I have a 1999 4Runner SR5 . it has about 136,000 miles and has a bad vibration only if the gas tank is under a 1/2 tank . or if I am pulling the horse trailer . I have had tires balanced and rims checked and all are good . U-joints are good also . What else could this be ? Thanks

 

Well if your pulling a trailer i can tell you your going to have vibration from the trailer no matter what... but the half tank of gas thing.... A car won't vibrate cause it has a half of tank of gas... Is it a steering vibration and Brake vibration.... an over all vibration... can you fell it good in floor? Is there any noise?

 

I have been pulling trailers almost everyday for 16 years , I know that some trailers will cause a vibration but nothing like this one . It isn't in the brakes . It vibrates the dash , steering wheel , floorboards and everything . No noise . It doesn't do it if the tank is over a half tank . Thinking it could be in the rear and have to do with the suspension and the weight of the extra fuel is pressing down causing it to stop or something . Never seen or heard of anything like this before .

 

What kind of tires are you running and when were the balanced? And Who? Tis possible its in the rear end. Get under and check Drive shaft bolts and seee if the have vibrated alittle loose. Its happened on a few trucks i've had pulling trailers. Anything loose? Broke leaf springs? Sure your u-joints good?

 

Had goodyear and a dealer check tires and balance less than a month ago . Don't have leaf springs . Bolts are tight and I know ujoints are good as I checked them (many years as a mechanic) and I replaced them . Running a goodyear tire for now .

Pretty sure rear shocks are gone as when you hit a bump they will squeak . Could that be causing the problem you think ? Never messed with suspension much .

 

When did you buy the tires? Are they new and did you have them rebalanced after 5k miles? I oh yea (slaps self) the 4runners have coil springs i forgots. Those shocks won't cause vibrations either. Could very well be the rear end as well. Whens the last time you checked and or changed the oil in the rear end? Whens the last time the drive shaft was greased? <- Those things need to be taken into account. If al else is not working I'd say the problem still is in the tires. I've been around alot of goodyear tires that just are no good at all. And people will balance them and re-balance them and send them out the door brand new still shaking. At that point it is best to get a new set of tires and try to avoid good years.... They are good alot of the times but sometimes you get bad tires from them.

 

get the tires road force balanced and the tech should be able to tell you if the tires are bad or not. they shouldnt be over 5lbs once done balancing them. if they're over 5lbs, your tires are bad. meaning your tires are running like an egg. thats probably where you get the shake. good luck. just had my tires road force balanced and thats what i found out about my tires. good years arent that well either but i heard that michellins are better and will eliminate the problem.

 

^yes sir

 

I hate the Good Years , They where put on by the dealer when I bought it 2 months ago . I am looking to replace them this summer . The rearend has new oil as of last month along with froont diff and transfer case , all got Royal Purple .
Thanks for the advice and help . Hopefully it is the tires .