grinding noise when releasing the gas pedal

When releasing the gas pedal (deceleration) I get an grinding noise (believe its is the diff/drivetrain, but still not certain). Not when coasting, not when accelerating only first phase when releasing gas pedal. Happens in all gears.

Made a video that clearly illustrates the noise. Noise starts at 7th second.

Propshafts have new UJ’s. I measured the backlash of the diff crown, this was well within green books margin.

Any help/guidance would be very welcome! thanks!

The intermediate gear in transfer case being helical also thrust fore an aft on its shaft, check its end float think you can reach it with a screwdriver from the small plate above mainshaft. Jack one wheel up and see how much play between axle and handbrake. Wheel flanges wear but would not expect grating noise.

Check and recheck prop u/js
Worn rear prop makes the most noise especially on the overun

Thanks for the input!

I did some check on the Propshafts/TC Intermediate shaft

Front Propshaft:

• No radial play
• No axial play on the UJ spiders
• Shafts was 1 dent off-set (phasing) ==> I realigned (assuming no phasing off-set on LR Series)
• Breather hole was stuck building pressure in the propshaft sleeve when compressing so I cleared the breather hole
• Can wiggle the shaft +/- 5 mm / 0.2" up and down half way the shaft/sliding joint ==> assume propshaft needs replacement?

Rear Propshaft:

• No radial play
• 1 mm axial play on one of the UJ spider arms: reinstalled, no play afterwards
• Aligning/phasing is OK (assuming no phasing off-set on LR Series)

After above checks and changes I still hear the noise during overrun, so i did a test drive with the rear propshaft removed: I still hear the noise (believe less noise than with rear propshaft attached)

I also checked the end float of the intermediate shaft (TC) which was 0,05" (so well within specs)

Still have no clue
Welcome any advise, Thanks!

Just had similiar fault on my landrover replaced one rear hub drive flange was expecting to have to change diff, removed rear propshaft and found diff pinion nut slack tightened to 85ft/lb and refitted problem gone.
Noit driven between changing flange and tightening pinion nut but did still have play after changing flange but little or non after tightening pinion nut.
Did not make sense to me as tightening nut will pull pinion away from crown wheel so more free play in my head, maybe pinion was going back and forward with on off load

Thanks Blackburn!

I believe you are right, I tried to tighten the fixing nut 85ft/lb (on the pinion shaft) but it was completely stuck. Had to take the complete diff out to get it loose. I noticed that several of the shims (under the bearing) were so worn there were even holes in them and some of the shims started to disintegrate into pieces.

Also the bearing showed some wear inside the cone.

So I believe either it lost preload which allowed the inner race to move and/or the bearing spin on the shaft (and pinion going back and forward)

https://youtu.be/Kf8h0pakLAc
I replaced the UJ’s and had the propshafts rebalanced.

Took the gear and transfer box out (main shaft brass distance bush was broken), double checked all end floats and other green bible specs.
Took the rear differential apart, replaced shims (did not change total thickness): end float of ring gear and the gear contact pattern seems fine.

But still hear this noise ☹

The grinding noise is only noticeable under no load situations at the neutral point between acceleration and deceleration. As soon as a load is placed on the transmission all is fine.

I only hear the noise at higher speeds (when switching between 3-4 gear).

Maybe it's just the camera angle, but the diff doesn't look in line with the prop shaft?

Are the engine and gearbox mountings good? The old pre-selector gearbox buses used to make that noise and it was nearly always caused by worn mounts.

Col

If you take the rear propshaft off and drive on front 4wd does noise go ?
Rear propshaft looks to be at a very steep angle what springs do you have?
Diff flange should be parallel to transfer case flange/ brake drum.
I am assuming series gearbox are the two gearbox mounting quadrants / spacers on the right sides.
Can you post some photos of propshaft ,gearbox and diff end.

Rear prop does not require rubber boot and should be fitted with sliding joint to gearbox end , check with rubber boot off that propshaft has plenty of room to slide when compressed.
Is there any sign of fretting where springs meet axle if rust red dust usually apparent.

Thanks for your suggestions!

Some answers:
- Springs: Rocky Mountain Parabolic Springs:
- Engine and TB mounts: all new
- Pinion Angle:
- These look like big angles to me, but do not know what the acceptable range would be
(Diff is tilted 1 degree upward, the TB 1,9 degree downward, propshaft angle 12,7 degrees upward))
- No signs of fretting
- Noise gone when rear propshaft removed on 4WD !!
Will add some pictures/clips asap

When you took rear propshaft off was sliding joint fully compressed under the rubber boot?
Angles are not that far out diff one will change with load and power on off a little.

approx 0,5-1 inch of margin[GALLERY=] [/GALLERY]

Can you set your camera up to film that sliding joint on propshaft?
Who,s make is the propshaft looks good quality.

Thanks!
Clip with view on the sliding joint below.
Do not know the brand (shaft was on the car when I bought it). A propshaft repair company in The Netehrlands did the propshaft overhaul few weeks ago (balanced, new UJ's, align etc)

Looking at that clip I think your U bolts are loose on the axle , or maybe some suspension bushes have failed diff nose is moving up and down a lot.

Thanks, appreciate your support! I also noticed the "roll" of the diff. I re-tightened the U-bolts before I made the clip, so will check the suspension bushes.

Can you set your camera up to look at front to axle of one rear spring.
If bushes and Ubolts are all ok the only thing left is excess flex in the springs.
Is the rear chassis all solid?
Some static photos of rear springs particularly rear swinging links would help also.

Changed the rear diff, unfortunately that did nit solve the grinding issue.
Clip with axle, spring / axle view


U-bolts are tightened. Not sure how I can check the bushes but will post some pic
Thanks!