freewayspeed drivetrain harmonic

kolcan900 · #1 (**permalink**) 09-20-2003, 10:20 AM

Hi, I,m new to this site, I,m excited that mabey somebody has answers out there. I recently puchased a 2000 4wd access cab limited tundra with 45k on it . I put a level lift kit on front and a rancho add a leaf in the rear. put some 18 inch wheels with 285 60 18 nitto tera grapplers on it. At exactly 80 miles per hour I get a distinct drivetrain harmonic. The cab noise is quite minimal up to 79 mph but easily doubles at 80 and this continues to 85 mph then dissapears above that. I took it to the local toyota dealer who said that it was normal and acceptable saying that mabey it was the rear diff with normal "gear lap"where the diff had a noticable harmonic at a specific speed. I suppose it would not be that big of deal but out here in the west where the freeway speed limit is 75 mph it seems that 80 is my ideal cruise speed. Any ideas?

RitcheyRch · #2 (**permalink**) 09-20-2003, 10:26 AM

The driveshaft might be out of balance

DevinSixtySeven · #3 (**permalink**) 09-20-2003, 11:20 AM

...on the other hand, maybe it's not gear lap

...but it sounds like a complicated explanation to me

.

i'm not familiar with the nitto tera grapplers, but if they are a tire that you can feel "stepping" between lugs at low speed, it might just be the tires. my tires do something similar.

...always lookin' for the simple explanations first

-sean

KLS · #4 (**permalink**) 09-20-2003, 12:18 PM

Tires. Those wouldn't be my first choice for 80 or 85 mph driving.

Ken

v8Toilet · #5 (**permalink**) 09-20-2003, 01:32 PM

Lift the truck up and put jack stands under the rear axle and front control arms so that the suspension is compressed under the trucks weight. Put the truck in 4wd drive and note the vibration. If it’s there start eliminating possible causes starting first with it in 2WD and then removing tires. Put the lug nuts back on if you remove the tires to hold the rear drums in place.

Through the process of elimination you should be able to narrow it down to tires, rotors, or the drive shaft. It might even be the drive shaft carrier bearing.

T'sTOY · #6 (**permalink**) 09-21-2003, 12:44 PM

As Sean mentioned, check the tires first.

You didn't mention if you had the harmonic condition before installing the new wheels and tires. I also have a tire related noise at certain sppeds, but it only happens on certain types of pavement. I think it's due mainly to the Geolander A/T II's open lug design and the wear that's occurred over the past 30K miles. I questions my dealer on the noise and wear issue and they said it's a fairly common occurrence.