Thread: Use of graphite or moly in diffs?

i have been thinking of adding cleenfuels addetive on the next change - their fuel product and oil system cleaners are great

see here :

http://www.costeffective.com.au/

Mick

Must be something in it as they are now moly coating projectiles( bullets for the uninformed) to slide down barrels without any drag.

FYI, use of moly on projectiles doesn't result in total loss of drag, and the main reason it is used is to reduce copper fouling in barrels. The fouling doesn't reduce life considerably during match use (most of the wear is in the barrel throat from the 50,000psi high temp explosions!) but it does reduce accuracy. There is a VERY small amount of copper vapourised by powder as it burns and this vapour is deposited inside the barrel. If there is enough relief in the bore surface it can gather enough to gaul and damage subsequent projectiles. When moly is used, it takes a number of firings to lay down a coating, but once established this coating prevents the gauling.

yeah our rounds at work are coated with black teflon type stuff for this reason - or at least i think thats what they tell us

Mick

I have used that shc50 mobil oil in my old series 2 landy what a difference that made,we had a fleet of 4wd trucks with snow ploughs and using 90/140 oil we would have to replace the bearings after the winter months were finished,switched to the synthetic oil the transfer cases did not need touching again just changed the oil every year.

Never put graphite in any thing that has roller, ball, timken bearings. These beargings need to roll not slide, graphite makes them slide and flat spotts them. Same reason you use different grease in wheel bearing/unis to ball joints, one slides one rolls. I run Castrol SAF-XA synth in all diffs

Macman, sounds like your a benchrest guy, i have read all the articles about moly coating and the subsequent bedding in procedures. Too much mucking about for me. i used it as a simplified description for the other uses of moly.

Mick, the SXT rounds, have a sort of wash, like a dark copper, on them, its not a moly coating.( check the packets at your next shoot) Instructors know all, are the gurus and when they don't know an answer they make it up.
the practice ammo has that coating on it to stop the barrels leading up, there was the green slime ,the black slime and the clear slime, don't know when you did you conversion course, but the first few I ran in the early days of glock conversions, you could peel the lead out of the barrels at the end of the course.( but that was in the days of the 900 rd conversions,)
That became a problem because the armourer at a well known facility west of sydney split some glock barrels , allegedly because of the leading( i saw a couple they were split/cracked under the breach) but thats another story.
Because the tolerances are so tight, the slime was added to the lead as a coating but it isn;t moly.


john

If the grease that is installed in the front CV housing is good enough for the extream pressures that the CV's undergo then surely this could theoreticaly be used in diffs..............this would solve the problem of leaking diff pinion seals, and cross contamination from the CV housings into the diffs.............hate doing axle seals, such a time consuming job for such a simple quick replacement.

Cheers

Originally Posted by Larns

If the grease that is installed in the front CV housing is good enough for the extream pressures that the CV's undergo then surely this could theoreticaly be used in diffs..............this would solve the problem of leaking diff pinion seals, and cross contamination from the CV housings into the diffs.............hate doing axle seals, such a time consuming job for such a simple quick replacement.

Cheers

Problem is, that while diffs have sliding contact on the teeth, they also have roller bearings. See the various posts above - MoS2 seems to be OK in diffs but not graphite.
However, you need to have a liquid lubricant in the diff as if you just had grease it would soon (as in a few revolutions) get squeezed completely off the teeth, and would not run back on like the oil does. Also, the liquid helps helps to cool any hot spots. The CV joints can live with grease as most of the time there is very little movement on the joint itself - and it can be made into a grease tight container itself as with open drive axles. Where it is in an oil filled ball swivel as in most Landrovers, the lubricant has to be at least semi-liquid.

John