Near the end of a 250 mile trip my 4Runner has developed a front vibration "only" at acceleration. I had originally suspected the drive shaft/u=joints, but upon inspection everything seems rock solid. I also did a quick check of the suspension, shocks ect., but nothing seems apparent. This started happening on the highway and the truck still seems to run straight (an alignment was done by Toyota not many miles ago.). Any suggestions, The search seems to point to the u-joints even if they appear solid.

 

when you put it into gear, do you hear a 'klunk' noise? if so, u-joints.

 

No klunk, no drive train play, no apparent bearing play front or rear either.

 

does your steering wheel shake??

your in 2x when you experience this i assume.

 

Steering stabilizer.
Caster/camber changes caused by the shifting of weight during acceleration maybe?
Keep in mind that while accelerating the rear end of the truck will 'squat' a little bit and this will change the front alignment angles.
Maybe wheel balance?

 

In 2WD, at all speeds. It just suddenly happened, it feels like your driving on the groove strip at the edge of the highway. It's constant and steady until you let off the gas then it's gone. I think I'll start taking things apart. Read a few threads stating the bearing in the u-joints were shot even though there was no play in them. It could be possible.

 

I have a 92 4runner and mine is doing the same thing.... i have no idea what it might be... it is not ujoint or anything it just shakes the 4runner while accelerating but not as much when on the gas very little... it will coast fine and go though the revs in neutral fine... it almost seems like there is no power and it just shakes the crap out of the 4runner.... i have replaced cap rotor wires plug fuel filter.... not sure were to go next...

 

Front u-joint on the rear drive shaft?

 

Motor mounts perhaps?

 

check the sparkplugs n wires

 

with my truck i checked everything fuel filter plugs wires coil tps ect... if i drive at like 4000 rpm in any gear and just have my foot on the gas ever so slightly it doesnt do it... but if i give it any more gas it will kinda stutter\shake my truck... im not sure if it has somthing to do with timing or if it is drive line related... yu think if it was driveline that at 4000 rpm while in gear it would do it no matter what.... it does not do it in neutral

 

Found it!!! Finally got around to checking things out more closely, Ujoints were fine, raised the back up, no play anywhere. Jacked up the front, no play and then Hmmmm why does this wheel not spin free?? Pulled the tire and found the brake dust gods had left a big present for me. Pads were almost down to the scraper and the rotor looked like the exhaust pipe on my bike. Caliper was completely seized, the other side was the same. I never had it pull left or right braking, braking was normal and the truck never took off from a stop with the feel of brakes being applied. I never expected this. Rebuilt the calipers, new rotors, new pads, new lines, bearings, grease and sweat. Vibration gone and gas mileage is up 3 MPG. I haven't gotten 15 MPG in 4 years, and the acceleration from a stop rivals the wife's Envoy.

 

nice now your wifey likes the yota again aye? you should show her how big the back seats are again lol

 

Glad you found the problem. So, the build up of dust caused this, or was it shoddy work?

Even though you found the problem to be your calipers, this is the same symptom experienced when my driveshaft started taking a dump. I'd let off of the acceleration, and the noise would disappear. Step on the gas, it would come back. Though at certain speeds, it wasn't as prevalent.

 

Not a dust build up but more of an issue with substandard pads. The tabs that alert you to a pad nearing it's lifes end were bent back to the point of being aligned with the metal portion of the pad. normally there is about 1/8 to 3/16 left when they begin to make noise. because the pistons where able to compress further than they normally do (passing the point of "You really need to change these dude") the pistons passed a ridge in the cylinders that didn't allow them to back off normally. In other words each time the brakes were pressed the pads were held tighter until more pad basically burned off instead off relaxing until applied again. This took it's toll on the rotors heating up, breaking down the bearing grease, cooking the bearings and just plain causing havoc. If you ever change your own pads and it is extremely difficult to compress the pistons rebuild the calipers. Don't just turn the rotors, repack the bearings and throw on new pads. JMO

 

My 87 4runner is doing the same thing, and rear wheels are not spinning freely BUT its drum breaks! ? Do i just back them off? they self adjust dont they?