Wheel Drive Oil Leak... Help!!!!!

[GRCameron]

If you examine the load path through the wheel flange into the housing, end thrust on the flange is reacted through the outer wheel bearing which is a deep groove ball bearing. The inner wheel bearing is a cylindrical roller bearing and is not capable of thrust loading. The three bolts on the inner end of the flange shaft, along with the press-fit of the outer bearing, prevent the flange from separating from the vehicle along with the wheel, and brake drum. If these three bolts loosen and fail one could be in peril of losing a wheel at speed - not a good scenario. I don't know if this has ever happened to anyone, but it is a possible failure mode.

There must be a significant amount of thrust loading on the wheel flange that stresses these three bolts beyond the clamping load they produce from torquing at installation or why would they loosen? Perhaps their initial preload is lost or reduced by embedment relaxation under the heads of the bolts or a soft component in the system (retainer?). Stronger bolts, higher preload (torque), and hardened washers lead to a solution that is better within the constraints of the existing design.

I guess I would take some damaged gears over a wheel separation, but I don't see the gears damage as an overriding issue. Failure of the inner flange bearing would probably happen before gear damage or perhaps simultaneous to it.

I worked with stuff like this a little bit before I retired, so I tend to look at things from the engineering end of things.

[pcolette]

It's my understanding and observation that it is the retainers (#11 & 23) that are the problem. The retainers are similar to the square washers on the oil pan studs. They have a slight concave/convex curve to them and are meant to act similar to spring/lock washers. Apparently they flex too much or too often and eventually shatter, leaving the bolts with no tension to hold them in place. I've often found that the square washers on the oil pan have cracks in them, perhaps from over-tightening, and they split in two.

If these three bolts loosen and fail one could be in peril of losing a wheel at speed - not a good scenario. I don't know if this has ever happened to anyone, but it is a possible failure mode.

Your explanation of possibly losing a wheel is very interesting - and scary! I may just have to get in there and do the upgrade on the other side.

[John L]

While I am in mine I will obviously be upgrading the one side that failed. If things go smoothly enough and have develop a little confidence in my abilities to handle it I may consider doing the other three as well. All I can say is I was lucky the failure must have happened pretty close to home as the gear oil poured out in my driveway. Otherwise I would probably be facing some gear damage as well. Once I tear into it I'll have a better idea. But, I'm hopeful the amount of oil that leaked out at home was an indication everything was pretty well lubed up to that point.

JL

[Jimm391730]

I believe that the retainers are intended to be bent, folded, stapled, multilated, ( ) around one flat side of bolts to prevent their rotation/loosening. If they were reused, the repeated bending might cause them to fracture and at that time they would have NO retaining properties at all; this would certainly allow the possibility of the bolts loosening.

You should never re-use these types of retainers; they should always be replaced with new if the bolts are disturbed (including just tightening the bolts).

[GRCameron]

The retainers being bent, folded, stapled, mutilated means that they are soft - soft enough that the heads of the bolts embed and lose their preload. This is why the bolts loosen and the joint fails even if the bolts do not turn.

Since longer bolts are not an option in this system as it sits, I believe hardened washers under the heads of higher strength bolts (class 12.9 socket head cap screws) and red Loctite are the right approach to this problem. Proper torquing (3-steps 50%, 80%, 100%) to achieve bolt stress 90% of yield strength should do it. You should know the pedigree of the bolts as there are many counterfeit high tensile bolts on the market...

I was going to write a short treatise on bolted joints but decided not to bore you all. And, it's kind of OT.

For a 2" thick explanation of bolted joints see "An Introduction to the Design and Behavior of Bolted Joints, 3 ed., by John H. Bickford, Marcel Decker Inc, 1995. It's actually quite readable!

Here is another good reference I just found: http://www.fastenal.com/content/documen ... eGuide.pdf

[Jimm391730]

soft enough that the heads of the bolts embed and lose their preload. This is why the bolts loosen and the joint fails even if the bolts do not turn.

If the bolts do not turn, they won't "loosen" (although you are right, they won't have the expected preload if the retainer crushes). But I doubt that it is the lack of preloading that would cause the problem; for the bolts to extend far enough to damage the backing plate they would have to rotate several revolutions to extend far enough to hit. Loss of preload won't change the length (in fact, they will shrink back to their un-loaded length, but we are talking miniscule measurements here). And the manufacturer has not changed this part of the design over the years (unlike a differential "execution II") so I expect that it works well if installed correctly. If the backing plate is damaged from the bolts my money is on the retainer not holding the bolts from rotating (either from being reused and failing, or never having been installed properly initially) and then the bolts unscrewing. The retainer is bent to interfere with the hex head of the bolts so the head cannot rotate - it is not a "lock washer" attempting to hold a spring preload, it just prevents rotation.

