With a manual trans you already have a second brake, just down shift watching your tach so you don't over rev your engine. Assuming your trailer brakes work good, your manual trans is back up or often in addition to on long downhill stretches  A jake or exhaust brake really is not needed with manual trans, usually used with auto trans as auto trans has no holdback on down hill other than holding unit in a lower gear, which can be damaging to a trans if not careful.

  Say What !!?

Saddleup ... In a comparison between a gasoline engine and a diesel ... The diesel has little engine braking with out some sort of restrictor.  Here's an explanation copied from the net.

A gas engine has more engine braking than a comparable displacement diesel because at low throttle levels a gas engine is working against a closed throttle plate. A diesel has a wide open intake manifold without a throttle plate.

Think of a diesel piston and cylinder like an air cylinder. If you press the piston up to near TDC with the valves closed, it takes a lot of pressure, right? But guess what, after rotating beyond TDC all that compressed air now pushes down on the piston to accelerate it to BDC.

A gas engine will generate about 25" of vacuum with the throttle closed, so when the piston comes up to TDC, very little pressure is there to push the piston on the down stroke. Then, when it wants to pull in a fresh charge, the engine has to pull against the vacuum. All this consumes energy and creates what is termed "compression braking".

Of course, a diesel does produce some compression braking due to mechanical losses and heat generation, but a similar displacement gas engine will always generate more "compression" braking.

As I said a diesel will provide some braking using a manual trans, down shifting using your tach....... I still stand by it from 40 years of towing, I do appreciate your quotes from the net, however remember boys..........  they are selling jake and compression brakes, its the net they will tell you what they want you to hear...

However, I respect your take on it... please respect mine..

tks

It is not a matter of respecting opinion or "take"

Logical explanations stand on their own.  Trot-on can downshift a gasoline engine car and his diesel engine truck to experience inherent engine braking between the two.

Exhaust brake not needed with a manual trans????     Sorry but where I tow I use the exhaust brake every time I slow down or stop.  Apparently you have never decended a 6-7 or 8% grade with 17.000# of trailer behind you.    I am on my 5th diesel manual pickup for towing and every one of them has had a exhaust brake, my service brakes last well over 100,000 miles and the trailer brakes at least that long. 

I have used the PacBrake on all of the trucks.  The current PRXB is considered a "State of the art" with its exhaust bypass valve.   The fact that  PacBrake stands behind the product is the biggest thing for me as a mechanic.   The brake will help your truck to slow the load so you can downshift easier without overreving the engine.  It usually takes a bit of towing to get familiar with using the brake in the most effective way.  After you have a ex brake you will wonder how you ever got along without one.