Engine/Transmission (1994 - 1998) Trying to track driveline vibratrion

[KMott]

Hi, I have been having trouble figuring out where this problem is coming from. When driving down the highway, if the truck hits a bump, it will sometimes start vibrating in the driveline. It seems that the rear driveshaft is vibrating on the slip yoke at the rear of the transfer case. I know this because i have already changed the transfer case and driveshaft and installed a transfer case saver. The old slip yoke was scored up and the tailbushing was worn. After changing the t-case/ driveshaft there was no effect, it is the exact same. When its vibrating, if i pull the t-case shifter into 4x4 the vibration goes away instantly. Any ideas on what could be causing it? I dont understand how its still doing it after replacing the driveshaft and t-case (and the replacement parts worked fine on the truck they came off)

Thanks in advance for any help,

kevin m.

 

[Fishin Guide]

Did you change the carrier bearing? This is the cause of many vibration issues.



Also, any rear end lift? If so, the carrier bearing should be shimmed.



And vibration after hitting a bump makes me think it's int he front end. But without driving the truck, it's only guessing on my end.



Dave

 

[KAlder]

Sounds more like front end problems. Sounds more like the all too common "death wobble". Check balljoints, tie rod ends, & track bar. If it only happens when you hit a bump, I can't see how that would set a driveline vibe off(not saying it can't, just don't know how).

 

[KMott]

Thanks for the replies, the front end has all been rebuilt, and ive experienced the death wobble before, this is a different kind of vibration. Its definately from the rear driveshaft. Judging by the wear on the last driveshaft slip yoke/ tailshaft bushing, if the truck hits a bump just right, the driveshaft gets into a vibration. Maybe a 'howl' is a better word. The only way it goes away is if i slow right down or if a put the t-case in 4x4, otherwise it will just keep howling away. Its almost like the driveshaft gets out of alignment and starts rocking in the t-case as its spinning.



'Did you change the carrier bearing? This is the cause of many vibration issues'

The truck has a solid rear drivehaft from the t-case to the rear axle. Or are you talking about bearings inside the rear axle? I havent had a chance to check the pinion bearing.

Kevin m.

 

[JRaymond]

i would also check your transmission mount. i had a similar problem and it was my transmission rubber mount. it looked great while installed in the truck but it fell apart when i was removing it(rubber was pulled apart from the metal)

 

[JHenry]

Are all of your u-joints correctly in line with each other? Are any of the u-joints faulty?

 

[Bill Lins]

You might try removing the driveshaft & reinstalling it 180 degrees from the way it came off, just to see if it makes a difference.

 

[Hammer]

When you had the driveshaft out and apart,did you mark it so that you could put it back together the correct way and not off a couple of splines?.



If its off then its out of balance and will cause issues like your having... Andy

 

[KMott]

one update, I have noticed that if i keep the transfer case in 4wd (but not front axle engaged- has 4x4 posi lock) the vibration never happens.



U joints are both brand new in the rear driveshaft. Im not sure how they could be out of line? When i had the driveshaft apart, the only thing that could have been different would be the slip-yoke could be off 180 degrees from its original position. Other than that i dont know how it could be off.



Keep in mind that this same problem existed before i put a different transfer case and driveshaft on. I wouldnt think that both driveshafts have the same problem.



originally posted by JRaymond 'i would also check your transmission mount'



I remember looking at the mount when i was changing the case, and it didnt look very healthy. I will take a closer look and let you know if it ends up being the problem. It would make sense. When i put the truck in 4wd it stops the vibration, so maybe it balances everything back out enough to stop the vibration?

thanks again for the help

 

[KMott]

Update, Since the last post i have replaced the trans. mount. It was cracked and fallen apart, and the one bolt was half backed out. I could push up and down on the driveshaft and everyhting moved up and down. After fixing the 'problem' the truck still does the same vibration. Tonight i raised the truck by the rear axle and checked for anything unusal in the drivetrain. The rear axle feels good, the only thing i noticed is a bit of up and down movement inside the t-case, but that may be normal.

Also i had removed the front driveshaft, and with the front driveshaft off, putting the truck in 4x4 will no longer stop the vibration.

All i can think of is that from the trans. mount being so bad, i have wrecked my old transfer case, and the new one too.

Any ideas?

I am going to try to get into a driveline shop on Friday to get an opinion.

Thanks for any input, Kevin