Bad Vibrations

[Rocket Heart]

Just returned from a round trip to Florida and back from Ohio. I have an 07 Itasca Suncruiser on aWorkhorse chassis with the 6 speed Allison transmission.

I know there is supposed to be the occasional slippage in and out of overdrive depending on grades and wind etc. In my case however I think it is extreme. My coach vibrates very badly both in 5th and 6th gear. It shakes the whole coach - it is definetly in the tranny because if you take it out of gear it stops or if you go downgrade it stops - the only time it vibrates is under load - small or especially big grades.

It also seems to do it more in cruise control than when I manually drive it. Any help appreciated.

[DenShaw]

I wonder if a drive shaft universal joint might be going bad. Their vibrations are road speed dependent and sometimes don't vibrate until certain speeds are attained. I sure hope it isn't the tranny. You might also have a carrier bearing worn if there are two drive shafts.

[Gary RVRoamer]

It is more likely the drive shaft, e.g. a universal join. Lack of lubrication on the universals or the drive shaft spline at the rear axle are common causes.

[Pubtym]

This info might help:

http://www.differentials.com/diagnose.html

[j.smith]

I had a similar problem (I have an '03 with the 5 sp); when I would start to climb a grade the coach would start to vibrate and when it downshifted it seemed like it was running on 4 cylinders. When I took it out of cruise and backed off on the throttle it would smooth out again until I tried to accellerate (increase the load); the higher the load, the worse the vibration. Like you I thought I might be having driveline or transmission problems.

Prior to the start of the vibrations I was in a very heavy rainstorm, I believe heavy enough to get water into the intake and to the MAF. When I got home I removed the MAF and found some crap (loose plastic shavings) on the screen. I cleaned it with some MAF cleaner from Autozone, made sure the intake air cleaner was properly attached and reinstalled the MAF. Have travelled about 20k miles since with no more vibrations. Try it, its alot cheaper than a tranny.

Remember you do not need to touch the wires on the MAF, just spray it down with the cleaner and let it air dry.

[Pubtym]

I agree with clean the MAF first...it's amazing all the signals-sensing it sends to computer engine and tranny brains. I clean mine every 20 M miles with CRC MAF Sensor Cleaner. Check my (Pubtym) photos on photo link top of this this web page. I have photos of MAF cleaning.

[David K]

Your vibration sounds very much like one that I experienced a year ago on my MH. It ended up being a bad U-Joint. Even though the joint was being greased as called for, the channels in the U-Joint were bad from the factory and the proper lubrication was not getting to where it should have been. I also had a problem with the ride height not being right on the coach -- this was corrected along with the U-Joints being replaced and all of the vibration problems went away and the ride is now back to smooth and quiet.

[Rocket Heart]

Had my dealer tech and owner drive it and it is more of a shudder than a vibration - I have an appointment tuesday with the local Workhorse dealer. Looked at the MAF cleaning - stupid question - what is a MAF M----Air Filter?

[Pubtym]

Quote:

Originally Posted by Rocket Heart Had my dealer tech and owner drive it and it is more of a shudder than a vibration - I have an appointment tuesday with the local Workhorse dealer. Looked at the MAF cleaning - stupid question - what is a MAF M----Air Filter?

http://en.wikipedia.org/wiki/Mass_flow_sensor

Specifically, the Hot Wire Sensor and Cold Wire Sensor. Note one of the listed drawbacks at the end of "Hot Wire' paragraph. A similar comment is mentioned under Cold Wire Sensor. This is the reason I clean mine with CRC MAF Cleaner every 20,000 miles. Makes a noticeable engine running difference...smoother.. each time I clean it..really an inexpensive tuneup...better than fuel injection cleaner!

[Rocket Heart]

The answer is: bad spark plug wires. The 4 rear plugs were bad - does not show up on the diagnostics but Workhorse knows about the problem. It is caused by the back 4 wires not getting enough air to them. I asked if this will be a reoccuring problem and was told that usually once changed that they're okay - we'll see.

I was also told there is a kit that you can purchase that runs cool air to the rear of the engine - I am going to check into that.

[Pubtym]

Tom,

Sounds accurate...I'm aware of the many WH burned wire issues...

Yes, there's a special WH kit WH can install...under warranty.. to increase the airflow to that plugs/wires area. You have to insist on it...as wire failure is probable again..

Also, the quality preferred wires set for your engine...very heat resistant.. are made by Taylor (60-70 dollars)...many WH 8.1L owners have switched over to them...because of the heat failure issues on the wires. WH will not install Taylors but another good mechanic shop will. I bought mine from Summmit Racing website.

I still recommend you consider cleaning your MAF..

Good luck..

[Rocket Heart]

Will do on the MAF cleaning - thanks for your input.