[nate5022]

My 89 W250 360 TBI 727, NP205 137k drivetrain shakes at park. I can see the transfer case lever vibrate back and forth, maybe a 1/16 or 1/8 inch but enough to be visible. I can also feel the vibration in the steering wheel. I don't notice it when driving. The engine mounts and mounts under the transfer case only have a couple hundred miles on them, and all the engine accessories other then the water pump are new within the last several years. The harmonic balancer visually looks ok, but is there another way to check it? Is there another possible cause of the shake? 

 

[712edf]

So it shakes/vibrates while running in Park, but drives normal?

Are you sure it's firing on all 8 cylinders? A misfire will cause unevenness.

Are the torque converter bolts tight? Any play in the water pump or fan?

Possibly stretched timing chain?

When did this start?

I've had bad vibrations at certain RPMs (in Park) but mine was due to wrong balancer (cast vs forged crank).

Bucky

 

[nate5022]

It drives fine idles a tad low at stops, but I only notice the vibration in park. It has relatively new plugs/wires/cap/hall effect sensor, but won't hurt to double check. I'll have to check the fan and water pump for play, it is the factory pump. I noticed it about a year ago, hence I changed all the mounts. It doesn't get driven all that much, once or two a week at very best. I thought maybe I was being overly picky, but when I drove it this morning it seemed like the vibrating of the transfer case stick was worse.  Any suggestions are appreciated..
Thanks.

 

[nate5022]

Can you check the torque converter bolts with the tranny in place?
Thanks.

 

[Canadian country boy]

Yes, you can check the T/C bolts in the truck. Just remove the lower inspection cover and you will be able to see them. You'll have to rotate the crank to be able to get at all 4 or 5 bolts (I forget the number of them).
What happens if you bring the bring the idle up just slightly with the gas pedal? (Just off the idle circuits ), does the shake go away? Is it a smooth rise in idle speed?

 

[nate5022]

When you bring throttle up the shaking stops. At a stop in drive the shaking is still there. Throttle acceleration is smooth, no stumble or hesitation. Plenty of power and no indication of misfiring. Will check water pump and other stuff this morning.

 

[chau8238]

Sounds like the idle is too low.

 

[nate5022]

Well I guess I could do the IAC reset.  Idle has seemed a little low since I replaced the EGR valve.

 

[Canadian country boy]

The idle is controlled by the computer, and the TPS and the IAC are responsible for the information the computer needs to control it. Do you have any stored codes? It could also be a fuel pressure issue also. How's the injectors? Are they old with lots of miles and are they clean? A fuel pressure regulator and/or fuel pump can also cause engine idle issues. Check your fuel pressure at idle.  Was it always like this or is this a new issue?

 

[ToxicDoc]

So it shakes/vibrates while running in Park, but drives normal?

Are you sure it's firing on all 8 cylinders? A misfire will cause unevenness.

x2 on this part. Ignition misses (bad plugs, wires, cap/rotor) will be rough at idle and better with speed

 

[nate5022]

Well I checked/reseated all the wires, cap etc. Nothing noticed there, they are all fairly new. Checked torque converter bolts and all were tight.  No play in water pump or fan. Took off air cleaner and visually inspected TB, looked really clean. It’s been this way for a while, but it doesn’t get driven all that often, just finally got annoyed with it . I’ll have to check fuel pressure this weekend, have to get a gauge from the parts house.  Got a FSM coming, found a used one on amazon for 4 dollars, so I can have the test procedure.

 

[712edf]

My Astro van had a spell where it would idle rough (shakiness) but run/accelerate great under a load.

Turns out to be several teeth missing from the gear on the bottom of the distributor shaft gear. This happened twice so I suspect my camshaft gear is shot too....anyways even though Dodge doesn't have a gear on the distributor shaft, your vibration could be ignition or valve train related (worn timing chain for instance).

Bucky

 

[Canadian country boy]

I agree that it typically sounds like an ignition problem but it still could be fuel related. How's the injector spray pattern at idle? When injectors get old, they can bleed fuel pressure at the seat, so at idle they can drip excess fuel into the chamber or be clogged a bit and cause a pulsating effect spray pattern. Maybe try a can of SeaFoam in the fuel system. I find over the counter products don't work all that well. Injectors typically need to be replaced around 120,000 miles.

 

[nate5022]

Well with mothers day and everything I didn't get a chance to tinker with it. I ran a can of seafoam thru it a few tanks back and it seemed to help.  I have been considering a rebuilt throttle body anyhow since we are about to move half way across the country and I want to make sure its ready.  I don't suppose there is any way to check the timing chain short of pulling the h2o pump and cover, which really doesn't sound like fun. Hopefully can get around to checking the fuel pressure and codes this week..

 

[comrade cheddar]

  Pull off one spark plug wire at a time (whilst it's running ) and see if it changes on all cylinders. I've had bad spark plugs and wires out of the box. The "eye test" isn't meaningful.
  Possibly a mechanical issue inside the engine.  Bad valve or wiped cam lobe?

 

[Canadian country boy]

I highly doubt it's a timing chain issue. Unless your enginges has nylon gears which I forget if it does or not but still doubt it. I've seen chains go much further than the miles you have on yours. But if you want to check, you can pull off your distributor cap and turn the crank back and forth and watch your rotor to see how responsive it is to the crank. Pay attention to how much the crank moves before the rotor moves. If you can rock the crank a ton before the rotor starts to move then you can assume the chain is badly stretched

 

[nate5022]

Thanks for the idea checking with the cap off. I'll have to try that on the long memorial day weekend, along with checking the other things. I wouldn't think at 137k it would be worn, it's had a fairly easy life, towing a boat during the summer with the original owner and hauling light loads and commuting  since I've had it.

 

[nate5022]

Well my FSM arrived yesterday but they sent me one for a Dakota, not a D/W series..   Hooked up a borrowed diagnostic tach. It's idling at 800 in park and about 620 in gear. Not sure what the idle is suppose to be, and searching hasn't turned anything up,  so wondering if anyone knows what the idle should be?

 

[ToxicDoc]

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