drivetrain vibration

[Winnielover4078]

Sent: 2/22/2005 5:53 PM

hi there, i just recently purchased a 72 brave, and am also new to this site. i have only had my winnie on the freeway a couple of times, but it has a noticeable vibration 55mph or more. i just recently had the tires replaced and balanced. being a new owner, i dont know exactly how smooth one of these things should ride! p.s. its not a front end shimmie or wobble. thanks kenny

[mightybooboo]

Sent: 2/22/2005 6:17 PM

When my u-joints were failing,I had quite a vibration in the driveline.Since the repair,its much smoother,but still a very slight on and off vibration.Very slight,have to know its there.
Remember,Im not one of the mechanics here,who will give you a hundred possible things to look at,and the fixes too.Just my experience.
But I did sleep at a Holiday Inn last nite.

BooBoo

[denisondc]

Sent: 2/22/2005 6:57 PM

As to how smooth a Winny should ride, it should compare closely to the ride of a Buick at the same speed.

A good way to tell if it is driveshaft vibration would be to chock both front wheels and the rear wheels on one side, so the RV cannot roll; then jack up the rear axle so the remaining two rear wheels on the other side are off the ground. Then run it in drive, till the speedometer is showing some speed like 35 or 40, and see if the vibration is there. Remember that when the speedo is showing 40 mph, the wheels that are in the air are spinning as if you were travelling 80 mph - over 800 rpm. If you dont want the wheels turning at that speed, you could remove both of them. Then you could run the speedo up to 60 mph safely. The drum would be turning as if you were going 120, but that wont hurt it.

If you have the vibration when driving on the highway at 55, but it goes away when you put it in neutral, and coast, then its not the driveshaft.
If yours has a center bearing to support the middle of the driveshaft like the longer wheelbases do, it could be that center bearing is bad, or that its rubber mounting grommet has come apart. There isnt any way to lubricate those center bearings, and its probably the original.
You could also try jacking the rear wheels off the ground, one side at a time, and turning the rear wheel pair. Check for the wheels being bent or a crooked mounting to the hub, and check for the driveshaft being bent. It should rotate with NO visible run-out at all.
Also check that the spring clamps are tight, so the axle cant "wind-up" under torque.

A friend with a Chevy based RV, a Suncruiser on the P30 chassis with 454 engine, had a vibration begin in his driveline, in the middle of S. Carolina. He pulled over and shook the u-joints, but didnt find any ones that seemed loose. So he limped along --- in mid Georgia the vibration got very much worse very suddenly, and before he got it slowed and onto the shoulder, the front U-joint had cracked apart, the rear transmission mount had snapped, and the transmission case had cracked at the bell housing, coming free from the engine! A failure I had never heard of. Cost him a tranny from a junkyard and two days lost from their Disneyworld plans. He hadnt greased the driveshaft u-joints since he got it.

Also: When the wheels on one side of the rear axle are in the air, and there is no "load" on the driveshaft, try wiggling each joint, including the pinion shaft yoke that sticks out of the front of the differential, and look for any lateral movement. When you turn the driveshaft, you should not hear much noise from inside the differential.
If you find out what caused it, let us know.