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

Exactly my point, its just a meter. Even if you lut in a tach that has a redline at 2300 rpm when the engine is designed to do stage 3 jakes at 2200

 

My truck is a 2020 Freightliner Cascadia with a DD15 engine and a DT12 transmission. Don't you think that when freightliner made the tachometer, that Freightliner would have made the redline on the tachometer to represent the actual danger point of RPM's on a truck with a DD15 engine and a DT12 transmission?

 

oh it will if you’re in a steep enough hill. I got the t680 with the paccar engine and tranny. Most of the time it’s ok but on mountain backroads use manual mode when engine braking cause it’ll downshift on roads I don’t want it to and end up having to mash the brakes so she doesn’t over rev or possibly worse back track to the gear and end up being in neutral for too long.

 

Do you own the truck? If so, take it to the dealer for a warranty repair. Then you can hear it straight from the horse's mouth that its fine.

 

I don't own the truck.

 

Obviously not. Same truck, engine, and tranny and I dont have that tach. Hey, I tried to help ya. You keep running down the hills with the jake at 1600 rpm while smoking the brakes.

 

I'm not saying that you are wrong. I was just asking questions, trying to learn.

 

Nope. I’ll run my truck my way.

 

singlescrewshaker wrote the following: "Most cases jakes gonna be most effective between 1800-2200rpm. Let her spin.!

Also, these new autos are synced up with the engine. I'd bet it won't downshift to an unsafe rpm.."

otterinthewater, you wrote that "if you saw 2200 RPM's on your tach, you would have a #### heart attack." singlescrewshaker is saying that the jakes are most effective in a range that includes 2200 RPM's, and he says that he bets that the transmission won't downshift to an unsafe RPM, even though i said my truck downshifted to 2200. If singlescrewshaker knows that my truck downshifted to 2200, and if singlescrewshaker says that he doubts that the transmission would downshift to an unsafe RPM, then it follows from that that singlescrewshaker don't think that 2200 RPM is too high. Yet you say you would have a #### heart attack if your tach was at 2200. I am surprised you don't see a contradiction there.

 

Pull the shifter stalk towards you to upshift, push it towards the dash to downshift. If you pull the driver side visor down, often times there is a sticker on there with instructions.