Shimming an axle tube

[Jean-Sebastien Stoezel]

I've probably shimmed half a dozen axle tubes, but I can't seem to get this one right.

Whatever the number of shims from 0 to 2, I seem to get a "clonk" whenever I push/pull on the wheel. With 0 shim I get a stiff axle up/down, with a clonk in/out. With 2 shims I get a good smooth axle up/down, with the same amount of clonk in/out. The play is not noticeable with the naked eye, but it makes a clonk.

I had the same issue when I reworked this side 2 years ago. Since then I've had about 50 sessions and I think the clonk in/out is about the same. I had forgotten about the struggle and decided to re-shim today.

Both the daisy spacer and the hexagonal cover(?) are new from the store (or where new when I installed 2 years ago and it did the same clonking noise).

Where is this play coming from, if it is not correctable with shims?

Jean

[budawe]

Make sure the bell on the axle tube is not distorted.

[Dietmar]

Jean:

I will second that- make sure the tube or the bell is not bent. Stand it on a flat surface and take some measurements. A carpenter's square works just fine.

Dietmar
www.quixoteracing.com

[Bruce Livermore]

Jean,
The axle tube shimming locates only the axle tube, not the axle, drum, etc. Once you've assembled it all the way to the wheel, there are a lot of other possible sources of a clunk.
My guess is that the clunk is coming from movement of the axle "blade" in the fulcrum plates. If this is true, it is not so much "axial" play as "angular" play.

Are you pulling/pushing straight in and out on the wheel (in the air, grabbing at 9 o'clock and 3 o'clock) or are you just pulling/pushing on the top of the wheel/tire? Axial play will show in the first case and angular in the second. The fulcrum plate play will show up as angular play and will vary as you rotate the wheel. You can check this with the car on the ground. You wheel the car in the air to really check for axial play.

If it's just angular play, I wouldn't worry about it, especially if it has not changed in quite a while. Next time you have it all apart, pull the axle and check the fulcrum plates and axle blade for wear and play. We need somewhat more clearance than the stock recommendations to get enough lubrication into those sliding surfaces and this is where the play comes from. Once it's all running and hot, and hopefully, full of oil, all is good. If there is a problem, it will probably show up as wear and/or galling of the plate and axle. Some of this wear seems unavoidable, at least for me...

Bruce

I just reread my post and realized that it I did not make clear what I meant by "angular play". I'm talking about rotating or rocking the whole wheel, drum and axle around the wheel bearing "in the plane of the axle". Thus the top of the tire can move in and out from the centerline of the chassis, lifting and dropping the axle in the side gears of the transmission. I am not talking about play in the direction of normal rotation of the wheel as the car rolls. Of course play between the axle and the fulcrum plates will show up with either type of rotation. Hope that makes more sense.

[Jean-Sebastien Stoezel]

Hi:

Thanks for the replies. I have to correct the initial post, I do see a bit of play in/out. I stoke a line between the edge of the drum and the back plate. I see play in/out of 1/16"? Most likely less. This is what makes the clonking noise, I think. Also the transmission is completely dry as I drained it for the coming season and reworked the side plates.
Maybe the clonk is more noticeable dry as there's no fluid to dampen any movement of the transmission.

Are you pulling/pushing straight in and out on the wheel (in the air, grabbing at 9 o'clock and 3 o'clock) or are you just pulling/pushing on the top of the wheel/tire? Axial play will show in the first case and angular in the second. The fulcrum plate play will show up as angular play and will vary as you rotate the wheel. You can check this with the car on the ground. You wheel the car in the air to really check for axial play.

I tried this and I think I mostly see play in/out. Indeed it is difficult to see angular play, maybe there's more in/out play than angular, and this is what I am seeing right now.

Jean:

I will second that- make sure the tube or the bell is not bent. Stand it on a flat surface and take some measurements. A carpenter's square works just fine.

Dietmar
www.quixoteracing.com

Make sure the bell on the axle tube is not distorted.

Ok, I will have to check this after the coming race wee-end, as I have already gooped up the plates and won't have time to clean up and rework. What is interesting is that both the plates and the daisy spacers where brand new out of the box when I installed them 2 seasons ago. And I noticed the clonking right at this time.
I will check this for sure after this race week-end, at this time though I don't think I have the time to do it before then.

Thanks again for the replies.

JS

[Hardingfv32]

Could there be play in the wheel bearing mounting system? Like the seal holding casting is not holding the wheel bearing in tightly.

Brian

[Bruce Livermore]

I think Brian is correct and that the bearing is moving in the axle tube.

If the play is between the drum and the backing plate, it has nothing to do with the axle tube shimming. The axle tube is located by the shimming. This then locates the outer axle tube casting which the backing plate and wheel bearing retainer bolt solidly to. The wheel bearing retainer is supposed to clamp the outer bearing race firmly in place making it "one" with the axle tube. The axle (and therefore drum) is located by the inner race of the bearing and must be clamped tight axially to it with the proper spacer behind the bearing and the right spacer outside it under the brake drum. If there is a problem with the axle to inner race stack-up, your drums would be coming loose and you would be have axle seal problems.

1/16" movement between the drum and the backing plate seems like a lot. It could be play in the bearing itself, but I very much doubt this as it would be VERY worn out before you could find that much play.

I just checked both sides of my car and while I can perceive movement (by feel on one side and by feel and sound on the other), it is very slight, probably less than .010" on the looser side. No time to actually get out the dial indicator today...

If the bearing is moving in the axle tube, you should be able to see this with the drum off. To check it you will need to make up a spacer to simulate the drum and at least lightly tighten the axle nut to make sure the axle doesn't move in the inner race of the bearing. Whatever the problem, looking at it with a spacer replacing the drum should allow you to see where the movement is. 1/16" should be easy to see.

My guess is that you have an incorrect bearing retainer on the side with the clunk. I know that there are multiple configurations of the retainers. I believe (though I can't put my hands on one at the moment) that VW made one style that has a deeper "pocket" from it's face to the outer bearing race retaining surface. Maybe this is from Type III or from an IRS Type 1, I don't know, but I remember scratching my head when I noticed the difference between two seemingly identical retainers as I held them in my hands.

Next time you get the chance, compare the retainers you have for the distance from the mounting surface to the next flat surface, which retains the bearing. They may not all be the same and they need to be. The ones with the shallower pocket (smaller distance) are the correct ones.

The other possibility is that there is something holding the (correct) retainer too far from the axle tube. I assume that all backing plates are the same thickness, but maybe not...
The only things between the retainer and the flat outer face of the axle tube casting should be the backing plate and the thin paper gasket. The large o-ring should not get in between the flat surfaces of the backing plate and the retainer. It must fit entirely within the chamfer of the retainer.

Bruce