360 LSD.

[perkabrod]

Is it reasonable to think that the bearing preload will be in the ballpark as long as the backlash/gear pattern is adjusted to volvo specs?

Preload is what is holding me back for trying to mount my diff, I'm too pedantic and have no experience in drive train, bad combo

It's great that you bring up discussion ride_on, it will help for future sales and I'm very interested to hear mote about the idea of the distancer, general interested in those sort of things since I'm studying mech eng.

[Ride_on]

my 343 is also equipped with one of these, no problems on assembly and a perfectly working LSD

Maybe you know what you are doing I was told this was a straight swap with no special tools. I didn't know anything about bearing preload or backlash, until now(ish). What torque did you use for the crown bolts, was the insert flush?

Anyway I have been thinking about how to do the preload after watching youtube, which according to the university guy these things are important for lifetime and noise. Although mine was fine with a bit of backlash for the 5 miles I used it, except the fact it was locked up.

Regarding backlash the output bearing preload is not related to backlash as such.

Bearing preload is related to right shim+left shim (squeeze between the sides)

Backlash is related to left shim mainly (position across the diff)

The procedure is to start with bearing preload but it seems to be without the pinion installed. Unless the pinion is loose I'd leave it in, so we need procedure which involves this.

Generally we can add torques, so if we can measure the baseline pinion torque at the output flange with effectively zero pre-load, we then can add on the requirement for the output bearing.

Alternatively, we might put the small shim in the LHS and make a big backlash (default is 1mm LHS, 0.8mm RHS, mine was 1+0.45), making the crown free to move for the back lash with maybe enough space to measure the torque directly.

There could be other variables, but doing both might give some confidence.

What I am not sure about is whether we need the starting torque or turning torque, although maybe the difference is small. Anyhow I plan to use a fibre glass rod with a sliding 0.5kg weight on it mounted on a drive flange.

We now have to keep the sum of the shims the same, so to control backlash any thing we take off one side we have to add to the other.

As to assuming ball park when assembled with the same shims, well I hope so but even putting in another Volvo diff or even the same diff with new bearing the manufacturer did not want to assume anything. Bearing preloads are controlled with very small changes.

[perkabrod]

Great write up, I understand the procedure a lot better know. It sounds a lot harder than expected.

If I have marked which shims where on left and right side respectively, and using the same crown wheel, would the preload then be determined of the torsen size in comparison with the original diff?

One could measure preload with a rod type torque wrench or an expensive dial type. All guides I've seen so far has said it is the rotating torque, not the giveaway torque.

If the preload was off by a lot I seriously feel the pinion shimming is out of my ability. If I got it right, the preload at the pinion will be determined by where the crown wheel sits with respect to both the lhs and rhs bearings on the diff. If everythings within close tolerance to the volvo diff the preload should be within spec as long as the same shims are used, then backlash will be set like you said by adding/subtracting

[volvodspec]

some of the parts aren't CNC'd so i expect there might be some tolerance issues there, mayby i was lucky. i have another LSD here ready to install, but that will take a while before i'm ready and have enough time.

i started with checking the height of the LSD and compared it to the original diff; this is a simple way to determine the bearing preload; the LSD was 0,05mm thicker wich the bearings (it's divided by 2) should be able to cope with easaly.
then i mounted the diff with new bearings, and checked the contact surface of the crownwheel to the pignon. there's special yellow paste for this on the market. in my case it was spot on but if it's off you need to reshim it.

all mounting torques according to the green books, i did clean the flange surfaces and shims with a special tool making it bare metal.

however, bearing preload and shimming the crownwheel only has effect on noise and lifespan of the diff; if it's constantly locking something else is going on

[Ride_on]

Yes I've already diagnosed the locking earlier, the insert that goes between he diff module and the crown was too wide. Myself and eric have the same measurements more or less. He hasn't built his up yet, but I found the diff locked up when the bolts where tightened to 90Nm, which I later found should be 138Nm in the green book.

The errant dimension is 77.3mm on the maximum diameter of the insert. This is intended for a 77.0 hole, and even though I heated my crown, there was a 0.2mm ledge to bend the diff module over. Once it bends it locks up. Definately worth checking.

Incidently how did you find the insert went in? Snug and flush? Did you have to heat it?

Just waiting for Atchi to come back on the fit, but thinking we probably need to narrow it down a shade.

The bearing preload and backlash discussions are just trying to figure out how to do a good job of it, doesn't look too hard.

On the output bearing pre-load, a 0.05mm decrease equates to a 0.6Nm increase in pre-load if you are in-contact. The range is 0.25-2.3Nm total, but if you have new bearings you need to be above 1.1Nm.

Eric, If you changed the bearing you have changed something otherwise the LHS shim (normally 1mm) should be as before for backlash. The new diff creates an unknown for the RHS.

BTW the pinion preload is another story, I intend to ignore that. The output bearing preload doesn't seem hard (if you can measure it), you may just have to change the RHS shim, or it might be fine.

On rotating and starting torques, looking at the video the guy talks about rotating rather than startup but at the end of the day he is measuring the maximum of both.

[miniswift]

Hi,

I have spoken to the guys who made these for me.
They informed me that it should be 77.0mm they had a problem with their Lathe and these were first goods made after refurb.

