Some Geniuses Are Swapping Cheap Volvo Parts Into Jeeps For More Grip Off Road

There are very few similarities between Volvo’s boxy wagons and America’s favorite off-roaders. However, the Scandinavians did know a thing or two about getting around in slippery conditions, given the snowy conditions in their home country. As it turns out, old Volvos can teach Jeeps a thing or two about putting power down off-road if you know what parts you’re looking for.

It all comes down to the Dana 30 axle. It was used up front in the XJ, ZJ, MJ, and TJ Jeeps—which means you could find them in Cherokees, Grand Cherokees, Comanches, and Wranglers once upon a time. The vast majority of these vehicles shipped with open differentials which came with one major drawback. If one of your front wheels started slipping, you’d get virtually no drive from the front end at all, because the open diff can’t send more torque to the wheel that still has traction.

The solution is to swap out the Dana 30’s stock diff with a limited-slip or locking differential. This woudl allow high amounts of torque to be sent to either wheel even if the other is sitting up in the air. The problem is that an LSD or locking diff center can be pretty expensive… unless you know of a secret junkyard source to find them on the cheap. That’s where Volvo comes in!

Swag In The Wagon

The Volvo 240 is a world-renowned piece of Swedish engineering, known for its reliability and unique styling. Most commonly found in sedan or wagon form, it later spawned the more modern Volvo 740 and the 940 in turn. These vehicles were built to survive in all climates, but particular attention was paid to ensuring they could handle the ice and snow of wintery European roads.

To that end, Volvo equipped these vehicles with a secret weapon. Certain models would receive a so-called automatic locking differential based on the Eaton G80 design. Well-known for its use in various GM applications, it’s referred to as a locking differential or a limited-slip differential depending on who you talk to. In reality, it’s a differential that locks up once one wheel has slipped relative to the other.

This video explains the method of action of the G80 differential.

The method of action is relatively straightforward, and is explained in the video above. There’s a small gear mechanism inside the differential which spins up to speed when one wheel turns faster than the other. As this mechanism turns, centrifugal force causes a small flyweight to spin out and trigger a catch that in turn locks the two output shafts of the differential together. It requires a difference in rotational speed between the wheels of around 100 rpm before it locks up.

Notably, the G80 is also set up so that the centrifugal force moves the catch itself out of reach of the flyweight at higher speeds. This stops the differential locking up beyond about 20 mph or so. The intention is to make sure the differential doesn’t suddenly lock up when one wheel hits a patch of ice on the highway or in similar situations. Under those conditions, a sudden hard locking of the differential could lead to a loss of control. A common modification in the Volvo world involves reducing the mass of the catch so it takes a higher speed to disable the locking action.

This setup was pretty perfect for Volvo’s application. It wanted a way to ensure its vehicles could find traction at low speed on snow and ice. A limited-slip differential that works at low speed was ideal. In the case that one wheel loses grip and starts spinning, the differential quickly locks up and allows the engine to still send high amounts of torque to the other wheel that has grip. Meanwhile, at higher speeds, where no locking action is needed, the G80 acts as a simple open differential.

The neat thing is that Volvo was using some Dana 30 compatible parts in its rear ends in a great deal of these models. That just so happens to match perfectly with the front axles used in the aforementioned Jeeps—the XJs, ZJs, MJs, TJs. That means if you’ve got an XJ Cherokee, for example, and you’re sick of your front end slipping around and doing nothing in the mud, you could get a cheap upgrade by stripping a Volvo in your local junkyard. Easy, right? Well…

The Challenges

You might be thinking this all sounds too perfect. After all, it’s an obscure mod to this day, and that’s for good reason. There are a few challenges

The biggest problem is actually finding the right parts. It’s not always easy to identify exactly which cars Volvo fitted with these G80 differentials. The Swedes threw these parts on a bunch of cars—mostly Volvo wagons with the tow package, as well as on some—but not all—of the Turbo models. If you spot a later Volvo 940 in the junkyard, it might have a G80 locker, too.

