I have a 1999 Dodge B3500 with the 5.2L, 46RE transmission 97k miles. Recently, the engine has produced a bit of vibration whenever I press on the accelerator. I just had the transmission flushed so I thought that perhaps they put the wrong fluid in it . Since the pan seal was leaking I decided to replace the fluid with Mopar ATF +4 and a new filter (both from the dealership). I made sure that the fluid level was good and took it for a test drive but the vibration is still there. It is most noticable in 1st-3rd gears but once it hits overdrive, around 45MPH, the vibration isn't nearly as noticeable. The thing that gets me is that it drives great. There are no harsh shifts or slipping, just a vibration that you can feel in your lumbar section of your back. The vibration is there when I increase the engine RPM with the transmission in neutral or park. Any thoughts on this would be appreciated. I don't really have the $$ to get it fixed but I'll take it in rather than risk doing major damage to it.

Could it be the viscous fan drive or perhaps the vibration damper. Since the vibration is there whether I am in gear or not, I would think that it wouldn't be transimsison related but then again transmissions are marvels whose innards are not to be understood by mere mortals.

 

This is engine related since the vibration is still there with the tranny in park or neutral. Is the "Check Engine" light on? If it is have the codes read and post them.

You can check the fan drive by grabbing the blades and try push/pull one of the blades towards the radiator and engine. If it had play that way then definitely replace the fan drive. Also if it turns really easily when the engine is off for 5 minutes or more then replace it.

Other possible causes to check:
1. Spark plugs, wires, cap and rotor.
2. Dirty or failing fuel injector.
3. Low fuel pressure.
4. Vacuum leak (vacuum lines and/or plenum gaskets)
5. Bad or broken motor mount

 

The last time I changed my spark plugs, I didn't get one of the Wire boots on all the way. There was a similar vibration to what you describe.

 

Looks like it is the water pump shaft. I took the fan off and ran the engine for a few seconds and the vibration was gone. I also noticed that the water pump shaft pulley had a good amount of play. Reading through the manual it says that there should be two bolts holding the pulley on but there weren't any bolts on mine. I wonder if that contributed to the amount of free play. I ran out of daylight so I will get back on it in the next day or two and report back here once I swap out the pump and take it for a test drive. Thanks for all the help!

 

If your pump has that much play then just replace it. There are no bolts on the latter water pump pullies. There are 4 holes that you can use to push some bolts in just attach the tools to remove and reinstall the fan nut. The play you feel is a worn out or loose bearing. Have you been loosing any coolant?

 

Well, it was definitely the water pump. I just finished putting the new one in and went for a test drive. It was great. No vibration to speak of. Since I had to replace the water pump, I decided to change out the bypass hose as well. I didn't want to put it all back together and have the bypass hose leaking (it is that little hose that connects to the top of the water pump--you know, the one you can't get to). Anyway, it wasn't too difficult to replace once I realized that I could get to it if I removed the accessory mount. The accessory mount comes off after removing a few bolts, you don't have to take off the AC compressor or alternator. In addition, removing the mount enabled me to get to the surface where the water pump seal goes so that I could clean off the remnants of the old seal better. No leaks and no more vibrations, I am one happy man. Thanks for all the help.