Low rumble under car: Torque Converter or other?
12-24-10, 08:08 AM
#1
Rookie
Thread Starter
Low rumble under car: Torque Converter or other?
Hi folks,
Since I bought the car a week and a half ago, there has been a low rumble under the car. I skimmed through the archives here and found the recommendation for a transmission oil change. I flushed it out (by the way, a good thorough flush to get red fluid running through when the old oil is in this poor condition requires 12-14qts, not just the 8.7 that the system holds) and indeed the old oil was like chocolate sauce. However, the transmission still shifted smooth as a baby's butt, both before and after the oil change. So it had no effect.
The rumble under the car seemed to me to be at the 40-50mph range under medium throttle and many other folks have reported the same.
However, I also noticed today that the very same rumble occurs when the car is in neutral, with the engine spinning at 2000-2200 RPMs.
Now I'm in new territory; never had torque converter or transmission problems on any other car. Would it still seem to be a failing TC, based on these observations?
TIA for your thoughts!
Since I bought the car a week and a half ago, there has been a low rumble under the car. I skimmed through the archives here and found the recommendation for a transmission oil change. I flushed it out (by the way, a good thorough flush to get red fluid running through when the old oil is in this poor condition requires 12-14qts, not just the 8.7 that the system holds) and indeed the old oil was like chocolate sauce. However, the transmission still shifted smooth as a baby's butt, both before and after the oil change. So it had no effect.
The rumble under the car seemed to me to be at the 40-50mph range under medium throttle and many other folks have reported the same.
However, I also noticed today that the very same rumble occurs when the car is in neutral, with the engine spinning at 2000-2200 RPMs.
Now I'm in new territory; never had torque converter or transmission problems on any other car. Would it still seem to be a failing TC, based on these observations?
TIA for your thoughts!
Last edited by andyman32; 12-24-10 at 08:31 AM.
12-24-10, 10:24 AM
#2
Lexus Champion
Did you change the transmission fluid filter?
Did you change the transmission fluid filter?
Did you change the transmission fluid filter?
Did you change the transmission fluid filter?
Did you change the transmission fluid filter?
12-24-10, 10:39 AM
#3
Rookie
Thread Starter
03-18-11, 09:38 AM
#4
Rookie
Thread Starter
Greetings folks - I changed out the transmission fluid & filter and it seemed to partially remediate the rumble but it seems to be creeping back for whatever reason. Now, here's another clue that may be relevant: the rumble is very consistently reproducible when I rev the engine up through around 2000-2200 RPM, even when the transmission is in neutral. Now, the torque converter would be spinning when I do this but it should have near-zero resistance from the gearbox side of the drive shaft, correct?
When in gear, the rumble did - and still does - occur when speeding up through slower speeds (i.e., 10-20mph) then again at around-town road speeds (say 45-50mph) I'm starting to think this might be related entirely to the engine speed and not road speed.
Visually, the motor mounts and transmission mount look virtually brand-new. There is absolutely no play that I can recreate between the motor/transmission and the frame. I know that bad mounts can transfer unwanted vibration through the frame but this really seems like the engine is vibrating pretty badly right around those particular RPMs.
Is there anyone else who has had this?
Any thoughts whether this is starting to sound more like a bad main bearing than a bad torque converter?
Thanks...
When in gear, the rumble did - and still does - occur when speeding up through slower speeds (i.e., 10-20mph) then again at around-town road speeds (say 45-50mph) I'm starting to think this might be related entirely to the engine speed and not road speed.
Visually, the motor mounts and transmission mount look virtually brand-new. There is absolutely no play that I can recreate between the motor/transmission and the frame. I know that bad mounts can transfer unwanted vibration through the frame but this really seems like the engine is vibrating pretty badly right around those particular RPMs.
Is there anyone else who has had this?
Any thoughts whether this is starting to sound more like a bad main bearing than a bad torque converter?
Thanks...
06-19-11, 01:06 PM
#5
Driver School Candidate
Join Date: Sep 2009
Location: VA
Posts: 34
Likes: 0
Received 0 Likes
on
0 Posts
Im having the same issue. I had it in my mind it was the driveshaft until i rev the car to 2000 rpms and noticed the vibration and rumble was still there in park or neutral. I have no idea what it could be at this point. I put used engine in my car because i purchased it with a blown HG and while replacing the engine took the time to change the trans fluid, strainer, mounts, timing belt, etc. Im lost at this point.
06-20-11, 05:33 AM
#6
If i remember correctly there was a TSB on the 1st Gen LS400 regarding a vibration around 2000 RPM's...I came across it while researching possible issues with a 90 LS400 i had purchased at the time..It seems they redesigned the tranny mount which i did purchase and after installation the vibration i was experiencing was gone...The original mount looked fine but i guess there was a flaw in it's original design..
06-20-11, 07:17 AM
#7
Driver School Candidate
Join Date: Sep 2009
Location: VA
Posts: 34
Likes: 0
Received 0 Likes
on
0 Posts
I was thinking it is very possible it is the tranny mount and plan to buy a new one to swap in. but the rumble/vibration starts at about 1900rpm and gets stronger up until about 4000 rpm when it goes away. it shakes the car badly as if a wheel is about to come of or like im speed down a rough road. If the mount doesn't fix the issue im thinking its the torque converter. my trans shifts smooth as butter but its still possible it could also cause this issue.
Trending Topics
06-20-11, 08:43 AM
#10
Driver School Candidate
Join Date: Sep 2009
Location: VA
Posts: 34
Likes: 0
Received 0 Likes
on
0 Posts
its rough cause it felt like a rear wheel or driveshaft until i saw it rumbled and would vibrate in park. that took everything from the tranny back out the running. motor mounts are new so its converter or tranny mount im thinking.
