How often did u use ur Jake Brake ?

I cringe every time I hear some hoopity company truck's engine brake being used to assist in upshifts across a parking lot. I use mine on grades and coming to stops to save brake linings.

 

Are they actually using it to assist in shifting or is it that they just don't know how to shift properly?. There are alot of drivers out there that, rather than learn to shift properly, they just shut the jake off or fart every shift.

 

I only use mine when I see "no engine brakes" signs. Rev it up to 2100 and let 'er rip.

 

All a Jake does is change your exhaust valve timing.
It opens the exhaust valve just after the compression stroke.
This causes all the energy absorbed during the compression stroke to be released through the exhaust in the form of compressed air before it can force the piston down.
In effect changing the engine in to a compressor.
The pressure in the cylinder chamber is the same pressure as when the engine is running during the compression cycle.
This is a lot less than during the power stroke so there is no way that it places to much stress on the engine.
What does however happen is that you get reverse torque through the drive line as the engine is now absorbing energy not producing it.
Gears , splines etc now contact on the opposite face.
If you keep switching between torque and reverse torque it is not ideal for the drive line.
It also puts added pressure on the exhaust valve cam follower , cam and valve springs because of the higher lift.
You can however use the Jake with out worry but to have it coming on between gear changes is not use it is abuse.

 

Anyone shift with it doing a 1/4 mile run?

The drags I've seen they didn't.

 

Save my Air brakes as much as I can so Engine braking is the way for me.

 

So if it's that much stress on a driveline how come I have over a million miles on my truck with only ever having to change one u-joint?

I use mine every time I need to slow down, every day, all year long. Unless the road is slicker than snot of course.

 

As king q said. As long as you keep the torque on the drivetrain constant and smooth things will last forever. Just like upshifting. However you can't feather the Jake as easily as the throttle so it takes practice to make sure you hit the gear perfect when downshifting so you do not put and torque on it in the form of acceleration then having the Jake's hit and it the opposite way.

There are applications where upshifting with the Jake can be helpful. However I strongly advise against it if avoidable. The applications I can think of where I have been known to do it is in soft fields in low gears while harvesting forage. Your trying to keep up with the choppers varying speed but when you go to shift the ground speed drops faster than the engine speed and you can't hit the gear. Were talking speeds down under 6mph so it doesn't take much for the mud to completely stop the truck. I would much rather have guys Jake shifting than trying to jam the gear in. We have a truck that has a 10spd with a lot of wear and if you force the gear it will get stuck in that gear. So then you have to pull the floor, pull the shifter and realign the forks. Got it down to about 10-15 minuted now but still.

Out on the road though we do not want them doing it.

Some companies will fire their drivers for Jake shifting.

Sent from my Motorola Electrify using Tapatalk

 

Excellent point. I am often in that exact situation and the only way to grab a gear is to jake shift but I DO occasionally see/hear someone jake shifting on pavement and have even seen it once with a guy that was bobtail

 

When you are racing you shift with the clutch and don't care about rpm matching.