U Joints

[geeves]

How long are others getting out of the rear U joint? I seem to be averaging 18 months with a nearly spectacular failure on Sunday. Had to remove the rear section of the driveshaft on the motorway and drive home in front wheel drive
One bearing cup is somewhere on the motorway and another 1mm movement would of seen the joint come apart. Not nice at 100kph

[pig75]

Never replaced a uni on any of my MU's. Maby the angel of the tail shaft is to steep

[geeves]

Im only running 50mm lift but was thinking about how axle tramp would hammer the rear joint but that should reduce the angle except when thrashing it in reverse?

[pig75]

It's a shame you can't drop the center bearing 20mm

[geeves]

Then it would be lower than the transfer case and right in the way. I dont need 5 ploughs. Rear diff,transfer case both cross members and maybe center bearing.
Maybe I need tyres bigger than a true 32 but then I would need the 4.5 diffs or the mythical 4.8s

[turnturn]

I've had a mixed bag with universals.
My 2.8 (UCS55) has done in excess of 300,000ks and has never been touched (standard suspension).
My 3.1 (UCS69) had only done 147,000 ks when I got it and it needed the rear universal replaced. When I went to do it I noticed that it had already been replaced before. The U-joint that I put in only lasted about 4000ks before spitting off two of the bearing cups in quick succesion (at 100 kph+). I'd like to think that I had replaced it correctly and have since replaced this again (for obvious reasons). This second new joint has been in for about 3000ks. This mu has had raised suspension in the past (I have returned it to pretty much standard height).
I have acurately measured the UCS55 driveshaft angles and they are within 1 degree (output of gearbox vs input of diff).
I have roughly measured the UCS69 driveshaft angles and think that the same two datums are at about 3 degrees different.
All information that I have found recommends that driveshaft angles should be 1 degree or less. I am currently looking into wedges to correct the pinion angle.
Just as a side note here is a picture of the factory universal vs the replacement. The factory universal has bigger journal diameters and is generally a bit beefier looking.

[wbski007]

99% of the time to much angle on the shaft is the cause of premature ujoint failier

[geeves]

The beefier knuckle on the original may be a bad lead. Ive never broken a knuckle and that would leave a thinner bearing cap which is the part that always goes. I also had damage to the yoke this time so a new driveshaft with new ujoints is going in tomorrow

[geeves]

Just out of interest how long is a Mu driveshaft
The rear section of the bighorns is 615mm not including the ujoints

[pig75]

760mm

[geeves]

interesting. The jeep wrangler though has a driveshaft of around 400mm. Ujoints are a very weak spot on them
Might have to lift the back end off the ground by the chassis and measure the angles. Cant do this inside the garage

[muzila]

I thought the jeeps had CV joints in the drive shafts to get around that angle problem or was that just an after market thing??

[geeves]

after market mod