I am new to this forum, having recently acquired an ’01 LC with 145k miles. It is in excellent unmodified condition. I’m hoping there is someone who solved this problem (or a Toyota NVH engineer!) out there to help me. I have a slight harmonic vibration felt through my heels on the floorboard (and slightly audibly) between 1500-2000 RPM when in OD (42-56 mph) and under slight load. No vibes felt in steering wheel. It is most noticeable right after trans drops into OD gear when accelerating normally. At 42-56 mph, if you take it out of OD, the vibration stops, leading me to believe it is not tires (almost new), wheel bearings, axles, diffs or drive shafts. The harmonic “pulses” about 100x per minute, if that helps. I’ve replaced the muffler, reinstalling the weight on the back of it, and rest of exhaust is good. My right side frame rail weight is in place. Engine revs freely with no vibration up and down its rev range in Park and Neutral. Transmission shifts and performs normally. I have to think combo of engine speed and OD gear is causing something in the truck to vibrate, but what? Appreciate any advice!
Slight harmonic vibration (1 Viewer)
- Thread starter Arekusan40
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
- Thread starter
- #2
Scanned a lot of forums about harmonics, and it seems they are a ****h to locate, so looks like I will start shot gunning for solutions. Does anyone think my analysis that it is not drivetrain-related may be incorrect? Could there be an imbalance in the drivetrain somewhere (e.g., drive shafts) that appears as a noticible harmonic vibration at only certain engine RPMs? Guess I'll start by trying the spare on each corner, rechecking bearings, removing each drive shaft, etc. before going to bigger things. Anyone think this is from worn motor mounts? Appreciate any help!
duggy
SILVER Star
Have you checked the plastic engine cover? Take it off and see if the noise comes back.
I have had a similar vibration for about 3 months. I am pretty sure mine stems from a broken sway bar mount. At least, I'm hopeful that is the cause. Symptoms began shortly after snapping the bolt while attempting to install new bushings.
Disregard I just re read the op post.
Look directly under the front passenger side, do you have one of these (see pic) bolted to the frame or are you missing it?
I had a question about it today (I wanted to remove it) went to the FAQ section and one of the possible reasons for its existence is to cancel exactly what you are having issues with. There is no clear answer for what at it is but some have suggested that it's there to cancel vibrations at certain speed. If you are missing it this could be the solution. Seems like its a piece we all want gone bc once you lift the lc you can see it just sitting there, like an anchor.
Look directly under the front passenger side, do you have one of these (see pic) bolted to the frame or are you missing it?
I had a question about it today (I wanted to remove it) went to the FAQ section and one of the possible reasons for its existence is to cancel exactly what you are having issues with. There is no clear answer for what at it is but some have suggested that it's there to cancel vibrations at certain speed. If you are missing it this could be the solution. Seems like its a piece we all want gone bc once you lift the lc you can see it just sitting there, like an anchor.
- Thread starter
- #6
Thanks for the suggestions. I do have the frame weight in place (also the muffler weight). I tried running without the engine cover and no difference. I checked for play in U-joints and ft wheel bearings and couldn't feel any. This weekend I rotated tires ft to rear... figuring if it's a wheel balance issue the harmonic might "feel" different. It didn't. Next step is to get them all rebalanced to be 100% sure it's not the tires. After that, i'll remove each drive shaft one at a time to try to see it it's front or rear drive train related. The fact it's more prominent when under load has me suspecting drive shafts or front axles. I'm thinking now the vibe doesn't actually stop when i take it out of OD... it just gets drowned out by the higher engine revs. I'll post what i learn next! All other advice appreciated!
ElHefe
SILVER Star
What grade fuel are you using?
- Thread starter
- #8
I use min 91 octane, as recommended. I also cleaned out the throttle body, changed the air filter, and checked to make sure the plugs were tight. Do you think the harmonic might be from the engine not running properly?
