Ferret erratic knocking from left hand side front.

[Malcolm Towrie]

Update: it was the inner tracta joint that partially seized due to low oil level. Our mistake, obviously. The long drive generated enough heat in the joint to blue the steel. As Richard said, the ensuing galling created high spots on one face and low spots on the mating face. So under load they locked together and prevented the faces sliding. The inner joint only pivots vertically to accommodate suspension movement up and down, so it didn't knock when turning, just when loaded.

The tracta joints look particularly susceptible to low oil level because their small diameter means they loose the oil splash sooner as oil level drops.

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Another question: we have no spare left front/right rear bevel box so I need to steal parts from some spare right front/left rear boxes we have. But the bevel gear design in the spares is significantly different. The bevel gear is one piece, incorporating the hub, unlike the original gear which has the hub riveted to the gear. Also the tapered roller bearing between the tracta joint and the bevel gear is much larger than the original. See the photo of a good spare below. Are they interchangeable?

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It looks a bit laborious setting up the bearing preloads, lash, and tooth contact without the special tooling in the manual.

Malcolm

[Lynn Eades]

Can you not dress up the old one Malcolm?

[Malcolm Towrie]

Looked a bit dodgy, Lynn. What with the bluing of the joint due to overheating and the quite bad galling. I'd rather replace it.
Malcolm

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[Richard Farrant]

Hi Malcolm,
I was pretty sure it would be a tracta. The problem is when topping up the oil, people often think that when the oil globs out of the hole as soon as they start filling, that it is up to level, whereas it is air pushing the oil back out of the horizontal level tube. The trick is to use a hand pump of low volume output with a small pipe that can be inserted right up the tube and thus letting air out as you fill, this is useful on other top up points as well. I have a converted grease pump which have been using for 20 years on many type of vehicles without issues.

regards, Richard

[motto (RIP)]

Having little experience with tracta joints I may be speaking out of turn but in general terms the importance of lubrication cannot be overstated. The joint in question appears to have been operated bone dry and simply filling the housing to the correct level with the correct oil may have solved the problem despite the appearance of the parts. I would have no hesitation in following Richard's earlier suggestion to remove the high spots and put it back to work. (Though he hadn't seen the damage at that point).
After all, any of the other joints in the vehicle could be almost as bad and you wouldn't know until it started talking to you.

David

[Richard Farrant]

Originally Posted by motto

Having little experience with tracta joints I may be speaking out of turn but in general terms the importance of lubrication cannot be overstated. The joint in question appears to have been operated bone dry and simply filling the housing to the correct level with the correct oil may have solved the problem despite the appearance of the parts. I would have no hesitation in following Richard's suggestion to remove the high spots and put it back to work.

David

Hi David,
It is difficult to judge the surface of the tracta parts in the photo, but when metal transference happened, a pit and a pimple, if it was only a small area, the surface could be stoned smooth and clearance checked and re-used. Our inspection standards (REME) stated that a certain percentage of area could be affected but still used as any small pockets/pits retained oil.

regards Richard

[Lynn Eades]

I saw it like David. Clean off the high spots put some lube on the mating components and see how smoothly they move relative to each other When you get it so that it all feels good put it back together.
I would doubt the colouration is serious. You will know when it is a problem,if indeed it becomes a problem. You might get many years out of that Tracta joint. That's why I made the suggestion.
The worlds supply of ferret parts will run out one day.
I may be wrong, but isn't it worth a shot?