Rear End or Drive Shaft Vibration Issue

[thegoswicks1105]

I am a new 4runner owener and would greatly appreciate any help. I just bought a 1992 4runner 2wd. Got a great deal on it ( I think) but it has this vibration issue. It starts at around 45mph and quits around 70mph. Occasionally when I can hit 80mph the vibration kicks in again. While pressing the gas or letting off in between those speeds, the whole vehicle vibrates. It feels like there are four 12" speakers with the bass turned all the way up. I just had new tires put on today and it is doing the same thing(tires are the same size as old ones). I also had it at the drive shaft shop today. They just looked at it (didnt balance the shaft) and said it looked fine. I am not sure if they checked the u joints or slip yoke for play. I will have to call them tomorrow and ask. I have read other threads that say it could be the u joints or slip yoke. It doesn't feel like it is in the front end. I am not a mechanic by any means but do consider myself somewhat mechanically inclined. If it is the u joints or slip yoke, how hard would those be for me to replace them? I had the back end jacked up the other day and when I moved the back tires back and forth it felt like there could be some slack in the rear end.

Any suggestions? Your help would be greatly appreciated.

Thanks

 

[KidVermicious]

How much slack? You shouldn't feel much play when rotating the tires back and forth. If you've got too much on one side, it's probably a worn axle shaft, too much on both sides could be ring and pinion. Any noises to go with your vibes? Howling or chatter?

Check the factory service manual sticky up top for ujoint/driveshaft replacement.

 

[Bad_Vision]

sounds like a u joint to me or a unbalanced tire. joints are cheap try them first then look into the tires and if thats not it then your left with the rear differential.
start at the cheapest and work your way up. the money you spend on the cheap stuff will be worth it in the end.

 

[fourwd1]

You can't always tell if a u-joint is bad while the drv shft is on the truck.
Unbolt it from the diff and move it around to check it.

Also, if you have a 2 piece drv shft you might have a bad center bearing.

 

[thegoswicks1105]

Thanks guys. I am going to try and replace the u joints this weekend. Should i go ahead and have the drive shaft balanced while I am doing the u joints? I will keep yall updated.

 

[fourwd1]

If the drv shft has not been damaged there should be no need to have it balanced.

 

[Bad_Vision]

agreed