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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / December 2007Noisy transmission bearings vs noisy diff: how to tell
Is there a way to tell apart noise from worn tranny bearings versus a worn differential in a FWD car that has a manual transmission and an open, non- hypoid diff? Would a noisy transmission bearing be noisy at any car speed in any gear while under load? Would a noisy differential be noisy only at a specific car speed under load no matter the gear you were in?  SignatureTegger > Is there a way to tell apart noise from worn tranny bearings versus a worn > differential in a FWD car that has a manual transmission and an open, non- [quoted text clipped - 8 lines] > -- > Tegge If it is transmission noise it will be noisy when the car is standing still, will likley change depending on what gear you are in. The sound emitted from worn bearings is in my experience is more of a rumble and worn gears tend to howl. golden oldie <hambruch@redshift.bc.ca> wrote in article <497a3aa4-ba68-4875-82e6-b8fc509f008a@s8g2000prg.googlegroups.com>... > > Is there a way to tell apart noise from worn tranny bearings versus a worn > > differential in a FWD car that has a manual transmission and an open, non- [quoted text clipped - 13 lines] > emitted from worn bearings is in my experience is more of a rumble and > worn gears tend to howl. Even in neutral with the clutch engaged, the output shaft is NOT spinning, and the sliding gears are NOT meshed with the countershaft gears.......SO, no noise when the car is standing still is NOT an indication that the transmission is okay. > golden oldie <hambruch@redshift.bc.ca> wrote in article >> If it is transmission noise it will be noisy when the car is standing >> still, will likley change depending on what gear you are in. The [quoted text clipped - 5 lines] > gears.......SO, no noise when the car is standing still is NOT an > indication that the transmission is okay. I'm not sure I understand these sentences. With the clutch engaged (pedal released) in neutral, the input shaft is spinning everythng inside the gearbox, no? My usual mechanic (now 50 miles away) tests for noisy bearings by parking the car near a wall so he can hear better, then repeatedly pressing and releasing the clutch in neutral. Last time he checked, which was two years ago, he said the bearings would rattle under that test when the pedal was released. I asked him when I would know it was time to replace the tranny, and he said when it "sounds like a freight train". I had two Toyota T50 trannies develop bad 5th gear bearings. They sounded just like this (whining/howling), but only when I was actually in 5th. The noise I've got now happens no matter the gear, only at 45-50mph, and only once the tranny warms up. The car is a '91 Integra with almost 300K miles on it. SignatureTegger Tegger <tegger@tegger.c0m> wrote in article <Xns99FB403C8516tegger@207.14.116.130>... > > golden oldie <hambruch@redshift.bc.ca> wrote in article > [quoted text clipped - 9 lines] > > I'm not sure I understand these sentences. With the clutch engaged (pedal > released) in neutral, the input shaft is spinning everythng inside the > gearbox, no? NO! If the output shaft were spinning, the car would be moving!!! The sliding gears are mounted on the output shaft. If they are not engaged, the output shaft is not turning - or else the car would be moving! > My usual mechanic (now 50 miles away) tests for noisy bearings by parking > the car near a wall so he can hear better, then repeatedly pressing and > releasing the clutch in neutral. > > Last time he checked, which was two years ago, he said the bearings would > rattle under that test when the pedal was released. You can check SOME gears and bearings in neutral - not all of them as you implied above. > Tegger <tegger@tegger.c0m> wrote in article >> [quoted text clipped - 8 lines] > engaged, the output shaft is not turning - or else the car would be > moving! I know the gears (except for Reverse) are actually in constant mesh, and that what locks them to the output shaft are the dog teeth on the synchro assemblies. Thinking more carefully, the INPUT shaft and all the GEARS would be spinning in neutral (clutch engaged), but the OUTPUT shaft would not, since none of the output shaft gears would be locked to the output shaft. That being the case, the output shaft bearings would not be spinning when the car is not moving, so there would be no way to check for noise from them with the method my mechanic used last time he did his quick check. All the other bearings could be checked by my mechanic's quickie method, however. >> My usual mechanic (now 50 miles away) tests for noisy bearings by >> parking [quoted text clipped - 11 lines] > > I see why, now. Thanks. SignatureTegger Tegger <tegger@tegger.c0m> wrote in article <Xns9A0443A9AF71Dtegger@207.14.116.130>... > > Tegger <tegger@tegger.c0m> wrote in article > >> [quoted text clipped - 23 lines] > check. All the other bearings could be checked by my mechanic's quickie > method, however. Except, of course, the reverse slider and idler gears..... > >> My usual mechanic (now 50 miles away) tests for noisy bearings by > >> parking [quoted text clipped - 13 lines] > > I see why, now. Thanks. > Tegger <tegger@tegger.c0m> wrote in article > <Xns9A0443A9AF71Dtegger@207.14.116.130>... [quoted text clipped - 28 lines] > > Except, of course, the reverse slider and idler gears..... Depends on the trans. Some trans have a synchro engagement of reverse so the gears are in motion along with the others. I would check that the oil is of the correct type and weight for the trans. >> Except, of course, the reverse slider and idler gears..... >> > Depends on the trans. Some trans have a synchro engagement of reverse > so the gears are in motion along with the others. > I would check that the oil is of the correct type and weight for the > trans. In this particular tranny reverse gear slides. And the oil in question is Honda genuine MTF and has been changed every year since new in 1991. SignatureTegger > Is there a way to tell apart noise from worn tranny bearings versus a worn > differential in a FWD car that has a manual transmission and an open, non- [quoted text clipped - 6 lines] > load > no matter the gear you were in? Tegger, the only time I have had a similar problem was when the differential bearings went out on an automatic transmission car of mine. It started howling at highway speed, and was somewhat less as the car decelerated. It, in this case, did not quiet as you got off the accelerator, it just changed with crankshaft rpm. I know this doesnt help much. I guess you could jack it up, put it in gear, and listen for the source of the noise. >> Is there a way to tell apart noise from worn tranny bearings versus a >> worn differential in a FWD car that has a manual transmission and an [quoted text clipped - 14 lines] > not quiet as you got > off the accelerator, it just changed with crankshaft rpm. This is iteresting. I wonder if mine will get like this with time. Right now it gets totally quiet when you're off the gas in gear. Diff bearings sound right to me. Final drive speed changes linearly with car speed. > I know this doesnt help much. I guess you could jack it up, put it in > gear, and listen > for the source of the noise. With the weather we've got right now, I'm not doing any servicing for a long while. No garage, you see. SignatureTegger > >> Is there a way to tell apart noise from worn tranny bearings versus a > >> worn differential in a FWD car that has a manual transmission and an [quoted text clipped - 32 lines] > > - Show quoted text - Don't discount the value of taking a piece of garden hose for a stethoscope and using it to find just where in the trans the noise is coming from (while the car is standing still, in case anyone is wondering). The noise can be auite localizable, says this veteran of several Civic manual transmissions whose bearings failed for no reason to the apparent surprise of all the mechanics. > Don't discount the value of taking a piece of garden hose for a > stethoscope and using it to find just where in the trans the noise is > coming from (while the car is standing still, in case anyone is > wondering). The noise can be auite localizable, says this veteran of > several Civic manual transmissions whose bearings failed for no reason > to the apparent surprise of all the mechanics. It's not possible for me to do any listening that would tell me anything. Let's just say my hearing is "approximate". I'm just going to let it go until it's too loud to tolerate, then replace the tranny. Thanks. SignatureTegger |
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