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!

200Tdi noisy transfer case

 

[German Gruner]

The most possible is bearings wear. LT230 has hipoidal gears. This is, their theets are oblique in order to get less noise (plain teeth gears usually sound as if they cry). But these oblique teeths do make axial charge, and this charge direction depends on effort of gears by braking or accelerating. When conic bearings specially from intermediate axle get wear, then you usually feel this kind of noise. After changing bearings and mounting with all indications from overhaul manual LT230 your transfer box will work just as new...

Regards

 

[hardebeck]

The most possible is bearings wear. LT230 has hipoidal gears. This is, their theets are oblique in order to get less noise (plain teeth gears usually sound as if they cry). But these oblique teeths do make axial charge, and this charge direction depends on effort of gears by braking or accelerating. When conic bearings specially from intermediate axle get wear, then you usually feel this kind of noise. After changing bearings and mounting with all indications from overhaul manual LT230 your transfer box will work just as new...

Regards

Thank you for the thoughts. This sound wasn't there before I dropped the boxes and replaced the clutch. Why would bearing wear suddenly appear after reinstalling everything? I dropped both prop shafts as well. Greased the zerks and didn't notice any significant play in the u-joints but I'm not sure i reinstalled the mating flanges in the original order. Could that be a factor?

 

[LRDONE]

I think your problem may be within the front diff. Now that both ends are tight and correct, you're amplifying a problem in the diff. If it ran 3 wheel drive for awhile at high speeds, I don't think that's good on them. If it were your transfer case it wouldn't be such a new problem. Front diff and front driveshaft problems travel through the HI/LO selector very well. Diff problems make noise on acceleration and deceleration.

 

[hardebeck]

I think your problem may be within the front diff. Now that both ends are tight and correct, you're amplifying a problem in the diff. If it ran 3 wheel drive for awhile at high speeds, I don't think that's good on them. If it were your transfer case it wouldn't be such a new problem. Front diff and front driveshaft problems travel through the HI/LO selector very well. Diff problems make noise on acceleration and deceleration.

Thanks. That was my original thought after I replaced the clutch. The first thing I did was drain the front diff and didn't see any debris so when I pulled the front hubs and saw the failed CV I figured that was the problem. There were no vibration or noise issues prior to the CV joint failing, and the whining/grinding started after I replaced the clutch and rebuilt both front hubs. If the diff was bad previously, wouldn't I have heard it? I'm now wondering if the propshafts are the culprits. Probably worth replacing the U-joints anyway but I don't know if that will matter if they are out of balance.

 

[hardebeck]

After climbing under the truck and thinking about this some more, I don't think it's the propshafts. U-joints have no play and the noise goes away when clutch is engaged/in neutral but still moving. I would expect propshafts would still be noisy if moving. I suppose the front diff could have been damaged with the shock of the CV joint failing. Since it doesn't make the noise when I'm coasting, maybe it only appears under load. I guess my next move is to drain it and pull the cover to take a closer look. Anything I should be on the lookout for besides chunks of metal?

 

[German Gruner]

To check for axial play in the diff pinion

 

[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

 

[LRDONE]

That sounds like a bad bearing in the transfer box to me. You could use a stethoscope or chassis ears to try and find the loudest point on the transfer box. Also, nice 911.

 

[hardebeck]

Thanks. Depending on which bearing is it possible to replace without dropping the transfer case?

Thanks re the 911 as well. I prefer classic vehicles that are analog and I can work on. I’ve found both German and British makes share quirky engineering; the Germans just tend to be more precise in their quirkiness.

 

[LRDONE]

To be honest, it's pretty easy to drop the transfer case. I have mine out currently, I removed it last week in the garage with hand tools and a jack. Then brought it to work. But I would confirm that the noisy bearing is in the transfer case first.

I hear ya on the German quirkiness too. I mostly fix Porsche for a living, super strong customer base here in Ann Arbor. Currently building a 964 motor for a customer.

 

[hardebeck]

Had a chance to pull the front diff and it looks pristine. No sign of damage and barely any wear to speak of.

I ran the truck while it was on the stands and listened to the transfer case with a mechanic's stethoscope. It was a bit noisy but I can't tell if it's normal. Holding the output flange and jiggling the front sounds like it's got more movement than is healthy:

LT230

Any thoughts on whether this is normal? My next step is to drop the transfer case and take a closer look. It sounds like the shift fork may not be fully engaging.

Also, for anyone who's interested, this is what I found when I opened up the right front hub:

 

[LRDONE]

The broken cv is new damage or this is the original damage that was replaced?

 

[hardebeck]

Original damage. After I replaced and test drove the new noise started. Seems to be coming from transfer case.

 

[LRDONE]

The center gears in that front diff look to have been replaced. I didn't know there were replacements out there. The cut on those gears looks like the gears I just replaced in the center diff in my transfer box. They have that sharp cut.

 

[kris812]

I did a write up on vibration and front output I suggest reading through.

The front output should have .005" thousandths play and no more.

You can change that bearing pretty easily. I used the flange as a slide hammer on the nut to remove it. And that nut was Jesus (500#+) tight. Someone hammered it in!

Secondly, has the vehicle been lifted?? If so the DS angles are fracked now. It'll take some angled trailing arms, double cardan DS, and spacers on rear to get it straightened out.