Spider gear thrust washers

[derekf]

Okay, somewhere in the process of pulling and replacing the axles on my 65, one of the thrust washers for the spider gears (it's an open 12 bolt diff) got completely mangled. I suspect it got caught in the remaining gears when one of the spider gears fell out.

I figured that since I have the axle for my 69 open, and would be replacing the diff with a TrueTrac, I'd just snag one of the washers from there -- but it does not seem to have any.

So, two part question. Do I need the washer (I assume yes, since it was there to start with), and if so, shouldn't the 69 also have them? I know it's been together for at least the past 20 years/250k miles so I assume that it's not something that causes a problem quickly?

[big gear head]

Yes, it needs the washers. All factory differentials have the washers, so your '69 should have them too. If not then they have been removed at some time. These washers prevent the pinion gears from eating into the case.

[derekf]

Thanks, BGH. I'll look through the 69's rear again, maybe they're hiding.

[derekf]

The washers for the 69 weren't the same as the 65's washers - the 69 washers (on the left here)
https://static1.pt-content.com/images/pt/2009/05/09051602-1.gif
have a little lip that fits inside the spider gear, and the 65 washers were smooth.

The 69's washers wouldn't fit in the 65's gears, so I swapped the spiders over too.

Will that cause any issues?

[big gear head]

The washers with the lip are for a standard differential. The washers without the lip are for an Eaton Posi. Be sure that these gears are correct for this unit. You might end up with a hand full of gear teeth if they are not right.

[derekf]

Wierd, then - the non-lip washers and spiders were in the open diff from the 65. Did I just dodge a bullet?

[big gear head]

I don't know. It is possible that the early standard differetnial used the same washers as the Eaton, but I wouldn't think so. be sure that you check it out well. I recommend that you find an old truck 12 bolt standard differential and get the washers out of it. Or maybe you can find someone with a 2 series car differetnial who will part with it very cheap. If you could find someone who installed a Power Trax then you could get their washers.