Loctite may be an alternative to the retainer, but will make repairs more difficult in the future.

John, hurry up and find out what went wrong! Inquiring minds want to know.

[John L]

My parts should be here Friday so my plan is to hopefully have it torn down and put back together by Saturday evening. But, this will be the first time I've done this so I will take my time, take plenty of pictures, and keep a log of what goes where. This may slow me up a tad; but I'll have some good documentation for the group to see once it's done. The hole in the backing plate is bigger than I thought. I't more along the size of a quarter which sounds similar to Paul's "blowout". I'll keep everyone posted. Hopefully I don't screw anything up.

[John L]

I just got to thinking, which is dangerous, and was looking for some input from the guys who may know.... Let's assume that the bolts hadn't backed out and broken the backing plate. Meaning that the wheel gear is operating as intended and no leaks. To perform the upgrade do you merely need to separate the backing plate from the housing, pull the gear assembly in tact out and then perform the upgrade to the bolts (as the upgrade is to parts still on the truck) then merely slide the assembly back together and reseal the plate to the housing? In other words, would you still need to pull gears and replace the O ring on the spline and the seals? If not, the upgrade is not as much work as what Berger posted on his thread as he had to replace bearings etc.... Obviously to replace the backing plate you have to go through all of those steps as well. But, if you can skip the steps involving pulling the gears and re-seating bearings the upgrade is not too much work relatively speaking. I just didn't know whether you had to replace these other items once you separate the plate from the housing and pull the assembly off.

This may put this entire thing into perspective for everyone and whether they should perform the upgrade merely to avoid replacing backing plates and going through the steps required to do so. Just some thoughts as I have three wheel gears with three operable backing plates that I'd like to keep in that condition.

JL

[undysworld]

Yours does sound similar to PC's situation. A buddy of mine who welds aluminum looked at the damaged plate and thought it could be repaired. The piece broke out cleanly from the inside, so it could easily snap back into place. Grind down the break from the outside and weld it back together. That way you do not interfere with the internal dimensions. I assume you'd have to be careful about warpage, but I don't weld aluminum myself.

IIRC, yes, you can simply split the wheel drive case and get to the retainers. So it's "relatively" easy in that you don't need to pull the gear. I believe you still need to fully disassemble the brake parts.

Edit: I didn't see it mentioned here, but as I recall, the parts from SAV were described as an "upgrade" kit, with a thicker washer, no lock-washer, and directions to use blue loctite.

[pcolette]

As Paul U. mentioned, the replacement washers are thicker than the originals to make up for the removal of the locking plates. The thicker washer keeps the bolts from hitting bottom in the threaded holes.

I found the old parts that he removed and took a couple of photos:

10-2-14 09-27 AM.jpg (477.17 KiB) Viewed 5633 times

10-2-14 09-26 AM.jpg (448.43 KiB) Viewed 5633 times

The locking plate for the upper (2 hole) fitting had broken and pieces were found in the gear oil and on the drain plug magnet. The lower locking plate was intact. There was no sign of Locktite residue on any of the old bolts so apparently none was used.

If either of the locking plates has broken it might be a good idea to consider if the bearings or seals were damaged by the metal bits. Paul U. and I decided to replace the bearings and seals for as a precaution.

[TechMOGogy]

Sorry - people are talking about an "upgrade kit"
Where do we find it SAV?
Is there an official SDP Service Bulletin about this "upgrade" - I can not locate it if there is one.
Here I thought it was just for the 2 bolts and now it looks like it is also for the 3 bolts?
Getting lost

[undysworld]

Sorry to confuse people. Hopefully this thread helps others in the future too.

We got the repair parts from Willy at SAV. Yes, there was a service bulletin that came with the parts from SAV, and I'd have to assume it was from Steyr-Puch. I believe we got the modification kit for both the 2-hole and the 3-hole applications.

I checked the SAV site and did not see any mention of it. ?? I assume he only sells the updated parts now.

Best advice about the part/s and bulletin might be to call Willy.

[pcolette]

Here's the Service Bulletin courtesy of Sarah at SAV:

Wheel drive gear mod.jpg

Parts needed are (qty 5) 04-10-10, ( qty1) 12 & (qty 1) 22.

[TechMOGogy]

I just got off the phone with her
She gave me the same document and same parts #'s and qty
Cheers and thanks to all - now I got it!

SAV site also says this when you go to part #11

[Jimm391730]

I stand corrected -- looks like Steyr has changed the hub assembly. I've only had to repair one leaky hub on my trucks and it had the three bolt system pictured; at that time (several years ago) I heard no mention of any change to the assembly.

I find it interesting that they now want to secure the bearing and the gear to the shaft with loctite, seems like they just floated before.