Noticed a bit of a leak on the u joint

Hello out there. I just received my 5 speed 1996 JA22W Jimny a few weeks ago and love it to death. I haven't had to do a whole to it yet, but I did notice there is a small leak at the u joint at the front end (trying to learn car terms, and trying to be more mechanically sound with the Jimny). Do I need a gasket or seal of some sort to fix this? Should I not drive till I fix it? Thanks.

Not sure wich end of the drive shaft this is, but the shaft itself has no oil in it so the oil might come from the transfere gear box flange or the front diff flange. both has a shaft seal and not too difficult to swap. If there is more oil on the gear/diff side of the flanges than on the U-joint it could be one of these seals.

Or could it be something drips down on the U-joint from above?

The slip yoke and its shaft seal coming out from the main gearbox is the most likely leaky seal on these cars. 
(the only drive shaft end with no flange.)

Thanks for getting back to me. I think it's coming from the front differential. I went ahead and ordered a seal to fix it. I also have read on these forums that GL4 gear oil 75/90 gearbox & transfer is what I would need to change out. It seems that the suggestion is to get Redline MT-90 full synthetic gear oil. Am I on the right path?

API GL-5, SAE 80W-90, hypoid

GL4 relates more to the syncromesh in a gearbox, but GL5 can take more surface pressure for the Hypoid gears so as far as I know, best to use the spec.

75/90 is the gearbox oil recommendation.

You want a GL5 in the axles, the additives are made for the extreme pressures and high sliding forces that you get in a hypoid differential. (One where the pinion is below the centre line of the crownwheel, like the Jimny)

BUT never put GL5 in a synchromesh gearbox as the additives eat away the brass in the synchro cones.

(So you need different oils for axles & gearbox)