 Gearbox noise, sounds like I'm in reverse... |
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| thomasotten |
 Jul 15 2008, 10:18 AM
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#1
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Senior Member  Group: Members Posts: 1,547 Joined: 16-November 03 From: San Antonio, Texas Member No.: 1,349  |
I recently installed a used gearbox into my car. Everything works fine about it, except that I when I am in first gear it makes that sound that gearboxes normally make when they are in reverse. I actually kind of like it, but I thought I would ask if this is a sign of something about to go seriously wrong. BTW, why do gearboxes sound different in reverse?
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| Demick |
Jul 15 2008, 11:18 AM
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#2
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Ernie made me do it! Group: Benefactors Posts: 2,312 Joined: 6-February 03 From: Pleasanton, CA Member No.: 257  |
Reverse noise is sometimes from straight cut gears. 914 has straight cut gears for reverse.
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| Dr Evil |
Jul 15 2008, 01:44 PM
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#3
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Send me your transmission! Group: Members Posts: 23,002 Joined: 21-November 03 From: Loveland, OH 45140 Member No.: 1,372 Region Association: MidAtlantic Region 
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Demick hit it on the head, rev is straight cut = noisy, 1st is helical cut = less noisy. I would be concerned about the noise. Why did you need to swap boxes in the first place?
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| thomasotten |
Jul 15 2008, 04:22 PM
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#4
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Senior Member Group: Members Posts: 1,547 Joined: 16-November 03 From: San Antonio, Texas Member No.: 1,349 |
QUOTE(Dr Evil @ Jul 15 2008, 11:44 AM)  Demick hit it on the head, rev is straight cut = noisy, 1st is helical cut = less noisy. I would be concerned about the noise. Why did you need to swap boxes in the first place? I was told that it was "perfect". It leaks a bit of oil, but other than the noise, it is OK. |
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| BMXerror |
Jul 15 2008, 04:26 PM
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#5
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Senior Member Group: Members Posts: 1,705 Joined: 8-April 06 From: Hesperia Ca Member No.: 5,842 |
Doc, correct me if I'm wrong, but my understanding is that strait cut gears are louder because there is nothing to control the thrust. I.E. Helical gears push the gear and shaft to it's endplay limit. Strait cuts don't so they float and cause a whine. If it sounds the same, I'd think you have a thrust issue on that gear. Is there some kind of thrust bearing or something on 1st gear, doc?
Mark D. P.S. My new engine has strait cut cam gears... Sounds awesome! |
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| Demick |
Jul 15 2008, 05:26 PM
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#6
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Ernie made me do it! Group: Benefactors Posts: 2,312 Joined: 6-February 03 From: Pleasanton, CA Member No.: 257 |
Thrust doesn't really have anything to do with it. It's simply how the gears mesh. Each tooth on a helical cut gear meshes gradually over a fairly large angle, so you don't hear each tooth mesh. Each tooth on a straight cut gear meshes across the width at the same time, so you can hear each tooth mesh.
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| Eric_Shea |
Jul 15 2008, 08:09 PM
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#7
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PMB Performance Group: Admin Posts: 19,278 Joined: 3-September 03 From: Salt Lake City, UT Member No.: 1,110 Region Association: Rocky Mountains  |
Are you sure you don't have a 915 knob on the shift lever? (IMG:style_emoticons/default/biggrin.gif)
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| Dr Evil |
Jul 15 2008, 08:19 PM
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#8
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Send me your transmission! Group: Members Posts: 23,002 Joined: 21-November 03 From: Loveland, OH 45140 Member No.: 1,372 Region Association: MidAtlantic Region
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QUOTE(thomasotten @ Jul 15 2008, 06:22 PM) QUOTE(Dr Evil @ Jul 15 2008, 11:44 AM) Demick hit it on the head, rev is straight cut = noisy, 1st is helical cut = less noisy. I would be concerned about the noise. Why did you need to swap boxes in the first place? I was told that it was "perfect". It leaks a bit of oil, but other than the noise, it is OK. Oh, well, if he says it is perfect, it must be (IMG:style_emoticons/default/rolleyes.gif) Seriously, there is no way it should be sounding like that in 1st. There are a few easily fixable, and easily incorrectly installable parts for 1st, but go too long and you will start to booger up more costlier parts. BMX, its how Demick said, yet again (IMG:style_emoticons/default/wink.gif) |
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| 749142 |
Jul 16 2008, 12:23 AM
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#9
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Member Group: Members Posts: 254 Joined: 8-January 08 From: Bakersfield, Ca Member No.: 8,545 |
QUOTE(thomasotten @ Jul 15 2008, 08:18 AM) I recently installed a used gearbox into my car. Everything works fine about it, except that I when I am in first gear it makes that sound that gearboxes normally make when they are in reverse. I actually kind of like it, but I thought I would ask if this is a sign of something about to go seriously wrong. BTW, why do gearboxes sound different in reverse? well if you want to get rid of it run a quart of duralube in it. i had a noise really bad in 5th put duralube in it and i havent been easy on the tranny and the noise still went away. my dad did the same thing with another tranny that had been in a 914 that was in a wreck and it was making a noise and it took care of the noise in that one too |
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| Dr Evil |
Jul 16 2008, 05:55 AM
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#10
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Send me your transmission! Group: Members Posts: 23,002 Joined: 21-November 03 From: Loveland, OH 45140 Member No.: 1,372 Region Association: MidAtlantic Region
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Ya, its amazing how lubricant can get rid of gear noise (IMG:style_emoticons/default/wink.gif)
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