2002 volvo v70xc - 3 rear angle gears blown out in 6 months

My 2002 awd v70xc wagon has blown out three angle gears since October of 2012. Every time I have been driving 70 mph on a highway for about one hour. A huge cloud of white smoke blows out of the tailpipe and hood and all I smell is burnt oil. Every repair has been my rear angle gear that essentially went off like a grenade. Every time I’ve paid for a new gear and the last time I also paid for a new coupling. I am now terrified to drive 70 mph and I’m afraid it’s going to happen again. Please help! Wat could be making this happen? Both my indie volvo mechanic and the volvo dealership have fixed it but neither can tell me WHY this is happening. I’ve read it could be mismatched tires - is that possible 3x in 6 months?

Mismatched tires on an AWD vehicle can cause undo stress on the drive components. The miss matched tires rotate at different speeds and cause the stress on the drive shafts and couplings. Tires of the same size, but different wear can cause it. Taking a tape measure around the circumference of the tire would prove or disprove this theory.

There would need to be a lot more info provided about this repair as there could be a ton of questions starting with just how mismatched are the tires as to sizes, why would a car owner continue to pay every few months for the same repair, and why would a shop even continue to do it?

If the tires are the cause of this problem then wouldn’t it be much easier and cheaper to replace the tires or least replace a few to even them; assuming the sizes are considerably off.

"Both my indie volvo mechanic and the volvo dealership have fixed it but neither can tell me WHY this is happening. - "

If mismatched or different tires wasn’t picked up by the dealer, I doubt that’s the problem.But, it depends upon what you mean by mismatched. Different sizes or significant tread design, yes…a little wear difference, no. I feel it’s not being installed right or it’s a design flaw.

Think of it. If the sizes were considerably off and it wasn’t picked up by neither a dealer or a mechanic who normal works on it and really was the cause, then you either have the two most incompetent people imaginable working on it. or you are deliberately and significantly mismatching the tires your self in a way they can’t see. It does not happen three times in a year or two with wear differences and no one mechanic who works on awd can tell.

I just read about the mismatched tires on a forum - no one has mentioned that when repairing it. ok4450 - I gave my indie mechanic the benefit of the doubt twice with the gear. Because the first one he put in there was used and it broke, he assumed it was a bad “used buy” so he put in another one. Now with the third one blown out he wanted nothing to do with me. I’m serious. He only gives warranties on his work, not his parts, so when I called him from Houston broke down on the side of the rode with smoke pouring out the tail, he said “sorry, I don’t know what to tell you. I’m stumped”.

So it’s now at Volvo of Houston (since that’s where it broke down, I live in Austin). Mechanic said they replaced rear angle gear then drove it on the highway and it started “whining”. They took it apart again and found a broken bearing? Now I’m waiting on that to be repaired. He said it could have been the culprit for the multiple gear blowouts but he’s not sure.

dagosa - I agree with you. But I don’t do anything to my tires, Discount Tire does all of that. I just emailed the mechanic at the volvo dealership about the tire theory and he said, “If my tech didn’t say anything about it then it’s a non-issue. That is something that we look for”. So there we go.

There has to be damage to the rear differential housing in order to have so many failures. At this point, I would not try to replace yet another pinion gear, but replace the entire differential, housing and gears with a salvaged unit.The pinion gear and ring gear have to mesh just right to work together with out destroying each other. In your case, with multiple failures, something is terribly wrong with something major. since it is not obvious to the mechanics, only a very expensive investigation will determine the cause. Replacing the entire unit is the most economical and probably the most reliable fix. I would not hesitate to put in a salvaged unit that passes a visual inspection, since these parts tend to outlast most cars. I have 3 cars with over 250,000 miles on them with original differentials that have only had fluid changes.

Picked up my car on Friday, April 26th. new angle gear was installed and the total was $1500.00. I got 25 miles down the road and the hood engulfed in smoke. Again. This makes time #4. I had it towed back to the dealership and no surprise there, the rear angle gear was blown out. The service foreman contacted Volvo Headquarters and told them they did not know how to repair the car. Volvo HQ just got back to us today (5/2/13) and said that it was my tires. Although they are identical in size, I have one brand on the front and one brand on the back. So, now I just spent $200 on (2) new tires and the dealership is going to put them on AFTER they put in the new angle gear they have to replace. I begged them to please drive it for an hour or longer, on the highway, at 70mph. If it turns out that two new tires were the problem all along I’m at a loss for words. How could something like that get by 2 specialized mechanics FOUR TIMES?

The only way tires could cause blown pinion gears is of they created an extreme load on the drivetrain. Bigfoot tires and some of these huge tires on jacked up trucks will do that, but I’m guessing that your V70 has normal size tires.

I’m going to guess a mismatch between the pinion gear and the ring gear. Perhaps if they were changed as a set the problem would disappear. Actually, I’m surprised they haven’t been.

Talk about a horror show; this is it.

Again, and keeping in mind that I’m not a Volvo expert, maybe a few general comments could lead somewhere.

Running a different brand of tire should not kill the angle gear. This would only be true if the outer diameter of the front and rear tires were vastly different. Even a slight discrepancy should not cause this so I tend to lean, right or wrong, towards someone missing something on the ratios due to the quick and catastrophic failures.

You’ve stated that the angle unit was replaced with a used one at some point but that does not mean the correct unit was installed. A little browsing showed that the 2002 gear ratio is different as compared to say a 1999 model. The gear ratios also show to be different between the automatic and manual transmission models and that is something that is not rare with any make of car.

One would hope that in all of this they would be verifiying the actual ratios they’re working with as to year, whether automatic or manual trans equipped, and so on.