Differential Housing

[rtaylor]

While under the rear end of the Z, I noticed alot of grease and oil on the pumpkin. I could not tell exactly where this oil/grease was coming from due to the accumulation of grease/oil. I looked at where the half shafts/rear end are coupled, but it does not appear that the problem came from this area. So I deceided that I would replace the cover gasket. I removed the drain and fill plugs and noticed a thin film of silicone on the back of the plugs.??? Next I pulled the cover. There was a thin film of silicone on the housing itself. As I looked into the housing I viewed some letters that looked like they were hand painted onto the gears with what appeared to me to be the same yellow paint that that auto dismantlers use to mark their parts. Did Datsun also use this paint on original assembly line installed parts? Does it seem that gears have been replaced? Keep in mind this car only has 25,000 miles on it. Did Datsun use silicone gasket sealer in 1971? Wasn't the sealer used like the opaque yellow looking stuff Permatex produces? Strange.

I replaced the cover, used black RTV and will wait and see if the leak is still there once it is up and running. Thanks guys

[240ZX]

If there is gear lube around the outside top area of the diff housing it is likely coming from the diff vent.....pretty normal occurance if the diff is overfilled. IIRC, Datsun used a normal fiber type gasket between the cover and housing...no silicone sealant. Of course gear lube can leak from the pinion seal or either output shaft seal. Just make sure you clean all the old gear lube off the diff after you have done your work, so you will be able to see exactly where the leak is, if it rears it's ugly head again!

[Arne]

Seems to me that the maintenance schedule called for the diff lube to be changed every so often, regardless of mileage. So the presence of an RTV sealant wouldn't be all that surprising to me, even on a low mileage car. Assuming, of course, that the previous owner followed the maintenance schedule.

As for the markings, it wouldn't surprise me to find that the gears were marked somehow during assembly and setup.

[LanceM]

Just bought a 4.11 R180 and the gears were marked with a paint marker.