Warning: don't mix chassis lube greases?

Hi List:

After a quick jaunt out to my local auto-parts supplier to buy grease gun and chassis lube, the warnings on the lube tubes stopped me *cold* in my tracks:

Warning: Never mix greases of different bases and compositions...you must disassemble parts, thoroughly de-grease, reassemble and inject new lube...etc.

Can list members give me a brief explanation with some understandable science (to back up your suggestion) to use just any old high quality lube and just inject it into the front-end (11 Zerk) locales in my 2004 Silverado 2500HD 4x4? I'm not talking about bearing grease here, just chassis lube.

Any ex or current Chevy mechanics out there with the *precise lube specs* and / or suggested lube manufacturer to use on my 04k truck?

Thanks!

Never, had a problem with chassis lube. Just used what ever I had, usuallygood-high quality lube. If anything, pump the joints till you see the new fluid come out.

some greases are made of teflon and some are made of grafite and i don't have any Idea what that red shit is made of. I usually use the good ole grey graphite grease.

Thanks, GTmud:

Though, a web-site with some highly technical grease manufacturing data says that ...the dangers of mixing greases that are not compatible must be understood and *avoided* to prevent lubrication failure...

(Site: GREASE, A More Comprehensive Understanding)


Yikes. This is deadly serious stuff, as if the two lubes (e.g. the original Chevy lube mixed with any other stuff of unknown compatibility is injected later) are mixed, there may be no lubrication taking place whatsoever; the two greases mixed rendering absolutely no lubrication or worse, a joint failure. Consequences: prematurely destroyed front end with no GM warranty.

Looks like I'll be researching my own query bit by bit:

The specific Silverado chassis lube grease (2004 user's booklet p. 6-14) is GM U.S. part number: 12377985; or Canadian part number: 88901242, and the categories to be used are either:

NLGI 2 Cat: LB (Prolonged relubrication intervals (>3200km). Mild to severe duty)

or,

NLGI 2 Cat: GC-LB (Mild to severe duty -vehicles in frequent stop and go service, trailer hauling, mountain driving- frequent temps at 160 celsius, infrequent excursions into 200 celsius)

*'If the thickeners are incompatible, the mixture will fall short of the properties of the individual greases. It is strongly advised that, in the case of greasing bearings, the old grease be purged or cleaned out from the system before a new one is introduced.' And, '...compatibility between greases (in the case of bearings or joints) is temperature dependent. As the temperature rises, the problems associated with incompatibility also increase...' Therefore, ' ...treat all competitors' products as incompatible unless strong evidence exists to the contrary...'


However there is no indication if GM part number 12377985 is Aluminum Complex, Lithium, Polyurea or Lithium Complex based. I'll have to dig more into this. But the evidence points to sticking strictly to the original manufacturer's lube, unless one wants to tear the front end apart, de-grease, re-assemble and apply a competitor's product.

To check out the reason you can't mix greases togather you might want to look up the FAA/NTSB finding on the Alaskan airlines plane the went down a few years ago near california. Basically the repair shop used the one type of grease and the airline mechanics used a different grease and the result was the grease turned into sandpaper, causing the jackscrew to wear to fast and fail inflight. Another thing improper greasing can do is seperate and not lube the metal causing metal to metal contact(the grease liquidfies).

Thanks, Rustcal:

You're right on the money there. I just got a link to a superb grease compatibility chart from a member of Woodalls towing truck forum:

http://www.mindconnection.com/library/handyman/greasecompat.htm

This chart and associated writeup is quite good. Have a look.

The site also covers the subject of two dissimilar greases when mixed turning into a water-like fluid, resulting in catastrophic failure of high pressure metal joints in friction.

Regards,
Derek-

Come on Guys!
There are 110 million cars crusing the roads. The only ones that I have seen where the suspension breaks is the one that should of had the suspension replaced or repaired 20k miles ago. Were not talking 20 year old air planes where they neglected to grease the screw for the previous 2 years as in the plane crash.
Chill out