January 23

1990 Mercedes 300E; Driveshaft Coupler Replacement



Mark: Hi, it's Mark from Top Local, we’re here with Bernie Pawlik, Pawlik Automotive in Vancouver, 18 time winners of Best Auto Repair in Vancouver, BC, as voted by their customers. How you doing, Bernie?

Bernie: Doing very well, Mark.

Mark: We're going to talk about an ancient 1990 Mercedes 300E with a driveshaft coupler replacement. We had a discussion about this. Why are we talking about a 27-year old vehicle?

Bernie: We're talking about it, because the driveshaft coupler actually is a part that's still used on modern vehicles. Even though this car is old, it's not a technology that's ... the technology that's still in use, and it's something that requires replacement. Recently we did one on the Cadillac STS a month a two or ago with a vibration issue. It's something that it's used on a variety of cars, rear-wheel drive only, or all-wheel drive, depending on the vehicle. But yeah, it's technology is still used nowadays.

Mark: What does a driveshaft coupler do?

Bernie: It connects the driveshaft, so this will be from the transmission to the rear differential. It connects the driveshafts, but it's used on vehicles that have independent rear suspension in place of a U-joint. A universal joint allows a lot of movement of the driveshaft. For instance on a truck, a Ford truck where you've got the differential, it's moving up and down when you hit bumps, you need a flexible coupler that's going to be able to take a lot of movement, maybe of several inches of movement. On this vehicle, this driveshaft goes across. It's pretty well straight from the transmission to the differential, but it needs a bit of a flexible coupler, because it's not exactly a straight shaft. It needs a bit of a flexible coupler at each end.

Mark: Yeah, so you've explained why we use this connection. Is this a time-consuming repair?

Bernie: It can be. It depends from car to car. This one, fortunately, on this particular Mercedes, it was the front coupler that was worn out. It was probably the easier of the two to get to. There's usually one at the front and one at the back, but it depends, again, on the vehicle. Sometimes you have to remove the exhaust, because the driveshaft's buried way up in a tunnel, and there's exhaust shielding and things in the way. Back in the old days, even earlier than this Mercedes, a lot of them were very accessible and easy to get at. As I said, they're used in a wide variety of mostly European vehicles but a lot of other vehicles would use them too, like I mentioned the Cadillac. I'll just get into a video.

Let's have a look at this video here. Just a second here. This is the actual worn out coupler. You can see some movement here. That part is actually broken. There should be no movement of that sort at all. Just to look again, look at this piece here. I'm going to move back a little bit from the video. Right here you can see the coupler pretty well. There's a rubber piece. There's six bolts, three on the driveshaft, and this end is attached to the transmission, to a flange on the transmission. There's basically a metal sleeve in here, and it's basically broken off the rubber coupler. That's what's wrong with this thing. But they do tend to crack. There's other things that can happen to them, but this one isn't actually broken. If it got any worse, of course, this driveshaft could start flinging around, and there would be a lot of banging.

Mark: How's the time frame for lasting with these couplers?

Bernie: I would guess this one may actually be original, which is 47 years old at this point, but the Cadillac we worked on was about a 10-year-old Caddy. It really varies. I've seen Mercedes that are 10, 12, 13 years old where they're worn out, so this one seems to have lasted quite a long time. It may have been replaced previously too. It's hard to say for sure. But I don't know, 10 to 20 years is an average life span for these pieces.

Mark: How would someone know or suspect that their driveshaft coupler was worn or wearing out?

Bernie: Excellent question. On this particular Mercedes, the owner had no idea, because nothing much was really happening, but I would suspect that when you shift from, say, reverse to drive, there would probably be a more pronounced clunk or thud noticed in the vehicle. The Cadillac we serviced, there was a severe vibration. When you go to accelerate slightly, the car would shake. That's another thing that happens. Visual inspection's an important thing. We talk about having your car serviced and visually inspecting them to look at them. And seeing if they're breaking is an important thing to fix it before it get to the point like this Mercedes. If it got really bad, you'd just hear a lot of horrible clunking and vibrations as you accelerate, or decelerate, or shift from gear to gear. Those are the kind of things you want to look for.

Mark: That would be similar with a U-joint, wouldn't it?

Bernie: It would be. Actually, it is. U-joints create similar things, clunks, vibrations, shakes. U-joints will actually squeak sometimes. They have like little needle bearings, and they're packed with grease, and they'll dry out. Sometimes a U-joint will actually make that squeaking sound when you accelerate, which you can hear sometimes. One of these couplers won't do that, of course, because it's a piece of rubber, but similar issues.

Mark: I think we answered this, but is Mercedes the only brand of vehicle that uses these?

Bernie: No. We did answer that. Yeah, there's a variety of vehicles, as I said. Cadillac comes to mind, Mercedes. A lot of other European cars use them. Not so much Japanese, but certainly American. You see them on American and European cars. There's probably some Japanese, but it slipped my mind for the moment. Japanese seem to like U-joints on their driveshafts.

Mark: Would this be something if you're having clunking or difficulty with your shifting, is that a reason to get this checked?

Bernie: Absolutely. Yeah, especially as I mentioned, if you're shifting from say out of park into drive or from drive to reverse, and you hear a loud thump or thunk that's unusual, that's definitely something to be looked at for sure. That's a definite cause.

Mark: There you go. If you're looking for service for your vehicle and it's got a bit of a clunk when you're shifting out of park, or you've got some vibration while you accelerate, might be your driveshaft coupler and you should see Pawlik Automotive in Vancouver. You can call them at 604-327-7112. Check out their website, pawlikautomotive.com, or our YouTube channel, Pawlik Automotive. Thanks, Bernie.

Bernie: Thanks, Mark.

About the author 

Bernie Pawlik

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