Diff setup question

[TimNZ]

Hi, I'm rebuilding the diffs on my Series 3, (basically just new bearings, clean, inspection).

I'm having a bit of trouble getting the contact pattern right, whilst maintaining a good amount of backlash. This is the contact patterns I'm getting now:


https://www.aulro.com/afvb/images/imported/2016/12/419.jpg


https://www.aulro.com/afvb/images/imported/2016/12/420.jpg


The "coast" side looks OK to me, but to get a continuous contact pattern on the drive side the backlash is out to 0.4mm. It also looks like the contact is concentrated at the root of the tooth. Am I right in thinking I need to reduce the pinion shim thickness?

Cheers,

[manofaus]

Remove shims to move pinion and thus move contact patch toward center. I aim for near 1/3 to 1/2 way for contact patch. Only because torque may load up pinion and move it. Can't you adjust the carrier bearings to get a better backlash?

[Blknight.aus]

Toe and heel move the wheel
Face and flank move the crank.

I think your a little too deep in both directions and need to back the pinion down away from the center line a fraction and then redo the wheel position

its a second hand series diff and I've seen plenty worse contact patterns than that still working.

[TimNZ]

Thanks for the advice, If I decrease the backlash the drive side pattern completely disappears. The bearings that came out of the diff were SKF, and have been replaced with Timken. The SKF main bearing height measures 23mm, the Timken 22mm. (I don't see an easy way to measure the taper grind).

I have decreased the shim thickness from 1.3mm, down to 0.8mm, the pattern is the same, but the backlash setting is improved. Can there be that much difference in bearing manufacturers?

At the moment the contact on the coast side is really good, which is a plus since it's the front diff and will for the most part be not driven. Conversely, if it howls like a banshee it's the hardest one to change.

Cheers,

[Tank]

Thanks for the advice, If I decrease the backlash the drive side pattern completely disappears. The bearings that came out of the diff were SKF, and have been replaced with Timken. The SKF main bearing height measures 23mm, the Timken 22mm. (I don't see an easy way to measure the taper grind).

I have decreased the shim thickness from 1.3mm, down to 0.8mm, the pattern is the same, but the backlash setting is improved. Can there be that much difference in bearing manufacturers?

At the moment the contact on the coast side is really good, which is a plus since it's the front diff and will for the most part be not driven. Conversely, if it howls like a banshee it's the hardest one to change.

Cheers,
Here's some info from Land Rover W/Shop Manual, don't forget the rear diff rotates opposite to front diff, so wear patterns are on opposite sides front to rear, Regards Frank.

https://www.aulro.com/afvb/images/imported/2016/12/333.jpg

https://www.aulro.com/afvb/images/imported/2016/12/334.jpg

https://www.aulro.com/afvb/images/imported/2016/12/335.jpg

[TimNZ]

Bit of strangeness with the main pinion bearing that came out of the diff... I grabbed the bearing just in case I had to get a replacement SKF, (in the case that I couldn't get the right shim to go with the Timken, bit of an out there problem, but I wanted to get it sorted before Christmas).

It turns out that the inner part of the bearing is SKF, but the outer cone is Timken. This makes me wonder if the pinion bearing has failed at some point and the mechanic has just replaced the inner part of the bearing and slapped it all back together, (judging by some of the other work on the vehicle this would not surprise me at all!).

This could have created a very uneven wear pattern on the crown wheel and pinion. I have a spare, so we'll see what the specialist says on Thursday.

Cheers,

[Tank]

I can't imagine that a cone from one manufacturer would match the tapered bearing from a different maker, you should have a set of matched bearings, as far as your mechanic mixing like with unlike, I don't see how you could do it, you can only buy tapered bearings as a matched set. Unless the mechanic was too lazy to remove the cone shell and just fitted a new tapered bearing from a set, OMG, Regards Frank.

[TimNZ]

Unless the mechanic was too lazy to remove the cone shell and just fitted a new tapered bearing from a set, OMG, Regards Frank.

Judging by some of the other work done on the vehicle, quite possible.

[350RRC]

Tim, you might find something helpful here:

Pirate4x4.Com - The largest off roading and 4x4 website in the world. (http://www.pirate4x4.com/articles/tech/billavista/Gear_Setup)

Its all about diff set up.

cheers, DL