How to diagnose bad lt230 output bearing vs differential issue

[_ExpeditionMan]

All,

Bought and swapped in a used transfer case and f/r diffs to replace older worn ones on my D1. Ever since I've been having issues with noise/vibration on declutch (it is a manual) and when decelerating in gear. Although it seems to have gotten worse recently. This was not happening before the swap. Cases below.

1) Accelerate at low speeds with no issues. Get to highway cruising speeds in fourth gear. Clutch in. Immediate noise (sounds almost like very fast grinding). Slot into fifth gear clutch return. Noise goes away immediately. Same thing happens going down from fifth to fourth or fourth to third.

2) in fifth gear cruising. Take foot off gas and start decelerating. Not touching brake or clutch (still in gear). Same grinding noises but with vibration. You can feel it in the pedal assembly and front floor (although I have no carpets). This occurs in both third fourth and fifth gears but mostly at speeds above 40mph.

I have done some initial investigation. Remove front DS drive around and try to replicate. Issues above remained. Replace front DS then remove rear DS and attempt to replicate. Issue 1 seemed to go away. Issue 2 was mitigated and I was only able to get it to occur during engine braking once and only briefly.

Therefore, i suspect something between the rear transfer case and the rear diff. I checked the preload on the pinion and the rear output flange with a torque wrench to RAVE spec and both were good. U-joints are old but I dont see any slop or play.

What next? Any suggestions for further analysis before I start guessing? Sound like any issue you've had before?

 

[discostew]

Check that you don't have the park brake too tight. There was a bulletin about that on Defenders

 

[_ExpeditionMan]

Check that you don't have the park brake too tight. There was a bulletin about that on Defenders

When I ran it without the rear shaft I also removed the drum. The shoes and remaining assembly were still in place. Would that have removed the possibility for the defender bulletin?

 

[discostew]

Yes

 

[discostew]

You didn't put a Detroit locker in the rear did you?

 

[_ExpeditionMan]

No. open and open. It sounds like gear noise but with vibration that resonates into the cab. Plus the grinding. The only reason I suspect more diff than transfer case is that I suspect a bad bearing would make noise/vibration all the time. Instead of just occasionally. And I am limiting my inspection to the used parts.

 

[discostew]

it's really hard to diagnose a problem like this from a thousand miles away. You could drain the oil into a clean pan and catch some from about the middle of the flow in a glass jar and look for metal in the oil.

 

[German Gruner]

I think your problem is rear diff pinion bearings.
Hipoydal gears tend to move axial when acceleration becomes desacceleration. This produces a typical noise as diff is dragging pinion when car is pushing gearbox and engine. When engine is pushing, pinion locates in its usual position and noise goes away.
This issue could be possible to occur inside LT230, but you did run it with central diff locked when each DS was token out. If transfer box output shaft bearings do have wear, by locking CD you could find noise is less. With locked CD you described only noise has changed without rear DS. So I think from this all, you should change rear pinion bearings
Regards

 

[_ExpeditionMan]

it's really hard to diagnose a problem like this from a thousand miles away. You could drain the oil into a clean pan and catch some from about the middle of the flow in a glass jar and look for metal in the oil.

Yeah I definitely appreciate the difficulty. It is really all of us rubbing our heads together and taking wild guesses. But it is free and helps me bounce ideas off of other similarly afflicted land rover owners. Regardless I appreciate the time users here take to read and respond.

 

[_ExpeditionMan]

I think your problem is rear diff pinion bearings.
Hipoydal gears tend to move axial when acceleration becomes desacceleration. This produces a typical noise as diff is dragging pinion when car is pushing gearbox and engine. When engine is pushing, pinion locates in its usual position and noise goes away.
This issue could be possible to occur inside LT230, but you did run it with central diff locked when each DS was token out. If transfer box output shaft bearings do have wear, by locking CD you could find noise is less. With locked CD you described only noise has changed without rear DS. So I think from this all, you should change rear pinion bearings
Regards

Thanks for the response. The one concern i have with this diagnosis (and I believe it is most likely) is that I was able to replicate issue 2 once myself without the rear DS installed. So does that mean the rear diff can make noise during coast without true load from the DS? I suppose so but it should be far less right?

 

[Harv]

I wouldn't expect it to make much noise when it's just along for the ride.