7x7 South Bend shaper, 2500, SK

[Chicken lights]

I know this is taking the conversation way off the rails from a shaper for sale in Saskatchewan, but regarding the gears in especially hypoid/spiral bevel/amboid gear sets, the relationship of the pinion to the ring gear is very finicky. If you're slightly off the thing will whine and make noise at higher speeds. This is why when pinion bearings get worn you'll often get a whine in your diff.

Cutting the profile on these is ridiculously complex and for many years, at least in North America, the Gleason company was the bunch to get machines from to make rings & pinions. They are still huge in it but of course there are other companies around the world doing it too.

The thing is that you have to start with the pinion gear in the housing. You measure the inner pinion bearing surface in the housing to the centerline of the ring gear rotational axis using specialized arbors and an indicator to establish the location of the shoulder of the pinion inner bearing to the housing. Comparing your measurement to the nominal depth spec for your diff, you use the + or - marking on the pinion gear to establish what thickness of shim you need under the pinion head to the pinion inner bearing to establish its depth of engagement into the ring gear. Once the pinion is installed with preloaded bearings you should then be able to set the backlash, preload and rolling contact pattern (with contact marking paste) of the ring gear. All set correctly the gearset should run quietly.

GM and AAM axles have marks on some, if no mark you assume nominal depth (I was at GM dealers for a few years). Dodge now has used AAM axles for a number of years too. Only built a few Ford diffs over the years, and only a couple Toyotas.

To make this level of precision in a complex contour like a hypoid/spiral bevel/amboid gearset requires a seriously special machine which is why they're seriously expensive. I can only imagine what a Swiss one would cost, lol! Of course gear grinders are used for spur gears too but just touching on diff gearsets and the like here.

I know some people aren't as into YouTube but here are a few links that might help illustrate.

Sorry if this was too long winded or didn't answer your question the way you guys were looking for, but I've always been fascinated by gears and gearing. Part of why I enjoyed working on transmissions and powertrains when I was pulling wrenches.

I’m sure you know this, but part of the reason to have backlash is to leave room for oil. Hypoid 80W90 is designed to not be very “squishy”, from what I understand it limits the metal to metal contact, giving gears a long life.

There’s other ways I’m sure, but I was told one inch pound of pinion drag per 1” of ring gear diameter. So a 9” ring gear you’d want 9 inch pounds of “drag”, spinning the pinion with a beam style torque wrench. Something in the recesses of my memory says that’s with new bearings. If you reuse the bearings measure the pinion preload before removing the pinion, and centre punch the pinion and pinion nut. Try to remember how many threads were sticking out. Then when you reassemble match up the marks when you gun the nut on

I’d say the hardest part about doing diffs is the fact they are all different, manufacturer to manufacturer. There’s 93 different ways to adjust everything, you end up with a junk drawer of shims bolts and c-clips. And ujoint clips too.

 

[Darren]

I’m sure you know this, but part of the reason to have backlash is to leave room for oil. Hypoid 80W90 is designed to not be very “squishy”, from what I understand it limits the metal to metal contact, giving gears a long life.

This is very true.

There’s other ways I’m sure, but I was told one inch pound of pinion drag per 1” of ring gear diameter. So a 9” ring gear you’d want 9 inch pounds of “drag”, spinning the pinion with a beam style torque wrench. Something in the recesses of my memory says that’s with new bearings.

That would be close for used bearings. Typical setup with new bearings would be in the 30 in/lb range, for automotive applications.

If you reuse the bearings measure the pinion preload before removing the pinion, and centre punch the pinion and pinion nut. Try to remember how many threads were sticking out. Then when you reassemble match up the marks when you gun the nut on

I have been doing that for years when doing pinion seals. If the nut is in the same place when it came off, preload will be the same. Won't work if changing any other parts of the stackup, yoke, bearings, etc

I’d say the hardest part about doing diffs is the fact they are all different, manufacturer to manufacturer. There’s 93 different ways to adjust everything, you end up with a junk drawer of shims bolts and c-clips. And ujoint clips too.

I have one such drawer in my box at work.

 

[phaxtris]

In all the gear sets I've done I've never came across one with the mythical +1/+3/-whattever

I've often wondered if that was a wives tale made up by someone trying to not scare off the new mechanic from doing a set of gears, or if I'm just really unlucky with the gear sets I've bought

It's always been put it in with what it had, check everything take it apart, adjust, check again.....repeat 4 more times until it's good

 

[Darren]

In all the gear sets I've done I've never came across one with the mythical +1/+3/-whattever

I've often wondered if that was a wives tale made up by someone trying to not scare off the new mechanic from doing a set of gears, or if I'm just really unlucky with the gear sets I've bought

It's always been put it in with what it had, check everything take it apart, adjust, check again.....repeat 4 more times until it's good

That's pretty typical in aftermarket gear sets, but you're right, not all of them are marked. Having a set of setup bearings honed for a slip fit can really help get you in the ballpark faster.

 

[calgaryguy]

That's pretty typical in aftermarket gear sets, but you're right, not all of them are marked. Having a set of setup bearings honed for a slip fit can really help get you in the ballpark faster.

This. The guys I know that do rear diff gearset changes have exactly this setup for ease and speed of setups.