BW78 diff gear backlash

[TdracerTd]

Hi there,

Changing diff gears. Does anyone have any info on the procedure and spec for adjusting the backlash when changing the gears. I have a dial gauge and magnetic base.

Thanks

[VK_3800]

Backlash is somewhere in the region of 0.007" if I remember correctly, but gear mesh is more important. If you get a good tooth pattern and the backlash is a bit out of spec that's better than compromising the mesh for the sake of correct backlash.

Hopefully you can find some indication of pinion installed height marked on both the original and the new one, so you know whether to add or remove shims (although with the Borg Warner/BTR I've always found them to be 0).

[TdracerTd]

Thanks vk, do you have or know of any document that details how to set these up? I don't expect that there is any great chance of me just throwing it together and it being okay. Lol.

[VK_3800]

From your first post I assumed that you had some idea of the process, what sort of details are you looking for that you can't find...?

[TdracerTd]

I have an idea of what to do and how to adjust, unfortunately there is no "how to" in the workshop manuals I have. I understand that the backlash is adjusted by the torque on the pinion nut and should be measure at one if the teeth on the crown wheel. And that the gear mesh is adjusted by shiing the centre. I'm sure that a little common sense should get me pretty close, but just don't want to miss anything. Are those the only 2 adjustments needed?

[delcowizzid]

pinion bearing preload is tension on the nut squashing the crush tube.pinion depth by shim backlash by side shims on carrier.ive had them done by the pros and get loud and noisy withen 10km ruining the gears in the process.the moment you move the pinion into a new housing bad stuff happens if you dont set the pinion height correctly.shimming the centre side to side isnt so important but requires a pile of shims to do it correctly.

[TdracerTd]

Forgot that I had a max ellery manual. Very comprehensive instructions in there. Should be no problem now. I find that the Gregory's is easier to find simple stuff like torque settings and capacities, but the max ellery's has information on procedures that the Gregory's just doesn't detail. Thanks for your help guys.

[jenko]

beg to differ, the backlash can be affected by both. Personaly in a high horsepower application I would remove the crush tube and make an appropriate spacer with provission for adjutment shims , set it up with the crush tube then remove it and make a solid spacer to suit by measuring the crush tube . the reason for this is with high hp you can actually crush the spacer more while in use,and also you can actually change your pinion seal without upsetting your gear set.
What you need to do is juggle the input shaft depth VS the crown wheel shims to acheive the correct contact pattern which you see by applying bearing blue to the pinion gear and seeing what pattern it leaves on the crown wheel

[delcowizzid]

yeah we used to kill crush tubes

[vlad01]

yeah it doesn't take much to stuff em.

I installed a low K nice diff in one of my cars, it must of had a small knock to the input flange collapsing the tube.

Drove 5Km before the pinion bearing crapped out and started to scream.