,500 miles later, does this seem odd? What causes a U joint to fail early?

The shop that replaced them both times is a reputable shop and we have been going there 20+ years, with no problems.

 

[mistaken1]

Wobbly drive shaft? (out of balance)

 

[doghead]

Is it lifted? Did they all go bad or just the rear most on the rear driveshaft? Do you grease them often? Do you drive in deep water? Has it been 10 years to go 6500 miles? I could ask a hundred more Q's....

 

[1986Blazerk5]

Is it lifted? Did they all go bad or just the rear most on the rear drive shaft? Do you grease them often? Do you drive in deep water? Has it been 10 years to go 6500 miles? I could ask a hundred more Q's....

Not lifted, 31's, both front and rear, i have never greased them, (how do i) I went in deep water 5,000 miles ago for less than 10 seconds, it has been about 2 years since the last ones.

 

[REGULATOR]

I went in deep water 5,000 miles ago for less than 10 seconds, it has been about 2 years since the last ones.[/QUOTE]


deep water will get inside them, little splash ok, but submerging them, especially since they were hot when they hit the cold water..

make sure you replace them with the kind with grease fittings

that way you can grease if you submerge

 

[rlwm211]

Lubrication is the key and there are different grades of U joints. I have found the greasable ones are not always the best, or the worst and it depends on the manufacturer. If you get greasable U joints, you will have to grease them yourself because 9 times out of 10 an Oil Change Shop will not grease anything when they change your oil. Even trusted repair shops can forget to grease a driveline. It is not really due to a lackadasical attidtude, as much as almost all of the new vehicles do not have any zerk fittings. A zerk fitting is what a grease fitting is called if I am not mistaken.

One other factor is hard acceleration, which is hard on U joints. That starting torque is quite high and with the posi in the rear, you are unlikely to spin a tire so the driveline takes most of the gaff if you jump on it.

Hard trail riding can also be a contributor to failure especially if you get into some off angle, and high suspension travel and articulation.

I know there is not an answer in this post, but I am trying to explain the possibles.

I would add that an unbalance, or out of round is a killer to a u joint. Make sure your drive shaft is not bent.

RL

 

[ranchhopper]

Look at the extreme angle of the rear driveshaft even stock they work that rear U-joint pretty hard.

 

[1986Blazerk5]

I checked my drive shaft and its not bent, that i can see

 

[akonitony]

One of the M1008s I have still has the original driveshaft and TC, and it has a fair amount of vibration. I took the original driveline out since it was bent by a forklift and had the tube replaced. It still had a vibe to it, so I took it back to the shop. They put it back on the lathe and then brought me back to show me the problem. It turned out the spicer yolk on the front that slips onto the TCs output shaft was actually manufactured off center. In rotating it one could see the shaft is not centered in relation to the yolks where the u-joint sits into. So I ordered a brand new yolk from my vendor who carries a full line of spicer products.
When it came in I dropped the driveline, and replaced that front section of yolk/slipshaft. To my dissappointment, the vibration was still there. I then dropped the driveline and took it to the shop. Once again on the lathe it showed the spicer part was manufactured off center. I am currently rebuilding this particular truck and lifting it witha variety of mods to include an upgrade to a NP205 TC with bolt-on rear yolk, so the vibration should dissappear with that, but it was very present right around 55 MPH, but would usually dissappear at 60 - 65 MPH.
I would think your loss of u-joints is due to faulty installation. I would try putting them in myself, or at least taking them to a different shop. They should last several years with normal use, and they are usually quite waterproof. Mater of fact, I have had trucks stuck in the middle of a lake before overnight and not had problems with water getting into the u-joints.

 

[akonitony]

One other thought: The Original spicer u-joints for the M1008 do not come with grease nipples (I like that word better than zerks), and the amount of synthetic grease in them is critical. Not sure what the M1009's look like, but I will go crawl under one of mine tomorrow and see. The new spicer u-joints I have received carry a warning in the box not to add any grease or loose any in the assembly process, so once again, I would point a finger at whoever assembled the u-joint(s) that are failing so early. And yes, I do realize I have four fingers pointing back at me, but I have actually gotten pretty good at putting those puppies together over the years...
and I have fudged up my share while they were still on the bench.

 

[1986Blazerk5]

If i dont have a zerk fitting how do i grease the U joint?

 

[akonitony]

If i dont have a zerk fitting how do i grease the U joint?

You don't. They are filled from the factory with synthetic grease that last a very long time (Like 20 years roughly).

 

[Flyingvan911]

The drive shaft doesn't have to be dented to be off balance. Very small differences can cause big vibrations at high speed.

 

[tlucca]

This is true.

 

[rnd-motorsports]

been in buisness for about 20 years now and have changed alot go with non greasable joints will last a lot longer as stated they do take a lot of gaff is what I think he said problem with greas zurks sorry nipples go bad or get a little dirt in them dont seal joint gets hot and momentum (spelling not my strong) throws gease out. drive shaft spins very fast at speed and then water gets en and joint short lived A good joint with good install will last a long time they are man made and do fail also just a small dint may not seem like much but the shaft as stated spins at a high speed so a liitle dent at speed could make for a vibe witch the joint has to handle