just bought a 07 2500 4x4 5.9 cummins,4spd auto,QC,short bed with 131,000mi. bullydog triple dog downloader,everything else stock.hard vibration between 55 and 75 mph.changed all u-joints,transfer case,balanced driveshaft,shimmed rear end to whithin 1 degree of trans. angle,balanced tires. bullydog adds 90 hp.pulling my hair out!!! please help! ANY ideas? It feels like a bad u-joint,but i've changed them already. I put the rear wheels on jacks and it vibrates without tires on. Any ideas welcomed!

 

was there any play on the output shaft from transmission or input shaft on rear axle maybe, Also is there a steady bearing on these trucks ive only been underneath mine twice and cant remember. but if there is push it up and down and check for excessive play there, ime no dodge mechanic but do work on semi's and see this quite a lot.
it seems you have eliminated a lot of things already. good luck and let me know how you get on.

 

Thanks for the reply! I didn't notice any excessive play on trans. or rear diff. Just had mechanic shop change rear pinion seal because they had to torque the yolk nut to 485ft lbs. I checked inside rear pumpkin and didn't see anything obvious. My trans. has started to surge in low gear.I don't know if that's related or not.

 

I am raising a flag because I dont think its that much 485 ft lbs more like 25 ft lbs if I can remember correctly ... Did a Dodge dealer do that or was a corner shop????brb with more info

 

It was a corner shop. Thats why I had them change it. It was vibrating before the seal change, but that was before I balanced the driveline. I will try to find the correct torque from the dealer! thanks!

 

Did they swap the bearing and crush sleeve also or just the pinion seal.

If that didn't swap the bearing and sleeve and is using the old ones then the pinion nut only gets tightened down until it takes 10 - 20 inch / lbs to rotate the assembly.

What he sould have done, because he wasn't taking the diff completely apart, is remove the tires abd driveshaft, then used an inch / lb torque wrench to measure the Torque To Rotate.

Then when he installed the new seal, you only tighten the pinion nut until you get the same resistance.

 

The other things I would recommend are these.

1 - Don't under estimate that you may have a tire out of round. Normally u-joint vibrations show up at lower speeds (5 - 15 MPH) and smooth out a bit at higher speeds. Tires being out of balance / out of round, ten to show their head at 40 - 45 MPH+ and smooth out at 65 - 70 MPH, depending on how far out of whack they are.

2 - Torque converter.....you have a stock trans and TC and are running that Bully Dog on 90 HP? I wouldn't be surprised at all to find the TC ballooned and ready to give up the ghost.

 

Wow! I've learned more in 2 days on this forum than I have in 2 weeks since I bought this truck! I will recheck the balance on the tires ASAP. I will find out what procedure they used on the rear diff.Tonight I put a hoseclamp on the driveline and rotated it until I got almost all the vibration out. The machine shop balanced the shaft without the yolk ends on it. Is this normal? Also I've been running 90hp extra for 2 days. Was set at 70hp extra until it wouldn't start the other day and I unhooked the batteries for about a minute. When it started back up it was back to stock! That really SUCKED! How much can I safely run with a stock setup? If I have to change the TC what do you recomend? thanks!!

 

A stock trasmission is really only good up to 40 - 60 HP over stock.

At about 40 HP, the stock TC starts slipping.

At 60 HP, the clutch packs start slipping.

Eventually, the TC balloons and fails....the clutch packs come apart and you're looking at a rebuild.

I would suggest that you turn the power down to 40 - 60 if you want it to remain healthy.

Also, the tires may balance fine BUT they may be out of round.

Put chocks on the front tires and jack one rear tire off the ground. Have someone else in the truck and give it some throttle whil you watch the tire. If you see it hop or other wise not spin perfectll round, you have an issue.

Then do the other tire.

To do the fronts, lift both rear, support with jack stand and lift one front tire. Watch for irregular spin.

Then do the other front tire.

Balance may be fine but they may be out of whack.

 

Thanks for chiming in on this Coal Train since you did Help me with that pinion seal and re torquing that nut again...
OP
Yeah dude you dont want to run Your bully dog turned up to 90 hp. I have bully dog also heard some bad horror stories about guys running it turned on extreme and tearing the trans up... Its not that our trans is bad or anything think of it like this our engines have 325 hp torque is sitting around 610 ft lbs. adding Hp and torque when its not designed to handle 425 hp and 900 ft lbs of torque...
I have the Triple dog with crazy Larry on box its 120 hp and 320 lbs of torque who knows if that is actual or not never dyno'd my rig... I mostly run tow economy once is a while I'll turn it up high but then again I dont beat on my truck to often. Once I do yes their is a difference and yes my TC does slip since it is a stock TC and Valve body Not only those you also have to watch your EGT and trans temp.. EGT needs to be lower then 1350 degrees F and trans seen my trans temp hit 250 ish degrees F with no load and on the skinny pedal... At some point in time you will want to get a Rail Pressure gauge those are different and is good to have..