rumble strip type vibration when I let off the throttle

[Bobd254]

Hi folks,
My 2000 Express 3500 Sportsmobile has a vibration/sound similar to a mild rumble strip when I let off the throttle, above 40 MPH.
I never noticed it before , but I just switched from old Cooper All terrain tires (2005, about time ) to a set of very quiet low milleage takeoff ironman rb-lt's 245 75 16E (I know its a cheap tire)
It rides vibration free while accelerating or at steady speed, but once I let off the accelerator , the low vibration begins.
I also just had new front bearings, rotors and pads done.
Has anyone experienced anything like this , or have any ideas ???
Thanks,
bob

[booster]

Originally Posted by Bobd254

Hi folks,
My 2000 Express 3500 Sportsmobile has a vibration/sound similar to a mild rumble strip when I let off the throttle, above 40 MPH.
I never noticed it before , but I just switched from old Cooper All terrain tires (2005, about time ) to a set of very quiet low milleage takeoff ironman rb-lt's 245 75 16E (I know its a cheap tire)
It rides vibration free while accelerating or at steady speed, but once I let off the accelerator , the low vibration begins.
I also just had new front bearings, rotors and pads done.
Has anyone experienced anything like this , or have any ideas ???
Thanks,
bob

When you say let off the throttle do you mean let off completely as in coasting or just feather it into constant speed?

[Bobd254]

When the throttle is fully released.
It doesnt matter whether I leave the transmission engaged, or if I put it in neutral.

I've had all kinds of noises in other vehicles;, bearings , axles, transmissions , wheels; but this is a new one!
Thanks

[booster]

Originally Posted by Bobd254

When the throttle is fully released.
It doesnt matter whether I leave the transmission engaged, or if I put it in neutral.

I've had all kinds of noises in other vehicles;, bearings , axles, transmissions , wheels; but this is a new one!
Thanks

It it changes with the speed you are going you are down to only the rotating parts that change speed, so everything from the output of trans to tires and mostly in the rear. Very few of them have much to do with drive coast so down to trans to wheels.


I would be looking at U joints or center bearing (if you have one) or possibly loose clamps on the rear U joint. Loose lug nuts can also behave kind of that way.

[Bobd254]

Thanks for the reply, I will have those items checked , the U joints and center bearng(if Ihave one ) ; I'll check the lug nuts myself, after the Virginia monsoons stop; better than the snow I used to have in Buffalo.

[Buc22]

Originally Posted by Bobd254

Thanks for the reply, I will have those items checked , the U joints and center bearng(if Ihave one ) ; I'll check the lug nuts myself, after the Virginia monsoons stop; better than the snow I used to have in Buffalo.

Just had to have my GM bolt 14 9.5 diff rebuilt for a rumble type noise I only heard when I left off the accelerator at 25 mph and above. Ended up being a Pinon Bearing and spider gears.

[Bobd254]

I havent had mine looked at yet. I've been spending too much time trying to get my MGB running after sitting for 10 years.
Now that I'm waiting for parts for the MGB, I'm thinking of setting the back of the van up on jack stands , and trying to see if I can see where the vibration is in the drivetrain.
I guess I shouldnt use my recalled HArbor Freight jack stands , time for new ones