[mnhoff]

can there be damage done to a jake brake by applying it for long periods of time?  The reason I ask we took a day trip today with our jeep from where our campground is just north of the state of Washington on the Canadian side. One portion of the trip was a 12 mile 7 to 8% decline with three 10mph switchbacks in it. I myself have never taken our newell down that type of mountain. More than likely a slow 40 minute drop in a lower gear with jake applied steady. Help on that if I should so decide that trip.

[Fulltiming]

No, you will not damage anything by keeping the jake on. You will need to stay in a low gear on a 12 mile 7-8% grade or you will over-rev the engine. That is what the jake was designed to do. Don't even think about going down that type of grade without the jake on. You will lose your service brakes long before the bottom.

[HoosierDaddy]

I've done a bunch of those grades going out east... Like Michael said just leave it on. I slow down to 30 mph or so as I begin the descent. Don't "ride" the brakes ...Stab them to slow down and then release them in order to let them cool.
You might want to have the Jake brake checked by a mechanic before the trip. My mechanic found malfunctioning solenoids on two of my cylinders when he checked them.

[mnhoff]

thanks guys. what is max rpm on the 8v92 when gearing down that I would not over run?

[Fulltiming]

2100 rpms max if you are under load, 2300 rpms max no load. I try to stay at 2100 max rpm descending a hill with the jake brake on but if it were to momentarily go up to 2200 or 2300 with no load before you could get it back down below 2100 with the service brakes, it should not hurt it.

Jakes work most effectively when the engine is up in the 1800+ range on an 8V92 so I try to pick a gear where I can maintain my speed going down a hill with the engine at 1800-2100 rpm. On a steep hill that may mean 2nd gear which tops out at 40 mph at 2100 rpm. On an 8% grade I doubt you will be able to use anything higher than 2nd gear without having to excessively use the service brake.

[Fulltiming]

Another good rule of thumb is if the fully loaded 18 wheelers are going down a LONG STEEP grade slower than you are, you are probably going down too fast. Get into the truck lane and enjoy the ride. You really don't want to find out all the downsides of having to take a run away truck ramp because you overheated your service brakes or lost air due to pumping the brakes.

If there are multiple 10 mph switchbacks, you will need to slow down enough to get back into 1st gear in advance of those curves. Trying to slow down from 35 to 10 on an 8% grade is a big deal so slow down WELL in advance by letting the jake slow you. Going down a mountain too slow may annoy others but it will be safe. Going down a mountain too fast is a potential disaster.

[Chester Stone]

Between Reno and Sacramento there is a 40+ mile steep grade and I used my Jake all the way. However, the transmission will heat up and mine got up to 254 degrees, but apparently no damage was done with synthetic oil.

[prairieschooner]

I like the "rule of thumb" ...go up as fast as you want to go down...just consider the reverse.
I bet Nancy will "not be happy" HA! but then you could always let her drive the Jeep down and that may help...at least with the looks she might give you.
Hope to get the air springs resolved so we can go for fish & chips soon.