You know the old ‘if it doesn’t fit, use a bigger hammer’? Don’t do that on a differential case.
My dad and I were replacing my front axles on my Matrix (145,000 miles, all by me). We’ve done CV joints a lot on previous Mazdas and Mitsubishis along with lots of other work, first time on my Matrix. No prob on driver side. Passenger side, stinker wouldn’t come out. My dad, who is a pretty experienced shade tree mechanic (retired plumber) decided to give the differential case a whack. Or a dozen. Or more. He even took a torch to it. As I cringed I grabbed a fire extinguisher to make sure it was handy. Finally he gave up. I found a garage that was open last Saturday that would install the shaft that I’d already bought. And they did. And they discovered that my dad had cracked the case. It wasn’t leaking and still isn’t as far as I know. Of course they didn’t tell me the differential was cracked until after they were done and I could have returned the shaft for a full refund and at least saved that money.
Over $3,000 to replace the tranny with a rebuild which would include the differential, 15 hours shop time. Considering I’ve been unemployed since last September, this is a difficult repair to bite. A friend of my dad’s, who has run a professional garage for 40 years, says it can be sealed with a liquid weld compound and that it should be fine. The fracture does not travel up to the bearing points if I recall correctly.
My dad feels really bad about this, not enough to buy me a new tranny, but real bad. My wife thinks it’s karmic whiparound for my brother and sister totaling different family cars.
My question is, what is the risk that I’m running of (a) total failure, and (b) what happens if the case totally fails. Will it toast the tranny? Does this liquid weld stuff work? My wife was speculating that if the differential failed, that the front wheels would immediately lock tight and I’d flip my car end over end. I think that since there’s a third power shaft going back to the rear differential to power the back wheels, that I’d probably do more of a corkscrew in the air. Maybe I should invest in some smoke grenades to see if I could produce a cool contrail.
I’m willing to park the car until we can come up with the $3K+, I’m not willing to drive it much longer as it currently is.
Repairing any car over time becomes a decision in weighing the cost vs the value of the car. You might consider this a worthwhile time to trade what is left in value of the car in for a new one. Otherwise, like any dealings with family around cars, it can become a contentious issue. Personally, I think pricing a used one would be the best and fixing it with liquid metal might be a distant last as a temporary fix. Remember that any fixes you continue doing yourself, is running the risk of doing something more to drive up the cost.
Absolutely agree, @dagosa, the cost of a rebuilt tranny and labor is right at the value of the car, KBB says $3300-$4100 (it needs a little body work as we live in snow/elk country). Since the car is long since paid off, I consider any repair spread over 12 months that’s under an estimated new car payment to be worthwhile, and the estimated cost of a replacing the tranny with a rebuild meets this criteria. The car’s engine is very sound: oil is changed regularly and aside from a scheduled timing chain and a problematic lower control arm replacement, has needed no service. It has new struts, new front rotors and pads, and now new front axles. I have a private agenda that I’d like to drive a single car over 200,000 or 250,000 miles, and I thought this could be the one. It’s been an extremely sound car and I’d like to get more life out of it if I can.
Trade-in is not an option until I get a job: we cannot afford a new payment as we had a tree fall through our roof last year that came within a vertical foot of killing my wife and we haven’t finished all the house repairs yet. And with a cracked differential, there’s an ethical disclosure issue on whether to reveal that issue or not for a trade-in, which makes an NPR donation the most likely outcome. I need to know how reliable the liquid weld would be and what would happen if I experienced a total failure.
It would help if you gave us a visual of the crack that is not leaking.
But think about it in these terms, if the tranny runs low on fluid due to the crack finally giving up and excreting the fluid, the only thing I see happening is that your tranny becomes warmer, then hot. As it is getting hot, you would notice some moaning from it as the gears enlarge due to heat. Then the gears start to eat each other until you start to lose speed and you just pull over to the side of the road.
I do not see the scenario of your car flipping over due to a locked axle, coming from an overheated transmission.
So I vote for a bead of liquid weld like JB weld that is rated for the correct temperature and see how it goes? If you are worried that you would happen to have failure in front of a semi that is not paying attention and don’t think you can pull off the road in time, then don’t drive the car.
If the crack is in an area that is not under stress, it likely will not get any worse. If it’s not leaking, leave it alone and drive on. Periodically look at it to see if the crack is getting worse or is stable and if there is any fluid seeping out. If not, do nothing. The nightmare scenarios are not going to happen.
If it is subjected to mechanical stress, then putting some glue over it won’t help. The only way to positively stop cracks from growing is to drill a small hole at each end of the crack. This removes the stress riser and prevents it from spreading. If this kind of condition exists and it were my car, I would do the stop drill holes at each end of the crack and heliarc the holes and crack, without ever taking anything apart.
@TwinTurbo
Thanks, I’d forgotten about drilling stop holes. My wife is an astronomer, and they’ve had to drill stop holes on mirrors to prevent their destruction.
If I recall correctly, the crack is on the bottom and back of the case and should not be a stress area. It is at a mechanic right now who is going to apply the liquid weld tomorrow, I’ll suggest it to my dad to call him about it.
@gdawgs
I didn’t think there was a serious issue of the car actually flipping, it was extended silliness. My wife was thinking about the physics of a bike flipping. Doesn’t actually apply to a car, but that’s what she thought.
fyi to the OP’er @Cloudster: I’m a shade tree mechanic, maybe not even that, but I do service the CV joints on my Corolla as part of the car’s routine maintenance. While it is usually no problem to free them from the wheel side, it’s not uncommon that they are difficult to free from the xmission side. They get stuck and won’t budge no matter how much wiggling, pushing, and pulling I try. Sometimes I’ll just leave them stuck, and only service the wheel side, as that is the side that gets the most wear. But when this happens to me, and I need to service the xmission side too, I usually get the best results resorting to a slide hammer to free it up.
Done properly, the J-B Weld should work fine. Inert Gas Welding would work better…At the bare minimum, you need to take the torch and sledge hammers away from Dad…