[MPerry]

I have been looking for insight to the Jake Brakes on a 903. I have seen an offhanded comment on a trucking forum about them being hard on the valve train of a 903. I realize its all subjective but does anyone have experience with Jakes on a 903 causing problems, excessive wear etc.... provided they are maintained and set to spec? Jacobs Engineering does not support the product on the 903, even though they support their other Jakes of that era. Should I take that as a sign I should remove them, or just keep them in spec realizing they will never be worked as hard as in a truck, and prob be problem free?

[dkarb]

I also have a 903 and have heard the same thing. (That the 903's weakness are the valves and therefore you should avoid using the Jake.) I asked a local Cummins mechanic (The only local Cummins mechanic left who has worked on 903s in the past) if it was OK to use the Jake with my engine and he said it should be fine. Maybe he wants more work.

[Fulltiming]

If the prevailing wisdom is that the use of jake brakes on the 903 can damage the engine, I would reserve their use for those situations where it is most important, ie emergencies and holding down speed on long, steep grades. Potential engine damage is not worse than risking burning out your brakes on a steep, long grade. The most important issues are: don't try to go down a hill faster than you can go up the same hill and always use a low gear. Speed is your enemy, especially on long (multi mile), downhill grades of 6+%. Use your emergency flashers, stay in the right hand or truck lane and always go slower than you think you probably can. You may annoy the folks behind you but you will still have brakes at the bottom of the mountain.

[Georgeb]

I’ve owned some 903s in class 8 trucks
We had a few problems with cam and cam rollers. Those units had 300,000 miles before 
We had issues. 
I would change the oil often and use the Jake

George