89 Cabriolet - What's this plug?

That is the plug you remove to check the igniton timing. Or to help set the camshaft timing. The clutch in spinning around inside that hole. That green plastic thing is unscrewed to check the timing. There is a plastic cork that is on a tether that is usually lost on a car that has been around for a while. The plastic plug or cork goes in the middle of the green plastic insert. No oil should show up as it is not a fill hole for any type of oil. It should be dry inside there.

You may have a rear main seal leaking or mabe an input seal leaking. If smoke came out of there then it may be due for service work.

Hard to get in first might mean that you just need to rebush the shifting linkage with a $10 rebush kit. Or you might be trying to say that the clutch is not properly disengaging making ist difficult to engage first gear. I vote for the rebush for challenging shifting. Of course that will do nothing about the smoke which might be driver error or bad seals.

There is another metal plug on the end of the transmission. It uses a

17 mm allen wrench to remove. Oil should be coming out of the hole when you remove that plug. Some of the transmissions require you to add oil unitl in just leaks out that level hole. You then add another pint or so through the speedometer cable.

Thanks for the comprehensive reply, Jim.

...now that I think about it, I suspect the 'smoke' may have been an overheated clutch. I drove it home in rush hour traffic, and I couldn't find first or second gear, so there was a lot of load on the clutch. Now that you tell me the clutch is in there, I suspect (hope) this is what I saw / smelled.

I'll take a look at rebushing the shift linkage.

Cheers, Geoff Glave Vancouver, Canada

I'd wonder if your clutch is slipping and you are smelling and seeing a burned clutch...

The green plug covers an access hole necessary for setting the timing of the engine and is not an oil filler plug. As it may be hard to remove, it is not necessary to go any further with it in what seems to be a clutch worn/slipping...I would check the clutch cable for any roughness. Al.