Community Forums

zinom · 08-07-2012, 01:40 PM

I have a strong vibration coming from the area of my rear axle whenever I accelerate (even if only slightly) at about 1500rpm. As soon as I take my foot off the accelerator the vibration goes away. I have had the universals replaced,adjusted ride height,had drive shaft balanced, line timing, line angle, and yokes checked. Cummins coach care in Coburg said it has them stumped. Has anybody out there had this problem or have any suggestions.

Midniteoyl · 08-07-2012, 01:59 PM

After doing all that, I would seriously look at the differential..

DonDee · 08-07-2012, 02:02 PM

Motor/trans mounts OK?

Perry White · 08-07-2012, 02:07 PM

Pinion angle maybe? When you accelerate it tries to turn the rear end over on itself. Maybe bushings letting pinion rise up and bind the u-joints.

zinom · 08-07-2012, 02:50 PM

Drives at universals are parallel; mounts secure...in fact engine seems to be running smoothly. Viabration does seem to be coming from rear axle. Differental or axel itself seem to be a culpurt... but so $$$$. I want to be sure I've eliminated all else.

FW5000DRIVER · 08-07-2012, 03:00 PM

Either your drive shaft has become unbalanced or one of these is bad: tie rods, wheel bearings, ball joint, struts, and or strut plates.

Perry White · 08-07-2012, 03:07 PM

Get one or borrow an HDHERO hd camera and mount it under the coach in a safe place. It takes a panoramic picture and it will telll you what it's doing. Either that or have your better half Velcro you to the bottom of the coach so you can watch it in 3D.

Also, Pinion angle should be pointing down about 2.5 degrees with the driveshaft centerline.

EngineerMike · 08-07-2012, 06:29 PM

Run the rig, then dip some oil from the differential, see if its got metal shavings.

zinom · 08-07-2012, 07:33 PM

Mike: No shavings;minor crud on the drain plug magnet. Oil did not smell burnt...but differential cover seemed pretty warm. Any idea how hot it should get. I'll check temp tomorrow with IR gun. Thanks for your input. Matt

Huey · 08-07-2012, 07:42 PM

What about the drive shaft slip joint? Could it be seized? Or maybe a midshaft bearing?

Mr_D · 08-07-2012, 07:43 PM

The diff. does get pretty hot. Not sure that I've ever seen a spec for it though.

EngineerMike · 08-07-2012, 10:03 PM

Should be able to handle 150 indefinitely, but guessing normal run range would be under that. Just a guess.
Here is a Toyota thread stating 130 after a diff rebuild on fresh gears.
Here is a technical paper from Amsoil on differential temp more specific to trucks.

larandshar · 08-07-2012, 10:18 PM

Pinion bearings or axle bearings will cause this vibration.
If you don't beleive me ask an old jeeper.

Marca · 08-08-2012, 07:48 AM

Matt,
Some of your post sounds like what we were experiencing prior to our differential problem the 29th of June. Ours started as a strange noise in the rear under the commode area (2006 40' Apex FDQS) and I (Marca) noticed it as I went to the back with (Chuck) driving. At first we thought it was tire/road noise as this was the first trip with our new tires. It was only on increased or steady acceleration and not when off the accelerator. We traveled 200 miles and stopped for the night. The next morning I drove some and Chuck tried to hear it but could not.

We traveled on and about 300 miles later, it was getting worse. It was now a strange noise clear across the back and a slight vibration. It was then noticeable up front in the driver/passenger area. We saw a Freightliner shop and at 5:00 PM on a Friday evening pulled in. Before doing anything else, Chuck crawled under and checked the temperature underneath. He could find nothing out of the ordinary at around a max of 135 degrees. The night foreman took it for a drive around the parking lot and agreed that there was indeed a strange noise coming from the rear. So we waited until morning. On Saturday morning, they pulled it into the shop and drained some gear oil from the differential. Sure enough there were metal pieces and shavings in it.

That started the week long process of finding the part, tearing it down, dealing with the warranty insurance people including an inspector making sure that yes, it did need replaced, etc. The part that failed was the pinion bearing and the holder that it is supposed to reside in. It appeared one of the ball bearings was damaged/missing and the bearing race was starting to destruct. Please keep in mind that this is a woman trying to explain this so if some of the terms are incorrect, I apologize. Also, we had to produce service records regarding the differential to the warranty company. The latest service on it had been done approx. 900 miles before this occurred and the synthetic gear oil was used. At the time of failure, the coach had 57014 miles on it. The repair shop said that it appeared that this one was in the early stages of failure but the problem is that after metal appears in the gear oil no one can determine how far or long one can travel before it fails entirely. We were lucky in that no other components were damaged. In order to repair it, they had to remove the entire rear end assembly including wheels, tires, brakes, etc. and slide the assembly out one side to get to it because of the coach wide brace underneath. It's not like changing a differential on a truck they informed us.

Thanks to IRV2, Engineer Mike, Cris Cratch, Kraig, Mike from Redlands, Sully and many others too numerous to mention, we were back on the road in one week and made it to Calgary.

I will be posting the part numbers on the original post later today. If you need any further information, please let us know. I forgot to mention that since this has been repaired and with the new Michelins, it is really quiet in the rear now. I never could rest back there going down the road but may be able to now.

Hope this helps. Good luck finding the culprit causing the noise.