Hi guys, thanks for reading this.
Well I just bought this truck 06 Doge Tam 5.7 155k miles, the guy I bought it from seemed to mechanically have mainted it pretty well , he had replaced transmission at 75k miles and just rebuilt engine 2 yrs ago. I bought it after he upgraded to a Ford, ugh. When I got it , it had an exhaust leak n he said he just didnt want to fix it any more, I bought it and replaced both exaust gaskets and the leak was fixed. After the rattling from the exaust leak was gone I started to notice a vibration between crusing between 25 and 45 mph, it feels like when a drive shaft is out of balance, as if I was driving on a road under construction, before they ad the asphalt. If I accelerate hard from stop I won't even feel any thing transmission seems to shift normal, it's just at crusing speeds and if I try to accelerate slightly between 25 to 45, I feel the whole truck vibrate, except the steering wheel doesnt vibrate. It does fine at all other speeds. I drove it with OD off and didnt notice the vibrations. I'd appreciate any advice. I'm just trying to see if I can get some advice before I start taking it to different shops and try to figure out whos being honest. Soo since I bought it I replaced the spark plugs, transmission oil atf+4 mopar and both transmission filters, u joints and engine oil and all brake pads.The truck came with 6 month old 35 inch tires and it seems to have a 2 inch lift. I didnt notice a change from any of the maintenace. Oh yea I replaced the front shocks as well, I've been looking online and I read some where that the splines wear out on the torque converters and that it could maybe be a bearing in the diff, but just not sure what to make of it not happening when OD is off.. thanks on adnvance

 

Sounds like maybe a misfire. Does it do it predominantly when you're on a slight incline at those speeds?

If the TC locks up at those speeds and you have a missfire you will feel it through the drivetrain as a vibration of sorts.

When was the last time you checked the plugs or Coil Packs?

 

I wasn't able to see the last part u where going to say,
I changed the plugs a week ago and they all seemed fine
I used champion platinum plugs and torqued them to 13 ft lbs,
I wish I knew why when I turned the OD off, I dont feel the vibrations.
And no check engine light on

Thanks for replying

 

Sorry, fixed that post. So my reasoning behind it is if it was transmission related I think you would feel it no matter what. I don't know if you would feel any vibrations with the torque converter locked up if it was the torque converter.
The reason why I'm leaning towards a misfire of some sort is because when the torque converter locks it's direct engine to transmission to rear drive connection. So any vibrations the engine makes you will feel in the drive train.
Misfires are more commonly felt at low engine RPMs, under slight load, with the torque converter locked up.
BUT, you're turning OD off.. you're also eliminating 2 gears from the equation too. So keep that in mind. Unless you can find a way to control TC lock and unlock without using the OD off or Tow/Haul mode you won't be able to eliminate the possibility of it being one of the O/D Gears.

I'm not trying to scare you or anything. A lot of what I've read about these 545RFE Transmission is that they're pretty stout.

 

And that right there might be the problem. These trucks just hate the rare-earth plugs. Throw in a good set of plain jane copper plugs. See if it doesn't run better.

 

Dang, thanks I really appreciate ur help, I guess I might have to take it in to a shop and at least now I have something to think about when they give me there diagnosis.

 

Not sure if I replied yet or not,
But it was doing this before I change the plugs too, the old plugs looked good,
But I think I am going to pull some and see if these platinums are fouling up
Thanks