I have a 350 BCC mileage unknown. I had the overhead run about a month ago and the mechanic told me everything looked really great.

My Jake Brake has done this since I bought the Truck Oct 06, but I never really noticed it that much until I started hauling logs off a steep mountain.

It will hold firm some of the time, and then it seems as if it is only holding back 50% that it should.

The best way for me to explain it is you know how it sounds when you have it around 2000 rpm going down a mountain and the jake is really sounding like a machine gun.

This is the way it sounds when it is only holding 50%.

When it is holding 100% you know it sounds like it is fluttering real hard, but really holding back.

It does not matter if I am loaded or empty, but does seem to do worse when I am loaded.

When they ran the overhead the mechanic told me the 1 stage of the 3 stage was left unplugged when the other shop did the injector.

After he plugged it back in, it worked fine for a couple of days, and now is back to its old self.

Any suggestions would be greatly appreciated as I am coming off a steep mountain grossing 90,000 or better.

Perhaps it came unplugged again. I think that I would take it back to the shop and ask them to check it again.

Check to make sure the wire isn't partially unplugged on that head again.

The 855 cu. in. Cummins like you've got, has 3 heads.
Just above each head, by the valve cover you'll find a wire hooked to a terminal,these wires activate the Jake brakes - 1 head for lo, 2 heads for medium, or all 3 heads for high. Make sure all 3 are secure, if not, then repair as necessary.

If all the wiring checks out, then the problem is internal - have a technician check it out.

Thanks for the great advice! Is it a complex job if I have to take it back to the Mechanic to get this done internally?

It could be as simple as the electric solenoid that the wires are hooked to. Start there first and think positive. The glass is half FULL, not the glass is half EMPTY.

I sprayed some starter fluid on the connections to see if this would help, and it did somewhat, but it still is not the same. Sometimes it will hold back, and then seems to let go of 50% of the holding back that it should be doing.

I'm wondering if it could just be the wires are so old that they may be brittle and having a short in them sometimes, because it does the same whether I am loaded or empty.

Any suggestions?

On the inside of the jake brake spacers there is another connection that could be loose or intermittent, but you'll have to pull the valve covers to get to it.

Or, as has been mentioned the solenoid on one of the jake units may be failing.

Thanks everyone for the advice, I am planning on taking it to the shop Monday and get it checked out, as it is no fun coming off a 10% grade mountain with 90,000 lbs gross and hearing your jake cutting out on you.

Took it to the shop on Monday, and the solenoid had went bad. They replaced it and its working fine now. Thanks for the advice everyone.