Full Synthetic Differential Oil Change

GnarlyBus · June 25, 2019, 07:30:23 PM

Hey Everybody!

Changing out the oil in the differential is the next maintenance item on my list. It doesn't leak but I've never done it before on the bus.

The manual says and I quote:

"Gear oil should be changed every 25,000-30.000 miles (40.000-48.000 km) on units run over 60,000 miles (96,000 km) annually. For units run less than 60,000 miles, the oil should be changed twice yearly (spring and fall) regardless of mileage."

!!!

I'm thinking of switching to full synthetic. I suppose something like an 85w140. Any recommendations?

Also, how would a DIYer get the oil into the diff? Long hose and a funnel running out to the side of the bus with someone standing out there?

buswarrior · June 25, 2019, 08:02:45 PM

cheap drill pump?

It doesn't like to flow, the 5 gallon pails are heavy, the oil stinks...

muscles and gravity are a game played once...

Your choice on lube... not sure there's any benefit for a busnut spending $$$ on synthetic.

Do what makes you happy.

happy coaching!
buswarrior

luvrbus · June 25, 2019, 08:14:31 PM

For 30 bucks buy a hand pump that fits the 5 gal bucket.it has other uses too ,85/140 is good but no need for a full synthetic on the old bus.you can buy the Gl5 at Walmart for 14 bucks a gal,the manual is rereferring to GL 1 lube lol and with operators that never happen

chessie4905 · June 25, 2019, 08:36:57 PM

Warm the fluid out in hot sun or whatever works to allow it to flow easily. Synthetic is overkill and money best spent elsewhere. Now if my coach had a drop box, I would use synthetic in it after rebuilding or replacing seals.

GnarlyBus · June 25, 2019, 11:34:01 PM

Look at this fill plug! No one told me I needed a Philips #8! Just kidding. This thing has been abused! Gonna see if I can source a replacement. Since we had the bus up I pulled the full plug and checked the level (we parked on a slope so the bus would be level when the rear is lifted). It ended up taking about a quart to fill up. I'm still planning on doing a full oil change but I figured I might as well top it off while I could.

I've read about a vent somewhere on the differential that must be working to avoid a gasket seal leak. I can't find anything about it in the manual...can someone tell me more about it?

chessie4905 · June 26, 2019, 06:19:02 AM

If it has a typical pipe plug...

https://www.mcmaster.com/pipe-plug

Or it could be a straight thread plug with a flange on the plug to stop it from going completely into hole.

GM Junky · June 27, 2019, 08:51:17 AM

For gear lube filling, try using an insecticide sprayer. Remove the spray tip,take a hacksaw and cut the three hole orifice off the wand. You may have to put a larger draw tube on it, simple to do but, certainly saves alot of time.
You can purchase a cheap plastic sprayer from HD, Harbor freight etc .. works excellent.

Glammers99l · July 01, 2019, 08:57:04 PM

Go get a cheap weed sprayer and fill it with your synthetic gear oil of choice,pump it up, and fill away. If my memory serves me correctly you'll nee 36-40 pints, and yes make sure the breather is clean. We run the synthetic rear end grease 500000 miles before a change on a seated coach.

Boomer · July 01, 2019, 09:59:23 PM

The rear axle vent is located on top of the axle tube. Just rotate the cap a few turns every time you grease the u-joints and check the diff oil to keep it open and breathing.

chessie4905 · July 02, 2019, 04:45:31 AM

A funnel and clear vinyl hose like in picture works nicely and is inexpensive. Put a clean drain pan under diff. to catch any overflow. Easy and cheap.

Brian Diehl · July 04, 2019, 08:08:06 AM

One important point no one has mentioned yet:

If you change to synthetic you must get all the old gear lube out. If you don't you may end up with foam. This should not be a problem in the differential, but will be an issue at the hubs. I was about to go synthetic myself until I realized I would need to pull the drive axle hubs to get ALL the gear lube out. There was no way I was going to risk getting foamy gear lube in the hubs. That made the decision easier for me. Quality gear lube has worked well so far. I have changed it 3 times over the course of the 12 years and 110,000 miles I've owned my bus.

Watch out for foaming. It is a real risk.

GnarlyBus · July 05, 2019, 12:08:48 AM

Good tip. I think I've decided to stay with conventional gear oil. It seems to make more sense for my use.

neoneddy · July 05, 2019, 07:43:25 PM

I recently added fluid to my diff, I first tried this 12v oil pump https://m.northerntool.com/shop/tools/product_200696884_200696884?gclid=CjwKCAjw6vvoBRBtEiwAZq-T1YbB1dEQbvtEaIsrB4bh1REX9csQNe_xqS8R6bOOzAT4SR41zhX_mBoC-VoQAvD_BwE

It struggled with the thick oil until I replaced the thin tube with an equal tube for both ends. I pumped in 1 gal in a minute or two. I tried a funnel and tube, was taking forever even at 80 degree ambient temp.

Oonrahnjay · July 22, 2019, 09:56:50 AM

Quote from: neoneddy on July 05, 2019, 07:43:25 PMI recently added fluid to my diff, I first tried this 12v oil pump https://m.northerntool.com/shop/tools/product_200696884_200696884?gclid=CjwKCAjw6vvoBRBtEiwAZq-T1YbB1dEQbvtEaIsrB4bh1REX9csQNe_xqS8R6bOOzAT4SR41zhX_mBoC-VoQAvD_BwE ...

That's what i use to change oil on my TDI. Works like a treat, I've had mine for years and it keeps on working.

neoneddy · July 22, 2019, 10:00:08 AM

I should have updated this.... turns out, you cant suck for a big hose and push into a smaller hose. For some reason the kit came with a 1/2 line and a 1/4th inch line. when I made them both 1/2 it worked better. Still a PITA to get under the bus. I actually dug a small pit I drove over, still not fun.