My truck sits 3-4 days a week (04.5 with 45K) occasionally towing (twice a year) my 10K (loaded) fifth wheel. The rest of the miles are combination highway/city. Use of 4WD is VERY limited (almost exclusively backing 5th wheel into my driveway). If there are 30 minutes of total usage on the 4WD since new, I would be surprised.

So, based on that, how often should I service the differentials (15K, 30K, etc.)?

 

I also use 4WD very rarely. I did my rear diff at 15K, but postponed the front until 30K since it still looked pristine. I'll definitely continue changing the rear at 15K as it was quite dark through normal unloaded driving.

 

I bet you find at 30k the oil in the rear end looks good. When they break in they seem to darken the oil.

Anyway, I did my last truck every 15k. The truck I have now I bought used at about 30k and I'm sure the axles were never done.

I don't think I'd go longer than 30k. Infrequent driving might also allow moisture to accumulate.

It would be interesting to send in a sample, with a baseline test of the same oil new...

 

The manual recommends changing every 15k. For the first change at 15k I think that is justified, but for every subsequent change after that, I think it's a little steep. You could probably go double or triple that after you change the original fluid out of the diffs.

I changed both of my diffs at 15k so that I could get all the wear particles out. Both the front and rear diffs spin full time because of the front hubs so there is no reason to not do one or the other, whether you use 4wd a lot or not.

 

I changed both Diffs at 15K. Put in Amsoil Severe Gear and am going to 45K and every 30K after that running the synthetic.

 

I changed mine when I first got my truck at 15k then 45K and then 75K. At 75K the fluid still looked good so I waited till 135K and the fluid still looked good. The 15K service I switched to Royal Purple in both differentials. I plan on sticking to the 60K interval as I tow only two to three times a year.

 

I've never changed fluid in either diffs in my 87 6.9. No problems. I changed them @ around 15K in my CTD. Now I guess I'll change the rear every 30 or 40K and probably change the front @ 100K. No combustion in there, and should get hot enough to evaporate moisture on long haul. Oil does not have to get to 212 to burn off or evaporate moisture. My 2 cents, and that is about what it's worth. HeHe

 

I have yet to change the front diff oil, and I have over 90k miles. Same with trans and tc. The rear was changed at 70k. But I have a long trip coming up, so ALL fluids will be changed for that.

 

I added a mag hytec pan in the rear, so with the extra 3 quarts of fluid in the rear I'm planning on going to 30K intervals instead of the factory recommended 15K. It has a dip stick, so checking the condition of the fluid is simple.

I haven't changed the front yet, I'm approaching the 30K mark and will be doing it along with the trans fluid. I'm debating on adding the front mag hytec cover, but it just doesn't seem worth it since the front is just spinning in 2wd.

 

But then they will match and both look good.

 

Bronco.....beware that some people have had some clearance issues with the MagHytec on the front axle. To my knowledge, MH has never really fixed this issue.

Don't get me wrong...I love MH and have their rear diff cover and dd trans pan. I went with the PML diff cover on the front though....no clearance issues and actually looks better, imo. The MH cover for the front just has an awkward looking shape (to me). I think the PML for the front matches the MH on the rear better than the MH front does..

And, you can't look at both at the same time anyway.

..

 

I think I'm going to spend money on the Defiant steering box brace first, I'm looking at placing that order today.

 

My buddy has a Powerwagon and has MH on both. No issues and looks/works great. Extra capacity is nice. He does some heavy towing and I think the diff got so hot the paint was peeling off the stock cover...

 

I need to do mine when I get back to the states. I am over 36k now and I havent done them. I changed the tranny and the transfer case, but opted to wait on the diffs and then I got unexpectly deployed for a year. Now my wife has drove from San Diego to Houston and it isnt getting done until I get home later this year. Hopefully it wont cause issues.

When I was in San Diego I looked at the oil and it was like 13 bucks a quart. Is it still about that? And it's what... 7 quarts? I know the rear gasket is reusable, what about the front?

Is there anything hidding behind the cover that you have to watch for when pulling it off so it doesnt fall out or anything that I should know about before I get in there?

 

I changed to the Amsoil Severe Gear in both diffs at 10K, also added the Mag Hytek covers to both diffs then as well. I changed them out again right around 35-40K. I figured since the Mopar fluid was good for about 15K the Amsoil would be good for at least double that of the Mopar.

I think that MH had a few interference issues with the earlier covers they made, but they DID resolve the issues in a slight design change. They also replaced those covers that interfered for the people who had them. After a certain serial number (which by now I am sure they are WAY past that SN) there should be NO fitment problems. When I bought my covers I actually called them to be sure I'd have no issues/problems and thats what they told me. My front cover has plenty of clearance.



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