Question on rear diff.

Here's a better pic.

Ok, I'm almost 100% sure that is the adjusters for the pinion bearings, You use a bar in the opening on the "gears" to set the bearing pre load, than the tang locks the adjustment when the cover is installed.

^^^yup^^^^ preload adjuster access,

Thanks guys!

Man that's great information!
I had not got to that area yet but was not sure what all that was for?

My KB3 has this and it was a puzzle.



I guess the next question is do we need to do anything with it?
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nope, once set-up the adjustment should stay good for the life of the bearing, if it is getting sloppy, than its time for new bearings and should be set when the bearings are installed.
I once had the dubious title of resident proctologist, as I did all the rear axles where I worked. Done them from small cars to heavy trucks and Motorcoaches (which sometimes turn "backwards, and have to be set with the ring gear on the other side)

Quick question Doc, while your here. What the best way to clean out diff, of old stuff. Can I pour some B9 in there and drain it out and add fresh oil. Not an expert on diff's so I really don't want to take anything apart, that may build into more unknown issues. (due to me pulling stuff apart..)
No known issues with diff except outside rust and rotten oil. Thanks.

You could use diesel, or any engine oil. with the wheels off the ground let the engine spin it for a few minutes, then drain. Nice thing about engine oil is that it will not dilute the gear oil as much as diesel would.
The most conservative approach would be to just change the oil a few times.
With gear oils, the GL number, the higher the more extreme pressure additive package. Higher is not better if not needed. GL 3 or 4 is fine, as these are not extremely hypoid sets (the pinion is closer to the centerline of the ring gear than the outside edge).

Thanks! But the truck is in a million pieces at the moment, so running diff on engine is no go. Diesel sound like the way to go, right? Since motor oil won't cut the oil enough. Wouldn't the diesel be better at getting the old crud out?

What kind of "crud" are we taking about? Shouldn't be like an engine pan. Your just looking to "wash" out the oil with any metal that has accumulated over the years.
Diesel is ok but you want to get it all out, so when you re-fill it doesn't dilute the fresh oil. SAE 10 or 20 engine oil should do the same, with less dilution if you don't get it fully drained.