Best way to flush moly grease from diff housing? (1 Viewer)

[John E Davies]

My front inner axle seals are leaking - I will do a Birfield job soon and need to know if there is a simple way to flush residual moly grease out of the diff area. It's not bad (not like lumpy oatmeal) just black gear oil. I replaced the gear oil and after 2000 miles it is very black again.....

I thought that after doing the Birf repairs and knuckle bearings and changing the inner seals, I could fill the housing with heavy motor oil (the cheap stuff) and run the truck in Drive with all 4 wheels off the ground. Drain and repeat, then install the gear lube. I am reluctant to use a solvent for fear it would damage the seals.

Would this be effective? Any concerns about leaving some moly in there? Maybe I should do the flushing prior to removing the Birfs?

I really don't want to, or see the need to, pull the third member.

Thanks

John Davies
96 LX450

 

[jesterb]

I don't see it harming anything. Just change out your diff fluid a little more often and you should be fine.

 

[Cruiserdrew]

John-Here is what I did when I had similar issues. Go to AutoZone if there is one near you and buy a 5 gallon bucket of Coastal 80w-90 gear oil. It will set you back about $24. When the new seals are in, refill the diff with the cheap gear oil. Drive for a normal day of commuting or whatever, and drain hot when you get home. Refill with cheap oil, drive for a week and drain hot. Refill a third time with the cheap stuff and drive for a month, then drain. Refill with the synthetic you like the best and forget about it for 20-30k miles. The cheap gear oil can also be used as a permanent fill since it meets all the specifications. For $1 per quart it's hard to go wrong and will clean up your diff nicely.

I would not under any circumstances run motor oil in a hypoid diff, but that's just me.

 

[John E Davies]

John-Here is what I did when I had similar issues. Go to AutoZone if there is one near you and buy a 5 gallon bucket of Coastal 80w-90 gear oil. It will set you back about $24. When the new seals are in, refill the diff with the cheap gear oil. Drive for a normal day of commuting or whatever, and drain hot when you get home. Refill with cheap oil, drive for a week and drain hot. Refill a third time with the cheap stuff and drive for a month, then drain. Refill with the synthetic you like the best and forget about it for 20-30k miles. The cheap gear oil can also be used as a permanent fill since it meets all the specifications. For $1 per quart it's hard to go wrong and will clean up your diff nicely.

I would not under any circumstances run motor oil in a hypoid diff, but that's just me.

That sounds like a winner. I wouldn't run motor oil under any kind of load - with the wheels in the air and free wheeling there would be essentially zero load on the gears.

I was just looking for a cheap lube that could be used to flush things. I hadn't thought of gear oil in bulk. I will check out Costco and other suppliers - I don't have an AutoZone in my town.

John

 

[sleeoffroad]

I have in the past when things were really trashed on the ShortBus and I wanted to wash out metal filing etc, ran ATF in the front diff while it was on the lift.

 

[Cruiserdrew]

That sounds like a winner. I wouldn't run motor oil under any kind of load - with the wheels in the air and free wheeling there would be essentially zero load on the gears.

I was just looking for a cheap lube that could be used to flush things. I hadn't thought of gear oil in bulk. I will check out Costco and other suppliers - I don't have an AutoZone in my town.

John

Wal-Mart, as much as I hate to say it, has cheap and acceptable gear lube in bulk as well. The 5 gal bucket is very reasonably priced and you can clean as you drive. I change the gear lube in my FJ40 so often-every trip where we go in deep water, that I tend to run the cheap stuff in that all the time.

 

[Rookie2]

I second the idea of putting it up on jack stands and put it in drive while running ATF or some kind of solvent through just before doing your axle service. I think the primary thing is to thin the lub up good so that you get a good drain. The problem with the birf soup is that it's so thick, it coats everything and doesn't completely drain. I went the coastal drain/fill route and obviously the color gets a little better with each drain, but if I had to do over, I would have gone this other route to get the junk out of there quicker.


Rookie2