I often see signs in smaller towns that say “no engine braking!” in reference to trucks. I’d imagine that it’s noisy or somehow dangerous. Google searches only turn up manufacturers of engine brakes.
What is it? Why’s it banned everywhere?
Engine brakes are devices, installed on the head of diesel engines, that basically turn
the engine into an air compressor. This makes the engine much more efficient in
slowing the truck. Some truck owners run modified, or straight, mufflers in the belief
that it improves engine performance. It probably does the opposite on modern,
computer controlled, engines. When using the engine brake w/ stock mufflers the
increased noise is minimal, but w/ more open exhaust systems they can be very loud.
There are, of course, some who like this effect, but it is very annoying to residents of
homes near truck routes, especially during early morning hours. You may notice that
many of these signs specify no “unmuffled” engine brakes.
The engine brakes are an important safety feature, as they aid in controlling downhill
speed w/o excess braking, which can result in overheating and failure of the brake
shoes.
Sorry, I’m a slow typist. Cecil’s article nailed it.
Slight hijack:
I’ve noticed in recent years that all the signs I’ve seen in California that used to say “Truckers: Easy on the Jake BrakeNext 5 miles” or something to that effect, now say “Engine” brake. The word “engine” is obviously a sticker/fresh paint or something that is covering up “Jake” since it is on a slightly different color background.
Whats up with that?
Read the Mailbag column, linked above. 
(P.S.: It’s a potential Trademark violation to use the term “Jake” brake when not speaking specifically about “Jacobs Engine Brakes”)
The link supplied by *tracer[\i] explains it.
Basically, the Jacobs company doesn’t want their neame to be shorthand for “noisy trucks”.
Too late…
I used to wonder this, myself. Then last year when driving in Boston while on vacation, I heard this godawful loud “thwacka-thwacka-thwacka-thwacka” sound coming from the semi in the next lane. I exclaimed aloud to my husband, “What the hell is that?!” He said, “Engine braking.” My immediate response was, “No wonder you see all those signs forbidding it!”
Having grown up at the end of a street, that had a sand & gravel pit at the other end of it, I think they should be outlawed, removed from all trucks, and destroyed in a public ceremony.
I can’t tell you of the number of times, I had to say "Wait a minute, a truck is going by… :rolleyes: " as one kicked it’s Jake Brake on directly perpendicular, and only 30yds away from my bedroom window. My window seemed to be the spot at which EVERY truck decided, “Time to slow down for the stopsign ahead.” :mad: :mad:
Actually, I know why we need them on the big trucks, and don’t REALLY want them actually outlawed, but some consideration would have been nice.
Now I live far away from that street, and NEVER have a truck begin braking just outside my bedroom window! 
-OP : Banned because they’re trying to keep me from blowing up trucks, after I snap from “One too many” trucks slowing in front of my house.
BRRRRRRRAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA <chugg chugg of the gear shift>
-Butler
Why haven’t they ever been marketed on passenger cars? If they save brake wear and cause no additional engine wear, it would be better than downshifting to slow down.
Bah.
Anyway, I need to go Xerox some paperwork…
I’m guessing that they don’t scale down as well. A big eighteen wheeler with a trailer is going to have a lot of inertia. A small coupe with one passenger is not going to have nearly the kind of inertia, and typically can handle slowing down properly with its own brakes.
On your way back will you grab a few Kleenex for me? I have a runny nose.
Since you’re up could you bring me a Band-Aid?
I just listen to my walkman when the loud trucks go by
A Pepsi would probably make your nose feel better.
Personally, I don’t like that brand of coke.