Vibration on Deceleration

[Motorhead-54]

I have a 1997 CC Intrigue 36' which I have only owned since November. I have put about 2,000 miles on it and ran into an odd issue on the way home today. As I left the campground I noticed a very pronounced vibration on deceleration. The coach ran smooth other than when under deceleration and it was a pronounced vibration (felt like driveline to me). If I tapped the accelerator the vibration went away until I lifted. On the outbound trip to the campground (150 miles) I did not notice any vibration.

Things that I did different today from previous trips....I carried a full tank of fresh water (110 gallons and I normally only carry maybe 50 gallons) and left the campground with less than 1/2 tank of fuel (probably less than 50 gallons and I usually run close to full which would have been 105 gallons). When I stopped at a rest stop it appeared to me that the rear of the coach was riding lower than normal. I refueled to a full tank (fuel tank is just behind the front axle) and added what I estimate to be 500lbs of fuel. I also dumped the air and let it reset to "Travel Mode"......the vibration went away completely for the remainder of the ride home.

My only guess....rear ride height was too low (I also had a TOAD on a dolly) and the combination of a full fresh water tank (just forward of the rear axle) and lighter front end (low fuel up front) caused a driveline angle that the coach did not like.

Thoughts?

[dennis45]

Originally Posted by Motorhead-54

I have a 1997 CC Intrigue 36' which I have only owned since November. I have put about 2,000 miles on it and ran into an odd issue on the way home today. As I left the campground I noticed a very pronounced vibration on deceleration. The coach ran smooth other than when under deceleration and it was a pronounced vibration (felt like driveline to me). If I tapped the accelerator the vibration went away until I lifted. On the outbound trip to the campground (150 miles) I did not notice any vibration.

Things that I did different today from previous trips....I carried a full tank of fresh water (110 gallons and I normally only carry maybe 50 gallons) and left the campground with less than 1/2 tank of fuel (probably less than 50 gallons and I usually run close to full which would have been 105 gallons). When I stopped at a rest stop it appeared to me that the rear of the coach was riding lower than normal. I refueled to a full tank (fuel tank is just behind the front axle) and added what I estimate to be 500lbs of fuel. I also dumped the air and let it reset to "Travel Mode"......the vibration went away completely for the remainder of the ride home.

My only guess....rear ride height was too low (I also had a TOAD on a dolly) and the combination of a full fresh water tank (just forward of the rear axle) and lighter front end (low fuel up front) caused a driveline angle that the coach did not like.

Thoughts?

Sounds like a driveline issue to me. Do you have air suspension? Bad air bag? Ride height sensor?

[Motorhead-54]

Originally Posted by dennis45

Sounds like a driveline issue to me. Do you have air suspension? Bad air bag? Ride height sensor?

Gillig chassis, air ride suspension, one bag per corner. 3 ride height sensors, 2 up front and a single in the rear which controls both rear bags. I suspect the ride height is probably set too low on the rear and the added weight of the extra water and the toad just pushed it beyond tolerance for driveshaft angles. Maybe time to get under there and measure rear ride height.

[dennis45]

Originally Posted by Motorhead-54

Gillig chassis, air ride suspension, one bag per corner. 3 ride height sensors, 2 up front and a single in the rear which controls both rear bags. I suspect the ride height is probably set to low on the rear and the added weight of the extra water and the toad just pushed it beyond tolerance for driveshaft angles. Maybe time to get under there and measure rear ride height.

I concur

[tlaffourtit]

if this is a front engine coach I would first check universal joints then yolks.

[Motorhead-54]

Originally Posted by tlaffourtit

if this is a front engine coach I would first check universal joints then yolks.

Rear engine diesel pusher 8.3 Cummins thru an Allison trans. I checked the rather beefy u-joints and they appear to be fine.

[tlaffourtit]

what type of suspension?

[96 Wideglide]

The additional weight should'nt make a difference. The ride height valve will just allow more air into the rear bags to compensate. This does'nt meen your ride height may not be out.

