Cars, Computers, & Random Thoughts
When your half shaft falls out
When your half shaft falls out

When your half shaft falls out

We had a rather stressful ordeal this week with our Mazda and didn’t have any time to work on the Laser. The only re-occurring issue we’ve had with the Mazda is the drivers front half shaft. It’s been replaced on 5 different occasions.
The first was when I noticed a vibration in the steering wheel and we couldn’t figure out quite what it was. Some investigating revealed the half shaft boot had torn and the axle grease was leaking out causing an imbalance in the shaft. The second was only a few months after that, when that same thing happened again. Next, we got a bad part that didn’t fit quite right so we had to change it out again. Then, a month or so after that replacement, the axle lock bolt backed out and sprung itself free as we were making a low speed left turn.


My dad drove out and we swapped cars, he was able to get the shaft back into the knuckle and drive it home where I fixed it two days later. That was close to home, about 15 minutes, so it was annoying but not a huge deal.
Not this time. This time we were in Sun Prairie, a good 45 minutes from home on a Monday night. The bolt backed out again and just to make things extra interesting, the half shaft decided to take the tire along with it. Luckily this was once again during a low speed turn into a parking space so we did luck out that way. The half shaft really wanted out though, it completely freed itself from the steering knuckle and also popped out of the articulating cup on the other side. At least the transmission shaft stayed in place, or I’d have had to buy 9 quarts of fluid to refill it with.


Luckily my dad was home, but the car trailer was another 10 minutes out of the way so Ali and I pushed the car into the spot and then headed in to do the shopping we’d come for while we waited. We also grabbed some dinner, might as well keep your energy up!

I had filled the spare tire with air when we got the car, and it’s a good thing I did, trying to winch a car onto a trailer with a flat is not fun. I was able to change the flat tire out relatively easily so we were ready to rock when dad showed up. We got the car winched on a bit and had to re-adjust the winch to get more length, meaning we had to make sure the car stayed in place. This is where I learned my emergency brake apparently doesn’t do much. Guess I’ll need to adjust that again.

After stopping the car and pushing it back into starting position I then repeated my mistake, putting the car in park doesn’t work with only one axle tied to a tire and an open differential. Now you know.
We once again got the car winched up and had Ali stand on the brakes while we reset the winch and pulled it up the rest of the way. We got a few odd looks but were soon on our way.


I jumped on Amazon upon returning home and ordered another half shaft and a new tire. It was the quickest way to get both parts at a descent price, most places were charging $70-80 and then a core charge of $20-30 on top of that. Amazon was at $60 with 1 day shipping.
Wednesday was the day of arrival, and after arriving home from work I made a mad dash to Hunt’s repair as they were the closest and only shop open until 6. I got there right around 5:55 and luckily they agreed to mount and balance the tire. It was also interesting to see what a new tire looks like next to the set I paid a whopping $200 for. Turns out I didn’t do too bad.


Way easier than doing it at home.
Way easier than doing it at home.

Then it was back home to do a quick half shaft swap. But first, I inspected the damage and made sure everything else around the half shaft had avoided conflict. I also did some science!


Now, since I had two old half shafts lying around I decided to test the whole “25-30 ft-lbs and a quarter turn” thing since I’ve had trouble with that. I put an old shaft through the knuckle and started torquing at 30ft-lbs and working up 10 at a time. I got to 110 ft-lbs before I couldn’t keep the damn thing from sliding in one hand while torquing with the other. So I’m not an expert, but I’m thinking maybe the torque rating Mazda gives is a little low.


The other issue is that the hole that the lock bolt threads into goes straight through into the boot. My guess is this was done to create an easy way to fill the boot with grease. It also means that when you put loctite on the threads it may get mixed with grease and be useless. The last bolt that backed out had red loctite on it, but it never hardened because of the grease in the threads.

I’m way too good at this by now so it was a pretty short ordeal. I even managed to do the whole thing without removing anything other than the outer tie rod from the knuckle, so I could move the knuckle as I pleased. Seriously, way too good at this. I had the transmission side removed and swapped fast enough that I hardly lost any transmission fluid. Not enough to move the dipstick level.


This time I torqued the axle lock bolt to 80 ft-lbs. I wouldn’t recommend it as I honestly don’t know if it will help or hurt anything. It could be that anything over 30 ft-lbs isn’t any use anyway. Ideally you will have loctite keeping it in place, but that obviously didn’t work the last two times I tried it. After running it Thursday and Friday I double checked and everything is still lined up. Good thing too as we had a 200 mile trip to make this weekend!


On a happier note, the Mazda has rolled over 150k miles! We got it with 113k on the clock a year and 4 months ago so we’ve been packing them on. I’ll be keeping an eye on the bolt to make sure it stays in place, hopefully the loctite takes this time. I want to be done with half shafts for a while.

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