06-20-11, 06:27 PM
#11
Rookie
Thread Starter
Yeah, I'm still having the issue. Strangely, it doesn't seem to be as bad when I let the car sit for a week then drive it, than when I'm driving it every day. I couldn't even begin to postulate why that is, but it's reproducible. Once the car is well into the drive cycle after sitting, or the second drive immediately thereafter, it's right back to making the rumbling noise.
I told my independent shop that the suggestion was that it was a failing TC and the guy looked at me like I was nuts and said, I've NEVER heard of a bad torque converter making that kind of noise. Well, OK guy. But the TC also doesn't seem to exhibit any bad behaviors which somewhat discounts the probability that that's actually the source.
Other than that... tranny mount. It's a '99 and the mount looks literally like brand new, but what else could it be?
My only other thought was that perhaps it's a bad main bearing - esp the output shaft - in the engine. Or maybe the transmission's input shaft bearing? Something where that 2000rpm engine speed, even when in park/neutral, creates some kind of harmonic effect that resonates up into the frame of the car.
For now I've decided, begrudgingly, to live with it. Since there's no 'smoking gun' to identify the problem, I'd potentially have to dump a LOT of money into it and still not come up with the right solution. Transmission mounts and even TC isn't too big of a deal, but main bearings, yeah. It is annoying though, and definitely detracts from the experience of driving the car, which is too bad, since it's otherwise such a nice car...
I told my independent shop that the suggestion was that it was a failing TC and the guy looked at me like I was nuts and said, I've NEVER heard of a bad torque converter making that kind of noise. Well, OK guy. But the TC also doesn't seem to exhibit any bad behaviors which somewhat discounts the probability that that's actually the source.
Other than that... tranny mount. It's a '99 and the mount looks literally like brand new, but what else could it be?
My only other thought was that perhaps it's a bad main bearing - esp the output shaft - in the engine. Or maybe the transmission's input shaft bearing? Something where that 2000rpm engine speed, even when in park/neutral, creates some kind of harmonic effect that resonates up into the frame of the car.
For now I've decided, begrudgingly, to live with it. Since there's no 'smoking gun' to identify the problem, I'd potentially have to dump a LOT of money into it and still not come up with the right solution. Transmission mounts and even TC isn't too big of a deal, but main bearings, yeah. It is annoying though, and definitely detracts from the experience of driving the car, which is too bad, since it's otherwise such a nice car...
06-20-11, 08:52 PM
#12
Yeah, I'm still having the issue. Strangely, it doesn't seem to be as bad when I let the car sit for a week then drive it, than when I'm driving it every day. I couldn't even begin to postulate why that is, but it's reproducible. Once the car is well into the drive cycle after sitting, or the second drive immediately thereafter, it's right back to making the rumbling noise.
I told my independent shop that the suggestion was that it was a failing TC and the guy looked at me like I was nuts and said, I've NEVER heard of a bad torque converter making that kind of noise. Well, OK guy. But the TC also doesn't seem to exhibit any bad behaviors which somewhat discounts the probability that that's actually the source.
Other than that... tranny mount. It's a '99 and the mount looks literally like brand new, but what else could it be?
My only other thought was that perhaps it's a bad main bearing - esp the output shaft - in the engine. Or maybe the transmission's input shaft bearing? Something where that 2000rpm engine speed, even when in park/neutral, creates some kind of harmonic effect that resonates up into the frame of the car.
For now I've decided, begrudgingly, to live with it. Since there's no 'smoking gun' to identify the problem, I'd potentially have to dump a LOT of money into it and still not come up with the right solution. Transmission mounts and even TC isn't too big of a deal, but main bearings, yeah. It is annoying though, and definitely detracts from the experience of driving the car, which is too bad, since it's otherwise such a nice car...
I told my independent shop that the suggestion was that it was a failing TC and the guy looked at me like I was nuts and said, I've NEVER heard of a bad torque converter making that kind of noise. Well, OK guy. But the TC also doesn't seem to exhibit any bad behaviors which somewhat discounts the probability that that's actually the source.
Other than that... tranny mount. It's a '99 and the mount looks literally like brand new, but what else could it be?
My only other thought was that perhaps it's a bad main bearing - esp the output shaft - in the engine. Or maybe the transmission's input shaft bearing? Something where that 2000rpm engine speed, even when in park/neutral, creates some kind of harmonic effect that resonates up into the frame of the car.
For now I've decided, begrudgingly, to live with it. Since there's no 'smoking gun' to identify the problem, I'd potentially have to dump a LOT of money into it and still not come up with the right solution. Transmission mounts and even TC isn't too big of a deal, but main bearings, yeah. It is annoying though, and definitely detracts from the experience of driving the car, which is too bad, since it's otherwise such a nice car...
06-24-11, 05:32 PM
#14
Driver School Candidate
Join Date: Sep 2009
Location: VA
Posts: 34
Likes: 0
Received 0 Likes
on
0 Posts
ok, i think i have the worst and most aggressive rumble/vibration of anyone, had me thinking it was the TC, driveshaft or rear going bad. I installed a rear tranny mount yesterday and i put like 300 miles on the car the last 48 hours and no more rumble. my mount looked good til i took it out and really checked it over and it was bad. TRANNY MOUNT FIXED IT.
06-25-11, 02:32 PM
#15
Driver School Candidate
Join Date: Jun 2011
Location: Ga
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
my 96 sc makes a whumping noise(I know, What is a whumping noise), that increases with speed. This is when it is driven after sitting for several hours. if you drive it immediately after the first time you dont hear it any or a bad. Sounds kinda like a wheel bearing or some type of part that after being driven and warmed up doesnt sound as loud or goes away, by the way the car doesnt vibrate when this occurs.