The Stovebolt Site Forums The Shop Area Driveline When to change diff oil?

Bought my truck 4 years ago and have never changed the rear differential oil. When should it be changed and how do you completely evacuate the pumpkin? There's no drain hole on the bottom, only the fill-plug half way up the pumpkin.

Thanks!

Either undo the bottom bolts or take the cover off completely. If the oil is rusty or parts fall out you may have a problem. Make sure the drain hole is on the lower half when replacing the cover. Also make certain the axle breather on top of the axle (driver's side) is free.

The owner's manual should answer the "how often" question. To get all the oil out of the rear end, I have always removed the rear cover, drained the oil out, clean up the lid and mating surface, new gasket and then filled it back up until the oil reaches the filler hole. I have only found the need to replace the differential gear lube after I had differential apart to replace a bearing or something. Of course if the vehicle was flooded or something then all the boxes will need an oil change.
hope this answers your question.

I'm going to do the same thing this weekend so I just looked in the service manual. I have a 46 1/2 ton and below is what was written in the original book.

"While seasonal changes of the lubricant are not required, it is recommended that the housing be drained and refilled with the recommended lubricant at least twice a year, or every 6,000 - 10,000 miles."

For the lubricant it came from the factory the manual says...

"1/2 ton Hypoid rear axle - SAE 90"

Hope that helps

Mike

I go to the drive in quick lube place, where they have a "vacuum" that sucks a differential or trans dry and let them change it - you can look at what they get out to see how gritty it is .... OTOH, I've had 50 year old trucks that I'm sure have never been changed and they're still working

Bill

I bet the manual was written knowing the trucks would be used for hard service. Back then I think people bought trucks to do actual work. I suppose now in the later years the fluid would last a pretty long time. Good advice on sucking it out, that would make quick work of it!

Mike

You can always modify a turkey baster or buy a suction pump from some place like HF to suck it out. I prefer to pull the cover off and then I can have a good look inside. The last time I did it I used blue silicone rather than a gasket. Works as well.

Thanks Sedgewick, GIJoe, Mike, & Bill for all your comments. I've never taken the cover off, so I guess it's time to look inside and see if I have any surprises. There's been no whine or rummblings coming from the rear end, so I don't expect to find anything bad, but it will allow me to visually inspect the "innards" and make an assessment of the condition of things in there. A good excuse to get some oil under my finger nails!

Thanks everyone.

If its been a long time since the gear lube has been changed you will be shocked to see how much sludge and gunk is inside. I've found that a can of brake clean helps clean things up.

You can drain the majority of the lube by removing one or two lower cover bolts. Once it stops flowing, replace the bolts. Then add enough kerosene or Diesel fuel to fill it back up to the correct level, jack up a wheel, and run the gears for a few minutes to circulate the solvent.

DO NOT DRIVE THE VEHICLE WITH THE SOLVENT ONBOARD. THE LUBRICATION PROPERTIES ARE SEVERELY COMPROMISED!

After circulating the solvent for a few minutes, remove the cover plate and drain everything. You'll be surprised how clean it will be inside.
Jerry

Thanks, that's a darn nice tip!

Yep Jerry, that's a good tip right there! Wouldn't have thought to do that or known that it would be okay to do it. No access to kerosene so I'll go buy a gallon of diesel. Will be a good project.

Thanks.

I've always been told that putting solvent in anything is a good way to loosen up stuff that clogs oil ports, damages bearings, etc... If you aren't rebuilding just draining and filling back up is the a way to go.