55-70MPH Deceleration Grumble (2000 Disco II)

bradartigue

Well-known member
Mar 7, 2018
112
17
Sandy Springs, Georgia
Hello everyone.

My Discovery 2 has a grumble coming from the drivetrain under deceleration from around 55-70MPH. It goes away at about 55MPH. The "feel" of the grumble can also be created by applying very light pressure to the gas between 35-55. Researching this is challenging, though I can say what it is not:

  • the front driveshaft as it is brand new and regardless the truck grumbled with it and the predecessor shaft
  • the fluid in the diffs or transfer case as it was replaced

When coasting uphill the sound does not occur; when downhill it is worse. Seems to start from the front but gravitate to the back. Seems to take on a different rhythm when heavily loaded (trailer, stuff inside). The Disco has:

  • OME 1.5" HD lift (new)
  • TW front shaft
  • Stock rear shaft, new rotoflex

Pinion shaft nut torque was suggested as it may "come loose with lifted trucks" - but in advance of checking I'm looking for those things that can be checked at home, I'm a competent garage mechanic but don't have a lift at home. I'd like to at least educate myself and eliminate the known issues before giving up and having the local guys seek out the issue.

Here is the laundry list of what I've researched:

  • Bearings...I've checked for looseness and can feel none, though I
  • Pinion nut as noted above
  • Rotoflex...seems to be a debate on whether or not it should be used in lifted applications
  • Differential spider gear
  • Transfer case bearing(s)

Thank you in advance

Brad
 

bgbrox

Well-known member
Dec 25, 2016
63
8
Golden, CO
How are your motor mounts? Mine were blown out and the biggest thing I noticed after swapping them was less noise while coasting.
 

rovercanus

Well-known member
Apr 24, 2004
9,643
244
I'll add them to the list of things to check. I think the body mounts are wonky, I've got a slight gangster lean to the driver's side.
OME springs are made to compensate for the weight of the driver thus your lean. I know, pretty stupid.
 

jprover2

Well-known member
Apr 8, 2017
146
10
Birmingham,Al
Noises are funny. You said you don't have a lift, but do you have jack stands that you can put the vehicle on with tires off the ground? If so have someone "you trust" sit in and recreate the situation. Then you could be under it to listen. If no jack stands, then pay a local shop to help you find the noise. They should be able to find it with a 2 post lift.