Changing gear oil (or ATF) in a transmission or differential presents its own set of challenges. By screwing an inexpensive hand pump onto the top of your oil bottle, you can solve one of them. (Image/OnAllCylinders)

Ever changed the oil in a transmission, transfer case, or differential? Then you probably have a big oily spot on your garage floor as proof.

That’s because, simply by the nature of being underneath a vehicle, their respective fill plugs are often in hard-to-reach locations—tucked close to chassis components, inside a transmission tunnel, or up near the vehicle’s floor. So, while draining a transmission or differential usually isn’t that tough, filling it back up can be really difficult without pouring a significant amount of gear oil on the floor.

ProTip: Never, ever, ever drain a transmission, transfer case, or differential without first making sure you can loosen (and reach!) the fill plug. Trust us.

Here’s the oil fill plug on the back of an AMC 20 differential. Thanks to the muffler, it’s dang-near impossible to get a squeeze bottle in there. (Image/OnAllCylinders)

Not only is this really messy, it can mean you’re wasting some money—especially if you’ve got a CVT transmission that demands the expensive CVT fluid (which we’re pretty sure is made from unicorn milk).

But a lot of oil companies try to help. Instead of using the standard quart bottles, they often put gear oil in long, squeezable bottles with a slim pour spout. While this is helpful in some situations, it falls short in many others. Worse case, it tricks you into thinking you’ve got the room for the bottle, only to find out you’re squeezing brand-new oil onto your floor. Ugh.

Royal Purple is one of many companies that uses these handy squeezable bottles. But they don’t always work well when you’re trying to fill oil in a tight space. (Image/Summit Racing)

Enter The Manual Fluid Transfer Pump

That’s when an inexpensive manual fluid transfer pump makes a lot of sense. For just a few bucks, it’ll keep your garage floor clean and put your oil and ATF where you want it—in the transmission and differential.

Simply screw the pump onto the top of the oil jug or bottle, and voila, your bottle of oil is now pump-operated.

Yup, just like those big mustard tubs at the ballpark.

Here’s that same AMC 20 diff. With the pump screwed securely onto the gear oil bottle, you just feed the tube into the fill hole and pump the top of the bottle. (Image/OnAllCylinders)

Of course, depending on what you’re filling up, it may take a lot of pumps. But if you’re only doing jobs like this a few times a year, than you may not mind the hand strain. If you do handle a lot of gear or differential oil changes though, then you may want to opt for an electric fluid transfer pump. Though they’ll likely cost a bit more.

Even in spots where you can access the fill hole from above, you often still have to navigate tight spaces—where you’ll likely make a mess if using only the bottle. This happens to be the front differential fill port on an older AWD Subaru. The CVT fill port is in an even tighter spot. Fun. (Image/OnAllCylinders)

Again, these pumps are really cheap considering the hassle they eliminate, so it’s a no-brainer tool to keep in your workshop.

ProTip: When you’re done using it, make sure to wash out the pump thoroughly to ensure the plastic of the pump won’t be eaten by the chemicals in whatever you’re pumping. It’s also smart to keep it clean and wrapped in plastic between uses, so it won’t collect dirt, grit, and dead bugs that could then be pumped into the teeth of your gears.

Cleaned and drying on an old T-shirt, we see the distinct pump components. The two clear pickup tubes pictured attach to the pump body to ensure oil is sucked up from the bottom of the bottle, so you’re not throwing any excess oil away. (Image/OnAllCylinders)

Plenty of Other Uses for a Manual Fluid Pump Too

We’ve mostly focused this article on changing gear lube and ATF, but there are a ton of applications in which a pump like this can be darn handy, like filling a marine outboard motor, pumping out engine oil, and even around the house for ordinary cleaners, degreasers, and whatnot.

While the manual fluid pump is definitely an unsung hero tool that can take a lot of the mess and stress out of an oil change, the better news is that you’ll also probably be able to find a good one for under 30 bucks.

Our particular hand pump features a dual-size cap, so you can attach it to smaller, single quart bottles of oil or larger gallon jugs like this. (Image/OnAllCylinders)
Keywords
toolbox hero, Tools, unsung hero tool
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Author: Paul Sakalas

Paul is the editor of OnAllCylinders. When he's not writing, you'll probably find him fixing oil leaks in a Jeep CJ-5 or roof leaks in an old Corvette ragtop. Thanks to a penchant for vintage Honda motorcycles, he spends the rest of his time fiddling with carburetors and cleaning chain lube off his left pant leg.