[Motorhead-54]

Originally Posted by 96 Wideglide

The additional weight should'nt make a difference. The ride height valve will just allow more air into the rear bags to compensate. This does'nt meen your ride height may not be out.

I agree with you but I am at a loss as to why the addition of the extra 500lbs of fuel up front seemed to cure the vibration...no sign at all of it after the fuel stop. The only other thing I did with perform a dump of the air ride system and let it reset before I rolled out of the fuel stop.

[TQ60]

Stop...

Air ride does nit care about weight as it is automatic.

Ride height valves will allow air in and out of aur bags to maintain same height regardless of carried weight. (Within capability).

Air or hydrolic levelung?

It corrected when you made a change so making the change made a correction...

If you have air leveling then you may have a sticky valve that did not go into travel.

Most have single valve front and dual in rear...check that.

Also get a tape measure and start your engine and place in travel mode on a flat surface like a parking lot.

Measure ground to top of wheel well in the fender on all wheels and record this in a notepad.

Both sides of each axle should be close.

Part of your "circle check" before leaving is to look at each corner ti make sure it is "on ride" or up in the air and ready to go

It will be after the dryer makes its blast.


Next time you have this issue touch nothing and get to a safe flat spot and remeasure.

If it is lower someplace then that is the bad valve.

[Motorhead-54]

Originally Posted by TQ60

Stop...

Air ride does nit care about weight as it is automatic..

Totally agree

Originally Posted by TQ60

Ride height valves will allow air in and out of aur bags to maintain same height regardless of carried weight. (Within capability)..

"Within Capability" ?

Originally Posted by TQ60

Air or hydrolic levelung? .

Total air system...no hydraulics

Originally Posted by TQ60

It corrected when you made a change so making the change made a correction... .

Agree

Originally Posted by TQ60

If you have air leveling then you may have a sticky valve that did not go into travel. .

The coach has a single height control valve in the rear. It is new which is what leads me to believe that perhaps the ride height was at the edge of being out of adjustment and the combination of extra water, the toad and the light front load pushed it beyond what the driveline could tolerate.....or some combination of the 6 valves on the rear leveling manifold did not function properly when I prep'd to leave the campground. The system is 18 years old and functions through a combination of electrical/mechanical actions.

Originally Posted by TQ60

Most have single valve front and dual in rear...check that. .

Just a single height control valve in the rear

Originally Posted by TQ60

Also get a tape measure and start your engine and place in travel mode on a flat surface like a parking lot. Measure ground to top of wheel well in the fender on all wheels and record this in a notepad. Both sides of each axle should be close.

After this event I will in the future measure and note the position at all four corners.

Originally Posted by TQ60

Part of your "circle check" before leaving is to look at each corner ti make sure it is "on ride" or up in the air and ready to go.It will be after the dryer makes its blast.

Previously my check was just to insure the system had given me the green "Travel" light. In the future, my walk around will include close scrutiny of the ride height on all corners.

Originally Posted by TQ60

Next time you have this issue touch nothing and get to a safe flat spot and remeasure. If it is lower someplace then that is the bad valve.

Hopefully there will not be a "Next Time". Today's task is to verify ride height measurements bottomside followed by keeping a log of measurements at all 4 corners.

My challenge with sorting this issue was I actually made two changes, fuel plus a reset of the ride height system. Not sure which resolved the issue.

Thanks for the input.

[TQ60]

The capability part was relating to the not caring about added weight and the air system maintaining ride height.

It is only capable of carrying a certian amount...above that bets are off.

Only put it there as some may add comments relating to overweight...

[jporietis]

Originally Posted by Motorhead-54

Rear engine diesel pusher 8.3 Cummins thru an Allison trans. I checked the rather beefy u-joints and they appear to be fine.

The only way to fully check U joints is to remove the drive shaft. Leaving the shaft in will not readily show a problem.

[TQ60]

The simple way is to have helper stand on the brake and while at idle shift from drive to reverse and watch for slop in the joint.