How to pin-point drive line clunks?

**OffTrack** · 3rd May 2012, 04:54 PM

I'm trying to track down a clunk in the the drive train that most noticeably occurs when lifting off the throttle at highway speed. Switching out cruise control also tends to be a trigger for the clunk.

I've come across a suggestion that moving the auto from drive to reverse can help track down the issue.

The method suggested was:

- high range, cdl unlocked, handbrake on, footbrake off
- high range, cdl unlocked, handbrake off, footbrake on
- high range, cdl locked, handbrake on, footbrake off
- high range, cdl locked, handbrake off, footbrake on.

I was assuming that handbrake on with CDL unlocked would mean you were testing just the TC/CD but after a bit of thought it seems like it must also test front driveshaft and diff.

Handbrake off should test, TC/CD, plus front and rear driveshafts and diffs

Checking with CDL Locked seems to be intended to eliminate the Centre Diff from the equation.

Anyway I gave these checks a go, and found it difficult to hear much beyond a faint dull clunk with the handbrake on. CDL locked and unlocked made very little difference. With the handbrake off, and foot brakes on I could hear a slightly more distinct clunk coming from what sounded like the rear diff or drive shaft.

I'm planning on videoing the universal joints while I do the D <-> R shuffle to see if I can get a more conclusive fix on where the clunk is coming from, but based on what I could hear the rear drive shaft or diff looks like it might be suspect.

If anyone has suggestions on a better way to narrow down the source of the clunk I'm all ears

cheers
Paul

**Blknight.aus** · 3rd May 2012, 05:10 PM

get under the thing when its up on stands and play with bits, turn them by hand and lever them with prybars... the clunks will normally turn up as excessive play.

**OffTrack** · 3rd May 2012, 07:22 PM

Originally Posted by Blknight.aus

get under the thing when its up on stands and play with bits, turn them by hand and lever them with prybars... the clunks will normally turn up as excessive play.

One of the joys of living in the inner urban areas is lack of work space, and no real space to store workshop equipment. I was hoping to be able to identify the issue without having to drive out to visit my parents to put the D2 up on stands.

Is levering with a pry bar the only way to check?

**Blknight.aus** · 3rd May 2012, 08:01 PM

you dont have to lift it all up on stands at once.... so long as you leave the wheels on and only jack to minimum clearance using just the jack to get the wheel off the ground is a workable, but not reccomended, substitute.

**Toppa** · 3rd May 2012, 08:18 PM

Originally Posted by OffTrack

One of the joys of living in the inner urban areas is lack of work space?

Ive seen your lack of space - i never though id get bush pin striping in the city!!

If you feel like a drive to yarraville, ive got a few tools in the shed, a car wash across the road with a good concrete slab and a set of ramps. I feel the need to return the nanocom favour.

If it makes you feel any better, i have the exact same clunk which has become more noticable after reseting the auto. I wouldnt mind trying to figure that one out also.

**OffTrack** · 3rd May 2012, 09:48 PM

It's good practice for tight tracks

I'll send you a pm.

Cheers
Paul

**Toppa** · 7th May 2012, 07:57 AM

Any luck finding a cause.?

Sent from my GT-I9100T using Tapatalk

**OffTrack** · 7th May 2012, 11:32 AM

Not yet. Had to drop out to my parents on Saturday and thought I might get a chance to put the Disco up on jack stands and take a peek. When I got out there Dad was fitting tyre to the rims of his current project and was using all 4 stands.

FWIW this is what he's working on - a 1921 Packard. Pics are posted to an american forum.

The offending wheels

If nothing else it has decent ground clearance, but the ramp over looks pretty bad.

cheers
Paul

**OffTrack** · 9th May 2012, 01:27 PM

Still haven't had the D2 up on stands, but had a look underneath with the transfer case in neutral and handbrake off with the wheels chocked.

I can feel a small amount of play in the sliding joint of the front prop shaft.

There is larger amount of vertical play in the output flange of the transfer case

There is a bit of backlash in the rear diff, and a very obvious clunk from inside the diff housing when you rotate the prop shaft back and forth. I think this is what I've been hearing when I lift off the throttle. I'm not sure how much backlash is acceptable but it doesn't sound particularly good to my ears.

cheers
Paul

**Robgw** · 13th September 2013, 10:44 AM

I have had a similar noise from my D2 for a while.

1) Never at low speeds - 0 - 50kph

2) Never settting off from standing or reversing

3) Only when im on the freeway or crusing at around 60 -80k, I take my foot off the the throttle I get a small clunk from the under and again when accellerating...but again not always..

Somebody told me this is normal as the D2 has a lazy drive train and a small clunking is normal?...

I cant see any issues underneath either.

By Car has clocked 90,000 . . .

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