Many of you have read about my drawbar failure. Here's something for you all to be concerned about.
I traveled to OKC and dropped in on Cummins - who is working to get my coach back on the road. The shop foreman had me go look at the driveshaft with him. This is the HD driveshaft associated with the 450 HP Cummins and 4060 Allison. At 112K miles, the u-joints were pretty much shot. They had obviously been well lubricated, but they're still shot. Yeah, they might have gone a bit further - just far enough to leave me stranded in the middle of nowhere. He said that the driveshaft runs too flat (FOT design) and causes the u-joint to develop rough spots.
Seems like we studied something about minimum driveshaft angle around my junior year working on my ME degree.
Replacing those u-joints is a tad costly.
Larry
[modified topic title to be more descriptive - Michelle]
You should have about 1 degree at each end of the drive shaft for maximum life in most vehicles but motorhomes can work with 1/2 degree at each end. Wonder if the mechanic knew that?
Pierce
Correct ride height should have enough angle. I will put an indicator on mine when I start the to do list.
Changing the ride height a tiny bit each year will let the joints run on a new spot and last much longer.
On our coach, the trans output is offset to the right of the axle pinion when at ride height. I didn't measure it, but maybe 3/16 - 5/16". This offset gives some drive angle for the U-joints at ride height. With the offset and the U-joints C-C distance; this angle could easily be trigged out. At near full jounce and rebound, the arc of the panhard will move the axle to the right, relative to the rest of the drive train, giving better horizontal alignment. This is good, since the vertical drive angle is pretty high at the travel extremes, and a compounding a horizontal component would not be desirable. IMO, good engineering for a less than ideal situation; unavoidable high drive angles at suspension travel extremes, resulting from having to use a short drive shaft.
I PM our driveshaft at every oil change (7K miles). Prior to greasing, I check the U-joints and slip yoke for play. ANY noticeable play in the U-joints, radial or axial, means they're done. Replacement is a fairly easy job
when at home, with proper tools, and the work can be done on the bench.Greg
Any red dust on the joints is a bad sign. Even at max lift on the bags, the coach can be driven over rough terrain without worry about the joints. Not an expensive job if DIY capable.
Larry, how about the part number for the U joints and are they Meritor or Dana? Probably all models don't take the same joint.
Pierce
I slip under and grease the U-joints every few thousand miles, grease is a lot cheaper than parts.
All the zerk fittings(except on the brake calipers) get synthetic grease every six months.
Searched for part numbers for my U joint . Nota
Does anyone have a part # for my Joints on the 87-88ORED . Cat 3208 with Allison 643?
I grease the coach twice a year with a Moly Grease.