Exhaust Brake on Auto Trans.?

[Snellville-Dave]

Can someone explain how an exhuast brake would work on a auto transmission. Do you have to pull a lever or is it automatically engaged, when you apply pressure to the brakes.

 

[rrausch]

I can tell you how the Pacbrake works on my 1995 with a 47RH Trans. (You have a 48RE) I also have an aftermarket Performance Transmission, the ATS Stage IV, but I used the exhaust brake before I got the ATS by using a Mystery Switch.



OK... When I was running a stock trans, I would be driving along and I'd need to slow down, and I'd throw the Mystery Switch which would force the TC Clutch to stay locked. Then I would just take my foot off the go-pedal and throw the E. B. Switch. Worked great, but I was always throwing switches and every once in a while I would forget to unlock the mystery switch while coming to a stop. The truck definitely didn't like that, and would buck and shudder while the stock TC clutch was locked but slipping--Ouch!--Not Good! But that's the way it was when I was running stock.



I got the ATS Stage IV trans and the TripleLok TC Commander and things are easier. Now I set my lock-up speed with a dial on the front of the Commander. I can set the Torque Converter to lock-up anywhere between about 18 mph on up to 55 or so. There is a steep, winding mountain road, which I have to descend about once every 2 weeks with no trailer. I put the Trans in 2 and I set Lock-up for about 20 MPH and I throw the Commander Switch. I do all this while stopped

at the Stop sign before I begin the descent. Then I take off. When I reach 19 or 20 MPH the TripleLok TC automatically locks up. Then, as I descend and take the curves, the Pacbrake automatically comes on every time I take my foot off the pedal and goes off every time I push the pedal down. Pretty neat. I put the Trans in 2 on this particular stretch of road, because it is so steep and winding, I know I won't need a higher gear. On a straight hill where I am intending to slow down from 70 to zero, I would be in D and I just keep the Commander set to 20 and keep the EB switch on and just let the trans shift down through the gears locked as the EB retards speed.



Now I am not sure if the 48RE can handle an exhaust brake without modifications like a Mystery Switch or not, but somebody here knows the answer to that. Hope this helps.

 

[Bill Stockard]

Originally posted by Snellville-Dave

Can someone explain how an exhuast brake would work on a auto transmission. Do you have to pull a lever or is it automatically engaged, when you apply pressure to the brakes.

Yes, an exhaust brake will work with a 48RE. It is effective as long as the torque converter is locked. The torque converter unlocks at speeds of approximately 40-45 MPH in Overdrive and about 1800 RPM in Direct (3rd). See TDR, Issue 41, pages 50-52 for more information.



On the '03 and '04 trucks (not the '04. 5 trucks), once the On/Off switch on the dash is turned On, the engine ECM controls the operation of the exhaust brake (PacBrake and Cummins E-Brake, I don't know about the others). When you take you foot off the accelerator pedal and it returns to the idle position, the exhaust brake comes on and closes the butterfly valve. As soon as you press the accelerator pedal and it comes off the idle position the exhaust brake turns off and opens the butterfly valve.



Bill

 

[gpeddicord]

auto and ex brake

Like rrausch I had an ats 47rh with triple lock tcc and electronic box. to make a long story short, the input shaft snapped in two after 10,000 miles on the trans. ATS would not cover. They say they now have a hardened input shaft. I think ex. brakes are too much for this trans. I recently put in a nv5600 into the truck. Difficult, but well worth it. No problems with ex. brake now.

Anyone who wants 411 on nv5600 swap, just ask