Can I drive truck up to 70mph safely with just the front driveshaft installed?

[Mattchu60]

Like the title says - I am tying to find a driveline vibration in my truck - its driving me nuts.

Here is what I did so far:

- balanced all four wheels
- New U-joints
- Removed front driveshaft and just drove in 2H

None of this helped - around 68-73mph I get a funky vibration - it starts off smooth and goes to medium vibration and back to smooth in about 2-3 seconds and repeats. I thought it may be the front shaft turning on its own, its not.

I should state - I installed a 14 bolt rear end recently along with new wheels/tires. Got the conversation joint on the rear of the shaft as well. My thought is that one of the new u-joints is causing the shake, but they seem tight.

Can I take the rear shaft out and drive this thing down the road using the front wheels or is that a very bad idea? I know there is a seal where the slip joint goes into the transfer case and oil runs out this sometimes when the shaft is removed, I can imagine the amount of fluid that may fly out if there is no shaft there to "plug" the hole

 

[Jims86]

Like the title says - I am tying to find a driveline vibration in my truck - its driving me nuts.

Here is what I did so far:

- balanced all four wheels
- New U-joints
- Removed front driveshaft and just drove in 2H

None of this helped - around 68-73mph I get a funky vibration - it starts off smooth and goes to medium vibration and back to smooth in about 2-3 seconds and repeats. I thought it may be the front shaft turning on its own, its not.

I should state - I installed a 14 bolt rear end recently along with new wheels/tires. Got the conversation joint on the rear of the shaft as well. My thought is that one of the new u-joints is causing the shake, but they seem tight.

Can I take the rear shaft out and drive this thing down the road using the front wheels or is that a very bad idea? I know there is a seal where the slip joint goes into the transfer case and oil runs out this sometimes when the shaft is removed, I can imagine the amount of fluid that may fly out if there is no shaft there to "plug" the hole

A red solo cup, duck taped to the rear housing should suffice for testing, but check the transfer case fluid level after you put the rear shaft back in.

 

[HotRodPC]

Just for ***** & giggles, try rotating the rear driveshaft 180 degrees and re install it. I've heard of this taking care of some vibrations. Yours sounds pretty bad though.

 

[Mattchu60]

I drove the truck to work today - this is really bugging me. Vibration doesnt seem to come from any certain spot, I feel it in the seat, then it moves to the steering wheel, then I had feel it has moved to the passenger side of the truck....doesnt make any sense to me.

This is really bothering me. Thing should be smooth as glass with all the wheels being balanced last week and new u-joints and the front shaft removed. I am wondering it it goes beyond the typical stuff.

 

[MrMarty51]

I drove the truck to work today - this is really bugging me. Vibration doesnt seem to come from any certain spot, I feel it in the seat, then it moves to the steering wheel, then I had feel it has moved to the passenger side of the truck....doesnt make any sense to me.

This is really bothering me. Thing should be smooth as glass with all the wheels being balanced last week and new u-joints and the front shaft removed. I am wondering it it goes beyond the typical stuff.

It seems that those rythematic vibrations is like that. it could be a bad bearing in the differential or axles, Maybe Transfer case too, but I`d think if it were the T-Case, it`d be gone by removing the drive shaft and running off of just the front.
Maybe the Harmonic Balance has slipped, might want to do a TDC test on that too.
Maybe a weight has fallen off of the flex plate if it is an automatic transmixer.

 

[Mattchu60]

Just to clarify,I have not tried removing the rear shaft yet and running with just the front. I have removed the front shaft and run with just the rear, but that changed nothing (I thought it was spinning on its own).

 

[HAZZARDJOHN]

I agree with flipping the driveshaft 180*. If it goes away or changes you at least know. I have done this in the past and it went away.

On the driving FWD only, when I was in my younger days I had a friend who had a half ton 1982 K10 longbed. It was a beatup pig, but it to this day was the fastest truck I have ever ridden in (500+ Horse engine, and a built TH400 that shifted like a baseball bat to the head). We were in town and he blew the rear end doing a burnout so he shifted it into 4wd and tried to limp it home. We got within a few miles of his house when the front end locked up, we went from 45 to 0 in a few feet (it felt like anyway) with no warning. Even with a seatbelt on I still went into the dashboard. We had to tow it home after that. I never did hear what happened, but ever since then I have been leery of driving with the front wheels only. If we were doing 70 I think the truck would have flipped over end! LOL

 

[HotRodPC]

Another thing you might try, and I know it'll sounds bad, but what you're trying to do is isolate certain items to eliminate them as probable cause. Kinda like you're trying to do with process of elimination by driving on the front shaft. Which BTW, you should be able to do for a short distance without much issue provided your fluids are good, hubs and bearings are healthy etc. Think about it, NP203's could be driving on FWD only in the right conditions.

But try this, get up to your speed where the vibration starts. Holding that speed with the gas pedal, slowly start to apply your brakes and see if the vibration or wobble tends to stop, get better or change. If you have bad bearings, axles or hubs walking around, applying the brakes gradually will center them and be holding them in place the vibration might improve or change. If this does make a change, then do the same thing but gradually apply just the Parking Brake. If no change there, then you know it's the front axle, if there is a change, then you'd know it's the rear axle. Of course you don't want to be doing this for an extended period of time. You'll be getting the brakes hot doing so of course and be knocking a few hundred miles of wear.

 

[Mattchu60]

I'll try what you suggested on my drive home today HotRod. I'll try to report back later on what I find out.

 

[Jims86]

I'll try what you suggested on my drive home today HotRod. I'll try to report back later on what I find out.

Remove both shafts, get it up to 70, and see if it persists.

 

[foamypirate]

Remove both shafts, get it up to 70, and see if it persists.

 

[Jims86]

no, seriouse....get the speedo to show 70, so he can make sure its not a problem with the T case.

 

[foamypirate]

no, seriouse....get the speedo to show 70, so he can make sure its not a problem with the T case.

I guess that makes sense. I just saw "remove both driveshafts and get up to 70" and started chuckling to myself before anything computed.

 

[Jims86]

I guess that makes sense. I just saw "remove both driveshafts and get up to 70" and started chuckling to myself before anything computed.

I wrote it like that on purpose, to see how many would bite!

 

[kleedus]

14 bolt and 10 or 12 bolt half tons the diffs are different in size

after putting the 14 bolt in your driveshaft would be pushed in more basically the pinion is longer on a 14 bolt then a half ton

I would check the length on the rear shaft you might need to have is shortened and rebalanced

your driveshaft slip yoke could be bottomed out in your t case

and if you run just the front drive shaft do not hot rod it. I tore a 205 right off of a 400 doing that. but it was fun burnin the front tires off