differential Grease problem

[Patrick in west falls]

I just bought the vehicle, it was a halfway decent amatuer restoration.
however I was surprized to find the diff. filled with fresh grease rather than 600w.
My suction gun doesn't even want to suck the stuff out, so I slowly started scooping it out the hole with a screwdriver.
I'm gonna pick up some kerosene today an spray it in there,
jack up rear wheels and turn them.
would i be able to loosen up pumpkin bolts and let this gunk drain out
(as theres no drain plug)

any ideas
tnx patrick

[Paul from Maine]

I'd just scoop as much grease out with the screwdriver as I could and then fill it with 90/140 (or is it 90w/140w?) and run it for awhile. Then I'd use the suction gun again. The grease probably isn't going to hurt anything, but I don't think it's a very effective gear lubricant. I would think with grease alone, the gears would just carve out a void in the grease where they revolve and then the gears would receive no further lubrication. But if you add some gear oil, the oil would fill those voids in the grease where the gears turn. I would guess that the oil churned up by the gear rotation and the heat generated by the gears would then eventually dissolve the grease in the pumpkin over time, especially if you kept using the suction gun from time to time. However, I am not an expert and my advice might be way off base. I'm just saying what I would try. Perhaps others out there have better suggestions.

[Jack Innes]

Patrick,

I would suggest to see what mixes well with some of the grease you have removed before adding anything new to the axle itself. The wrong thing could cause more trouble.

The manual for the 1911 Cadillac 30 specifies a mixture of grease & motor oil as the lubricant for the transmission & rear axle. The mixture should be just liquid enough to flow back into the groove cut by the gears. You could try this & then, as Paul suggests, run it for a while & suck it out & fill with the correct oil.

Remember when you are done the lube level should be about an inch below the fill plug.

[redmodelt]

When all is done use 600W oil that you can get from the parts suppliers. No you can not just open the rear end by loosening the bolts on the housing. About 1920 up there is a paper gasket between the two housings and if you did open it too far, there are 4 steel thrust washers (plus 2 bronze washers (read on) sandwiched in between) that could come off their retaining pins. Then there is the drive shaft to housing bolts.
While you are cleaning out the rear end, check to see if there are any silver/gray colored bits in the oil, if there are, probity means that you still have babbitt thrust washers and those need to be changed. If they go you can loose pinion to ring gear contact and brakes.

[Paul,WI]

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Well given the person put in greese and not oil I would be concerned about what else he may have done. I would pull the rear end off and take it apart for a good inspection and make sure everything is correct in there. There are some really good videos on how to do this as well as a book from the MTFCA. If you choose not to take it apart then the examples above will all work. Like they state you need to get an oil in there and run it for a while to start mixing with the grease you will still have some grease in there but it will not hurt anything as long as you have some good heavy oil for the gear to turn in.