Backlash issue - Sals diff

**phibbzy** · 3rd April 2014, 10:42 AM

Hi all,

I've been tracking down a backlash issue for quite a while now...

Upon taking off from a standstill there is a take up and an aggressive "clunk" from the under carriage. When on power there is no issue but when moving along and removing power quickly there is another take up and then a clunk.

When lifting one wheel of the vehicle with a jack & idling in 1st high, upon applying slight power and then releasing it the take up is enough to move the vehicle.

There is about 1/8 turn of slack in the prop shaft between either wheel (of the ground ) moving.

I have ruled out either by testing or replacing:

Front & rear flanges
Front and rear half shafts look fine removed - no sheering of the teeth
UJ's in both prop shafts
Gearbox mounts & engine mounts
transfer case rear & front flange play LOOKS within spec. There does not appear to be any play between the engine (flywheel locked) and the hand break thus not an issue with the output pinion sheering
there is only a fraction of the slack in the front diff (around 1/32 of a turn?)

It's starting to look like the rear sals diff has an excessive amount of play in it. Can someone confirm how much play there should be? The diff gets rather warm on 50km trips - not impossible to put my hand on but rather uncomfortable! Around the same as the gearbox/transfer.

Is it possible to reset the backlash of it, or am I to look for a new diff center? Any further tests I can try on other equipment?

**clive22** · 3rd April 2014, 11:39 AM

Hi

Check you're ball joint on the A frame the symptoms sounds characteristic of this being worn.

Worn ball joint allows diff assembly to rotate a small amount then clunks when runs out of play.

Temp/Heat in Sals sounds about right uncomfortable to touch or somewhere about 60 degrees.

Clive

**steveG** · 3rd April 2014, 11:43 AM

What play do you see when you put the handbrake on, jack up one wheel and try to rotate it?
Any backlash has to be from handbrake drum rearwards.

With the vehicle in gear (engine not running) and handbrake on, jack up one front wheel and see how much it rotates. Any backlash is between clutch and front wheels
Repeat with the center diff locked. Any play is between front output flange and front wheels.

That should give you a pretty good idea of where to concentrate your efforts on.

I doubt that the backlash is in the Sals, but its possible.

Steve

**rick130** · 3rd April 2014, 11:44 AM

You'll burn skin on a Sals after a good highway run of a couple of hours, hypoid dffs generate a bucket load of heat.

**Bearman** · 3rd April 2014, 12:02 PM

Another thing to look at if you narrow it down to the rear is slop in the diff centre. It is unlikely it is backlash between pinion/crownwheel but more likely slop in the side gears/pinions. They do have replaceable thrust washers under them and is not a big job to replace them. Check the gears and crossshaft for wear while you are at it - it all contributes to slop at the wheel.

**harro** · 3rd April 2014, 12:08 PM

Sounds like you have checked all the usual suspects.
It looks like centre out and backlash reset as you have said.
Shims for the sals.
Have a look at this;
Land Rover Addict Forums

Cheers,
Paul.

**phibbzy** · 3rd April 2014, 12:36 PM

Originally Posted by clive22

Hi

Check you're ball joint on the A frame the symptoms sounds characteristic of this being worn.

Worn ball joint allows diff assembly to rotate a small amount then clunks when runs out of play.

Temp/Heat in Sals sounds about right uncomfortable to touch or somewhere about 60 degrees.

Clive

I've had a bar on the A-Frame joint and there is no play, so I have ruled that one out.

**phibbzy** · 3rd April 2014, 01:13 PM

Originally Posted by steveG

What play do you see when you put the handbrake on, jack up one wheel and try to rotate it?
Any backlash has to be from handbrake drum rearwards.

With the vehicle in gear (engine not running) and handbrake on, jack up one front wheel and see how much it rotates. Any backlash is between clutch and front wheels
Repeat with the center diff locked. Any play is between front output flange and front wheels.

That should give you a pretty good idea of where to concentrate your efforts on.

I doubt that the backlash is in the Sals, but its possible.

Steve

Rear driver wheel jacked up, hand brake on, rear pass wheel on the ground - wheel rotates AROUND 30 degrees (memory serving me here, will confirm tonight). With both wheels on the ground, hand break off (and indeed without the prop shaft on the vehicle at all) the rotation on the input pinion on the sals is about 1/8th of a turn before any take up.

Front in the same circumstances seemed good - pinion was only moving a FRACTION.

I'll look into these shims in the sals. Guess its time to get a manual from somewhere and finally invest in that DTI gauge?

2stroke · 3rd April 2014, 07:47 PM

Have you checked the drive flanges? The most common source of backlash, even lack of drive in extreme cases.

**85 county** · 3rd April 2014, 08:06 PM

Originally Posted by phibbzy

Rear driver wheel jacked up, hand brake on, rear pass wheel on the ground - wheel rotates AROUND 30 degrees (memory serving me here, will confirm tonight). With both wheels on the ground, hand break off (and indeed without the prop shaft on the vehicle at all) the rotation on the input pinion on the sals is about 1/8th of a turn before any take up.

Front in the same circumstances seemed good - pinion was only moving a FRACTION.

I'll look into these shims in the sals. Guess its time to get a manual from somewhere and finally invest in that DTI gauge?

Na forget that, just get a locker

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