If it gets worse with deceleration (from speeds above 60MPH), suspect rear drive shaft (u-joints, balance, CV).

Also bear in mind that the entire driveline (front and rear) is connected through the transfer case, so vibrations from the rear can be felt in the front and vice versa.

A simple troubleshooting step in this case would be to index/mark the front drive shaft and remove it. Then see if the same speed/conditions reproduce the sound. If the sound/vibration is the same, then replace the front drive shaft (matching index marks) and index/mark the rear shaft and remove it. Then take a drive in 4Hi and see if the sounds/vibrations are reproduced.

If there is no difference in sound/vibration, take a look at your diff bearings (axle, pinion, etc.), hub bearings and check the diff tolerances (clearance, backlash, etc.).

My first guess is that there will be a significant reduction in sound/vibration with the removal of the rear shaft (even the low speed sound/vibration). The rear section of the driveline is under power/strain with normal driving conditions (which is 2WD on vehicles without full-time 4WD), so the rear driveshaft, axle and hubs wear at a faster rate than the front.

Good luck with the vibration and fix. Please post the result/solution when you have one... your experience with this issue may save someone else time and effort.

 

I have a 2wd so no front driveshaft. I replaced the rear u-joint last week, and when I was taking the shaft out I could tell that someone had taken it out before...makes me wonder. The old joint was pretty stiff and I was surprised that the new one was also stiff after it went in. I don't know if this is how it is supposed to be or not.

 

Your rear driveshaft has (or should have) a total of 3 u-joints. If the rear u-joint was bad, chances are that the front joints are too. All u-joints on a drive shaft should be replaced at the same time... the allows the shaft index to be reset.

In other words (and if you read my first post, this is synopsized), the u-joints settle into an arc of rotation and wear at specific points in their travel. Indexing/marking the driveshaft for removal is necessary to maintain this same (and very specific) arc of rotation when the shaft is reinstalled. If all new u-joints are installed (and not just one), the arc of rotation (travel) is not "settled in" or worn, so the shaft can be installed at any index.

Bear in mind that the front two u-joints are part of a double-cardan joint that also houses a CV-ball. These u-joints are not available at most auto-parts stores and the dealer will tell you to replace the entire driveshaft (at a cost of $1150). A driveline shop will be able to re-build the double-cardan and replace the u-joints for around $200 (parts & labor).

If you're willing to drive to Marietta, I highly recommend the father/son team at American Driveshaft (765 S Cobb Dr, Marietta, GA 770-499-9804)... they are subject matter experts and their pricing is reasonable.

 

PS - they will exhibit an obvious sigh when you bring in your 4Runner... the rear shafts in these are notoriously troublesome.

 

Yeah, I probably should have done both joints at the same time, but the first one was such a PITA i didn't feel like messing with another at that time. There must be different shafts because mine only has 2 joints, one on the slip yoke and one on the flange yoke. Alright, I guess i'd better get that front one changed out then...can't wait!

 

*UPDATE*
Went to see the guys @ American Driveshaft in marietta and they showed me that my slip yoke was worn out. Rather than spending upwards of $150 on a new slip yoke I opted for his option to replace the u-joint and weld the caps to the yoke. They ended up not welding them but instead compressing the bores and staking them so the caps would fit snug. Walked out with a new u-joint and balance for $50, reinstalled the shaft and guess what? NO MORE HUMMING NOISE!!!! Thanks to mickwheeler for recommending the shop! Oh yeah, when I had the shaft off, I looked at the yoke on the differential and noticed both the nut and pinion shaft looked nice and shiny, almost new. makes me wonder if the previous owner had it rebuilt...

 

@tunnelmotor99 - You're more than welcome, those guys are awesome. I'm glad it worked out and without too big a dent in your wallet. As for the nut and pinion, not sure about a rebuild... though mine still look new after 250K miles.

 

I have the same problem, except mine starts wobbling around 50mph and I know the cause. My rack and pinion bushings are shot. Completely. It was a bit hard to figure out, but there is a simple way.

Get the skid plates off, then get under your rig while it's on the ground, ie not on the jack. While the motors running reach up and grab the steering shaft above the steering box. Watch out for the header, that SOB is hot! Rotate the shaft and watch the rack and pinion, if it moves about the bushings are shot. I'm doing mine tonight in fact, got the kit lying under the desk here.

 

Got the new bushings in. I tried to do it without taking off the sway bar but just couldn't get the C-shaped one to go in. I knew that if I pulled the SB I would pop a bolt and sure as shhht that's what happened.

Took it for a test drive,no vibs brother

 

I had the vibration while accelerating problem as well. Front U-joint on my driveshaft had rusted and a chunk had fallen off (probably during my truck's semi-annual cleaning ). Since having that replaced, now there's a constant vibration above 60mph, going to get an alignment this Friday followed by a rebalancing, tires only have 10k on them. Probably time for new suspension components up front soon too. We'll see what happens to this issue after those fixes.

 

i have 2000 tacoma with the same exact problem two years and running luckily i just got remanded and blamed it on the accident so now i have free truck with all new has going in very soon

 

Dued... Your engrish....

 

sorry i meant to say i got rearended and now i have a paid off truck with a SAS going in soon

 

Hey, hey, hey! Got steering rack bushings installed today! Wow, what a difference. Most of the vibration is gone. It no longer sounds like I'm talking into a fan at highway speeds. I think the rest of the vibration is from the warped brake rotors, so those are next. If you guys haven't done these bushings, you need to hurry out and get some! Well worth it!

 

who's your buddy? post #9.

you get the Energy suspension s rack bushings or just replacement OEMs?

Hokkaido that is funny dued...post #52

 

@Ron - I purchased a set of (Energy Suspension) steering rack and sway bar bushings when I was trying to resolve my own vibration issues. Since my driveshaft was the problem and I have no vibration at speed or while braking, I decided to put off the bushing install. I'm either lucky or I'll probably have to install them soon... when I do have to install them, I'll remind myself of your timely advice (post #9) and string curses together in your honor.

 

just went through this myself took the rear wheel seal finaly going out to find out that the rear bearings where chewed up compleatly just put new bearings in and wow what a diferance surprisingly It has been going on and I had been chasing it for about 30,000 miles 2 sets of rims, 3 sets of chewed tire,new u joints,brake rotors,new shocks,and whatever else i forgot but finaly its smoth and what a great ride again. Also something I learned while driving 18 wheeler If you look at something in the car while its shakeing such as the seat if its shaking forward and back its something with the tires and if its vibrating side to side its mechanical driveline bearings rotors and such. hope this helps.

 

Wait - you replaced the rear wheel bearings? Or did you mean control arm bushings? I'm still fighting the steering shake.

 

there are brass bushings on the inside of the spindle that hold the cv axles steady if these start getting loose the half shafts can start swinging around in the middle causing vibration i had this prob for a while before i found the prob grab your half shafts and give them a shake if they have movment replace the bushings you can get them at a dealership for about $100 or so and its four bushings you need a pull hammer to take the old ones out witch you can rent at autozone!

 

Had the same experience with a new set of tires. they tried twice to get it to balance and then defended themselves by blaming the new tires and bilstein HDs.

Then i read THIS:
http://www.4runners.org/writeups/haweka/index.html

Then i coughed up the $100 for an balance using this tecnique and the 65-70mph shake is gone..