Hey guys, I'm having a problem that I really hope some of you can help me with. I just recently finished getting my KA-T car together, its a fairly serious car: fully built, 20 pounds of boost, AEM EMS standalone, methanol injection etc etc. About a month ago I dynoed 430 hp/410 torque to the rear wheels. Needless to say the car is extremely fun to drive, except lately I have been getting this nasty sound from the manual transmission.
The sound is sortof like a very loud whine/almost rattle, it sounds like a bad bearing or something like that. It is ONLY present with throttle, and most prominent in 3rd gear above 35mph. The sound is present in 1st and 2nd as well, but not as loud. I think it is more speed related than gear related. Also like I said the sound is only there when I have throttle on. It is loudest with just a little bit of throttle-- once I get into it some more the sound gets quieter (but it is still there). Gliding in gear with no throttle there is no sound.
It sounds like while I'm driving that the noise is coming from the front (bellhousing) area of the transmission, maybe even the clutch/back of engine area. My perception of where its coming from could be off though because I cant replicate the sound without driving the car under load.
Just today I swapped out the transmission oil with some Lucas heavy duty 80-90wt stuff. The "old" oil (just put in a month ago) did not look bad at all, and there were hardly any metal shavings at all on the magnetic drain plug. The sound has not changed one bit after changing the oil.
Also note that the car has not been driven very hard since I put the turbo engine in. I have been in boost plenty, but I have not abused the transmission or clutch: always rolling the throttle slowly. I have not done any real "launches" yet, nor tried any burnouts or anything else like that.
I'm hoping you guys can help me track this issue down. I can think of a few possabilities: maybe input bearing on the transmission, some meshing problem with the input shaft splines or possibly gearing in the transmission (although new Lucas oil should have helped that). Maybe a bad pilot bushing? The noise is extremely loud with very little throttle... Maybe someone here can help me out with a diagnostic procedure? What can I do to narrow down the possabilities? Anything I can do without actually pulling the transmission just yet? Ever heard of these symptoms before?
Anything you guys can do would really help. Thanks!!
Weird transmission issues: please help!
I dont have any messengers other the yahoo and havent used it in awhile..lol I know I am behind the times. Internet stuff doesn't do to well with me for some reason. and this computer all though on DSL hates to download things without some friggen error popping up.
The only thing I could think it could be in the trans would be a gear chipped or something along those lines. At least by the description of the sound as it only makes it when its loaded much like a bad rear diff would do.
The only thing I could think it could be in the trans would be a gear chipped or something along those lines. At least by the description of the sound as it only makes it when its loaded much like a bad rear diff would do.
hahah its alright man, probably better to keep this on the boards anyways in case someone else has the same problem in the future.
Hmmm... well, I have reason to suspect the diff also...
Is it possible the sound could be originating in the rear, and somehow rattling the driveline in some manner as to make it sound like the noise is coming from up front? Any way I can confirm or deny this rear end theory *without* removing the rear end and swapping it with something else?
Hmmm... well, I have reason to suspect the diff also...
Is it possible the sound could be originating in the rear, and somehow rattling the driveline in some manner as to make it sound like the noise is coming from up front? Any way I can confirm or deny this rear end theory *without* removing the rear end and swapping it with something else?
yea I know this will be hard as it is with any car buff, but you need to let someone else drive your car. You sit in the back seat and listen for the noise this will give you a different perspective and you can lean over the rear seat and see if the noise is infact from the diff or the trans. This will help you be sure as to were its coming from.
Yea much like your pinion gear in the diff when it becomes pitted or worn in an unusual way it emitts and audable whine when lightly pushed against the ring gear while under a light load. well if your input gear where similarly pitted like that you would hear that same whine. problem is though typically any gear noise in the trans will go away when in 4th or only be heard in fourth as 4th gear is 1 to 1 it doesn not use the counter shaft for output. So typically if you can find a specific gear that wont or will cause a noise you can isolate what gear or bearing is causing the noise without even tearing the trans apart.
I did some testing with it today, and there is no doubt that the noise is coming from the transmission/bellhousing area. I even climbed into the trunk to make sure.
The noise is present pretty much in any gear, just MUCH quieter in 1st and 2nd (I think speed related)... Once I shift into 3rd around 30-35 or so the noise starts to get really loud.
Does this seem to suggest it is not an internal gear bearing? What about input shaft splines maybe, pilot bushing or possibly a rubbing throwout bearing? Anything else I can check before I pull this stupid transmission off?
The noise is present pretty much in any gear, just MUCH quieter in 1st and 2nd (I think speed related)... Once I shift into 3rd around 30-35 or so the noise starts to get really loud.
Does this seem to suggest it is not an internal gear bearing? What about input shaft splines maybe, pilot bushing or possibly a rubbing throwout bearing? Anything else I can check before I pull this stupid transmission off?
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s13sr20chris
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Re: (fiznat)
if its gear specific like that...im really leaning towards inner trans goodies.you have fsm? those trannys are so easy to go through. when did it start?
Like I said it makes the noise in ALL gears, including 4th and 5th. It is loudest with just a little bit of throttle (in any gear), however it is much louder once I get into 3rd, 4th, and 5th. It makes noise in 1st and 2nd but it doesnt sound nearly as loud, nor does it rattle as much. You can tell its there though. I need to make an audio recording of this. Will do tomorrow.
I wanna say a bearing as there is not one gear in the trans that stays loaded in every gear. But typically when its a bearing you here the noise in nuetral when the clutch pedal is released and you rev the engine. I am leaning toward the center plate bearing on the main shaft as the source of the noise as it is the only one that would generate a noise under a load in every gear and not do it in neutral when reving the engine and clutch out.
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s13sr20chris
- Posts: 4148
- Joined: Tue Jun 10, 2003 9:32 am
- Car: '89 Nissan S13 w/redtop running 13psi and not leaking fuel anymore
- Contact:
Re: (NISTECH)
dang!
you catch that fiz?
that was pure buttah!
you catch that fiz?
that was pure buttah!
Just a quick update for anyone who ever has the same problem:
**Scott/NISTECH was right! Rear end noise all the way!!**
I ended up pulling the unit out just to make sure before I pulled the transmission off, and suprise suprise-- the magnetic drain plug had stalagmites (or is it stalagtites??) like crazy. I ended replacing the rear end with a nice KAAZ unit and the noise is completely gone! You were right Scott, thanks!
**Scott/NISTECH was right! Rear end noise all the way!!**
I ended up pulling the unit out just to make sure before I pulled the transmission off, and suprise suprise-- the magnetic drain plug had stalagmites (or is it stalagtites??) like crazy. I ended replacing the rear end with a nice KAAZ unit and the noise is completely gone! You were right Scott, thanks!