Exhaust Brake on a Auto

[jrandol]

Can someone explain to me why an exhaust brake on a stock auto transmission is bad? What upgrades should be made to make an exhuast brake work well?

 

[amsoilman]

Can someone explain to me why an exhaust brake on a stock auto transmission is bad? What upgrades should be made to make an exhuast brake work well?

Well first off, you must be able to keep the (TCC) torque converter clutch in the locked condition, otherwise the exhaust brake will do no good at all due to the "slippage" between the pump and the turbine/stator of the torque converter. These are the 3 main items in the make up of the torque converter.



A torque converter is a type of "fluid coupling" if you will, which allows the engine to spin somewhat independently of the transmission. When conditions exist such as correct speed, temp, and engine RPM, the TCC will lock and the 3 main parts (pump, stator, turbine) will essentialy become as one unit, thereby making the power from the engine be directly connected to the drive train (no slippage). During "normal" decelerating, such as releasing the foot throttle, or tapping the brake will unlock the TCC, and the vehicle will essentialy "freewheel" until the vehicle comes to a stop.

An exhaust brake will do no good if the TCC is not locked, so therfore you must use some method to keep the TCC from unlocking when the throttle is released or the brakes are applied.



A side note here too: If the exhaust brake were activated with the TCC not locked, the fluid in the transmission will become overheated very fast due to the slippage inside the torque converter.



There are several methods of doing this. Some have installed a manually activated switch that will keep the TCC locked, some have installed small electronic boxes that do the same thing, only in an automatic fashion. These boxes are connected electricly to the (PCM) Power control module and will sense vehicle speed, engine speed, and throttle position to determine when to "unlock" the TCC so when the vehicle stops, the engine will not stall. Kinda like a manual transmission if you came to a stop without pushing in on the clutch.



Hope this helps.

Best regards,



Wayne

amsoilman

 

[TowPro]

What Amsiolman said, PLUS!



As you slow down with your convertor locked, be it by the box or manual switch, your trans is not pumping enough pressure to hold the clutch inside the converter locked tight enough, and it will slip some. Some now, much more later.



I looked into this. I needed the lock box, and a a kickdown thing a ma-bob. It looked like $600. 00 plus the price of the exhaust brake. I can't afford it.

 

[JohnMcIntyre]

Not in your back yard.....

Some useful links on auto transmission limitations and appropriate upgrades (including exhaust brakes) are in my sigfile. Take a look if you want, also look around, search previous threads on the TDR and make your own mind up. Be objective. Better still, if thre's another TDR member close by, take a ride to see/hear/feel the before & after difference with these mods already done... . I would offer, but I'm kind of out of your way.....

 

[GAmes]

Signature

JohnMcIntyre:-laf :-laf :-laf

 

[RADdodge]

Ditto...

on the sig - had to read it twice though.



I use the Smartcontroller and Pacbrake. Works well, unless you wash the engine and don't lube the thing. Say, anyone know the best way to unstick a Pacbrake and what lube to use? Thanks.