Differential Oil Change ISC 8.3

[tmw188]

Is changing this fluid as straight forward as one might think? I know to make sure the fill plug can be removed for refilling before draining, any other suggestions?

[jacwjames]

Yup, about as straight forward as on a car/truck. I just used a 5 gallon bucket to catch the old oil. Can't remember how much I used, just bought extra and took excess back.



I did mine at ~90K miles. If you don't have it here's a copy of the lubrication guide for your Roadmaster chassis.

[tmw188]

Thanks Jim, I don’t have that publication- thank you. I don’t have any records of that service being done. I have 71,000 I want to do it while I’m indoors on level concrete before I might loose my indoor storage🥲

[Lowflyer1]

I had mine done at Speedco (Love's) couple years ago, it was only $138.00 total.
Actually turned out to be cheaper than purchasing just the oil myself, Spirax S6 75W90SYN Gear oil.

[vettenuts]

I did mine when I bought the coach because I had no maintenance records. There are a couple of differentials that are used and each has their own fluid specification. I used a synthetic to reduce maintenance requirements.

[vettenuts]

Originally Posted by jacwjames

Yup, about as straight forward as on a car/truck. I just used a 5 gallon bucket to catch the old oil. Can't remember how much I used, just bought extra and took excess back.



I did mine at ~90K miles. If you don't have it here's a copy of the lubrication guide for your Roadmaster chassis.

That’s a nice manual. The Freightliner manual I have isn’t as explicit.

[tmw188]

How level left to right, I’m assuming reasonably level should be fine but don’t like assuming? One end of the axle may hold more oil than the other although it is what it is. What’s your opinion?

[mackwrench]

Originally Posted by tmw188

How level left to right, I’m assuming reasonably level should be fine but don’t like assuming? One end of the axle may hold more oil than the other although it is what it is. What’s your opinion?

Reasonably level is ok, the wheel ends should still be full, even when you drain the center section.
If you look head on at fill plug, it'll be just a little higher than bottom of axle housing. Once oil runs out fill hole, it's full.

If wheel hub was removed, then jack opposite side to fill the hub....wait a good bit, then recheck level.

[vettenuts]

I use a laser level to check side to side using a rule to measure. If one side is low, I will drive it up on wood enough to get level.

I used the Mobil Delvac synthetic that meets the Mercedes/Detroit differential specifications and is on their list of approved lubricants. (My coach has the Detroit differential.). Best price was from Summit Racing by quite a bit.

[tmw188]

So there is another plug about half way from the top plug which I assume is definitely the fill, what is the other plug for? I originally thought that was the check level plug but is too low for the axles?

[twinboat]

Originally Posted by tmw188

So there is another plug about half way from the top plug which I assume is definitely the fill, what is the other plug for? I originally thought that was the check level plug but is too low for the axles? Attachment 377829

Differencal oil tempeture sending unit. Some trucks use them.

[mackwrench]

Twinboat is correct, the check and fill is the top plug, with the tag. You'll fill it till it runs out that plug hole.

The lower one is for a rear differential fluid temperature sensor....as he posted.

[tmw188]

Good, I was wondering about that. Manual is calling for the GL-5 or MT-1 oil spec. I’m assuming a synthetic version of that is good. I don’t think the Penzoil version they list is a synthetic?

[mackwrench]

Originally Posted by tmw188

Good, I was wondering about that. Manual is calling for the GL-5 or MT-1 oil spec. I’m assuming a synthetic version of that is good. I don’t think the Penzoil version they list is a synthetic?

Not sure, but any GL-5 synthetic will be fine. I use Mobil 75W-140