Moly additive for gear oil

[Sluggy]

Anyone ever add moly to help with wear and tear/ shock load for diffs, t cases and manual transmissions? Would it have any negative effects on certain styles of diffs? Just a general question, trying to think of ways to help improve drivetrain life for a street driven rig.

 

[lt1yj]

Moly or molybdenum disulfide is used in a lot of high contact pressure scenarios. Under very highly concentrated load the molybdenum disulfide squishes and makes a barrier layer between the mating steel surfaces.

This keeps the steel from touching and creating wear. Oil performs the same function under lower contract pressures.

Moly in lower contact pressure conditions can act as a fine abrasive and actually accelerate wear rather than prevent it. Primarily because it's almost a crystal under low loads.

My personal opinion is that moly is used in many applications where it does more harm than good. Roller bearings and softer material sleeve bearings are a good example of where moly is often used and does not provide a benefit.

There are a lot of applications where it is needed. Especially in mining equipment that sees very regular use at the machine limit like an excavator digging into a high bank 24hrs a day 365 days a year. Wheel loader bucket linkage is another good example where it's a benefit.

 

[Slander]

Anyone ever add moly to help with wear and tear/ shock load for diffs, t cases and manual transmissions? Would it have any negative effects on certain styles of diffs? Just a general question, trying to think of ways to help improve drivetrain life for a street driven rig.

Is this just a street driven truck or a wheeler being driven to and from the trail? IMO if it's the later, changing your driving habits would do far more good to keeping the drivetrain alive than some gear lube additive. I just dump whatever synthetic gear.lube is at the store into the diffs on my street driven crawler and change it annually for the year, evrey 2 years for the front.

 

[Sluggy]

Wheeler that hits the trails and also my daily if I'm not in the mood to drive anything else. Changing driving habits is a tough one, I'm already babying it compared to the buggy. Just have some expensive parts that I want to keep for the life of the rig and not replace.

 

[AKnate]

It's rare for those parts to fail from lube other than when there isn't any or it's more water than oil.

Chevron XDM 75w90 is a great oil. As is SynGear HD. Available in 5 gal pails.
If you use a bunch, check with your local bulk lube place. They'll also have way more selection for equipment and farm.
Like trying finding TO4 50wt for final drives at Schucks.

 

[Sluggy]

Moly in lower contact pressure conditions can act as a fine abrasive and actually accelerate wear rather than prevent it. Primarily because it's almost a crystal under low loads.

So if I'm understanding this correctly, it's great for the ring and pinion. Not great for the bearings involved with the r&p

 

[ThePanzerFuhrer]

I vote no. Moly is not good for bearings. Stick to the standard gear oils for you rear end. If you want to spend money get some 75-90w synthetic.

 

[AKnate]

So if I'm understanding this correctly, it's great for the ring and pinion. Not great for the bearings involved with the r&p

I only deal with it for grease.

We spec it for pins/bushings and other low speed applications.
In high speed stuff, like wheel bearings it's not good. The info I have from people way smarter than me say potentional for increased wear and heat.

 

[lt1yj]

So if I'm understanding this correctly, it's great for the ring and pinion. Not great for the bearings involved with the r&p

It would be great for a ring and pinion if they were under max load all the time. When they are under light load the moly would increase wear. It's extremely rare for our rigs to be under heavy load. 95+% of the time we run at low-moderate loads. The only time you'd get a benefit is that 1% of the time you're maxed out on torque and barely moving. Even then the surface damage to the gear is marginal with high quality oil.

I never recommend moly for roller bearings of any kind.

 

[Slander]

Wheeler that hits the trails and also my daily if I'm not in the mood to drive anything else. Changing driving habits is a tough one, I'm already babying it compared to the buggy. Just have some expensive parts that I want to keep for the life of the rig and not replace.

I'm in the same boat you are I just change the fluid more frequently to look for signs of stuff going wrong and to keep fresh stuff in there.