Actual picture of the sludge that came out of my truck:

Illustration for article titled Gear Oil

I’ve been on a mission to change all the fluids on my truck, having never done it before, and having no idea of the age of some (any) of them besides the engine oil and coolant. As a refresher, this truck has, of course, a front and rear diff, transmission, transfer case, and two steering knuckles, all of which have fluids that could very well pre-date the Nixon administration. So I spent the last couple nights crawling around under the truck draining and replacing, and I have exactly zero pictures because I could not possibly handle my phone with the condition of my hands while doing this.

I will take a picture - or better yet, make a GIF, of the supposedly 140W gear oil that came out of the steering knuckle. It was quite literally the consistency and color of molasses in January; maybe even closer to a smooth peanut butter. I drained it into a 1-qt plastic yogurt container (it only filled it about 20%) and I swear I could leave it upside-down for 5-10 seconds without spilling any. Alarmingly, one side did not drain ANY fluid out. I did notice that side looked drier than the other, which was one reason for doing this in the first place. I’ll make a note to top that off again.


The transmission had a fair bit of shine to it from bits of metal shavings, though nothing big. Probably way overdue for a change on that one.

I’ve also learned the value of those 5-gallon pails with a long-handled pump on the top, for moving large volumes of even 90W gear oil. I borrowed one for the 140W gear oil from a friend, because his bucket was low and he wanted an excuse to buy a new full one. But I don’t have one for the 90W, and I’ve now been through a gallon using a tiny hand pump on a quart bottle. It’s been a real treat. I’ve got probably another gallon to go between the transmission (halfway done when I ran out) and the transfer case. At least the transfer case is super easy to reach! In hindsight, maybe I should have emptied the 140W, then put 2 gallons of 90W in that bucket so I could use the sweet pump.


Thankfully, this isn’t something I’ll do every year. It’s been good to spend time getting to know all the working parts of the truck, though, and bringing all the basic maintenance items up to date. Maybe next year I’ll start chasing some oil leaks. The oil pan gasket, for example, looks to be doing very little to contain oil. On the other hand, automatic perpetual oil undercoating!

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