AlexD Posted April 15, 2008 Report Share Posted April 15, 2008 Thanks to Mark (http://www.v70r.com/forums/index.php?showuser=2563) who sent me his failed collar gear (this is what connects the transmission to the AWD angle gear) I have been able to con my partner into looking into the problem (he does materials science stuff for BAE aka Brittish Aerospace). Here are the first pictures of the failed unit and a brief note about what appears to have happened. Next step is: what can be done to fix it?Overview:Inside the transmission is an open differential. One output goes to the front wheels, the other to the rear wheels. For packaging reasons, the output to the rear wheels does not come straight out of the transmission's rear on its own, instead it exits via a hollow splined shaft. The drive shaft for the right front wheel fits inside the spline to the rear wheels.As you can see in my very rough sketch, the power then must go from the hollow spline output of the transmission to the hollow spline input of the angle/bevel gear assembly. Once the power had been rotated 90 degrees, it exits on its way to the Haldex unit and then the rear wheels.The output shaft of the transmission and the input shaft of the angle/bevel ear assembly are connected via a "collar gear." Some AWD failures are the result of the bevel gear itself being damaged, this will not cover that issue as I don't have a bevel gear for anyone to look at. So, the first thing that Rob noticed was that the metal is very, very soft. The part is made of manganese steel which is typically used in applications that require high ductility ("bendyness") and impact resistance. Apparently 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 it was mid-range on the B scale (next softest scale). So the initial assumption when we ran it by BAE's tank transmission person was that either they just totally used the wrong metal, the supplier used the wrong metal, or this was for some reason specifically designed to fail first. Apparently in this type of setup transmissions may use parts that are deliberately designed to fail before other more expensive parts do. Angle gear anyone? Who knows.Rob is going to heat treat some of the material and then look at them under the electron microscope to see if it improved the structure of the metal at all. Apparently cryo processing may just trade one bad property of the metal (too soft) for another (too brittle) and could ultimately result in the same sort of failure sooner, or just make no difference. We'll see. If we want a part that won't fail first, this probably will mean that we have to have a part made of a totally different metal. The failed area is on the right Link to comment Share on other sites More sharing options...
Needsdecaf Posted April 16, 2008 Report Share Posted April 16, 2008 Great post, Alex. In speaking to one of the master Techs at Keystone Motors Berwyn, JRL's favorite Volvo repair dealer / shop regarding the angle gear failures, he noted something curious. Steve speaks to a lot of the engineers at Volvo Sweden, who noted that one of the biggest problems with the input "spline shaft" / "collar gear" is inadequate lubrication. He noted that on re-assembly of the transmission to the angle gear, this area is inadequately lubricated despite the instructions to do so. Link to comment Share on other sites More sharing options...
AlexD Posted April 16, 2008 Author Report Share Posted April 16, 2008 Great post, Alex. In speaking to one of the master Techs at Keystone Motors Berwyn, JRL's favorite Volvo repair dealer / shop regarding the angle gear failures, he noted something curious. Steve speaks to a lot of the engineers at Volvo Sweden, who noted that one of the biggest problems with the input "spline shaft" / "collar gear" is inadequate lubrication. He noted that on re-assembly of the transmission to the angle gear, this area is inadequately lubricated despite the instructions to do so.I'm not sure how much of a factor lubrication would play in this instance. According to the transmission engineer that we consulted, he said the failure was really due to the wrong metal being used. Link to comment Share on other sites More sharing options...
geoguy Posted April 16, 2008 Report Share Posted April 16, 2008 Awesome post!Sounds like this collar was either deliberately or inadvertently built as a sort of shear pin . . . - Mark Link to comment Share on other sites More sharing options...
defgh1 Posted April 16, 2008 Report Share Posted April 16, 2008 Nice work and thanks for the post. Doug H Link to comment Share on other sites More sharing options...
