Just changed the lubricant in my '84 5 speed tranny. After draining the old oil, I noticed another larger drain plug further forward on the transmission. This one is on a flat cast aluminum bottom plate with 10mm bolts around the perimeter. So I drained this section too. Both drain plugs have magnets. There are also two fill plugs. Can anyone explain these two reservoirs which seem to be connected?

The Haynes Manual says to use SAE 80. I used Castrol 80W90 'Hypoy C'. Will this be ok? Seems pretty thick, esp. for the cold winters. The old oil was quite heavy too, with that gear oil odour.

 

80w90 will be fine. I havent seen any other drain plugs on those tranny's other than the one in the center of the bolt on pate. I have done literally hundreds of them

 

Thanks Jake for confirming the oil is good. The other drain plug is about 10" to the rear of the one you describe, but horizontal, facing the passenger side. No digital camera on hand, but it should all be ok.

Gordon