I was getting my oil changed the other day and the mechanic was trying to convince me it was time to change out the fluid in both the rear and front differentials. Since this was the express lube type place I declined his advice in favor of the expertise found on this forum. So, the question is how frequently should the fluid in the differentials be changed? What's involved - is this a DIY ? They wanted $60 for the rear or $100 for both.

 

ALL fuid changes are generally a DIY but if you are taking your truck to a mechanic for an oil change, it may be easier to have someone do it. Really up to you and your personal preference bud. The prices seem reasonable. The "book" says to change your dif fluid every 100k. I would never let my diff fluid run that long so i generally change em every 30k or so... depending on what im doing, how I am driving etc. Some Mercedes came out and say "never change dif fluid unless needed" meaning: unless something happens, the fluid will last a damn long time and will only get thicker with time (not always the case!!). Get a Mag-Hytech dif cover and you will have extra fluid capacity, a drain plug and dipstick!! An awesome quick upgrade!

 

I swear the book says 150k before any diff fluid changes, but hell, do it whenever, not like it won't help. Pretty sure you have to remove the rear cover only and let that sweet smell pour into a pan. Let them screw with it at the quickie lube.

 

Yup, just looked it up... your right. "under normal driving conditions = 150k" but they say if you tow, off-road or operate under heavy/work conditions you should every 100k.

I will stick with every 30k...

 

It's one of those things that people I think take for granted. I'll be changing mine soon enough too. Also, if you submerge in water for periods of time or even once they say you should too.

 

If you do regular towing, or launch boats on occasion, I personally would change the diff fluid every 50Kmi, however since the factory fill is synthetic, and you don't regularly tow etc, 100Kmi seems just fine........

 

I've towed my boat several times the last two summers. And when the lakes were really high around here this year I might have submerged the rear diff once or twice. Is there a step-by-step guide for this?

 

No worries bud! But i would def. change the fluid. It is pretty straight forward. Start taking off the diff bolts. The gasket will usually hold it in place and keep its seal even with out the bolts. Next, make sure you got some kinda of big pan to catch and hold all the lovely smelling fluid (probably should be step one!) Take some type of small screw driver and as you hold the top half of the diff cover SLOWLY pry the bottom away from the housing. Be careful, there is no drain plug or spout so it will just pour out. Pry slowly til it starts leaking. Hold it.... pry a tad it more once the flow slows down... remember this is gear oil so it pours about as quick as syrup! Once youi have got the diff off the housing let the fluid drip and drain for a bit. Next, take a razor and clean off the diff cover and the housing )where they meet) because there will be a ton of gasket residue crap suck to both. Once clean re-apply a liquid gasket, or they may have a regular gasket at a local parts store, and put the diff cover back on. Take out the filler plug and fill with fresh new diff fluid to about that level (should be able to stick finger in diff hole and feel fluid). Re-install diff plus and test drive. Hear nothing wrong? then your prob good to go (I am not too familiar with your exact model (assuming you have the 5.4 L engine with the 9.75" rear) so you may wana check (which gasket, etc).