Vibration 40-55mph

[mjlayton]

I bought a 96 Dolphin 535 on a chevy chassis last fall. Drove it from Flint, Michigan home to Terre Haute, IN about 550 miles. Had a vibration starting at 40 peeking at 48 or so, and stopping completely at 55. Steering was sloppy, so I replaced the bell crank and had it aligned, took off 3year old double coin tires and installed new Michelin XZE on every rim except the tag axles (still double coin). The vibration is now more of a hum, like you're running on worn out rumble strips. You can feel it in the seat at it's peek, same speed range. It's livable, but I'd like to track it down. Any help would be appreciated.

Thanks,

Mike Layton

[wolfe10]

I would check tire/wheel RUN-OUT-- easy and inexpensive to do.

Next "suspect" would be a drive shaft/U-joint issue.

[wildebill308]

The first thing I would do is check your u joints in the drive shaft also check for play in the carrier bering you might have two of them. Vibration in that speed range is most likely in your driveshaft.

Bill

[rsbilledwards]

Interesting here, he stated that he replaced 4 of the tires and "the vibration has been reduced to more of a hum like running over a rumble strip". Sounds to me as though the other 2 tires are suspect.

However, in order to check the shaft joints, block the wheels so it won't roll and then take it out of gear or park, so there no load on the shaft. You should be able to move the shaft a little and feel any movement in the universal joints, it should be minimal.

Another way to check the joint would be to drive it long enough to have all components warmed up maybe 20 miles or so a little farther won't hurt and dirt cheap to do. Shut it down and then crawl underneath and check the universals for excessive heat. If one is a great deal hotter than the other you likely have found a failing joint. Since you removed 4 of the tires, one might wonder what the production dates were or are on the other two, maybe older than they appear and are acting like a box of rocks, less so since you removed some of them.

Check the slip joint between the two halves of the drive shaft. This should be tight and "no" lateral movement, but it should slide freely.

Could it be the carrier bearing between the two or three shaft sections. There maybe some disassembly of this assembly to check accurately.

I had a 993 Porsche TwinTurbo a few years back that had a similar problem...the tires were hard as rocks and it rode like it was on rocks. When I replaced them it was unbelievable how nice the ride was. The tires were just plain old and we know not all tire are created equal!

[mjlayton]

It's been a while. We found a cause for most of the vibration. When I had the motorhome serviced this spring we found the tag axle bearing had excessive play. got a spec sheet from Dexter, lubed the bearings, pre-loaded as instructed, and reinstalled the wheels. Not gone, but reduced a great deal. Thanks for everyone's input.

Mike Layton

[wolfe10]

Mike,

Thanks for the update.  Glad you found the problem and it wasn't too major.