Seized final drive fill plug

I need to change the final drive fluid in the '78 100/7 I just bought, but I can't remove the filler plug. I've been squirting it with penetrating oil periodically for a week or so. Ive heated the case, Ive heated the plug, I've gently used a Makita cordless impact driver in forward and reverse. Just won't break loose. Any Ideas?

Are you talking about the vent plug on top or the check plug on the back? I think you could fill it from either?

Have you tried turning the bike upside down and filling it that way?

OK, just kidding there... I don't think you should be trying to the heat the plug, that will just make it tighter in the hole. Since its a steel plug in an alumimum case you got to be carefull that you don't strip the threads as the alumimum will give before the steel and in removing it it could take the threads in case with it, like I did years ago with the exhuast nut on my first R50/5. I would have thought heating the case might have worked but if it is fused that badly makes one wonder when the last time it was removed to change the gear oil??? I work it a bit more with the impact wrench and see if it breaks lose as you continue to soak the threads it with light oil as you have been.

RM

Before going much further, I'd let that sucker soak with some good penetrating oil for AT LEAST 24 hours. Preferably, multiple treatments over the next few days.

I wonder if a PO used red loctite to secure the fill plug...for some stupid reason...

Red loctite requires a good bit of heat to release...

PT9766 said:

Assuming it is the rear "level" plug you are working on if penetrating solvents have not succeeded, warming the case and cooling the plug with ice or dry ice and then prudent use of a hammer-powered impact tool or a longer "breaker bar" with high quality Allen key, of the socket drive type, will usually be effective.

PT9766

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The '78 did not have a level plug or a fill at the vent plug. It had one fill plug at about the fill level and a drain plug on the bottom. I would think that heat is part of the answer at least. The steel should not expand as much as the aluminum. I have noticed over the 37 years that steel plugs in aluminum cases on BMW seem to tighten up while they are in there and many folks torque them in too tight.
The issue with the aluminum flower nuts on the aluminum heads on the /5 was a different issue.

some good penetrating oil, followed with a few deftly administered "smacks" to get some vibrations going- usually helps the p-oil to penetrate.

Thanks for the advice guys, I guess that I'll keep on trying as I have been. One of the problems is that the previous owner didn't believe in crush washers I guess. Several of the other plugs on the bike were without also.

GOT IT!
Tried more of everything, More P oil, More Heat, More pounding with the impact driver, But in the end it was the More TORQUE that did it.!

jfduclos said:

GOT IT!
Tried more of everything, More P oil, More Heat, More pounding with the impact driver, But in the end it was the More TORQUE that did it.!

Thanks for the advice guys, I guess that I'll keep on trying as I have been. One of the problems is that the previous owner didn't believe in crush washers I guess. Several of the other plugs on the bike were without also.

Click to expand...

Sounds like the PO did not take proper care of the bike. If you haven't done it or don't plan to---I would go over everything on the bike from front to rear.