Switching diff to M-1 synthetic question
 

I will be putting the rear end cover back on after the left side axle is in place. After the silicone has 'set' and it's ready for the fluid to be put in, should I run some clean regular oil few a few miles then replace with the M-1? I'm thinking that by doing it that way, the reg oil will act as a cleaner for the diff. Thoughts? :confused: :)

Dale, don't you have that theory reversed by 180 degrees :confused:

It's my impression that the syn basestock oils are the ones that contain the powerful detergents...certainly not the petro-based equivalents. However, since we're discussing gear lubes, I'm not 100% certain this is true. It certainly is for engine lube oils.

The synthetic gear oil will clean much better than regular dino gear oil.

My suggestion is to fill up with the Mobile One gear oil and continue to observe the recommended 30,000 mile change interval. You could cut that short for the first change if you wanted, perhaps after a year of use if you don't put 30,000 miles a year on the car.

If you clean the gunk from the bottom area of the differential that you can reach, that's plenty clean.

Ken300D

what about using a pressurewasher to clean out the diff then spraying a light lube oil on the gears to displace any water, then putting it back together and filling with M1 Gear oil?
I would not drive with standard lube oil in a diff... that sounds destructive.

I can only assume you have your tongue planted deeply into one of your cheeks when typing this!

BUT WAIT! That sounds like a great idea. Now if I can get a pressure washer from the local tool rental...

I guess I didn't state it well in my original post!

What I meant was that I would like the diff to be as clean as REASONABLY POSSIBLE so instead of putting the M-1 in and mixing with the residual dirty dino, it would be cleaner IF I were to put CLEAN dino oil in for just a short period THEN drain it and refill with M-1.

Does this make sense? Thanks (for the serious replies!) :)

I switched to M1 last year. Did an abbreviated interval for the first fill...2,779 miles to be exact (I just checked the spreadsheet :) ).

I'm sure when I drain next time it will look like new fluid coming out. Just the way I like it!

btw - your initial post made sense to me...I guess you are in trouble!


Tim

Just put in the M-1, run it like you said and drain it. Refill it with more M-1. By doing it the way you said with the dino, you will still have some dino fluid left over because using the drain plug will never get every drop out. Spend the 30 bucks, pick up 3 bottles of M1 and use a bottle and half for each fill and refill.

When I switched our two SD's over I drained the old brown syrup out :eek:, filled with M-1, ran them a couple months, drained again (pretty dirty yet again) and then filled with M-1 again, they've not been changed since, that was over 3 years ago....hmmm:rolleyes: Maybe I'll do it again soon.

Our 300D I recently drained, but it had clean dino in it! :eek: I was amazed. That proves it had a good mechanical maintenance history (runs very well and smooth). I filled it with M-1 and sealed 'er up. Won't have to worry about that one for a long time. :)

Mobil-1
 

I recommend wiping the inside bottom of the diff with a clean rag and some solvent, to remove as much crud as possible, then filling with Mobil-1 and drving normally. As has been suggested, a change after one year would be reasonable. The subsequent fill of M1 should be good for at least 30,000 miles after that.

With all of the axle changes I had to do recently, I ended up draining and filling my diff three times in a year. The inside looked cleaner each time. Even the original dino oil came out fairly clean the first time, over a year ago. The Mobil-1 that replaced it came out clean each time except for a little suspended crud that I removed with a coffee filter (a slow overnight process :D).

Aside from being a better lubricant, the Mobil-1 has better cold-flow qualities, always nice to have in snow country. Although I no longer live in a cold climate (for which I daily thank God), I do occasionally visit one, and it's nice to do anything I can to make the old diesel run better.

Jeremy

Since you have the diff already open, why not find some decent cleaner (not sure if brake cleaner is ok to use) if you are that concerned. I can't imagine the inside to be that dirty. If its "dirty" there may be a different issue.

Last year, I just replaced the dino with M1 and its been fine. Whatever it is we all have been doing probably exceeds recommended maintenance requirements anyway.

Thanks for the replies! I will take the advice of most and go ahead and fill with M-1 and change in a year or so. May let it go longer as I do not put that many miles on annually. I do agree that by changing over to synthetic, it will be 'miles ahead' of the dino anyway. :)