Ferret erratic knocking from left hand side front.

[Malcolm Towrie]

We drove a Ferret about 15 miles to a Canada Day parade with no problem but during the parade, it started to knock once loudly when braking to a standstill. This was coming from LHS front, outside the hull. By the end of the parade, the knocking was much worse. Multiple knocks, erratic, not related to wheel speed, like someone hitting the outside of the hull with a hammer, and only when drivetrain was loaded. I could feel the impact on the hull from the inside. When coasting downhill, i.e. unloaded, there was no knocking.

No obvious loose suspension parts. Pulled the brake drum off and no breakage or loose parts.

For info, I dismantled the hub a while back to replace the brake backing plate.

Anyone experienced this ?

Malcolm

[Robin Craig]

It might sound like one thing but may be another.

I had a bevel box input bearing go (long story) that sounded like that as the input flange thwacked around as it destroyed itself.

I am sure it will reveal itself shortly in a pile of expensive broken bits

[Richard Farrant]

Hi Malcolm,
If this is what I think it is, I have dealt with it on numerous occasions, with Ferret as well a Saracen, Stalwart, Fox, etc. It could well be a metal deposit between the a tracta fork and knuckle on an outer tracta joint. Due to localised heat a pit occurs on one part and a deposit on the other and when driving in a straight line this does not create any or much noise, until you steer off centre and the pip is then not aligned with the pit and then knocking occurs. What you could do is jack up both wheels one side and get someone to turn the rear one and watch the front wheel, if you have the steering slightly one way you may notice the wheel kick as it turns. Depending on how big an area is damaged it is permissible to stone down the damaged to regain working clearance, the pit actually serves as an oil retainer, just depends how bad it is.

regards Richard

[Malcolm Towrie]

Originally Posted by Richard Farrant

Hi Malcolm,
If this is what I think it is, I have dealt with it on numerous occasions, with Ferret as well a Saracen, Stalwart, Fox, etc. It could well be a metal deposit between the a tracta fork and knuckle on an outer tracta joint. Due to localised heat a pit occurs on one part and a deposit on the other and when driving in a straight line this does not create any or much noise, until you steer off centre and the pip is then not aligned with the pit and then knocking occurs. What you could do is jack up both wheels one side and get someone to turn the rear one and watch the front wheel, if you have the steering slightly one way you may notice the wheel kick as it turns. Depending on how big an area is damaged it is permissible to stone down the damaged to regain working clearance, the pit actually serves as an oil retainer, just depends how bad it is.

regards Richard

Richard,
This noise happens when going in a straight line and only when the drivetrain is loaded. Steering left or right doesn't seem to make any difference. And it's not a regular click-click while turning like I have heard from pitting of CV joint bearing surfaces. Sounds more like what Robin is describing.

Malcolm

[Grant Hopkins]

Sounds familiar, I had a bevel box go on my Ferret in the RH rear position. It started to clunk and got rapidly worse on the way back to park it, it even locked up a couple times and I had to move it in reverse briefly to unlock and continue ahead. I wouldn't recommend driving it until you figure out exactly what is wrong, it could become a very heavy and difficult to move roadblock.

[45jim]

Insect suspension ball joints, steering joints and wheel nuts to ensure tight and serviceable. If all OK, disconnect the driveshaft from the transfer box to the suspect bevel box. Drive the Ferret around a parking lot to see if the noise is related just to the suspect wheel station. If noise stops suspect u-joint on driveshaft or bearing on bevel box input or transfer box output or the transfer box itself. If still knocking from the wheel station you know your problem is the wheel station itself, remove the outer hub cover and remove the sun gear and replace the cover. Move the vehicle carefully in a straight line. The tracta joint and bevel box will be disengaged and should remain stationary. If the noise goes away your problem is there and you will have to remove the wheel station to further diagnose. If the noise is still there you will have to dig further into the hub itself as this may be a bearing failure or a broken gear in the reduction hub.

[Malcolm Towrie]

Originally Posted by Grant Hopkins

Sounds familiar, I had a bevel box go on my Ferret in the RH rear position. It started to clunk and got rapidly worse on the way back to park it, it even locked up a couple times and I had to move it in reverse briefly to unlock and continue ahead. I wouldn't recommend driving it until you figure out exactly what is wrong, it could become a very heavy and difficult to move roadblock.

Grant, what had actually failed in the bevel box?

Malcolm

[Malcolm Towrie]

Originally Posted by Robin Craig

It might sound like one thing but may be another.

I had a bevel box input bearing go (long story) that sounded like that as the input flange thwacked around as it destroyed itself.

I am sure it will reveal itself shortly in a pile of expensive broken bits

Robin,
Did you hear the input bearing get noisy before the flange thwacking started? Or did the bearing just collapse, like they do if the cage suddenly breaks up?

Because in our case, the front left wheel station was running smoothly and quiet until the knocking started quite suddenly.

It's off the road until this is fixed, which may be take a while due to other priorities.

Malcolm

[Malcolm Towrie]

Originally Posted by 45jim

Insect suspension ball joints, steering joints and wheel nuts to ensure tight and serviceable. If all OK, disconnect the driveshaft from the transfer box to the suspect bevel box. Drive the Ferret around a parking lot to see if the noise is related just to the suspect wheel station. If noise stops suspect u-joint on driveshaft or bearing on bevel box input or transfer box output or the transfer box itself. If still knocking from the wheel station you know your problem is the wheel station itself, remove the outer hub cover and remove the sun gear and replace the cover. Move the vehicle carefully in a straight line. The tracta joint and bevel box will be disengaged and should remain stationary. If the noise goes away your problem is there and you will have to remove the wheel station to further diagnose. If the noise is still there you will have to dig further into the hub itself as this may be a bearing failure or a broken gear in the reduction hub.

Thanks, Jim. Good logical diagnosis. We've inspected brakes and suspension so far. All looks good.

Malcolm

[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.



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?



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

[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]

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?

[Malcolm Towrie]

I just found these responses. I guess MLU doesn't send an email when people post.

It comes down to a judgement call, doesn't it, and my judgement was the two inner tracta joints and shaft forks in the bevel box were too badly damaged to reuse, and I was lucky enough to have spares so I replaced them.

The bevel box is back together and has been reinstalled in the Ferret.

Malcolm

[Lynn Eades]

Great to hear you have mobile again, Malcolm. As the owner your judgement is tops in my book.
David and I were just offering our advice / opinion, hoping it would help you.

Of course it came with a 100% money back guarantee.

[Malcolm Towrie]

Not quite mobile yet, Lynn, but getting there.

So the inner tracta joint is all new, but just to let you know about the outer tracta joint; the hard chrome plating of the hub shaft fork had some pits (due to fatigue spalling, I think), which had caused some galling on the mating tracta joint "ball" (jeez, the part names are complicated). But this damage had not been causing any running problems prior to the inner tracta joint seizing so I happily stoned off the high spots on the joint "ball" and reused the parts.

Now, knowing I have a money back guarantee makes me feel even more confident.

Malcolm

[Lynn Eades]

We're a helpful lot here Malcolm