I have a 2010 Dakota, 2WD ST. I have been experiencing some vibrations when i hit 35. I have done the speed test in 1st and 2nd and there is no vibration. Only in drive. I have changed all 3 u-joints and replaced the center support bearing. I did notice some play in the companion flange on the differential. Is this normal? There is no fluid leakage though. Also, is it possible to convert from a 2 piece drive shaft to a single drive shaft.

 

35 mph, 1st gear, no vibration
35 mph, 2nd gear, no vibration
35 mph, 3rd gear, vibration

Is the above correct?
Standard or automatic?
Engine size?

 

That is correct.
It is a automatic with a 3.7 V6

 

High frequency vibration like a buzz or low frequency vibration like a wobble or slow shake?

The drive shaft will be at the same rotational speed at 35mph for any gear so I would lean towards a trans or engine issue versus a driveshaft issue. Something like how the TCC hesitating to engage when accelerating. Maybe a loaded misfire that mostly shows at low load, low RPM. Like 35mph in third versus accelerating harder and still being in 2nd at a higher RPM at 35mph.

​​​​​Is the vibration only there when accelerating to 35 or do you feel it when your speed gets down to 35 when slowing to a stop?

 

Rodslinger: Its a wobble. Happens when I accelerate, haven't noticed anything when I'm slowing down. Also, its intermittent. Sometimes when I go 35 or more, there is nothing. Then when I slow down and have to accelerate again, the vibration returns.

 

I would be curious to see if it changes if you put the trans in tow/haul mode. It will hold the RPM's a little longer and change when the TCC engages.

Is maintenance current? Plugs, air filter, etc...

 

 

Automatic transmission fluid. Pump / Torque convertor are slightly starved. The level is low, the pickup filter is cracked or plugged, or the fluid is past useful life and is time for a changeout service. Suggest you start there.