148am Posted February 14, 2017 Share Posted February 14, 2017 I've seen it mentioned around here that you can test a front diff with a torque wrench on the axle nut with a front wheel in the air, but can't for the life of me find it again. Anyone know details / specs to look for, or if it's actually a valid test? My 05 OBXT with 5MT has some squeal/whirring noises that are vehicle speed related, and I found the front LH wheel barely spinning when accelerating the car through the gears with all 4 wheels off the ground. Link to comment Share on other sites More sharing options...
whitetiger Posted February 14, 2017 Share Posted February 14, 2017 the front diff is an open diff. if all 4 wheels are off the ground, and there is some resistance on the front left wheel, the diff will only spin the right side. that may indicate a bad bearing somewhere. can you spin the front left wheel easily by hand with the car in the air? Link to comment Share on other sites More sharing options...
148am Posted February 14, 2017 Author Share Posted February 14, 2017 If by easily you mean the only resistance felt is the weight of the wheel & tire with no brake drag, then no, it does not spin easily. I can spin it with some effort and front RH spins opposite direction as I'd expect. I do know the brake is dragging to some degree, that's also on my (lengthy) to do list. Thanks for the quick reply. EDIT: I should add that while accelerating through the gears with the car in the air, the front LH wheel lurches forward as the clutch was engaged smoothly after an upshift. Link to comment Share on other sites More sharing options...
whitetiger Posted February 14, 2017 Share Posted February 14, 2017 you should be able to tell if there is unwarranted resistance on it. Link to comment Share on other sites More sharing options...
148am Posted February 14, 2017 Author Share Posted February 14, 2017 You said "bad bearing", meaning a bearing on the front diff specifically, or did that include any bearing downstream from the front diff? I'll do some more looking when I can get it the car in the air again. I had my helper/driver for just a few minutes over the weekend. Link to comment Share on other sites More sharing options...
whitetiger Posted February 14, 2017 Share Posted February 14, 2017 it would be either the diff, or the wheel bearing or brakes. something dragging on the left wheel drive line related components only. Link to comment Share on other sites More sharing options...
148am Posted February 14, 2017 Author Share Posted February 14, 2017 Thanks again, much appreciated. Link to comment Share on other sites More sharing options...
148am Posted February 14, 2017 Author Share Posted February 14, 2017 @whitetiger, if you don't mind: the noise that made me get under there in the first place is a squealing which starts around 25mph and is loudest at around 40mph (any gear or neutral), and is coming from around the prop shaft carrier bearing. Car is at 133K mi, PO had the center diff and bearings replaced at 114K, prop shaft replaced with a used unit for howling noise at 115K, then prop shaft again at 118K with a new clutch. The heat shield under the prop shaft is gone (was a Wisconsin car originally) - would it be reasonable to think that the carrier bearing's grease is getting baked without the heat shield in place? Is there another explanation for that bearing to fail? Am I possibly hearing the prop shaft transmit sound from a failing bearing(s) inside the transmission? Link to comment Share on other sites More sharing options...
whitetiger Posted February 14, 2017 Share Posted February 14, 2017 so now you are talking about the rear driveshaft support bearing? Link to comment Share on other sites More sharing options...
148am Posted February 14, 2017 Author Share Posted February 14, 2017 Correct. Sorry if I wasn't clear. Link to comment Share on other sites More sharing options...
whitetiger Posted February 14, 2017 Share Posted February 14, 2017 so if the sound is coming from that bearing, you need a new drive shaft. there should not be that much of a heat issue that far down the exhaust stream. Link to comment Share on other sites More sharing options...
148am Posted February 14, 2017 Author Share Posted February 14, 2017 It didn't seem likely that there'd be that much direct heat on the carrier bearing there, just seems odd that this would be the third driveshaft replacement. What all could contribute to that bearing failing? Soft drivetrain mounts (mine are definitely soft OE) causing excessive load on the center bearing? Link to comment Share on other sites More sharing options...
whitetiger Posted February 14, 2017 Share Posted February 14, 2017 no way to know for sure, other than the part needs replacement. Link to comment Share on other sites More sharing options...
148am Posted February 14, 2017 Author Share Posted February 14, 2017 Fair enough, and thanks for your thoughts. Just trying to avoid needing another one in another 15K. Link to comment Share on other sites More sharing options...
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