Axles floating in and out - cause?

The American · Postby **The American** » Sun Oct 09, 2016 4:56 pm

I was inspecting, checking PPF bolt torque when I noticed that the differential and axles are moving in relation to each other more than I would have expected. When I twist the drive shaft, the right hand axle pushes out about 5mm, and pulls back in when the drive shaft is twisted in the other direction. The diff is a Torsen.

Here's a clip of the movement:

Hopefully someone with some differential expertise can tell me if this needs attention!

manga_blue · Postby **manga_blue** » Sun Oct 09, 2016 5:32 pm

Backlash on the main assembly is meant to be 0.07mm. Given that yours seems to be about 5mm then I'd say yes you have a problem. Possibly you might find some of your main carrier bearings in the oil.

Postby **NitroDann** » Sun Oct 09, 2016 6:05 pm

That was my diagnosis but I wasn't confident enough to post it

manga_blue · Postby **manga_blue** » Sun Oct 09, 2016 6:14 pm

I'm not 100% either but it does point towards the carrier bearings or the thrust washers breaking up. If there are no chunky bits in the oil then maybe it's possible that the carrier bearing caps have moved?

hks_kansei · Postby **hks_kansei** » Sun Oct 09, 2016 7:57 pm

The lash on the tailshaft looks about the same as on my car.
My diff was rebuilt about 30'000km ago give or take.
(If course that's not to say mine is perfect, but I'm confident in the guy who built it. If anything a season of motorkhana clutch dumps probably did it.... If it stuffs the ring gear I'll just buy a 4.7 and shove it in)

As for the half shafts shifting in an out, my first guess would be that the retaining circlips have either broken, or weren't seated properly when installed.

The American · Postby **The American** » Sun Oct 09, 2016 8:13 pm

The half shafts don't move in and out by hand, it will only move in conjunction with the pinion. It feels like the axle is solidly clipped in to its place in the carrier, but the carrier is moving to the side when the pinion turns it.

There's no whine that I've noticed when driving it, but I can hear a whine on overrun in some of my videos (the microphone is in the boot).

I haven't been exactly kind to it in the last 2000km.

manga_blue · Postby **manga_blue** » Sun Oct 09, 2016 8:44 pm

Mine's now got about 90deg of play in the pinion but at least the driveshafts don't pop in and out like that. Mine took several thousand laps of abuse to get like that and still hasn't failed (but it now whines a bit). The pinion play does makes it hard to manage the throttle effectively when you're competing.

The American · Postby **The American** » Sat Oct 15, 2016 4:04 pm

I had a chat with a diff and transmission guy during the week who said he's built about a 100 mx5 diffs over time.

He was unconcerned with the amount of movement I described. He said that 5mm was a little more than you would expect, but that 2-3mm would be normal and to a certain extent necessary.

So, this morning I climbed under the car with a set of digital vernier calipers. Inspite of what the video looks like (and it looks exactly like that in person), the maximum movement I could measure after multiple attempts was 2.4mm.

I drained the oil and observed the crown wheel and it is not moving side to side.

There were a few small metal chips attached to the drain plug magnet.

It now seems less likely that it is about to perish. Taken together with the lack of significant obvious noise, perhaps I've jumped the gun.

On the upside, I now have a spare freshly rebuilt 3.63 T2, thanks to 97MXV.

flycasta · Postby **flycasta** » Mon Oct 17, 2016 2:16 pm

I would suggest there is something wrong inside the LSD...... if the shafts are tight in the side gears and there is no movement linearly unless the tailshaft is turned I would suggest the internals of the Torsen are on their way out if not already. You should not have that much movement be it under load or not. What you are seeing is possibly the Torsen winding up the spider gears and in turn pushing the side gears apart forcing the driveshafts outward....... allow that to keep happening and the shock load will lead to a failure. I would think possibly the thrust washers that the side gears push against under load have either worn significantly or been destroyed. That movement will cause the oilseals to fail and eventually dumped all of your diff oil.

****** watching the video a few times if it was the side gears I would expect them to turn the axles at the same as the internals wind up the side gears but it isn't. Have you tried to push the shaft in and out when the driveshaft is out or only when it is in you tried to pull it out? My initial thought was the Circlips as suggested by Nik. what is the result of turning a wheel do you get the same result? Does the car clunk when you drive it and take off? Are both sides moving the same when you turn the tailshaft?

flycasta · Postby **flycasta** » Mon Oct 17, 2016 3:34 pm

Can anyone else replicate the same with a diff that they know is good would be the next question........ would help answer the question of if its normal or not.

The American · Postby **The American** » Mon Oct 17, 2016 5:43 pm

I do think it is at least partly within the Torsen. My understanding is that there are friction plates at each end of the Torsen unit that the gears press against and that can wear. It feels as though the movement is winding up theses gears as the crown wheel rotates. The drivers side halfshaft is the one that moves.

It is on a trailer at the moment. Next time it is on the ground, I will experiment to see if the movement can be replicated from the wheel side of the equation.

I'm less concerned by it now that I've measured the movement and found it to be less than it looks

The American · Postby **The American** » Mon Oct 17, 2016 5:49 pm

flycasta wrote:Can anyone else replicate the same with a diff that they know is good would be the next question........ would help answer the question of if its normal or not.

That would be handy! I have one sitting on my bench, but no axles fitted...

flycasta · Postby **flycasta** » Tue Oct 18, 2016 7:09 am

I have a couple of diffs under my bench with T2's and a T1 fitted and some stub axles or cv's..... is yours a T2 or T1? I am just a little worried by the fact that only one side is doing it as well.

I have some stub axles I can put into 1 of the diffs and check but the stub axles or CV's in your case should be basically solid because most of the free play should be in the CV joint not the inside of the diff. Just dont give it a hard time and try and load the axle before taking off....... could be a ticking time bomb.

I still have a feeling it could be the circlip and it may not be moving due to the angle it is on and you not being able to get enough leverage on it, thats why I suggested to try and push it back in when the stub has been pushed out by the tailshaft.

The American · Postby **The American** » Tue Oct 18, 2016 8:37 am

There is no free play of the halfshaft without moving the prop shaft - you can't push it back in or pull it out, which would suggest the circlip is secure.

I could also see the crown wheel through the drain hole - it's not moving side to side, which I think eliminates the carrier bearings.

So of the 2.4mm, at least 2mm of it would appear to be in the Torsen itself. I believe this one is a T2.

I wonder how much movement is possible before the gears in the mechanism misalign? There are two, possibly three, brass friction surfaces in there (either end and the middle) .5mm on each of those?

flycasta · Postby **flycasta** » Tue Oct 18, 2016 9:22 am

It definitely wont be the side carriers otherwsie you would have all sorts of meshing problems and a lot of crunching etc.

Is it an SE turbo diff or an NA diff? The Turbo has the bigger 28 spline stubs and the torsen itself is different internally. If it is an NA torsen then it wont, or shouldn't, have any brass friction plates. An NA T2 will have a series of spring washers in the middle with a white metal teflon coated thrust washer that has a layer of bronze between the white metal and the teflon and then it should have some hardened thrust washers between the case and the side gears...... they are the same hardness as the side gears so they dont wear too quickly. The SE torsen will have 2 big thrust washers with 4 lugs, to stop them from spinning which get located on the shafts of the spiral helical gears internally, between the side gears in the middle and then the hardened washers between the case and the side gears. There will also be a spacer shim between the hardened washer and the case to take up any clearance on both types from memory.

If the Torsen is still factory, not modified, then it is possible that the hardened washer, which are around 2 - 4 mm thick, has destroyed itself on that side allowing the movement.