So how do you find one? The gang at Enlisted Budget Videos on YouTube have had great success with this swap, and they use a simple rule. They hunt for late 1980s and early 90s models of the Volvo 240 and 740, looking for Turbos and those with the tow package. The latter are easy to spot with their obvious towballs hanging off the rear. A good tell is whether the rear end has a plate that says an “ANTI-SPIN” differential is fitted, though this isn’t a surefire way to tell. Word in the forums is that some later Volvo 940 models also feature the G80 differential which can be used in the Jeep application.

Having researched this article, I’ll provide a bit of advice. You can spend hours trying to untangle which Volvos originally shipped with a G80 and which didn’t, and which housings are compatible and it goes on and on and on. It’s worth remembering to a degree that none of this stuff is well documented, with forums full of dead links and incorrect information. Adding to the problem, many of these cars have been chopped and changed many times over in the four decades since they were built. My advice is to simply hit the junkyard and get under the cars and figure it out. I’d hoped to provide a more definitive list of which models are properly equipped but it’s nearly impossible to do so beyond “Turbos and models with the tow package are your best bet.”

If you go with this swap, you’re going to have to pull the differential out of the Volvo, and then strip it down. What you really want is the G80 diff center itself. You’re then going to want to swap the ring gear to suit your Jeep’s existing axle ratio—because you can’t use the Volvo ring and pinion in the Jeep axle housing. It’s worth noting that manual-equipped vehicles typically have a diff carrier set up for 3.55 gearing or higher. Meanwhile, autos tend to have a carrier suitable for 3.73 gearing or lower. It’s worth taking that into account when you’re trying to pick the right carrier to suit the final drive ratio you’re aiming for in your Jeep.

You’ll also need to get the diff properly installed, with the correct backlash and preload and all that. You can do this yourself with the right tools, or farm it out to a pro shop if you’re not comfortable. However, in the latter case, you might find a professional diff shop might be reluctant to muck around with something you yanked from an old Swedish wagon.

When it comes time to put your Jeep back together, you might also find your drive shafts don’t quite fit. In the case of an XJ Cherokee, it’s necessary to cut 3/8″ of an inch off the driver’s side axle to make everything work. Other applications may differ but should be around that much or less.

Is it worth it? The answer is it depends. If your Jeep needs better traction in the slippery stuff, and you can snag the right Volvo diff on the cheap, and you can install it? Yes, this is a great mod. If you have limited time, limited wrenching experience, and no taste for navigating decade-old forum threads… I’d look elsewhere. Your local four-wheeler shop could probably sort you out an easier solution.

There are also a lot of people online with serious opinions about the G80 locker.  In various GM applications, the G80 was referred to as a Gov-Lock differential, but it soon gained the nickname “Gov-Bomb” for its propensity towards self-destruction. However, it’s worth noting that in those applications, the G80 is usually used in the rear end on heavy full-sized trucks, versus being used up front in a lightweight older Jeep. Plus, the G80 is still offered as an option by GM to this day—suggesting it’s not as bad as some might make it out to be.

In any case, there is proof that this swap can work in a Jeep without major issue. “We’ve used it in a racing application and so have friends of ours,” said Kevin of Enlisted Budget Videos. “Never had an issue using it in full time [4WD]… We’ve used it specifically in a rock environment before and it appeared to do quite well.”

A G80 differential can make your front end a lot more useful out on the trail.

The difficulty and risk does not invalidate this swap by any means. Just because something is a little tricky to pull off, it doesn’t mean it’s not valuable. This is a neat budget solution for having more off-road fun with your Jeep—it just takes some fiddling to pull it off. Ultimately, that’s what makes it so cool. There’s nothing quite like finding a serious performance upgrade languishing in a wet and rusty family hauler in a dirty old junkyard. There are gains to be had everywhere for those with wrenches and the will to believe!

Image credits: Lewin Day, Volvo, Enlisted Budget Videos via YouTube Screenshot, Scott “Purdy Man” Overton via YouTube screenshot