If the bearings in the rack and pinion are sintered metal; they have
voids in the metal structure that are infused with oil and make it a bearing
or bushing. If the oil leaves the bearing it will start galling the metal.
I would be very careful using grease. Grease will not penetrate the
sintered metal structure and if the grease dries out like it sometimes does
then you have a major disassembly, clean up and repair. Some of the new
synthetic greases may be better but I have no experience with them.
Ron Fraser
-----Original Message-----
From: owner-tigers@autox.team.net [mailto:owner-tigers@autox.team.net] On
Behalf Of Tom Hall
Sent: Thursday, April 07, 2005 4:07 AM
To: Dan Eiland
Cc: tigers@autox.team.net
Subject: Re: Steering Rack Lubrication
At 10:13 PM 4/6/2005, you wrote:
>Can someone explain why we use grease on wheel bearings and on steering
>column bearings, while using gear oil to lubricate the bearings in the
>rack and pinion and the differential? It would seem to me that the rack
>and pinion bearing and the steering column bearing would share more
>load and force characteristics as would the wheel bearings and the
>differential bearings. I'm confused as to how the engineers chose
>lubricants for the different bearings.
You might consider the contact surfaces and observe that the bearings
generally have rolling contact whereas the gears have sliding contact. I'd
also consider the viscosity, film strength, heat transfer capability and
additive requirements. Oil may work as well in rolling contact such as the
differential carrier bearings but grease must not have adequate physical
properties when it comes to sliding contact applications. It's designed to
stay essentially in one place. Tom
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