GRINDER32

iTrader: (1)

I have a 1988 pickup, 4x4, 22re, no lift, 31's. I have a odd harmonic vibration around 55mph and up. Doesn't matter if I'm in 4th or 5th gear around those speeds i have the vibration. As a process of elimination I took my front driveshaft out and drove it; couldn't get more than the typical tire/road noise out of the truck no matter how fast i went. So thinking my front driveshaft was messed up i took a trip to the local drive shaft shop where they told me everything was in perfect condition, Cardan joint, U-joints, and a balanced shaft. So now i am perplexed on where this could be coming from, it makes me think that the truck is engaging in 4 wheel drive when it shouldn't be... but i could be wrong. If anyone can lead me in a direction or have had this problem and solved it let me know! I think it could be locking hubs, CV joints/axles, front diff, or transfer case... any help is greatly appreciated!

Rerunn

Check your rear u joints

GRINDER32

iTrader: (1)

Literally brand new... and the vibrations stopped when the front shaft was out so it isn't the rear

Punchy

Auto?, Manual hubs?, ADD?

GRINDER32

iTrader: (1)

Its all manual. I don't have my hubs locked in unless need be.. maybe they need to be rebuilt?

arlindsay1992

iTrader: (8)

If your hubs are unlocked and you're in 2wd then the front shaft, CV's, and diff are not turning. Tires balanced? Alignment straight? U-joints are new, but are they good?

arlindsay1992

iTrader: (8)

Check pinion flange for tightness, and same with the output flange at the back of the transfer case.

GRINDER32

iTrader: (1)

I have checked all u joints throughout the truck and they are good, and I agree with the fact that the front end SHOULDN'T be engaged but I only get vibrations when the front end is connected to the transfer case via the driveshaft but who knows... also the drive shaft shop had suggested i check the tightness of the pinion flange so i will try that tomorrow.

GRINDER32

iTrader: (1)

Not taking anything away from the suggestions but my thought process has been turned away from things like balanced tires, correct alignments, etc. because the harmonics/vibrations are only present with the front drive shaft connected and from what i know things along those lines don't know if a driveshaft is present or not... I had to drive over 200 miles for a last minute business trip (no front drive shaft) and didn't get a single sign of the harmonic vibration i have been chasing, but as soon as the front drive shaft is back in and i hit 55mph and over the truck starts singing to me

Punchy

One of the front CV shafts must be turning and making the driveshaft spin, Not saying the problem is the shaft but may be adding to the load against the Diff bearings.

GRINDER32

iTrader: (1)

I feel like something is engaging in the four wheel drive system that shouldn't be thus giving me the harmonic vibrations. Obviously these trucks were never meant to drive highway speeds in 4 wheel drive so I have begun the process of elimination to find the issue. The manual locking hubs will be coming off tomorrow and gone through to make sure all is well and replace any parts that need to be. I will update if the issue dissipates with the hubs being worked on or if the issue remains... Thanks for all the help everyone!

Chaser Johndoe

I am having the same issue but mine goes away at 62. also if I push on the shifter a little it goes away. Also doesn't do it in 4th just 5th. Let me know what you find out so I can try it on mine.

RJR

There are a couple of quick tests you can do before you start taking stuff apart, that will give you more insight as to what might be wrong. Basically, if the front drive shaft is turning and causing vibration while you're in 2WD, it's because either (a) the hubs aren't unlocking, or (b) the transfer case isn't shifting out of 4WD. To figure out what's going on:
1) Jack up the front end of the vehicle so both front wheels are off the ground. With the hubs unlocked, rotate each front wheel and check that the corresponding CV axle is NOT turning. If it is, your hubs are stuck in the locked position. You'll need to take them apart, clean them, check for broken springs, relube, and reassemble.
While you've got it jacked up, turn the hubs to the locked position and make sure the CV axles DO turn, indicating that your hubs are actually locking when you want them to.
2) If all is in order with the hubs, unlock them, lower the jack, put the transfer case in 2WD, and crawl under the truck and try to turn the front drive shaft. It should turn fairly freely. If it doesn't, your transfer case is stuck in 4WD, and the internal workings need attention.

GRINDER32

iTrader: (1)

Haven't been on and didn't see everyones comments but Thursday on my lunch break I determined something was wrong in the hubs because that was the only possible option left. Today I took my hubs apart and upon doing so I found that the spring had come out of the clutch while it was in the locked position and would not allow the left front hub to fully be "free" when in the free position. So after a hour of some cleaning and some grease it rides good as new. The previous owner obviously neglected these hubs because they were rough but nothing a little TLC didn't fix! Basically the vibration came from the left front being locked in while the right front was free, so I had constant 3 wheel drive! But everything is fine now and has been gone through.

I also threw on a set of new Bilstein's and let me tell you what, I will never use another brand again. I am absolutely amazed of the quality of the shock itself and how much it improved ride quality and responsiveness over the KYB's that came out.

Thanks again everyone, and as a word of warning these hubs are supposed to be checked, cleaned and regreased annually per the manual I have.