133,000 miles should I change the oil in the front and rear diffs? as far as I know it's never been done since it was new.

 

I looked in my owner manual pdf and kept seeing reference to footnote but never found it.
Look in yours.

I think it's a good idea. Had mine done when I bought it.

 

what would you put back in, just standard gear lube or ???

 

Mine has a G80 rear which calls for AC Delco 75w90 synthetic, so I just use it in the front as well. Pretty sure the front only calls for regular 80w90 though

 

I say change out both.

 

dano.. just use what the owner manual says to. You CAN go synthetic if you want but it's a slightly different paradigm from engine and trans. Esp a road truck.

And here's the thing. sooner or later gonna have to do bearings. Dont reuse fluid, so why go the expensive route.

 

I was wondering about synthetic, if it would be a good idea or not. but I see what you mean that sooner or later I will have to tear in to and be throwing it away. I did about 14 months ago had to have a seal replaced on the front diff drivers side. I don't thing it ever run dry, but I bet it didn't do it any good. I am going to look in to changing the oil in them possibly in June I don't have any problems or noises at the moment and getting ready to leave on a trip I don't want to tamper with things to much and create any problems.

I just trying to think of all the things I need to look in to soon since I am trying to get caught up on my maintenance schedule. a lot of things got skipped at the 100,000 mile mark. I changed out the fluid on the transfer case about 12 months ago when we did the transmission, so those are both done. front drive shaft was replace just over a year ago. but the rear shaft and the diff's have had nothing done to them since they were new or prior to (8 years ago) 73,000 mile when we got it.

 

Well, sounds like you're on top of it. What you can do is pull the rear driveshaft and check the universals for smooth movement.

 

pull the drive shaft (rear) and replace transfer case rear seal and checked u-joint last Saturday while I had it on the lift they felt smooth added a little grease to the rear u-joint it was not dry but was not full either. tonight while I was replacing the last upper ball joint and had it on the lift I checked both diffs rear one was full and some what clean oil in it. transfer case was full but... the front was a different story, it was not dry but I couldn't touch the oil with my little finger.

I added 4 oz. of Lucas oil treatment and 8 or 9 oz. of 80 W90 oil to it to fill it up. Any idea how much the front should hold?