LT230 grinding noise?

[Hardebeck]

Hi all, at my wit's end and looking for suggestions. I think it's the transfer case, but here's the issue.  Recently purchased 92 200Tdi with LT77 and LT230, 98,000 miles. Had a moderately noisy throwout bearing when I bought it so when it stranded me on the highway I assumed it was the clutch (yes, I know).  Lowered the transmission and transfer case with no apparent issues, replaced the clutch with heavy duty unit from LOF, and problem persists. Pulled right front hub and found swivel ball full of rust, no grease, rusty bearings, broken CV joint.  Replaced both side swivel balls, CVs, etc.  Test drive had a grinding/whining noise from what seemed to be the transfer case (this was new).  Couldn't shift from H to L.  Pulled console again, found missing pin on difflock linkage, replaced, same issue.  Shift linkage seems to be binding and maybe transfer case not completely in gear?  This time pulled shift mechanism, linkages, diff shift housing, cleaned up, couldn't find any obvious issues, reassemble, H-L shift and diff lock seem to work properly now.  Test drive and still same grinding/whining.  Videos in attached link where I tried to capture the noise. Low speeds around my driveway.  Noise seems to go away when clutch is engaged and especially loud when engine braking. Looking for any suggestions/ideas to look at next.  Could the CV joint failing at 60mph somehow have damaged the transfer case?  Was in H with no diff-lock of course.  According to records, both transmission and transfer case were replaced with reconditioned unit in UK in 2016, about 20,000 miles ago.  Appreciate any and all help!

92 200Tdi noisy transfer case

[Stellaghost]

Have a check of your prop shaft universal joints ( the drive shafts from the transfer case ) they could be dry and/ or have play in them, also check the transfer case output shaft bearings

Regards Stephen

[Bowie69]

Perhaps take the linkage back off and select the range and difflock manually, and try again, it may still be out of adjustment. 

Otherwise if it's not props as above, then need to look elsewhere... 

[Hardebeck]

Just climbed under the truck and I don't think it's the propshafts.  The u-joints have no obvious play and the noise only appears when in gear and moving.  If I'm coasting with the clutch is engaged or have the transmission in neutral, the propshafts are rotating and I would think if they were the source of the noise I'd still hear it.  I had thought maybe the hand brake was dragging but the same logic would apply. If that logic is sound, I should be able to eliminate those as the source.  I would think the same logic would apply to the diffs, unless the noise only appears when there's a load being applied. Still scratching my head.

The noise really sounds (to me) like gears that aren't fully engaged.  I assumed transfer case because that seems to be the source of the noise but not sure. Definitely front end so maybe the front diff.

Edited November 25 by Hardebeck
added more content

[FridgeFreezer]

You can remove a propshaft and drive it in diff lock to narrow it down front/rear, just remember the rear prop holds the handbrake drum on!

[Stellaghost]

4 hours ago, Hardebeck said:

Just climbed under the truck and I don't think it's the propshafts.  The u-joints have no obvious play and the noise only appears when in gear and moving.  If I'm coasting with the clutch is engaged or have the transmission in neutral, the propshafts are rotating and I would think if they were the source of the noise I'd still hear it.  I had thought maybe the hand brake was dragging but the same logic would apply. If that logic is sound, I should be able to eliminate those as the source.  I would think the same logic would apply to the diffs, unless the noise only appears when there's a load being applied. Still scratching my head.

The noise really sounds (to me) like gears that aren't fully engaged.  I assumed transfer case because that seems to be the source of the noise but not sure. Definitely front end so maybe the front diff.

If your coasting there is no load on the joints so you may not hear anything, not always a good policy to check prop shaft play on the vehicle unless your going to the trouble of jacking wheels up so you can rotate the joints whilst still on the car

Regards Stephen

[JohnnoK]

Chock the wheels to prevent the vehicle rolling away and disconnect both propshafts at the transfer box and run it again to see if it repeats.

Run through the gears and listen if the noise changes pitch... if the pitch changes as you go up through the gears, then it could be TC related.

I can't see the propshaft failure causing a TC issue, in my mind that would affect the diff.

[FridgeFreezer]

2 hours ago, JohnnoK said:

I can't see the propshaft failure causing a TC issue, in my mind that would affect the diff.

A seized sliding joint can push against the bearings in the diff/TC and destroy them, but there would likely be oil everywhere.

That said, if OP found one CV totally dry and full of rubbish the whole truck could need a damn good once over to check all the oils etc. as it's clearly not been done.

[Hardebeck]

Update - I put the truck on jackstands in my garage, removed both propshafts, and ran it. The noise from the road test was gone. Added several videos to the album (link below) that show me running through High and Low, diff lock engaged and disengaged, and running through 1-4 and reverse.  Shifting the transfer case was a bit difficult in the beginning, but it seemed to loosen up a bit by the end and I'm able to hit all positions easily now.  The diff lock seemed to work; light came on and I verified both outputs were locked when not running.  There is about 1/8 or so free play in the transfer case outputs when the difflock is engaged and I held the propshaft brake steady while turning the front output (there's a video showing this). I'm not sure if that's excessive.  There was no strange or concerning noise unlike the road test, but the transfer case and transmission were free wheeling so maybe the noise only appears under load.  I couldn't detect any obvious issues with either diff although the front had a bit more play than the rear in the rotational axis but no play in either in and out (video).  Both propshafts appear to be in good condition; all U-joints move freely and smoothly, no play detected in the endcaps, and the spline joints also move freely in and out, no side to side play (video).

I'm a bit stuck figuring out my next move.  Should I should drain and pull the front diff to see if there's damage?  I changed the fluid and saw nothing metallic, and it's quiet and smooth when rotating either front tire by hand on jackstands. However, when the right CV joint gave way perhaps that shock and vibration down the axleshaft buggered up the diff.  My other thought is that it is indeed the transfer case, and the problem had nothing to do with the CV joint issues.  When I started digging into this after the clutch and the hub overhauls, that's when I noticed that the top pin that connects the diff lock linkage to the sliding rod in the shift mechanism was missing.  I'm now wondering if the PO removed this pin to "fix" an issue with the transfer case and just left it in High.  I don't think I ever tried to shift the transfer case previously until I changed the clutch and reinstalled everything.  When I tried to shift, maybe I undid PO's previous fix?  Yes, I know I should have tested H, L, and diff lock before I bought it, but I took my buddy's word that everything was working properly.

Appreciate thoughts and suggestions as I contemplate what comes next.

Troubleshooting 92 Disco 200Tdi with noisy transfer case

[fmmv]

Another, more western, way to check propshafts under load is to drive it and then feel them (gingerly) for heat. It's amazing how hot they get when seized, in a short distance - not too far from home. A bit of warmth is OK, but you should be able to touch it. Could also be the handbrake, again absence of heat is good.