I bet it's your spare tire. I had this problem, lowered the spare put some towels between the spare and the 100 series, cranked the spare up as tight as I could. No more vibration.
Try hitting the six zerks on your drive shafts with some grease. I get weird vibrations too at around 1850 rpm. Fresh grease reduces it by 90% or so. I spent a lot of time chasing the same problem you describe and freshly greased drive shafts makes a world of difference.
apalt
apalt
Any updates? I have the same problem.
What have you tried to correct your problem?
Just reread this thread and realized maybe I have a similar issue possibly.
Just got the truck and it has a vibration type feel from 1500rpm to about 2000 and then its smooth as silk.
Its pretty much a cream puff, no rust underneath, recent service everything is great and all its just bothersome.
I have not tried to grease the zerks yet since I got it (have not had the time yet) I'll see if it improves after that and then maybe move on to that spare tire trick and post back
Running 93 octane btw
I can't wait to order my scangauge this weekend and the heater hose T's since PO had no clue when they were done last though they look "ok" on visual but that doesn't mean anything
Just got the truck and it has a vibration type feel from 1500rpm to about 2000 and then its smooth as silk.
Its pretty much a cream puff, no rust underneath, recent service everything is great and all its just bothersome.
I have not tried to grease the zerks yet since I got it (have not had the time yet) I'll see if it improves after that and then maybe move on to that spare tire trick and post back
Running 93 octane btw
I can't wait to order my scangauge this weekend and the heater hose T's since PO had no clue when they were done last though they look "ok" on visual but that doesn't mean anything
- Thread starter
- #15
Hi, I am the original poster. I still have the pulsing harmonic between 1500-2000 rpm after it drops into OD. I have rotated and re-balanced the wheels, took the engine cover off, placed towels between the spare and the body, tightened the spare against the rear cross member, tried driving without the spare, drove with 400 lb rocksalt in the back, ran two cans Seafoam, cleaned throttle body and mass flow sensor. My frame and muffler weights are in place and I use 91 octane gas. I greased the driveshafts and the joints feel good. When weather is warmer I will try disconnecting driveshafts one at a time but doubt it's that because driveshafts spin the same in OD or not. The fact the harmonic goes away with OD off leads me to believe something induced by the engine specifically at that load (OD gear) and that rpm range. Maybe it's a normal engine harmonic amplified to the frame by hardened engine mounts... I guess I could change the mounts and see. For now, I've been living with it... when driving 60-70mph it's not apparent. Also have a new problem... blew my front diff today driving up a moderate grade snow covered hill. Ugh. Have a separate thread looking for advice on that one!
Sorry boss let me get this one : you feel vibration then you driving or when you idling in the driveway around 2000 RPM?
- Thread starter
- #17
Kreiser, it is when driving. It's felt through my heels on the floorboard (and slightly audibly) between 1500-2000 RPM when in OD (42-56 mph) and under slight load. It is most noticeable right after trans drops into OD gear when accelerating normally. I can't replicate the vibration running the motor at 1500-2000 RPM in neutral (there is no load so it's different).
I have twice the miles on my truck which makes me think it is an age issue more than miles. The only difference is mind starts around 40 mph. It is more noticeable on smooth blacktop roads. I have had a transmission shop look at the it and he thinks it is the motor mounts. Also could be the front diff bushings. Both are on my todo list to change. Good luck.
Last edited:
I narrowed down my vibration to being that of the transfer case at 1600-1800 rpm. Could this be what you are feeling/hearing? Place your hand on the transfer case shifter and see if the vibrations increase when hitting your range of rpms.
I have the same problem with my '99. I feel vibration in the gas pedal and coming through the floor mats. My Toyota tech never heard of it before. I figured it's going to be relegated as a "ghost in the machine" and non-fixable. Eager to see where this thread leads! Thanks for all the updates and posts everyone. Will pay more attention to my RPM and whether turning O/D off makes it go away like Arekusan40's situation.
