Posted by Glen on Wednesday, March 30, 2005 at 12:44PM :
In Reply to: New Spin on the Ole Knuckle Grease Issue posted by Paul (in NY) on Tuesday, March 29, 2005 at 2:05PM :
I did a little looking on the web about tracta joints and found some info on Jeep and Land Rover applications concerning lube specs. The Land Rovers required the same gear lube as the differentials which leads me to believe they had better knuckle seals to keep the lube in. The jeep info wasn't quite as descriptive but it seems they used felt seals and the jeeps guys have different opinions about what lube to use in the knuckles.
The use of leather seals on the axle shaft and hub seems to be the reason why Dodge changed the lube spec from semi-fluid chassis lube to regular grease. With the semi fluid grease all is good until it migrates into the hub area and when the knuckle level got low more was added, so more could end up making it's way to the hub bearings and eventually overwhelming the leather hub seal and causing leakage and comtaminating the brake shoes. When the switch was made to regular grease for the knuckle the leather seals were less likely to cause a mess. The only problem then is there's less lube for the inner axle bushings because #2 grease doesn't replenish the areas it's been slung from because of it's consistancy. If the axle bushings don't have adequete lube eventually they will wear and cause the inner seal to leak gear oil into the knuckle area. So with the leather seals you can have a hub seal leak soon using semi-fluid grease when it gets to the hub or a knuckle leak later when using regular grease because the axle bushings wear prematurely.
Tapered roller bearings at high speed when run in gear oil will outlast ones run in grease. Grease is primarily designed for low speed-high load sliding surfaces. If it can be kept in contact with the surface it lubes it works well. The tracta joint is a sliding surface but it's not operating at a low speed and if lubed continually there will be minimal wear. The grease applied to the tracta joint will eventually work it's way from the sliding surface and while it may look like it's stuck to the knuckle joint pieces it's probably not doing as much as it could to keep the contact areas properly lubed.
Like Clint said below if Chrysler had used something better than felt seals for the knuckle, gear oil would be the first choice. And with the felt seals weeping and semi-fluid grease migrating to the hubs leather seals, regular grease keeps the brakes dry but shortens axle bushing life.
My choice would be to use the semi-fluid grease to give the bushings and knuckle joints as constant as possible supply of lubrication and prevent brake shoe contamination by using modern neoprene double lip seals at the hub ends. Also neoprene seals in the axle tube should do a better job of keeping the diff gear oil out of the knuckle.
I'm running the National double lip seal on the rear hubs of my 1950 PW and not using the outer seal to prevent gear oil from getting to the bearings so they have a constant supply of 85-140w.
It's obvious why Dodge switched to regular grease for the knuckle....cuts down on leaks for a while when using leather seals.
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