THIS IS MY FIRTS POST. THIS IS A GOOD SITE I LEARN A LOT FROM YOU GUYS. I HAVE A VIBRATION AT A CERTAIN RPM I DONT HAVE A TACH BUT THE VIBRATION IS IN THE GAS PEDAL.THANKS.

 

Brian, can you describe the vibration a little more? What driving conditions are you in when this happens, does it happen when in gear, in park etc?

The vibration you feel is in the foot pedal, but could be originating elsewhere. If you can provide a little more detail, maybe we can help you out a little better.

 

THE VIBRATION IS IN ALL GEARS AT THE SAME RPM. EVEN WHEN YOU GIVE IT GAS JUST SITTING THERE.

 

Can you describe the vibration. Is it just in your foot pedal, or does the whole truck vibrate?

Do you notice an engine miss at this rpm? That could explain the vibration, but could be caused by a whole pile of problems. Is there smoke associated with the vibration? Do you loose power?

If you are mechanically inclined, I would suggest picking up a troubleshooting and repair manual from cummins. It's a bit expensive, but worth it. I can look in my manual for you if I get some time and a detailed description, but I'm having a busy day so no guarantees.

I f you give good details, I'm sure the other guys will chime in with some advice for you. Good luck with it.

 

ONCE YOU GET PAST A CERTAIN RPM IT SMOTHES OUT. IT ALMOST FILLS LIKE THE THROTLE IS FLUTTERING. THERE IS NO POWER LOSS NO SMOKE.COULD IT BE THE THROTLE LINKAGE IT IS VERY LOSE.

 

I'd take care of that then, and see if that corrects the problem. Maybe some new linkage. Doesn't sound like linkage from what you are saying though.

 

Im gonna say your flexplate is going if its a automatic. Go underneath and remove the tin cover to see where your ring gear and torque converter are. I bet youll find metalic type debris. You feel it thru the floorboards etc at all rpms dont you? It a common problem on first gens. If thats the case the trans will have to come out to replace it. you can do a search here for more info. Dodge will get around $280 for it and Cummins will get $90 for it, same part. Some run the 2nd gen plate which is supposed to be a direct replacement. Look in the tech facts I think the part # is there for what you need.
Im curious so let us know. By the way, when typing in capitals it means your screaming at us. Which if its your problem its understandable

 

It may well be the flexplate...they make strange sounds and vibration when theys start to fail.... the one thing you need to be
aware of is they can fail in the blink of an eye, leaving your stranded.
Pull the cover and use a scew drive to try and move the flexplate
front to back. If it moves noticably then next you need to break out a mirror and a flashlight. Look up and see if you can visually identify any cracking.
BTW, Piers Diesel Research has a solid upgrade flexplate they sell, one which I am using in my own truck.
Here is the link to their web site, give them a call..

http://www.piersdiesel.com/

I would try to eliminate other things first though.
Look to see if your throttle mounting bracket, linkage etc is tight for starters..

pb...

 

My son's 92 had similar symptoms and it turned out to be the injector pump bolts were loose, the vibration became worse and sheared the bolt off that attaches to the block. What a pain to repair!!!! Might be worth checking???.........

 

I'm thinking that it is most likely not the flex plate if the truck vibrates when sitting in park. Am I off base? I haven't done a flex plate so I don't know, but maybe this will help get the list of potential problems down a bit.

Sorry Brian, I haven't had any chance to look in my manual for you.

 

If the engine is running the flex plate is turning. So yes if it were the flex plate it could vibrate in park.

 

Mine sure did. Felt like the truck had solid engine mounts. strange enough it would seem to quit when I hit the brakes Go figure that one. It also toned down at higher rpm. I didnt even notice it till I got home from a 5 hour trip.

 

Make sure your throttle cable isn't touching the intake manifold or anything else, and it has a slight sag in it between the firewall and the mount. The engine moves relative to the firewall and if there's no slack it will vibrate. Also, when you push on the pedal, the cable moves and wants to straighten out, sometimes against the manifold. Took me awhile to figure that out Jim

 

Hey guys thanks for the help. it turned out it was the trottle cable rubbing on the brake boster. thanks again

 

DUH !!!!!!!! .............5 spd's don't have a flex plate.....sorry...my bad...

pb....