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Ryeguy475 · 12-26-2018, **(Subject: CM 871 help please )**

Hello,
I own a 2009 871 450hp. It has a vibration under load that I just cannot seem to solve. When it’s parked I can rev it up and it’s fine, unloaded it isn’t too bad until...I go up a hill. Loaded it’s worse. I know it’s coming from the engine. This is what I’ve done so far... in frame 90k miles ago. New vibration dampener 4 months ago, new motor mounts, new clutch, reman trans. I did the injector leak test that I learned from Rawze, found #6 was leaking, replaced that. Made no difference!! I did the leak test again to make sure and it passed, no bubbles. This thing is driving me insane! I found a local Cummins “guru” that worked for Cummins for 16 years, he plugged into it and went for a ride with me, he agreed the vibration was coming from the engine. It’s almost like a slight fuel knock or similar. He did the cyl cutout test and it passed. The only thing he saw that he didn’t like was fuel pressure was 240 idle and 265 under full load when I was pulling a hill. He thought that was low pressure. My fuel economy hasn’t changed since this vibration started 6 months ago.[/align] Any ideas or thoughts are appreciated!

marek4792 · 12-26-2018, **(Subject: CM 871 help please )**

How are your u-joints, carrier bearing, and driveshafts? I found a bad injector on my truck over at Haggai's doing the bubble test with the key first then by hand. When I was barring the engine I could get it to turn but then it would get really hard to turn like almost you're gonna break something tight and note where it got tight pulled out said injector sure enough it was dripping quite abit from the tip when held upright after holding it 90° from the ground when removing the injector..

Roysbigtoys · 12-27-2018, **(Subject: CM 871 help please )**

(12-26-2018 )Ryeguy475 Wrote: Hello,
I own a 2009 871 450hp. It has a vibration under load that I just cannot seem to solve. When it’s parked I can rev it up and it’s fine, unloaded it isn’t too bad until...I go up a hill. Loaded it’s worse. I know it’s coming from the engine. This is what I’ve done so far... in frame 90k miles ago. New vibration dampener 4 months ago, new motor mounts, new clutch, reman trans. I did the injector leak test that I learned from Rawze, found #6 was leaking, replaced that. Made no difference!! I did the leak test again to make sure and it passed, no bubbles. This thing is driving me insane! I found a local Cummins “guru” that worked for Cummins for 16 years, he plugged into it and went for a ride with me, he agreed the vibration was coming from the engine. It’s almost like a slight fuel knock or similar. He did the cyl cutout test and it passed. The only thing he saw that he didn’t like was fuel pressure was 240 idle and 265 under full load when I was pulling a hill. He thought that was low pressure. My fuel economy hasn’t changed since this vibration started 6 months ago.[/align] Any ideas or thoughts are appreciated!

I too had a engine vibration about 3 years ago ......or at least I thought so. It only vibrated when climbing elevations. It turned out to be the stupid transmission heat exchanger leaking anti freeze into the tranny and for some reason that caused my vibration. I took the stupid exchanger off, flushed it with the tranny with ATF, refilled with 80W90 and my problem went away.
This fall the tranny finally started giving me problems when shifting from hi/lo so I replaced my 13 spd with an 18 spd. I am now looking for a good air to air cooler that will mount right up to my 09' Pete 386...any suggestions?

Ryeguy475 · 12-27-2018, **(Subject: CM 871 help please )**

Wow that is interesting. I’ll check my trans for antifreeze in the oil, I know I never liked the idea (or location) of having that cooler on the transmission. For the air to air I can’t help you, I bought a new one for my ‘10 kenworth t800 and it was $900 with a two year warranty.

Ryeguy475 · 12-27-2018, **(Subject: CM 871 help please )**

I just checked the trans, no engine coolant in there.

Rockhwy · 12-27-2018, **(Subject: CM 871 help please )**

Check ride height on rear suspension my friend had similar problem ride height was low he adjusted to spec vibration went away

Ryeguy475 · 12-27-2018, **(Subject: CM 871 help please )**

Ride height hasn’t changed , I’m riding on rubber block suspension. All the suspension parts are in good shape.

Waterloo · 12-27-2018, **(Subject: CM 871 help please )**

I had a vibration like that... After the second in frame it went away. I wonder if they skipped a step or two when they in framed your motor? Seriously.

slowpoke · 12-27-2018, **(Subject: CM 871 help please )**

just to mention, when mine had an (engine vibration with a slight fuel knock) turned out to be a timing actuator i started by swapping out rear metering actuator with a known good used one i had no change. put that one on front cyl. no change except now i could hear knocking at idle, put original back on still knocking then swapped out front timing actuator, knocking gone almost immediately, engine smoothed right out, pulled right down to 1150 rpm and up to 1800 rpm just to try, still no knock or vibration. but i was lucky enough to have kept two actuators as spares . there not cheap just to try out.