Why Volvo Bevel Gears (Spline Collars) Fail

From 2 other forums who tend to look at things through science: not rose tinted specs. Tests completed by a BAE USA engineer. There are also some useful links etc pointing to pics etc of "the problem that doesn't exist." Here's the V70R.com thread, since I find posting pictures on Swedespeed to be an unnecessicary pain, you'll need to go to V70R.com to see them: So the final verdict is in. In essence the new collar gear / spline gear that FEO sent was identical to the old one. The part is made of manganese steel which is typically used in applications that require high ductility ("bendyness") and impact resistance. As before, this seems an odd materials choice for the application to start with. Transmission parts of this sort are usually rated in terms of hardness using the Rockwell scales. Specifically, most gears for this type of application are on the "C" scale, usually in the middle. This part didn't even rank on the C scale and both the old and new part ranked at 60 A. Here's it straight from teh horse's mouth "They are about 60 Rockwell A scale (HRA). This is pretty soft. The hardness of most hardened steel and other hard alloys start just above this hardness level. We usually use the Rockwell C scale (HRC) for heat treated steel (quenched and tempered). Typical hardness of average material of this type is in the 30 to 40 HRC range. (Equivalent to 65 to 70 HRA) The A scale ranges from 20 to 92 HRA." In English this means that they expected a part of this nature to be hardened steel, which is more normal for gear types and links in transmissions, but this didn't even manage to rank on the scale used to rate the hardness of tempered steel. I.e. it's soft metal. As far as hardening the part, it is just not possible. I asked why and was sent the picture below. This is a picture of the crystalline structure of the metal itself. The steel crystals (yes, steel is actually a crystal) are the dark sections and the alloy section is the lighter coloured material. The alloy used in this part is not hardenable but the steel is. However, this would not yield an improvement overall since there is such a high percentage of alloy materials in the part. It was explained to me like this "It's like putting marbles in play-doh, you can make the marbles as hard as you want, but if you can't change the play-doh it will still fall apart just the same." So if the part was more steel than "play-doh" then we could harden, but as it is we can't. On to the next part! This is the start of the V70R.com thread: Edit: Here are related threads: Poll: how many failures have 06-07 GTs had? Passing the hat for new collar gear This is a much wider problem than some people on this forum are willing to believe. You can take a horse to water.........

first two forum links don't work, is it a case of being blocked or are they just dicky links ?

Finally Fixed. I'm outta here 

Hi Guys, just to close things down, I had Squires (Midlands Volvo Specialists) replace the spline sleeve yesterday. Great job, done fast and saved me hundreds of pounds. A little heat was required, and the failure was at the Angle gear end. The sleeve looks not man enough to me, also there is only about 10-15mm of interlock. Volvo quoting clients for changing the Angle Gear is a FRAUD!!!!! The car feels great, no tyre squeal when pulling out of uphill T junctions. If your front's squeal at junctions get your AWD checked out. Volvo after sales support really are the pits. I'll never use Volvo main agents again and I'll never buy another Volvo. Not because of the car, but because of the people and their attitude. My father once read a Volvo head of marketing interview, where he reckond that it cost Volvo tens of thousands to gain new customers which is why they did their utmost not to lose clients. How things change. Thanks to those on the forum who saw me as a genuine bloke with a car problem that shouldn't be there and should've been fixed by Volvo with some percentage of financial concession. I'm off to tinker with my Triumph Daytona T595. Thanks