Ferret erratic knocking from left hand side front.

[Robin Craig]

Malcolm the honest answer is I can not recall the sequence of noises during the failure.

As Jim said raise that side off the ground and you should quite quickly be able to diagnose the troublesome component by disconnecting various items in the drive train.

The cause of failure on the bevel box was a very nicely painted over breather for the bevel box. It had several layers of paint, it is something I warn about often and loudly to new and keen Ferret owners.

[Malcolm Towrie]

Robin,
Why would a plugged breather cause such a catastrophic failure?

Malcolm

[Richard Farrant]

Originally Posted by Malcolm Towrie

Robin,
Why would a plugged breather cause such a catastrophic failure?

Malcolm

Malcolm,
Failures are often due to lack of oil or low levels. With a blocked breather the pressure build up could force oil out of the bevelbox / inner tracta via the cork seal around the inner tracta housing, also it could well pass the seals in the challis and overfill the outer tracta and hub, seen this quite often. It pays to check the levels frequently.

[Robin Craig]

Malcolm,

Richard eloquently and precisely said what I would have replied.

[Phil Waterman]

Hi Guys

Was wondering if any of you have used and IR gun to check the drive train temperature on a Ferret?

On my CMPs I make it a practice to check the drive train of trucks after any drive of length. Using a check sheet I record the different points, transmission, transfer case, brake drums, wheel bearings, etc. If anything is out of line it jumps out pretty quick. The one time I didn't check a +10 F (of norm) wheel bearing temp that was out of line the next time I drove the truck nearly lost a wheel the axle nut keeper had failed.

Would think with a complex drive train like a Ferret you would get a good hold on what normal temps should be.

Cheers Phil

[Malcolm Towrie]

Good point, Phil. It's a lot easier to reach round the tire with the gun than crawling in there. A great way of picking up an oil level getting dangerously low.

But be careful with those cheapy IR cameras with the laser sight. They will read dangerously low if not used properly. This is because the area of the so-called "spot" seen by the camera gets bigger the further away the object is. If you are looking at a small hot object 10' away with a cool background, the gun will give you the average of the 2' diameter circle it is seeing at that distance, even though the laser dot is right on the hot object. So get as close as you can.

Malcolm

[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.

DSC02822.jpg

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?

DSC02863.jpg

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

Malcolm