I have now done 70 fun filled miles in the car and there is a noticeable whine from the diff on the over run. The whole rear axle is a later one from a 36 Ruby which was already on the car. Obviously I put new oil in during the re-build (SAE140) and so I decided to check the condition of this oil to see if it gave me a clue as to what was wrong. The oil came out somewhat dark and I soon collected a number of small metal flakes with a magnet. Thinking that maybe they were a result of my poor cleaning of what was a very sick diff casing, I was not too worried, but then I looked at the oil in the sun. It is completely full of extremely fine bronze or brass dust which gave the dark appearance out of strong light. They are so fine that they don't seem to want to settle. Where is this coming from? The only part that I can think of is the oil thrower.
Now to admit some naughty pre-conditions. My car was sold with a rear axle problem. I found what looked like aluminum paint instead of oil inside and all the pinion bearings had collapsed and bits had come into the diff. See photo It must have sounded terrible. So I managed to find a matching number pinion and crown wheel which are installed - aligned as best as I could at the time. (I aligned it using red paint, but now that I have gear blue a second try is in order).
The torque tube would not come apart as the oil thrower would not come out with despite lots of heat and a C spanner almost cutting off the lugs. As the pinion seemed to spin cleanly I decided to run with the replacement torque tube/pinion assembly as is.
Purists will be cringing, and no doubt I got what I deserved; but even so, were has the bronze dust come from? Remember, none of the parts in the photo have been re-used.
Graham
18-01-2023, 09:31 AM (This post was last modified: 18-01-2023, 09:32 AM by Colin Reed.)
Hi Graham
i dont know what experience you have regarding mechanical repairs
But from my point of view when some one says that a part has been re built
the problems with the gearbox and diff should not be happening
try and find a mate or a club member who has done this type of work before
and ask if they would give you a hand next time
you will find that for some one to show how it is done will be much easily under stood than trying to follow written
Instructions
Hope that does not sound patronizing
Best of luck
Colin
NZ
Oil that looks like silver or gold paint should set alarm bells ringing. Stop driving it until you discover which piece of metal is being ground to powder!
It's hard to know where to start Graham, even the 'experts' among us hesitate when it comes to axle set-up.
A certain amount of gold dust is not necessarily fatal - there are bronze bushes in the differential and also the side adjusters.
Steel particles which you can pick up with a magnet would worry me more, but if you have re-used an old CWP then a small amount of debris from re-bedding is perhaps to be expected.
It troubles me that you weren't able to strip the torque tube assembly - in particular did you check it for any end float?
The likelihood of re-using a CWP pair in a new axle and getting silent operation is fairly small. If it's noticeably worse in one direction you might want to tinker with the settings a little.
It's hard to give concrete answers, and tempting to say "give it to a specialist and have it rebuilt properly" though that is likely to cost you an arm and a leg. If it were mine I think I'd be looking around for a spare axle which I could build up nicely over a period of time as an eventual replacement.
I blew a back axle once and had the good fortune to have just passed the brow of a hill, and was able to coast 1/2 mile down to my Dad's garden gate (I'd already come 250 miles through the snow...) I don't expect ever to get that lucky again. It's not a thing you want to be trying to fix at the roadside.
I'm aware of the risks of internet 'fault diagnosis' But the Bronze you're seeing in the oil could well have come from a problem with a bearing cage in the axle. Older ball and roller bearings often had their cages in Bronze rather than the steel or even plastic used on most modern bearings. The whining on the overun combined with metal flakes could well be caused by endfloat on the pinion. The helix on the pinion means that it's being 'pushed' on drive and 'pulled' on the overun. The pair of angle contact bearings behind the pinion roller are there to resist backwards and forward movement of the pinion. Wear in these, or the pinion nut coming loose will result in endfloat which causes nasty noises, flaking of the gear teeth and tooth breakage if it's not fixed.
The back axle on my saloon was getting progressively noisier so I drained the oil ready for inspection and found fine bronze particles. Upon dismantling, this was found to be from the ball cages of the thrust bearings.
This was a short nose banjo vintage axle.
Bearings replaced and re-meshed and everything has been fine since (touch wood).
The pinion assembly is the usual culprit in A7 diff demise in my experience, very often the lock nut on the thrust bearing is not tight enough, the bearing spacer then wears creating end float. This state of affairs with the pinion punching back and forth is not favourable for many components as you can imagine. Contrary to Chris experience I have successfully swapped around CWP and even got miss matched CWP to run quietly, but there is a LOT of work and messing around to achieve this.
Thanks all for your comments. It has been hard to get advice even though Auckland has NZ's largest population, there don't appear to be any experts available. The best advice so far has to get another back axle, but they seem to be non existent now.
It sounds as if the pinion assembly that I could not dismantle needs investigation. Thinking about it, why did someone remove that and the crown wheel from a back axle? So I may have inherited an old problem. Time will tell.
Cheers Graham
"Now to admit some naughty pre-conditions. My car was sold with a rear axle problem. I found what looked like aluminum paint instead of oil inside and all the pinion bearings had collapsed and bits had come into the diff. See photo It must have sounded terrible. So I managed to find a matching number pinion and crown wheel which are installed - aligned as best as I could at the time. (I aligned it using red paint, but now that I have gear blue a second try is in order).
The torque tube would not come apart as the oil thrower would not come out with despite lots of heat and a C spanner almost cutting off the lugs. As the pinion seemed to spin cleanly I decided to run with the replacement torque tube/pinion assembly as is.
Purists will be cringing, and no doubt I got what I deserved; but even so, were has the bronze dust come from? Remember, none of the parts in the photo have been re-used.
Graham"
Not sure what you are telling here ?
Did you use the old pinion or was the 'new' pinion in a replacement torque tube ?
The photograph seems to show a very strange front pinion bearing assembly ??
