Landy89 · Mar 15, 2011

I need a little help diagnosing the source of a knocking sound and more importantly if it is a problem or not.

1989 Defender with about 400,000kms on it. New 300tdi motor and new R380 gearbox. The transfer box and the read diff is original. Front diff is a year old. Wheel hubs have all been inspected in past 2 months and tightened.

There is signifigant slack in the drivetrain such that when i shift gears there is a clunk sound from the propshaft. I can turn the prop shafts significantly by hand before they catch inside the transfer box. If i shift gears carefully and slowly, i can eliminate the clunk sound, but i would rather like to know if i have a problem that needs to be repaired or not. What do you think?

jamesmartin · Mar 15, 2011

i would check drive flanges and half shafts remove caps and get somone to rock it on the clutch ,rear diff ,a frame ball joint ,its difficult to explain free play in t/box as it has diff which adds to movement ,

Landy89 · Feb 4, 2013

Hi

I recently overhauled the transfer gear box and the transmission, in the process changing the main shaft and the input gear. This made a huge difference in removing almost all of the slack i had in the drivetrain. However, there is a little bit of slack left and I know exactly why: the rear drive hub flanges are not a perfect fit with with the rear drive axle shafts.

Should I replace only the rear drive flanges or should I replace drive flanges and the axle shafts? I am wondering that someone might have some experience with this type of thing; that is, that perhaps the metal of the shafts is of higher durability and perhaps doesn’t wear at the same rate as the flanges? Replacing the shafts is a bit of a problem for me as I would have to smuggle the shafts in my luggage, whereas the drive flanges are much easier to carry in my luggage. The car is not in europe.

Also I am using 85W-140 in both diffs and the transfer case. This has been recommended to me by an LR parts distributor in south america; I assume so because of the temperatures I drive in are between 30 and 40 C. I never drive in temp below 5C and very rarely below 20 C. I had 90 weight gear oil in the diffs and transfer case a few years ago, but it was a constant source of leaking seals. I never thought much of the 85W-140 being a problem up until now. Recently the rear drive flanges were leaking oil (gasket was non-existent it turned out), and when I removed the drive flanges to inspect, I noticed that the oil was completely black, despite the oil in the diff was clean. Do you have any opinions on this?

Brown · Feb 4, 2013

I've done this job and discovered that there was a lot more wear on the female splines on the flanges than on the halfshafts themselves, so yes, maybe they are made out of something harder. But have a look and see what shape the splines are. If they're a nice V shape you're probably OK for a while yet, whereas if they're sawtooth shaped then it's worth renewing. I just replaced my flanges, and got the sort with screw-on caps so I could put some oil in there and keep the splines moist. It more or less eliminated the clunk I'd been getting on taking up drive.

jamesmartin · Feb 4, 2013

Landy89 said:
Hi

I recently overhauled the transfer gear box and the transmission, in the process changing the main shaft and the input gear. This made a huge difference in removing almost all of the slack i had in the drivetrain. However, there is a little bit of slack left and I know exactly why: the rear drive hub flanges are not a perfect fit with with the rear drive axle shafts.

Should I replace only the rear drive flanges or should I replace drive flanges and the axle shafts? I am wondering that someone might have some experience with this type of thing; that is, that perhaps the metal of the shafts is of higher durability and perhaps doesnt wear at the same rate as the flanges? Replacing the shafts is a bit of a problem for me as I would have to smuggle the shafts in my luggage, whereas the drive flanges are much easier to carry in my luggage. The car is not in europe.

Also I am using 85W-140 in both diffs and the transfer case. This has been recommended to me by an LR parts distributor in south america; I assume so because of the temperatures I drive in are between 30 and 40 C. I never drive in temp below 5C and very rarely below 20 C. I had 90 weight gear oil in the diffs and transfer case a few years ago, but it was a constant source of leaking seals. I never thought much of the 85W-140 being a problem up until now. Recently the rear drive flanges were leaking oil (gasket was non-existent it turned out), and when I removed the drive flanges to inspect, I noticed that the oil was completely black, despite the oil in the diff was clean. Do you have any opinions on this?

thicker oil wont hurt ,but will cool less efficiently on long road journeys ,id replace shafts and drive members

Brown · Feb 4, 2013

Just seen the other bit of your question. I've drained quite a bit of oil out of axles over the years and it's always been black, no matter what colour it is when it goes in. It often looks sparkly in sunlight with all the little bits of metal in there. I think the main thing is not so much the colour but whether you refresh it regularly. I haven't got my manual to hand (it's out in the car) but I think it's supposed to be changed every 24,000 miles.

Landy89 · Feb 4, 2013

thanks for the replies. I think I will change only the drive flanges for now and see how that turns out. I guess i will also keep the 85W-140 oil in the diffs and transfer case, unless someone tells me otherwise.

It was strange to me that the oil in the caps on the drive flanges was black, while when i looked in the diff, the oil there was clean. I try to change the oils in the transfer case and diffs about every 20,000kms.

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