Rusty gear teeth

[h67st]

The bull gears in my differentials have pretty healthy rust pitting in them, what do you think about using them in a hobby truck? The wear patterns are light. I'll never haul significant loads with it, won't run very many miles.

[Rob]

2 hours ago, h67st said:

The bull gears in my differentials have pretty healthy rust pitting in them, what do you think about using them in a hobby truck? The wear patterns are light. I'll never haul significant loads with it, won't run very many miles.

Stoned or sanded off they will probably be fine. Water in the bottom of the bowls? Tom get you fixed up?

[h67st]

I think he's still socked in with wet ground. Our local truck trans/diff shop told me they have a parts room full of old Mack parts so I'm going over there today to see what they can find. They have so much that it's not inventoried...the guy who's worked there for 40 years has it in his memory (I hope his memory is better than mine).

[gxbxc]

If his memory is like mine 40 years is instant recall yesterday  and tomorrow  are the problem 

[h67st]

On 3/31/2019 at 10:35 PM, Rob said:

Water in the bottom of the bowls?

Yes, this truck hasn't moved under its own power since the 80s so water in everything.

[fuzzy buzzard]

Still too wet to get wrecker around back to pull first truck out of way. Concrete and rock are a rare commodity out here on Ignorant Ridge. But mud - now that's a different story!!! 

Keep us posted on what you find at local shop.  

[Vladislav]

On 4/1/2019 at 3:23 AM, h67st said:

The bull gears in my differentials have pretty healthy rust pitting in them, what do you think about using them in a hobby truck? The wear patterns are light. I'll never haul significant loads with it, won't run very many miles.

If the teeth have the most of their surface with rust pitting in them I would use them. If you see some teeth with the most surface covered with deep rust (actually the surface is gone) as I found at many spots I would look for a swap. Not sure which kind of carriers you have (actually don't remember) buty if they're multiple bolt (24?) mounting pattern the bull gears seem intercheangable with CRD92/93 units which are pretty common being used in R's, DM's etc.

How are the diff bearing races doing? I told you of my experience finding them pretty rough in no less than 8 or so Mack diffs.

[h67st]

5 hours ago, Vladislav said:

If the teeth have the most of their surface with rust pitting in them I would use them. If you see some teeth with the most surface covered with deep rust (actually the surface is gone) as I found at many spots I would look for a swap. Not sure which kind of carriers you have (actually don't remember) buty if they're multiple bolt (24?) mounting pattern the bull gears seem intercheangable with CRD92/93 units which are pretty common being used in R's, DM's etc.

How are the diff bearing races doing? I told you of my experience finding them pretty rough in no less than 8 or so Mack diffs.

You mean the races in the housing that's inside the bull gear? They're badly worn. I wonder if that's just from years of use or unmatched tires from side to side or (?).

[Vladislav]

I mean the races of the bearings the interaxle diff assembly (with big bull gear) spins on. Those that attached to the housing by two big clamps, like mains on a cranckshaft. I found them badly pitted in 3 or 4 R-model diffs I've taken apart and 3 of 4 diffs of military NR models I restore. Too large scale of damage to the units which were seen in a working condition until I took them apart. So seems like a typical issue just not many folks are familiar with since not many get that deep into their trucks.

Those races have very special style. One has threads for a nut to set pre-load and another has a flange. Both are expensive. What was found interesting to me those on the NR (made in 1945) had Mack part## on them and none of any others. The bearing cones were made by Timken. So seemed like Mack produced bearing races(!) at some time. My original guess was they couldn't hold the quality good enough for such precision and wear resistant product such a bearing is. But those in R-model carriers were made by Timken and Bower. So probably the matter is just high stresses during a long time.

[h67st]

On 4/9/2019 at 3:06 AM, Vladislav said:

I mean the races of the bearings the interaxle diff assembly (with big bull gear) spins on. Those that attached to the housing by two big clamps, like mains on a cranckshaft. I found them badly pitted in 3 or 4 R-model diffs I've taken apart and 3 of 4 diffs of military NR models I restore. Too large scale of damage to the units which were seen in a working condition until I took them apart. So seems like a typical issue just not many folks are familiar with since not many get that deep into their trucks.

Those races have very special style. One has threads for a nut to set pre-load and another has a flange. Both are expensive. What was found interesting to me those on the NR (made in 1945) had Mack part## on them and none of any others. The bearing cones were made by Timken. So seemed like Mack produced bearing races(!) at some time. My original guess was they couldn't hold the quality good enough for such precision and wear resistant product such a bearing is. But those in R-model carriers were made by Timken and Bower. So probably the matter is just high stresses during a long time.

Actually my bearings are in really good shape (one of the few things in these diffs that are good).

[Vladislav]

I've got good berings of the pinions and the cross shafts the small bull gears cut on. Only the diff ones was the issue. Bought them new both for the NR and the R.