Medium and Heavy Trucks
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So i wanted to start with a couple questions about your truck that you are experiencing the vibration with. Could you tell me what kind of chassis is this motor in? Is it a highway Tractor that pulls the same weight or is it a certain application? When the vibration happens where do you feel the vibration the most? the entire truck? the seat? the steering wheel? If you could elaborate the best you can on when it happens it would help me a lot. When you had the drive line checked is that all they did, or did they inspect anything else on the chassis? Does the motor have any fault codes or any other symptoms at all? Have you had any recent repairs at all like tires, diffs, transmission? anything at all? please take your time, the more information you can give me the better we can narrow down your issue. Thank you and I look forward to getting to the bottom of this issue for you.
10-4. So with the ISX I've seen a few things that could relate to the symptoms like that. First, most common cause is usually the motor mounts. Or, it could be just one of the motor mounts could be causing the vibration. Depending on the chassis and the transmission in your truck they typically have two rear motor mounts, one front mount. Second would be if you have a manual transmission it usually have a large bar, that mounts accross the rear of the transmission that allows it to move with torque but dampens the movement through the this bar.
I would recommend having those two components inspected thoroughly. I think your drive line is perfect considering you had it checked already and the symptoms you describe are definitely more towards the front of the truck like your thinking.
I'm thinking that its highly unlikely that the motor has anything internal wrong. It's going to be something simple the majority of the time. I would simulate torquing up the motor and having someone watch the motor from the side while its under torque to truly rule out the motor mounts. I've found that they can look perfectly fine but they are split and only separate when the motor is torquing like your experiencing. If you are hooked to a trailer leave the brakes applied on the trailer and just slowly release the clutch while someone is looking from the side of he truck ( in a safe position of course) The engine is meant to move a bit but you'll notice it will seem a bit excessive if the mounts are defective.
The piston slap they are reporting could be your air compressor. I've had every ISX I've ever maintained had a very loud knocking noise but watch to see if it's only knocking bad while the air is building. It will stop knocking once the air dryer purges and it stops building air. I like to look on the bright side and eliminate the very minor options first because 95 % of the time it is always something minor and not anything more serious.
Does your local Cummins have a dyno? or any other repair facilities around that could run it stationary? Unless Cummins thinks there is something genuinely wrong internally I would definitely recommend sending it back. Otherwise, it may need a stationary drive to narrow the symptoms. It may be worth the investment before it causes your truck any further damage.
Sounds like I may only be able to offer any further advise on where you could take it to get the diagnosis. Otherwise I want you to be happy with your diagnosis so if you have any other questions please shoot away.
This is of course possible but if this was the case it would of done this from the very beginning when the truck went into service. Calibrations just don't change and if the top end set was done then it would rule out any mechanical issues in the top end of the engine.
Has it always done this from when you bought it new?
I would recommend before getting Cummins to start calibrations on the motor and possibly tearing it down, rule out all your engine, and transmission mounts. As for the engine knock, run it with my advice to see whether it is the compressor that is knocking.
After those two issues are ruled out then I would book back into Cummins and make the recommendations on the calibrations. Depending on those results I would recommend seeing if Cummins has a dyno to run your truck on. Like the other gentlemen has mentioned you want to find this issue before it would do further damage to the truck.