When draining differential fluid....

[RBAJJK]

I know the recommended process is to bring the fluid up to temp then drain. My question is simply can I drain it cold (well 80 degrees in FL), but let it drain for 24-48 hours and get a similar complete drain.

I will be refilling with Mobil 1 75w/90 gear lube. Should not have to do this again for several years, I think.

Thanks from the newbie.

Brian '96 Gulfstream Scenic Cruiser 250hp, Alpine Chassis

[RBAJJK]

I know the recommended process is to bring the fluid up to temp then drain. My question is simply can I drain it cold (well 80 degrees in FL), but let it drain for 24-48 hours and get a similar complete drain.

I will be refilling with Mobil 1 75w/90 gear lube. Should not have to do this again for several years, I think.

Thanks from the newbie.

Brian '96 Gulfstream Scenic Cruiser 250hp, Alpine Chassis

[Jay W]

Brian, I am no differential expert so consider what you paid for this advice
I don't think the 80 degree change will hurt. IMO the main reason to drain at operating temps is to remove more crud. Even at room temp you will get most of the fluid out in a couple of hours or so.

Are sure 75w90 is the right weight ?
I recently did my 05 Spartan and used 85w140.

[Rock-Rocker]

The advantage to draining the diff when warm is the fluid will still have most of the impurities in suspension and flow faster allowing a scouring affect. The bottom line is you would get a better removal of impurities and more removal of the old oil. I have done it both cold and warm and never had a problem in my daily drivers. I make a point though with the MH I do it warm since all the drive train is under more severe load conditionds and I want as much of the old oil and metal shavings out as possible. Also whenever I change my diff oil, since it's such a small amount I drain it in a container that I can inspect the oil visually for metal shavings/particles. If any discoloration such as a milky color would tell me water got in there somehow. If the drain plug doesn't have a magnet on it I stir the oil with one checking for metal. If there is water you have to find where it's getting it at (usually the rubber breather hose is broken off or cracked). If there are a small amount of metal particles in the oil and it's the first change then that may be normal due to break in. If it looks like alot then there may be a problem on the horizon. HTH

[RBAJJK]

Thanks Rock and Jay,

I'll follow up once the differential is done. I'll bring it up to temp before draining.

Jay, as far as the weight of the oil, my '96 alpine suggest 80w/90 for normal service, and the higher 140w only for severe duty - which my 4000 miles a year certainly is not. But I appreciate the question and will call Spartan to confirm. The change is costly given the 9.9 Liters (10.5 quarts) the manual says is required - so better do it right the first time.

Thanks again.

[toban]

I just changed mine in a DSDP 2004. I had 80/90 or 85/140. I changed to 75W90 which all the truckers use. I went to a lighter semi synthetic oil because it can get cold up here and 85/140 would be too thick and had to move the vehicle. The Meritor manual shows all kinds of different weight oils for different temperature applications. They all have no limit shown on the maximum temperature but show how cold the oil will efficiently operate at.
My differential took almost 4 gallons from a 5 gallon pail.

Toban

[quikduk]

I changed mine out and added about 10.5 quarts. To my surprise, it appears to require more so I will check again and add more till it starts to drip out of the fill hole and I can feel the fluid at the bottom of the opening.

FWIW, I used the same 85W140 Walmart gear oil I have been running for years in my other vehicles so it should be fine. If it bugs me, I can easily change it to semi or full synthetic.