1994 LS400 - Grinding/Whirring noise when braking to a stop.
10-05-12, 01:21 PM
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1994 LS400 - Grinding/Whirring noise when braking to a stop.
Hello everyone 
As it is my first post despite being a member since 2010, I would like to quickly say thank you in advance to all those who have helped others with their issues here. They have greatly helped me diagnose and fix a variety of things during the time I have owned one of the best vehicles I have ever owned.
I will also resist the temptation to say everything I am curious about in one post. haha.
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Today I am having an issue that I can not seem to search out any really good ideas for online or in the forums.
1994 LS400
When coming to a stop I am hearing a grinding/whirring noise coming from what I am guessing to be... the transmission/torque converter as I hear it coming from the area under the shifter / console.
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(I will be going to take some video / audio to post up to this soon)
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This noise is only prevalent when braking in the last 20 or so feet of braking unless you jam it REALLY hard i suppose (haven't tested it, but it did make some noise on the highway when someone almost cut me off)... . It is NOT as noticeable when braking in Neutral (it may also be the brakes are grinding a tad due to thin rotors and a pad swap without changing rotors, and that's why I am still hearing something and it's actually not there at all. but let's keep it simple) It's definitely very different sound and progressively worse being in drive, drive with o/d off, 2nd, and of course 1st being worst.
- If I keep the transmission in first, or any gear, and coast down in speed against the motor's compression, I do not hear any noise, even in first from higher rpms and letting off.
- if i apply the brakes at a standstill, and load the motor a bit, you hear a grrrrrrrrr coming from the same area not just a nice solid motor load sound ( again... t/c?), but it's not the exact same as the added grinding/whirring sound when braking.
Acceleration makes no noise. Transmission shifts smoothly, there's power to the wheels, but she feels a bit old and sluggish off the line, definitely does not spin the wheels from a standstill.
However she rips from 50km/h+ - even kicking down to 1st gear, or hold 1st up to 50, and then booting it, until she's really warmed up, and then she feels like she's fighting herself a bit or something and the power curve definitely falls off.
=========================================================================
-- what ideas do you guys have as to what this grinding/whirring during braking sound might be?
-does a dying t/c do this under braking?
-does a transmission (hence why hearing it the most when holding 1st gear with the automatic shifter do this under braking?
----------------------------------------------------------------
any ideas are greatly appreciated.
Thanks Everyone!
Dan
N. Vancouver, Canada
As it is my first post despite being a member since 2010, I would like to quickly say thank you in advance to all those who have helped others with their issues here. They have greatly helped me diagnose and fix a variety of things during the time I have owned one of the best vehicles I have ever owned.
I will also resist the temptation to say everything I am curious about in one post. haha.
--------------------------------------------------------------------------------------------------------------------------------
Today I am having an issue that I can not seem to search out any really good ideas for online or in the forums.
1994 LS400
When coming to a stop I am hearing a grinding/whirring noise coming from what I am guessing to be... the transmission/torque converter as I hear it coming from the area under the shifter / console.
---------------------------
(I will be going to take some video / audio to post up to this soon)
---------------------------
This noise is only prevalent when braking in the last 20 or so feet of braking unless you jam it REALLY hard i suppose (haven't tested it, but it did make some noise on the highway when someone almost cut me off)... . It is NOT as noticeable when braking in Neutral (it may also be the brakes are grinding a tad due to thin rotors and a pad swap without changing rotors, and that's why I am still hearing something and it's actually not there at all. but let's keep it simple) It's definitely very different sound and progressively worse being in drive, drive with o/d off, 2nd, and of course 1st being worst.
- If I keep the transmission in first, or any gear, and coast down in speed against the motor's compression, I do not hear any noise, even in first from higher rpms and letting off.
- if i apply the brakes at a standstill, and load the motor a bit, you hear a grrrrrrrrr coming from the same area not just a nice solid motor load sound ( again... t/c?), but it's not the exact same as the added grinding/whirring sound when braking.
Acceleration makes no noise. Transmission shifts smoothly, there's power to the wheels, but she feels a bit old and sluggish off the line, definitely does not spin the wheels from a standstill.
However she rips from 50km/h+ - even kicking down to 1st gear, or hold 1st up to 50, and then booting it, until she's really warmed up, and then she feels like she's fighting herself a bit or something and the power curve definitely falls off.
=========================================================================
-- what ideas do you guys have as to what this grinding/whirring during braking sound might be?
-does a dying t/c do this under braking?
-does a transmission (hence why hearing it the most when holding 1st gear with the automatic shifter do this under braking?
----------------------------------------------------------------
any ideas are greatly appreciated.
Thanks Everyone!
Dan
N. Vancouver, Canada
10-05-12, 10:23 PM
#2
Hey Dan, i'm From Van but just move to Vic.
anyways, i'm not an automatic transmission tech but you should isolate the brakes and resolve that issue first to make sure you're not getting some sort of weird harmonics through the chassis. these cars are very good at killing and dispersing NVH so it could be the brakes... not likely but you should sort that out anyways.
it's likely NOT the capacitors in the ECU before that gets posted.
a few easy things to check and rule out would be the hardy discs and centre support bearing for the drive shaft. a worn out hardy disc and support bearing can and will cause odd noise issues from the area under the shifter. while under there check the tranny and motor mounts. those are where i would start. pull the cover off the
if you have access to hoist, try running the car up in the air with the car in gear and dragging the brakes and see if you can pinpoint where the noise is coming from. you can do this on jack stands if you feel adventurous, trust your skills and the person int he car loading it up...... i am not suggesting you do it this way and in no way condoning it. if you do such a thing and the car falls on top of you, i in no way take responsibility for the result by suggesting it.
we are on an American website... don't need to get sued! haha
anyways, i'm not an automatic transmission tech but you should isolate the brakes and resolve that issue first to make sure you're not getting some sort of weird harmonics through the chassis. these cars are very good at killing and dispersing NVH so it could be the brakes... not likely but you should sort that out anyways.
it's likely NOT the capacitors in the ECU before that gets posted.
a few easy things to check and rule out would be the hardy discs and centre support bearing for the drive shaft. a worn out hardy disc and support bearing can and will cause odd noise issues from the area under the shifter. while under there check the tranny and motor mounts. those are where i would start. pull the cover off the
if you have access to hoist, try running the car up in the air with the car in gear and dragging the brakes and see if you can pinpoint where the noise is coming from. you can do this on jack stands if you feel adventurous, trust your skills and the person int he car loading it up...... i am not suggesting you do it this way and in no way condoning it. if you do such a thing and the car falls on top of you, i in no way take responsibility for the result by suggesting it.
we are on an American website... don't need to get sued!
haha
Last edited by Shmee; 10-05-12 at 11:34 PM.
10-05-12, 11:26 PM
#3
My 91 makes a weird sound at the end of a regular stop, But I noticed it went away right after washing the car, I pulled off the wheel and noticed a rust movement on the very top coil of the coil spring. I am guessing there is supposed to be some type of plastic shield between the coil and top of strut? or maybe some grease ? I have other more urgent things to get to so it is not a priority for me.right now. Try spraying water into the fenderwell especially over the top of the tire. See if that works.
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