front driveshaft pulsing vibration

viperbluelx · 03-24-2011, 07:14 AM

Since regearing to 4.88's I've had a pulsating vibration that starts around 70mph, but you can also very slightly feel it at 45mph. I hadn't had time to mess with it till a few days ago when I took the time to disconnect the front driveshaft and tie it out of the way and the vibration is gone. The front shaft u-joints all feel good and there was no vibes with the 3.73's. Should I worry more about caster angle or driveshaft angle? With the UCF skid on I pointed the front pinion at the shaft so I'm sure caster is off but it doesn't drive bad, but could it cause a vibration? Driveshaft balance?

pilotkc · 03-24-2011, 07:17 AM

Which type driveshaft do you have?

rideraa · 03-24-2011, 07:24 AM

It may be that your are turning more RPM's now with 4.88 gears ?? And show a existing balance / wear issue that was not present at lower RPM's.

Did the tire size change to bring the rpm's back down any??

And as you mentioned, it may be driveline angles, front should be straight-shaft & pinion.

Above stuff is pretty common that you may already know, may help ??

shrubeck · 03-24-2011, 09:05 AM

If you figure it out, I want to know. I've had the same problem for years. I'm just in the habit of disconnecting the front shaft before a long drive, but I would much rather fix the problem. I have 4.56 gears on 33s with front and rear woodies btw.

viperbluelx · 03-24-2011, 02:28 PM

Factory driveshaft in the front.

**msiefer** · 03-24-2011, 03:56 PM

If your pinion angle looks reasonable then it is probably time to have the front driveshaft checked out and balanced. I'm just in the process of putting my 4.88s in and my driveshaft is at the local driveline shop getting a new slip spline and re-balanced. I'll let you know how it turns out.

**Imped** · 03-24-2011, 05:04 PM

Balance.

780406jeeper · 03-24-2011, 05:18 PM

Good luck. I have had the same problem with my jeep since I lifted it. RE 4.5 Super flex, 4.56 gears and 33's. Same speed starts that pulsating vibration. I had Jeep check the stock driveshaft 2 separate times, they said it was straight and balanced. I had local shop in Mesa Az build me a whole new shaft. Same deal. Had them try rebalancing two times too. Now have a Tom Woods shaft and no difference. I installed everything on my jeep with the exception of the gears. I have played with the driveshaft angle so many times it isn't funny adding a degree up, a degree down, straight, nothing. Ultimately Tom Woods said that it is a 'balancing act' no pun intended. We want to use a thicker tube for denting resistance strength, but need a smaller outer diameter to clear the transmission and such during articulation. Based on the longer length of the TJ front shaft, there is a point in which even the most perfectly balanced shaft will start to 'flex' out of straightness when spun fast enough.

Ulitmately, I either slow down to the point it doesn't do this, or I remove the shaft.
Kevin

viperbluelx · 03-24-2011, 05:23 PM

Quote:

Originally Posted by 780406jeeper

Good luck. I have had the same problem with my jeep since I lifted it. RE 4.5 Super flex, 4.56 gears and 33's. Same speed starts that pulsating vibration. I had Jeep check the stock driveshaft 2 separate times, they said it was straight and balanced. I had local shop in Mesa Az build me a whole new shaft. Same deal. Had them try rebalancing two times too. Now have a Tom Woods shaft and no difference. I installed everything on my jeep with the exception of the gears. I have played with the driveshaft angle so many times it isn't funny adding a degree up, a degree down, straight, nothing. Ultimately Tom Woods said that it is a 'balancing act' no pun intended. We want to use a thicker tube for denting resistance strength, but need a smaller outer diameter to clear the transmission and such during articulation. Based on the longer length of the TJ front shaft, there is a point in which even the most perfectly balanced shaft will start to 'flex' out of straightness when spun fast enough.

Ulitmately, I either slow down to the point it doesn't do this, or I remove the shaft.
Kevin

sucks to hear, too bad there aren't strong affordable hub lock-outs for the front of these

780406jeeper · 03-24-2011, 05:36 PM

I agree. It has been something I have wrestled with since we bought our jeep new. As soon as I have accepted that, now I have this OPDA issue eating at the back of my mind.

My jeep has 48,500 miles on it, I am on my 3rd front driveshaft with each being rebalanced at least twice. Tom himself explained the thickness/vs length, vs diameter issue. Makes sense why those super duties all have 5+ inch diameter shafts because of their length.

For what it's worth, the TW driveshaft is the best out of the three I have tried.
Kevin

**Imped** · 03-24-2011, 05:41 PM

I don't have this problem and I have 4.88's and the stock shaft. There's a chance for all of you.