Topic: 86 4runner vibration

[RogueDogg]

I recently picked up a 86 4runner & after putting some $ into it to get it road worthy, I have discovered that while driving between 60 - 70mph the truck shakes/vibrates as if a tire is out of balance. With that said let me list what I have done to it:
1. Replaced pads, rotors, shoes, drums spring hardware, wheel cylinders & rebuilt the existing calipers
2. (4) Brand new 31x10.50/15 BFG AT balanced of course
3. Replaced rear 3rd member to get rid of a gear whining since I ran it with little to no oil for about 1000mi before I could get the fill plug out.
4. New auto trans mount
5. (2) New motor mounts
6. (4) New stock Monroe shocks (kinda squishy if you ask me )

I have asked a few friends & here is what they think:
1. Driveshaft/u joints are bad ( I don't think this is the case )
2. Wheel(s) are out of round/bent ( possibly since I don't know their history or treatment, however the tire shop didn't mention anything when mounting/balancing my new tires )
3. Wheel/axle bearings ( not so sure this is the problem, inspecting them they felt & looked good however I'm no bearing expert nor was I able to "properly" torque/seat the front bearings onto the spindle during reassembly however there is no free play left/right up/down afterwards & seem to have the same "drag" as before )

Soooooo....after all that, what would you suggest I focus on as the cause?

[fordh8r]

This may sound like a stupid question...but...by chance, would the front hubs just happen to be locked in?  

[RogueDogg [OP]]

This may sound like a stupid question...but...by chance, would the front hubs just happen to be locked in? 

Good question & nope they're free and in great working condition

[fordh8r]

Good question & nope they're free and in great working condition

"Free" as in the 'free' position or as in their working operation?

If anything, have you looked at the rear shaft...joints? Damage of any kind? T-case oil, output shaft?

[RogueDogg [OP]]

"Free" as in the 'free' position or as in their working operation?

If anything, have you looked at the rear shaft...joints? Damage of any kind? T-case oil, output shaft?

Free as in the free position yes, rear shaft & ujoints look/feel good, tcase oil not sure and output shaft haven't checked, wouldn't either of those cause vibrations possibly at varying speeds not just 60-70mph? Literally when I hit 60 I start to feel the whole truck shake & I've never gone faster than 70 so I would assume it would on keep shaking past 70...

[fordh8r]

You might be surprised at the speeds when shaking will happen. Hypothetically, it would seem logical that a vibration, once it starts, will only continue to get worse as speed increases, right?

Quick story...I damaged my driveline recently in Hollister and it wasn't real bad but I managed to drive home the 90 minutes or so. Well, it started vibrating at about 40MPH and got progressively worsened to about 50MPH. at around 55 it started to go away and at 60-65 you couldn't even feel it!    Yeah, no lie!

You might even have a u-joint that is siezing and not turning smoothly which may cause you issues at speed and won't feel loose if you grab the driveline and shake/move it. You might even look to see if the driveline is phased correctly (Yokes positioned the same at both ends) this could cause a vibration too. All good things to check. Basics! 

[RogueDogg [OP]]

Yeah looks like I'm just going to have to start tearing into things to get it sorted out, at least it's still drivable since it's my DD, thx for the suggestions!!

[fordh8r]

No problem! Hope you find what ever it is that's causing you your issue!  

[Snowtoy]

Where are the vibs being felt, steering wheel, seat, or entire cab?

The tire shop if competant should have found a bent rim.

[Rocksurfer]

Just because the hubs are in the open position doesn't necessarily mean they are not still locked in. Under normal use you can bend the ear tabs on one of the bands inside. These tabs are very wimpy and can bend and are what pull the engagement gears apart and hold the hub open. If they are even bent a little the hubs will not fully disengage and cause the front driveshaft to spin. This will cause a high speed vibration/shake. Also old worn steering and suspension components will also create a high speed vibration/shake, and as stated before worn out driveshafts and worn or loose pinion and pinion bearings will cause this too.

[2manytoys]

I had an 86 4Runner with the same symptoms. Ended up being a siezed u-joint like fordh8r mentioned.

Missed it at first becaused I checked for a LOOSE u-joint. It felt tight so I assumed it was OK.