When it comes to lifting your pickup truck, you might be lost. There are so many areas to place your jack, but how are you supposed to know which spots are safe? More specifically, is it ever a good idea to lift your truck by the rear diff?
If you want to lift your truck, you should never do it from the rear diff. Mechanics might lift from this spot because their jacks are stronger, and they have expertise that helps them do so safely. If you try lifting from the rear diff, your jack can slip, and your truck can crash down on you.
In this quick guide, I’ll answer that question and many more. I’ll teach you some best practices when it comes to lifting your truck, and you’ll learn how to do it safely
What Is a Rear Diff?
The rear differential, or rear diff, of your truck, is a housing that holds a special set of gearing inside. It takes incoming power from the driveshaft and translates it into motion in both of your rear tires. This is harder than it sounds because the driveshaft is at a 90-degree from the axle of your wheels.
The differential will also allow your rear tires to spin at different speeds. This helps with control through turns, driving offroad, and maintaining control on slippery roads.
If you hop under your truck and look at the undercarriage, the rear diff is right in the middle of your rear axle. You’ll see the driveshaft go into the housing, and the axle shaft comes out, making a T-shape. The gears are inside of the enclosed housing because any amount of dust or debris in the gears can ruin the diff’s functionality.
Why Would You Lift a Truck?
In this context, I’m not talking about lifting a truck by making it taller while you’re driving around. I’m going to be discussing the process of jacking up your truck so you can do work under it.
There are a few reasons why you might lift your truck:
- Increase visibility. During the troubleshooting process, seeing the area in question can help a lot. In some cases, it’s the only way to see the extent of the damage under your truck. You’ll need to lift the truck high enough to comfortably crawl underneath and look up.
- To do work on the wheel assembly. To rotate your tires, do brake work, or put on new wheels, you’ll need the wheel assembly to be floating off the ground. The best way to do that is to jack up your truck so the rear wheels are floating, which allows you to work on two wheels at once.
- To repair/ replace parts of the undercarriage. If you’re draining your oil reservoir, working on the brake lines, or replacing your exhaust system, you’ll need to have enough room to crawl under the truck and get to work.
The Science Behind Lifting a Vehicle
The force behind jacking can be a little confusing if you don’t really think about it. Some people assume that jacking is akin to lifting your truck from a certain area.
In reality, you’re pushing an area of your truck. If the area is reinforced and a designated lifting spot, then the point will be rigid and sturdy. As you keep pushing, the area will push against the jack, and want to push the jack through the ground.
Since the jack is even more rigid and fixed, it wins the fight. As a result, the jack will elongate and lift the part further from the ground. Since the part is tied into the rest of the truck, that corner of the truck will start to lift off the ground.
I’ve been very intentional about my wording here for a few reasons, and those points will come up throughout the article.
One reason is that your jack and lifting point both need to be very sturdy. If your jack is too wimpy or the lifting point is too weak, then one of them will break and your truck won’t continue lifting.
Another reason is because of all the forces at play here. When you have a truck jacked up, the full weight of the truck is supported by the jack, ground, and lifting point independently.
Check Your Owner’s Manual for Lift Spots
If you want to know where to jack your truck from, you can refer to your owner’s manual. In most manuals, they’re very specific about where the lift spots are. After all, the auto manufacturer specifically built up those areas so they can support the force associated with jacking up your vehicle.
In general, the framework of your truck is a good place to start. From there, I would suggest using your owner’s manual to find other spots.
Mechanics Can Lift from Other Places
You might be asking about lifting from the rear diff because you recently saw a mechanic doing it. The truth is that mechanics have a lot more liberty when it comes to truck repairs.
They have bigger jacks, stronger tools, and way more experience than you or I do. I have a buddy who is a mechanic, and he can successfully do things to his truck that I can only dream of (and I’m not brave enough to attempt).
The simple answer is that you should never repeat something you see your mechanic do. They take shortcuts and rely on their expertise to get them through the process.
What Happens if You Lift from the Wrong Place?
Lifting your truck from the wrong location can lead to a range of different problems.
Breaking the Component
If the component isn’t strong enough to support the weight of the truck, then it will simply break. I’ve seen people try to jack their car from their front bumper, then the bumper simply ripped off.
The same can be true for some of the components along the underside of your car.
A jacking point has to be reinforced and strong enough to withstand the forces associated with jacking. If it isn’t, then something’s going to break. If you put your full weight on a piece of paper, the paper is going to break, and you won’t be supported — it’s the same physics at play with jacking your truck.
The Jack Slipping
A very common issue is a jack that slips because you’re grabbing the wrong spot. Either the wheels of the jack, the base, or the saddle that’s supporting the truck could slip or move.
When this happens, there’s a wide range of problems that might happen as a result.
If the saddle slips, then the part could fall out of the saddle and your truck will drop on the jack. The jack can puncture parts, break apart assemblies, or burst lines on the underside of your truck.
If the base or wheels of the jack slip, then the jack can move out of position or fall over. This will cause the entire truck to drop to the ground, crushing anything underneath it.
If you jack along the side skirt of your truck, then the saddle can crush the bodywork along the side of your truck. I’ve seen this happen too many times — people use the outside edge of their vehicle and start jacking. As they crank the jack and it moves up, it simply squishes the side of their car and wrinkles the bodywork.
This can quickly turn into rust and it’s relatively expensive to fix the problem.
Damage to the Undercarriage
If you choose a random flat area on the undercarriage of your truck to jack from, you can run into issues. Your fuel pump, oil reservoir, exhaust system, and fuel lines can be punctured and crushed as a result of jacking your truck.
Just because it’s a piece of flat metal doesn’t mean it was designed to handle the weight of your truck as you jack your vehicle.
Is Lifting a Truck by the Rear Diff a Good Idea?
The rear diff might be a weird shape, but it’s in the perfect position to jack up your rear tires. This could save you a lot of time and energy if you just need to jack from one place and suddenly get access to both tires.
This leads to a simple question: is lifting a truck by the rear diff a good idea? If you’re asking for personal use, then I have to say no.
Using an underpowered jack or trying to jack your truck without enough experience can lead to serious damage to your vehicle, your jack, and yourself. If your jack isn’t strong enough to support half of your truck alone, then it could fail and drop the truck on you while you’re underneath, doing your work.
Mechanics might jack from the rear diff because they’re experts, their jacks are very strong, and they know what they’re doing. It’s the same reason why a surgeon can cut you open, but you definitely shouldn’t try doing that on your own.
Some things are better left to the experts. Also, experts make everything look easier, so I wouldn’t suggest DIY’ing something you see your mechanic do.
Lifting your truck by the rear diff is never a good idea. Mechanics might do it, and they know how to do so safely, but you shouldn’t try it on your own.
If you want to learn more about your truck, explore the rest of my blog. I have a lot of content that can help you optimize your truck-owning experience. As always, check out my list of highly recommended truck products.