Pedestrian A Posted April 16, 2008 Report Share Posted April 16, 2008 Excellent post! The material is not designed to take this kind of punishment is probably the main reason. Is the S60/V70 2.5T AWD using the same parts? I wonder how reliable these parts perform in the 2.5T AWD cars. Maybe these parts just can't handle the extra torque and power from the R. Link to comment Share on other sites More sharing options...
flyfishing31568908306 Posted April 16, 2008 Report Share Posted April 16, 2008 great stuff alex.thank rob for us also.mike Link to comment Share on other sites More sharing options...
canucklehead Posted April 16, 2008 Report Share Posted April 16, 2008 Awesome post!Sounds like this collar was either deliberately or inadvertently built as a sort of shear pin . . . - MarkWhich would be OK if it were cheap and easy to replace. Link to comment Share on other sites More sharing options...
pilgrim1568908314 Posted April 16, 2008 Report Share Posted April 16, 2008 Great analysis Alex, lots of information here.It would be interesting to do PMI (Positive Materials Identification) and hardness tests on a collar that is in use but had not failed.Perhaps your buddy could test yours.I'm wondering if Volvo's QA/QC program has failed and left them with a bunch of substandard collars out in the wild?Thanx again. Link to comment Share on other sites More sharing options...
AlexD Posted April 16, 2008 Author Report Share Posted April 16, 2008 Great analysis Alex, lots of information here.It would be interesting to do PMI (Positive Materials Identification) and hardness tests on a collar that is in use but had not failed.Perhaps your buddy could test yours.I'm wondering if Volvo's QA/QC program has failed and left them with a bunch of substandard collars out in the wild?Thanx again.Well, I had a collar gear with the same failure rate. The big problem is the material used, it seems that this is not a case of a few bad gears, but simply that a weak material was specified for reasons we don't know. The 2.5T AWD and others just don't produce as much torque and the AWD programming is also different so it is not used as aggressively as the R's system. I think this accounts for why they have not failed in the same numbers. It would be interesting to see what the XC90's system uses, I know that the angle gear module itself is different itself (the 6 speed auto is basically the same) but I don't know if the collar gear is different. Anyone want to send me some new collar gears? Link to comment Share on other sites More sharing options...
pm2000541568908310 Posted April 16, 2008 Report Share Posted April 16, 2008 Thanks to Mark (http://www.v70r.com/forums/index.php?showuser=2563) who sent me his failed collar gear (this is what connects the transmission to the AWD angle gear) I have been able to con my partner into looking into the problem (he does materials science stuff for BAE aka Brittish Aerospace). Here are the first pictures of the failed unit and a brief note about what appears to have happened. Next step is: what can be done to fix it?Nice! What was the move that pushed it over the edge? -mk Link to comment Share on other sites More sharing options...
JAGMAN Posted April 17, 2008 Report Share Posted April 17, 2008 I wish that mine hadn't failed, but am quite happy that the failure was the collar gear and not the input/output shafts of the tranny/angle gear. Without more info, I'd be concerned that if you harden it too much you'll break the really expensive parts of the drivetrain if a failure occurred. Glad to see someone is paying attention to this.OBTW, I saw a post a few weeks ago (can't remember which website) that said Volvo had switched to a different/stronger metal. Link to comment Share on other sites More sharing options...
AlexD Posted April 17, 2008 Author Report Share Posted April 17, 2008 I wish that mine hadn't failed, but am quite happy that the failure was the collar gear and not the input/output shafts of the tranny/angle gear. Without more info, I'd be concerned that if you harden it too much you'll break the really expensive parts of the drivetrain if a failure occurred. Glad to see someone is paying attention to this.OBTW, I saw a post a few weeks ago (can't remember which website) that said Volvo had switched to a different/stronger metal.When were they implying a switch was made? Anyone know how much this part costs? Anyone want to buy one for the cause? Link to comment Share on other sites More sharing options...
JAGMAN Posted April 18, 2008 Report Share Posted April 18, 2008 When were they implying a switch was made? Anyone know how much this part costs? Anyone want to buy one for the cause? If I recall the new part was mentioned within the last month or two. As for price, the old one cost me ~$80. Link to comment Share on other sites More sharing options...
mark1568908316 Posted April 18, 2008 Report Share Posted April 18, 2008 Wow Alex, that was fast! Great write up.I'll quiz my shop to see what part number they got. As I recall they said it was a kit and came with new seals. -Mark Link to comment Share on other sites More sharing options...
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