2nd Gen Non-Engine/Transmission Differential Fluid Changeout Frequency

[Waltz]

Did a search of the forums w/o success. Currently running Amsoil 75W-140W synthetic oil in rear differential with a Mag Hytec cover. Oil has 30K miles on it. As I haul a 13K fifth wheel 3-4K miles per year would like to receive feedback on how frequent one should change out the differential oil. Manual recommends 15K miles, however with synthetics would think that one could extend this interval significantly. Thanks in advance

 

[klenger]

I tow about the same as you and use the same fluid. I changed it when new, and again at 30K, and will continue to do it every 30K.

 

[24V-DSL]

Additional questiion....

I use Amsoil 75-90 Series 2000 in both diffs. I don't tow.



I'm coming up on a planned 30K change, but I pulled both dip-sticks yesterday, and the fluid looks brand new, as it has the other times I've checked it. No color deterioration... . nothin'.



Do I change it or not??

 

[24V-DSL]

TTT...

Anyone have input on my question?



TIA

 

[JJW_ND]

Some observations .....

I have had rear Diff fluid look like new and come back with TAN over the limit ... needs to be changed. This was with 30 - 40K on Amsoil 2000 75W90. I also have had fluid look horrible gray/back with 90K on a front diff and expected the worst only to have the sample come back with good for continued use.



If pulling very offten especially in the summer, I would stick with 30 - 50K changes. Especially the the first 100K miles on the diff. After that it seems things run cooler and cleaner and you could go the 50 - 75K. Oil analysis is the only way to know for sure. Running empty could go indefinately as long as water stays out.



The front diff can really be ignored as it just does not wear the oil out. As long is not water gets in it can go until the unjoints need replacing.



jjw

ND

 

[24V-DSL]

JJW-ND

thanks for the detailed explanation. Makes sense to me, especially the front diff. Hadn't thought of it that way.