Engine Vibrates at 2400 RPM

[mrbornery21]

1995 6.5 crew cab dually 4x4 turbo diesel 5spd. I believe the engine is out of balance. When in neutral or when driving engine vibrates like a tire not balanced. I can drive down the freeway and turn the truck off at 2400RPM and engine still vibrates, So it should not be a fuel, or timing, or compression issue. Plus just to clarify compression is good, injectors are new, timing dead on, fuel filter is new. Engine smoothes out under 2000rpm and above 2600rpm
Vibration is at its worst at 2400rpm, vibrates the cab of the truck a little and you can feel it through the shifter. I have taken the belt off to see if it was any of the accessories causing the vibration, but when I take the belt off the computer cant sense the rpms and it runs like sh*t. And I cant get it to 2400rpms blows smoke everywhere. I thought I might have came close to the 2400rpm mark once and it seem as though the vibration was still there, Hard to tell when the engines freaking out without the belt on. Well Im thinking its the HB or the Flywheel thats causing the vibration. Question, If a main cap on the crank gets loose could it cause the crank to flex and vibrate, or if a rod is slightly bent could it cause it to vibrate, just some ideas I was thinking of. engine makes no unusual noises.

Im going to put a different HB on, Then I guess Ill have to pull the trans to get the flywheel checked to make sure its balanced. Im so damn tired of working on this truck!

If any one is interested Ill sell it for $4500. I have $2900 in recent parts in this truck and I bought it for $1500. with a blown engine. I would love to walk away from this truck and break even I just want what I got into it out of it. I really am tired of working on this thing.:mad:

[More Power]

You can measure the slack in the timing chain by just removing the oil fill pipe on the front of the engine - then rock the crank back and forth to determine how many degrees the crank can move before the gear on the injection pump begins to move. Anything beyond 3 degrees is on the edge of tolerance. Four degrees is beyond the tolerance. Rock the crank by first removing the crank pulley, then use a 15/16" socket and flex-handle on the damper bolt.

A loose timing chain can produce a resonance in the chain at specific engine rpms. This causes injection and cam timing to resonate, which can affect how smoothly the engine runs at specific rpms.

Checking the harmonic damper and crank pulley would also be a good idea.

I know some who have unbolted the transmission torque converter from the flexplate, slid it back a bit, then ran the engine to determine whether the transmission was a contributor to these sorts of problems.

Jim

[mrbornery21]

I dont think its the timing chain, because I can drive down the freeway get the truck up to 2400rpm going down hill, leaving the standard transmission in gear, and shutting the engine off vibration is still there at 2400rpm with engine off. But the timing chain is a great idea! But im sure its not my problem. Something is not balanced right I hope its just the HB and not the Flywheel, My luck it will be a bad crank , Thanks Jim

Jesse

[Robyn]

If it will do it moving or standing still then it may be a clutch gone south.

The flywheel can certainly be an issue. Was the truck originally a 5 speed?

If not and the manual tranny was stuffed in, was the correct flywheel used??

There could also be an issue with the clutch too as in dampener springs going away.

You see this more often with an auto tranny thats had a converter rebuilt and it was done poorly.
The 6.5 is an externally balanced engine, I am not sure if any othe flywheel will fit that engine but if so someone could have used the wrong flywheel.

Like using a 400 SB flywheel on a 350 or a 396 flywheel on a 454. Gonna shake rattle and roll.


Fill us in with a little more info???


Robyn

[mrbornery21]

Yes the truck was originally a 5spd, when I replaced the engine I had to buy a new clutch kit , troughout bearing, pressure plate, pilot bearing. And even had napa resurface/hone the fly wheel. Flywheel is a single mass flywheel.

Story on this truck is the 1995 engine blew beyond repair so I picked up an engine on craigslist $1600 it was a 1997 engine with 9000miles on it that came from a 1ton pickup equipted with an automatic trans. So I removed the automatic flywheel and put the standard flywheel from the 1995 on the 1997 and put it in my truck. I also left the HB that came with the 1997 engine on it because it looked in better shape than the 1995 HB. I did research and called parts houses and the have same part#s for auto HB's and Manual HB's so there should be no difference. This doesnt rule out that the 1997 HB could be out of wack. Also I couldnt use the 1997 brackets cause it swiched the place of the alt,and the ac pump. so I put the 1995 brackets on the 1997 engine, Also I Kept the 130gpm HO water pump, and the dual themastat setup on the 1997 engine!

(Fill us in with a little more info????)

Robyn, let me know what kind of info you want and I will post it. Thank you for your reply:)

[More Power]

The pilot bearing and input shaft bearing on the trans is a possibility.

Jim

[JohnC]

I have taken the belt off to see if it was any of the accessories causing the vibration, but when I take the belt off the computer cant sense the rpms and it runs like sh*t. And I cant get it to 2400rpms blows smoke everywhere.


This doesn't make sense to me. The PCM doesn't sense RPM off any of the accessories. The only connection is that the tach won't work. The vacuum pump is the only accessory that has an immediate effect on running, but at no load it shouldn't be noticable. If you're blowing black smoke under no load conditions, I would not be quick to dismiss this as a problem.

That said, are you sure the problem isn't just something ( a hose or similar) conducting vibration from the engine to the body?

[mrbornery21]

Thanks John C. I forgot that the waste gate on the turbo will stay open, When I take the belt off the engine. This causes the engine to run like it did when I had a bad vacuum pump. Because there is no vacuum to hold the waste gate close, No boost, computer cant sense boost, not enough air to burn the fuel. When I take the belt off, I will wire the waste gate closed. This should solve the running rough without the belt on problem. Now I should be able to see If the vibration goes away after I take the belt off.

I thought it might be the turbo down pipe hitting the frame but I pushed it out of the way, and had a friend run it up to 2400rpm and vibration was still there.

Im positive its something on or in the engine thats not balanced

A friend told me That my motor mounts could be wore out causing the slightist imbalance to be exaggerated

[mrbornery21]

Changed HB and pully out today! And took off fan and belt . Vibration is still there. So I guess Im going to have to pull back the trans and run the engine, then take the clutch off and run the engine, then take manual fly wheel off and replace with automatic flywheel that came with the engine to see if thats my problem. Then if that dont work Ill pull the front differential out to pull the oil pan off and see how the crank and rods and main caps are doing!:mad:

[mrbornery21]

Well In the mourning Im going to replace the Trans mount and the Engine Mounts. Probably wont make the vibration go away, but hopefully it will make it less noticeable. They look tired anyway!

[JohnC]

I wouldn't run it with just the flex plate on it. It isn't a flywheel. When the automatic is installed, the torque converter is the flywheel.

[mrbornery21]

John C, Are you sure? I thought the torque converter/clutch assembly is balanced to Zero and the flywheel/flex plate was counter balanced to the crank, Hint the big counter weight on the flex plate. Just like how the HB is counter balanced to the crank. These are just my thoughts I am not 100% sure.:rolleyes:

[JohnC]

You need the mass of the torque converter to produce the flywheel effect.

[mrbornery21]

Well changed Engine mounts and Trans mount. And now It doesnt just vibrate at 2400rpm, It shakes at idle and vibrates at 2400rpm. So long story short it made it worse. I guess changing the motor mounts tightened everything up and made my Imbalance more pronounced now:mad: