Posted by: bkivey | 16 December 2012

Grease Monky Pt. 2

In my previous post I detailed a recent car repair experience, motivated by a bad drive shaft. I also explain my repair rating scale. As promised, here are my observations on replacing the drive shafts.

Drive Shaft

Category 4

Replacing the drive shaft on a rear-wheel drive vehicle isn’t difficult; on a front–wheel drive vehicle, it ranks just below engine or transmission removal. Fortunately, there are many videos on this procedure, and most of them point out the same problem areas. I did find some things that weren’t addressed in the videos.

Spindle Nut

The spindle nut is the first problem, because it’s torqued to a high setting at the factory, and by the time you need to remove it, it’s likely been on the car for years. This nut is what holds the wheel to the drive shaft, and to the car. The nut has become accustomed to it’s position in life, and is unwilling to move. After removing the wheel cover, loosening the spindle nut is the first step in this repair. Most home mechanics don’t have an air driven impact wrench, so the procedure is to put a socket on a breaker bar, add a length of pipe for leverage, and stand on the end.

Every video I watched commented on how difficult this nut is to remove. One guy said it took him a couple of hours. I’m a well-proportioned 210 lbs., and I couldn’t get the nut to budge. After twenty minutes of this, and slowly rounding off the nut faces, I decided that this wasn’t worth my time or effort. I drove the car to a local mechanic, and asked him to take off the nut with his impact driver, then torque it back to factory spec. My thinking was that after years in place, the nut was mechanically welded to the drive shaft, and breaking it loose and re-torquing it would make it easier for me to remove it. The mechanic charged me $20 to do this, but when I got back to the driveway, I was able to loosen both nuts with little trouble.

Engine Crossmember

On my particular car, accessing the left side drive shaft requires removing the structural member supporting the engine. The procedure is to support the engine with a jack, and remove the support. This isn’t hard, and is described in my car’s repair manual, but not mentioned in the videos. You do need to use a wooden block between the jack and the engine, as many engine blocks are made of aluminum, and very easy to damage.

Removing the Drive Shaft from the Spindle

The spindle is the key player in the front suspension. The brake rotor, strut (shock absorber and spring), tie rod (steering), and ball joint all bolt to this part. The drive shaft runs through it to the hub attached to the wheel. In all of the videos I watched, popping the drive shaft out of the spindle was fairly easy. A few blows with hammer on the end of the shaft, and it’s out. Hitting the end of the drive shaft isn’t good for the part, but you’re replacing it anyway.

I waled away with the hammer, and the drive shaft didn’t budge. It was obvious that I’d need a gear puller to force the shaft out of the wheel hub. My puller was one I’d used to remove gears from shafts, and wasn’t up to the task. A trip to the auto parts store and $40 later, I had a more robust puller. This did the job of forcing the shaft out of the hub. I’m not weak,  but it took a lot of effort to generate enough torque to do the deed. I was concerned that the hub would warp or the puller would break before the shaft came out. This was the biggest deviation from the videos. The drive shaft didn’t just ‘pop’ out.

Removing the Drive Shaft from the Transmission

This part actually went better than advertised. Several videos mentioned the difficulty of removing the drive shaft from the transmission. The procedure is to take a pry bar or long, stout screwdriver and carefully prying the shaft out. (Fun fact: years ago I bought a 12″ flat head screwdriver, and have used it to drive screws exactly once). On my car the left side shaft is hard to get to, but both shafts came out on the first try. If you haven’t drained the transmission, you’ll want a pan underneath to catch the transmission fluid.

The rest

As the repair manual says, installation is the reverse of removal. Be careful of the new drive shafts. They are strong in compression, but have zero strength in tension. It’s easy to pull a CV joint apart, and if you do, you’ll be buying another drive shaft.

I mentioned that I’d decided to replace both shafts, even though the left side was the one needing replacement. On inspection, I found that the outer CV joint boot on the right shaft had split wide open, throwing grease out, and was in imminent danger of failing. So replacing both was a good idea.

Make damn sure you torque the spindle nut to spec, because it’s the only thing between you and your wheel coming off.

If you attempt this repair, take your time, watch the videos, and don’t cut corners.

 

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