He wants us to rectify over here as send it back alone will cost £80.

I'm not sure how to do this. Is this part heat treated?

Sorry I'm not much of help here, I have sold few of them and all others were OK. .

I shall ask what we can do to help.

Cheers
Atchi

[perkabrod]

Hi,
...I have spoken to the guys who made these for me.
They informed me that it should be 77.0mm they had a problem with their Lathe and these were first goods made after refurb.
...

The batch I ordered from had the wrong tapped bolt threads too but that seems to have been sorted out with newer units.
I hope the gear train does not have any off spec parts as well

Some guy in Sweden test fitted the distancer a few years ago and he had to drill it out because the fit was so tight.
My distancer fits poorly, which I guess is mostly due to the large outer diameter. But if the whole distancer is made manually in a lathe with wrong spec then I guess all the tapers/radii is off too.

If new orders are being sent out I'd be happy if there was a chance that he could make me a new distancer.



If not I need to find a way to get that part machined, seems hard to mount on a lathe.

EDIT: Found this old video from when I got mine delivered. The fitting seems fine between the distancer center hole and torsen center gear so that's good.
It has been mentioned before but worth mentioning again because it's an area of improvement. The spline is cut slightly off center which can be seen in the video https://www.instagram.com/p/pQ9pAEDZbK/ ... =perkabrod

[Ride_on]

I don't mind getting my insert trimmed locally, hopefuly my friends lathe will be up to the job, otherwise a couple of replacement inserts would be a good backup. Perhaps the supplier will provide replacements.

When I am talking about heat, some diff parts are very tight and the larger part can use a little heat to expand it a little. 0.3mm is too much.

Did you put any of the other questions to them?

77.0 sounds like a tight fit with no clearance, but as Eric says the other dimensions are not tight.

[Ride_on]

I've had a go at machining and basically failed to sort the problem, although the insert does fit better without heat, it is still not flush. We couldn't figure it out at the time and simple depth and thickness measurements did not seem to add up, and sure enough the diff bound up on assembly, however I think I've figured it out now.

The problem is that the 2nd step on the crownwheel is not a precision machined surface and is not flat (on mine anyway), if you take simple measurements you will end up with the wrong shaped part. Its cone shaped.

I think possibly the design intent was that the base of the insert would sit on the bottom on the bearing surface, but mine is short because when I measure the depth of the hole I am measuring from the peak of the cone. We did consider it might be something like this but knew with the cutting tools we had couldn't cut it anyway.

I suggest the middle surface in the insert be cut to float well above this surface. Say reduce the top part to 4.5mm and keep the overall height. It looks like it is only supporting the endfloat of the small gears, so doesn't need to be rigid at the outer edge but the designer would need to confirm.

Bearing surface for original beveled gear

IMG_2193s.JPG (62.43 KiB) Viewed 13664 times

2nd surface not flat

IMG_2191s.JPG (62.79 KiB) Viewed 13664 times

Measurements

Insert.JPG (23.21 KiB) Viewed 13664 times

[Ride_on]

Well good news so far. I took the insert and crownwheel to a machine shop and got them to shave off 0.5mm approx from the bottom of the wide part. This reduced the thickness from 5.1mm to about 4.46mm as per the last diagram in the previous post but didn't change the overall thickness (12.16mm). The part is hardened so needs ceramic cutting tools. They added a little undercut in the corner just in case.

The gives some clearance to the inacccurate surface.

The part is now nicely flush, I couldn't measure any non-flushness, and sure enough bolting up the crownwheel the diff is still free to move for the first time.

Reduced to about 4.46mm

IMG_2198s.JPG (68.12 KiB) Viewed 13645 times

Nice and flush

IMG_2196s.JPG (41.08 KiB) Viewed 13645 times

I'd definitely recommend leaving the crownwheel with the machine shop with flush requirement, as this middle surface is not precision it may need a little more clearance in some cases. So they may need to adjust the diameter and middle dimension so that the base sits down properly in the precision bearing surface.

[perkabrod]

Great news! So they took of material on the crown wheel, deepening it a little? I will have to measure my fly wheel to see where I'm at. I have an extra crown wheel with a damaged tooth too that I could compare with to see if they differ much.

[Ride_on]

No they didn't modify the crownwheel (its hard to put in lathe with the bearing on, could be milled I guess), sorry I should have been clearer about that, I would only modify the new parts by default.

I just left the crownwheel with them to check the flushness, but my calculation for clearance worked out ok. Previously I had thought it was the diameter that was the problem but could not see the other problem until the first problem was corrected, so the whole thing needs to go for matching up.

[Ride_on]

So the diff is back together and tested on the road with good results so hopefully that will be the end of it for now. Grip and control was pretty good but I'm a bit down on power using the 360 exhaust and although the roads were wet no real challenging situations for the diff.

I didn't get any alternative pre-load shims and just swapped them round to get the backlash down to non-visible movement but a definate clunk.

[classicswede]

I do have a few spare shims here you can have if you need them

[miniswift]

Thank you for your effort.

I have informed all of your hard work to manufacturer.
I hope if there is any more batch it will be spot on.

Cheers
Atchi