Checking and topping off rear end gear oil?

[Mosin]

Sent: 8/11/2008 10:52 PM

Hi All,

Pandora is a 1976 D26-RT (440/727 trans). Does anyone know how I would go about checking to see if the rear end gear oil is full? If it is low, is the procedure to top it off relatively simple (i.e. fill until it spills out of hole)? Last, what type/grade gear oil to use? TIA!

Dave




From: denisondc
Sent: 8/12/2008 4:09 AM

On mine there is a square headed pipe thread plug on the rear cover. I use an adjustable wrench to unscrew it. It was very tight the first time I removed it. As per the service manual, the fluid level on mine should be right at the bottom level of that hole. This assumes the axle is level. I added 80w90 wt hypoid gear oil until it was oozing out, then let it dribble till it stopped. I add a small amount each time I have the hubs apart for checking the rear brakes, because that differential fluid is the long term lube for the rear wheel bearings. The short term lube is the grease you pack in them upon reassembly.
I hope you are greasing the zerk fittings on the driveshaft each 2000 miles, and that you replaced the driveshaft center support bearing.
I have an 87 Chevy van whose driveshaft u-joints didnt have zerk fittings; so I replaced them with new ones that did have the fittings, just so I could grease 'em periodically.




From: Moesyn
Sent: 8/12/2008 11:31 PM

Thanks for the response. I was a bit surprised to find a round rubber plug instead of a bolt at the oil fill hole (!) but the level was almost to the top (about 1/8 in below so I topped it off with 80w90) and there have been no leaks in the past so I guess the plug is sufficient.

As for the driveshaft/lubrication, I had the center support bearing replaced ~3K miles ago(there is no lubrication for the center support bearing, correct?) and the driveline U-joints replaced about ~1,300 miles ago.

Re. your recommenation to lube the driveline u-joints every 2000 miles, roughly how many "pumps" of my standard 14" grease gun should I give each zerk since these are spankin' new? I am not used to looking at fresh u-joints (i.e. without grease spewing everywhere) so these inherently seem "dry" to me... yet I don't want to overdo it and blow the seals. Thanks again!




From: denisondc
Sent: 8/13/2008 3:54 AM

I use a single pump of my typical hand operated cartridge gun. Too many pumps and the seals would just get shoved aside and you would see grease squeezing out; though I dont think it hurts the seals. As the driveshaft spins, the extra grease gets flung away from the center of the 'cross' and down into the ends of the cross by the centripetal forces anyway; pushing the old grease ahead of it, out past the needle bearings and then past the rubber seals too. The way to tell if the u-joints on an old RV or truck have been greased is to look for the arc of grease on the underside of the coach above each u-joint. Some evidence of fresh lubrication is normal there. One reason I replaced the u-joints on my G20 Chevy van was because the 'grease arc' was missing, & the van was 20 years old.
As your u-joints are new, it will probably be fine to grease them each 4k miles. Even if you greased them each 10k miles, I believe it would be more often than most folks do it. Yours may or may not have grease fittings on the spring shackles. On my Winnie the manual calls for lubing them each 4k miles. They are harder to do, since I have to jack up the frame to take the weight off, or the grease wont go in. The same thing is true for the kingpin/bushings on the front axle. I always lube them with a jack lifting the axle so the vehicle weight is off the joint.
You're right that there is no way to lube the center support bearings. But they seem to last 20 or more years anyway. Mine failed (by siezing) in 2005, when it was 33 years old. I had removed it in 2003 to check it - when it spun smooth and quiet - so I put it back on!! [Not one of my best decisions.] At least it failed on a warm sunny day on a country road with a wide grassy shoulder; not in the middle of a shoulderless causeway or flyover.