Axle play - how much?

[demuire]

How much side-to-side axle play is acceptable? I've got a KE35 Corolla with an RA28 diff, running Bluebird TRX rear discs brakes. I bought the diff already set up with the brakes.

For as long as I can remember since I put the diff in there's always been a clunking sound from the back of the car when I go around some corners, but I've never really known what it was. I have a clutch style Cusco LSD and I know this makes clunking sounds as it engages and disengages.

Anyway, last event I did I noticed that at least one of my discs was occasionally scraping on my caliper when I went around some corners, it only happened when I was coasting around corners. Looked under the car, and it looks like there's oil leaking from one axle, and there's a little bit of misting from the other.

Took the calipers and discs off, and measured the play in the axle. Right axle is about 1 or 1.5mm, no sounds, left axle is about 3.5mm, with a clunk as it goes from one extreme to the other. How much is acceptable? I had a look at a spare axle I have and noticed that there is some side-to-side movement in the bearing (which is new), so I guess some play is normal. But how much?

At the moment I'm thinking the right axle is fine, left axle needs to be addressed... Maybe I need a spacer between the bearing and the disc brake backing plate? The left one has been replaced before (a few months after I originally got the diff in), maybe it's not quite the same as the right one?

Any ideas?

[beanpole]

You must have been getting some other severe symptoms such as bad knockoff?

The numbers you are quoting must be at the very high end of unserviceable?



Kev

[demuire]

what is a knockoff?

[fro]

Knock-off is when the brake disc wobbles enough to "knock" the pads and pistons back into the brake caliper... next time you go for the anchors, more of the pedal travel is taken up pushing pistons and pads back out to contact the disc again.

One of the first signs that you're wheel bearings are rooted/loose is that you get more and more knock-off.

[Spac]

1.5mm of play is bad - anything over 0.5~1mm usually results in pad knock-off, schitty sounding bearings, and general uncoolness.

3mm is just horriffic!

I'd replace BOTH rear wheel bearings post-haste.

[demuire]

Have not noticed the pad knockoff (and don't think I really know what it would feel like). Bearings turn smoothly and don't make any sounds at all. But yes, agree that 3.5mm is definately not good at all. If I get some time tonight I'll pull that axle out and see if I can see anything unusual...

[fro]

Originally Posted by demuire

Have not noticed the pad knockoff (and don't think I really know what it would feel like).

You'd notice that the pedal travel is long on the first application, and then "pumps up" for the next application. It doesn't alter the pedal feel per se, just the travel.

Originally Posted by demuire

Bearings turn smoothly and don't make any sounds at all. But yes, agree that 3.5mm is definately not good at all. If I get some time tonight I'll pull that axle out and see if I can see anything unusual...

Isn't there a retainer, to keep the axle in the diff? I'd be looking at that first, 'cause if the axle isn't held in properly, the bearings will be rooted in no time.

[demuire]

No, can't say I've noticed the extra travel in the brake pedal.

Umm, from taking the axles out last time, it seems like the only thing holding the axle in the diff is the bearing? Like, looking at the axle from the splined end in, first there's a metal collar, then there's the bearing (I think the collar holds the bearing on the axle), and then there's the plate that bolts onto the diff (with the disc brake backing plate sandwiched between). This plate is free to move along the axle between the bearing and the hub. So it looks like the only thing holding the axle in place is the actual bearing itself? Maybe the collar has moved, so the axle is no longer being held in where it's supposed to be?

[Bede]

The outer race of the bearing should be sandwiched between the plate and the axle housing and the inner bearing race should be sandwiched between the bearing collar and the axle. Neither should allow movement of the bearing.

[demuire]

Originally Posted by Bede

The outer race of the bearing should be sandwiched between the plate and the axle housing and the inner bearing race should be sandwiched between the bearing collar and the axle. Neither should allow movement of the bearing.

OK, both axles are out. The bearings are 17mm thick. They appear to be fine, compared them with a brand new bearing I have, and they have the same amount of side-to-side play in them (about 1mm, maybe a little less, hard to tell) and they all roll without any gritty feelings or sounds about them.

At first I took the left one out, and then measured the distance between the diff end of the bearing space and the outside edge of the disc brake backing plate, and that was 20mm and I thought "a-ha!". But then I took the right axle out, and it was the same. Measured the axles, they seem to be the same length. Measured the position of the bearings on the axles, they're the same. Hmm.

I'll take some photos.

Maybe I'll swap the axles around and see if the problems swap sides too? Or maybe I've just been lucky with the right axle, and I should really shave the backing plates down 3mm or something? Hmm.

[demuire]

Well, swapped the axles around and same problem with same sides. Did notice that the right bearing is pretty tight in the diff housing, so maybe that's why it doesn't appear to have any play, where's the left one isn't really very tight (it's not loose either).

I'm thinking that I need to get a 3mm spacer made to go inside the diff before the bearing goes in, so that the bearing is properly sandwiched between the retainer plate and the inside of the diff?

The only problem I can see with this is that there's 3mm less bearing being supported by the diff housing itself. Is this a problem? There's still a fair bit of bearing being supported by the diff...

The other option is shaving the disc brake backing plates 3mm, but being alloy I think that might affect the strength of it significantly... And considering it supports the caliper...

Here pictures:

[Davie]

Hi

you sound like you've just about got it, the bearings will be moving in the housing, I had a similar problem with the Sunny a long time ago, the fix was to space out the bearing. If the bearing is still fully inside the housing the 3mm won't be a problem. The othe thing is what about the sline engagement to the diff?

Been while since I've played with rear wheel bearings but anything over 0.25 mm is too much with rear discs, particularly opposing piston type.

As for knock of, if you are using Bluebird sliding calliper, it will mask it to a certian extent, particularly when you are using the brakes heaps and there aren't that many straights. Rear brake knock off in a solid rear axle car will normally manifest itself in a straight line, from my experience, but I could be wrong it seems to go against common sense.

[demuire]

Ta for that. Normally the bearing sits with 13mm inside the diff (and 4mm outside, I guess the original drum brake backing plate was 4mm thick). Putting a 3mm spacer in there will make it 10mm inside, 7mm outside. Hmm. I suppose the car isn't too heavy and since it's mainly on tarmac doesn't really jump too much...

Splines are ok, after all they've been sliding around in there for a little while now and the car still drives fine.

I suppose the other option is to find a bearing that is 20mm thick and will sit on the correct spot on an RA23 axle? Hmm. Don't really like my chances of finding that, but will make a few calls today anyway.

[demuire]

No such bearing exists (the next closest ones are all too wide), so have ordered 2 new spacers. Hopefully they work!

[Daniel]

You can get shims to take some of the play out they sit between the axle housing and the bearing retainer - but I think 3.5mm of movement is too much to shim out.