I have a 1999 5.9L 4x4 Durango with about 130,000 miles, about a week ago I had the freeze plugs replaced because of a small leak. Before this it was running like a champ, no issues at all. After I got my truck back, it is running rough to the point it seems as if the truck is going to rattle apart. On idle it seems to be ok but when i put it in gear the entire truck begins to shake when under a load. When the RPM's are between 1000-1700 and 3700-4500 it shakes almost like the engine is out of balance and is using gas like crazy (about 9 miles to the gallon, prior to this I would average around 19 MPG). At highway speeds, around 2100 rpm it purrs like a kitten no issues at all. The check engine light is NOT on and it is NOT pulling any codes, everything has been checked. No vac leaks or connections loose and it had a tuneup less than a year ago. I have done lots of online research so I am pretty well versed on the potential issues but none of them seem to point to the exact problem I am having. If anyone has an idea a response would be greatly appreciated. Thanks all!

 

If it's rattling real bad could be your harmonic balancer.

Its a weight that keeps all your internal parts in balance and if it slips or gets thrown off just a little bit, throw everything out of whack.

 

If it is the harmonic balancer, wouldnt it cause the shake all of the time? The issue i am having is, it did not have problems till immediately after the mechanic put the freeze plugs in. When I got the truck back it had the issue. Thank you for the input, Ill put that on the list to check.

 

If the mechanic messed with or took off the harmonic balancer to do the work, then I'd agree 100% with widow on that one.

 

I've seen it where it only does it in a window of RPM speeds. Also, I'd have the mechanic print out all the work that he actually did so you can get an idea of what was touched to check first.

Also, I re-read it and you say when you put it in gear it does it, have him look at the torque converter. I had an old '86 "Dodge-asaurus" that the torque converter was shot and it was clunking into gear and used gas bad.

 

I was going to say that....lol. You beat me to it White.

 

Thanks guys, I have noticed a clunk every now and again when i shift into gear. Ill check that out. I looked at the balancer and i dont see any visible damage, it may be a possibility he may have slipped when he was pounding the plugs back in. I do know he removed the front tires to replace the plugs (there is just enough room to get to them) and i just looked at all of the bolts and connections in the area and there is no visible signs of removal, its pretty dirty lol. I love this ride and im pretty pissed about it i need to fix it asap. Any and all information is greatly appreciated, Thanks again!

 

Yeah I'd be willing to bet the torque converter is acting up and on it's way out. How long has it been since the transmission fluid has been replaced?

 

I had the transmission serviced about a year ago, come to think of it we put synthetic back in. Could this be my issue? After a long drive on acceleration I did notice a metallic sound up front every once in a while. I will definitely look into that. Thanks.

 

Well as long as it is ATF +4 synthetic you should be fine. Anything else such as Dexron or Motorcraft will do terrible things to the transmission.