How do you use the jake brake on a truck with an automatic transmission?

I think if I saw 2200rpm on my DD15 I have a #### heart attack.

Set your speed at the top of the hill. Let’s say the Siskiyu (spelling?) pass. You’ve got 42k in the box. I’d say 35mph. The auto will most likely be in 9th. As you approach the drop force it down into 8th and put it in the lightest Jake position. Then like a video game cycle in more jakes as you need them. If the truck exceeds 40mph apply service brake to bring it back to 35. I’ve done that hill a hundred times and rarely touch the brake. I’d give myself bonus points if I could reach the agricultural check station on the California side without using brakes or the accelerator.

 

When the RPM is too high, all you do is tap the accelerator for an instant, just enough to disengage the jake.

The gear should shift higher and the brakes should come right back on with the higher gear.

Usually takes less than a second, and by hitting the accelerator, the jake disengagement happens before the accelerator even has time to make you go faster.

You have to keep trying it until you get a feel for it, then you will do it without even thinking.

The whole reason you would want a higher gear is if you were going too slow down the mountain anyway, so disengaging the brakes for half a second is actually working towards what you want, which is to go slightly faster.

As for an alternative means of selecting a higher gear, my automatic gear stick has up/downshift button that will manually change gears if the RPMs are appropriate. Both my automatic Peterbilt and Automatic freightliner had these buttons. However I rarely use it, because working the accelerator is easier.

 

Does your truck have a manual mode? It will solve a lot of your problems. Most automatics do have a manual mode but companies can disable it in the ECM. The jake is the same as in a manual truck, on/off, high/med/low setting. Only real difference is that the trans will sometimes automatically shift the gear to stay in the proper rpm range to prevent stalling or damaging the engine from pushing the rpm too high.

Everything else is the same, proper speed and gear for the hill depending on your weight. If your RPM is going too high then you're going too fast for that gear. Likewise if it is going too low, no point in trying to stall the engine.

 

Can you use manual shift mode?... Or does the company have that locked out?

If you can put it into manual shift mode you should be abke to control the shifts instead of the computer.

 

Can you post a picture of the shift lever?

If it's like this one (I think most newer freightliners), the center part with the A and M is a push button to toggle between auto (A) and manual (M) mode. Once in manual mode, flipping the lever up/down (like the turn signal lever) will shift up and down.

 

For real long grades I usually find whatever the right gear would be to nearly fully hold me back. While it’s in stage two jake I let it go up 2/3 mph above my safe speed/ speed limit and once it goes over I then put it in stage three to bring myself back down. Truck will only down shift if you’re making it clear you’re attempting to slow down/stop instead of maintain a speed. If you’re over revving you want to give the brakes a good stab in stage 3 and it will downshift for you. Some of these cascadias have descent mode where you can just hit the brakes set cruise and it’ll maintain your speed, my 2018 doesn’t.

 

As others have posted. Use manual mode, choose a gear, usually 10 or 11, select engine brake setting as you would in a manual trans truck. I do it daily in a 2019 T680.