Exhaust brake operation

[Arv]

Maybe someone out there can answer a question I have. When I engage the exhaust brake the tach goes up to 2 - 2.5K and the readout on the transmission range selector goes to 2nd gear. Is this correct?

Arv
2003 Journey DL 39QD
with 330 CAT

[Arv]

Maybe someone out there can answer a question I have. When I engage the exhaust brake the tach goes up to 2 - 2.5K and the readout on the transmission range selector goes to 2nd gear. Is this correct?

Arv
2003 Journey DL 39QD
with 330 CAT

[Joe-K]

Yep!! That's how it works (Simple answer)

Now for some more detail.

The way your chassis leaves the Freightliner factory, the transmission ECU is programmed to utilze a 2nd gear preselect when the exhaust brake is activated. There are actually two things that activate the brake. The first, is having the exhaust brake switch turned on. The second is having the accelerator pedal released. You can travel with the exhaust brake switch turned on all the time, and control the braking action with your right foot on the accelerator.

When the exhaust brake activates, the transmission attempts to downshift to second gear. In most cases though, the motorhome speed is too high to permit the actually downshift to 2nd, however the display will change to read 2. This automatic preselect of 2nd gear raises the engine RPM's to the max safe level permitted by the engine/transmission computer. Simultaneous to the engine RPM increasing, a pneumatic cylinder closes a damper on the exhaust near the turbo to restrict the exhaust flow from the engine. The purpose of the engine downshifting is to bring up the engine RPM's increasing the volume of air being pumped through the engine and attempting to pass through the exhaust. The faster the engine is turning, the more effect the restriction on the exhaust flow will be.

As the motorhome continues to slow, the RPM's drop in each gear, permitting the transmisison to downshift through the gears. As the downshifting occurs, you will see the engine RPM's jump up as the next lower gear is selected by the transmission.

Once the transmission downshifts until it reaches the "preselected" 2nd gear, the motorhome slows until it reaches a programmed speed of around 10 mph, and the exhaust brake disengages automatically. You then use the foot brake to complete your stop.

There is a lot of discussion regarding the selection of 2nd gear as a preselect. The tranny can be reprogrammed to use another gear if you don't want the automatic downshift to 2, but I'd suggest using the system as is for a while to see how you like it.

2002 Winnebago Journey DL 36GD
Freightliner Chassis, Cat 330
Chevy Malibu Toad, Blue Ox Aventa II, USG Brake

[RedT]

GOOD expaination, Joe-K!! Couldn'ta dun it better myself!! <G>

Red T in Glendale, AZ -
'04 Itasca Meridian 36G
'02 Saturn Toad

[Zimectrin]

We ran a long distence (25 miles) with the engine brake 'on, traveling up and down in a hilly country, as suggested by Joe. After some time (30 min) the check engine light came on and we lost power. We pulled off the road and wondered what it would be like to have to actually use Winnebago's tow service. After about 20 min we started the engine and continued our travels with the engine brake only on when actually needed. Called a diesel mechanic and he said "running with brake switched on for long periods caused a fault in the computer. The computer d-rated the engine to protect it" I don't know if I buy the explanation, but I throw it out for comment.

Steve & Sherri
Winnebago Journey DL 39QD
"Cutie pullin Echo"
<A HREF="http://www.wunderground.com/US/UT/Spanish_Fork.html" TARGET=_blank>
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[Canuck]

Hi Steve,
Although I don't have a Winnebago, I can report that I drove 1500+ miles between January 2 and 4 this year to bring my moho home and I had the exhaust brake turned on the whole time and did not experience any problems.
Canuck

2002 Triple E Signature A3607GW
300HP Cat 3126E, 6Sp Allison

[Red]

I sure am not a diesel mechanic but we have driven many miles with the exhaust brake on, sometimes on purpose and sometimes because we simply forgot. On our previous motorhome ('99 Cheiftain)it would kick off the cruise when it engaged but on this one ('02 Ultimate) it does not so you can drive a long way and not even know it is on unless you encounter a long down grade.

[BucknJeff]

Steve,

You got some bad information. Leaving the exhaust brake switch on will not create a malfunction code. The experience you had was likely mis-diagnosed.

It is likely you experienced an engine brake actuator problem, and the loss of power, and resultant codes may be attributed to that. Stoping for a period of time to let it retract may have inadvertantly solved the issue.

If it is functioning correctly, the exhaust brake can and should be used as JOE K described above. It takes a little getting used to, but after that, its wonderful. We turn ours off in moderate "slow and go" traffic to avoid excessive downshifting.

HTH

Buck n Jeff
Murphy (boxer)
2004 Horizon 40AD
2004 Suzuki XL-7(or)
2003 BMW F650 Dakar
2002 BMW K1200RS
FMCA F287652
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The only time you should really turn the Exhaust Brake off, is on wet, icy or snow covered roads. If the brake is on, when you encounter these conditions, the rearend will meet the front real fast.
I had that experience going around DC on the 495 race track. I went sideways for about a 100 ft with the toad on the back--during rain.
Now, if the roads aren't dry, the brake is off.

This is covered very well in any MotorHome Driver's Safety Course.

If you get a chance to take one--do it, it's the best education you can get while owning a MotorHome.

Tomcat F15
"Every day is a learning experience."

[Stan Kohagen]

I have a '05 Itasca Meridian 36G. When I use the exhaust brake, taking my foot off the accelerator, the transmission almost immediately drops to 2nd. The transmission does not go through the gears, the resultant slowdown is extreme, with high rpm's, and jerking everytime I do it. Is there any way of changing this?
Stan Kohagen

[targaboat]

Stan,
If I understand your descrption correctly, things will take care of them selves by something failing. The engine is redlined at something close to the 2500 rpm area and it does not take much over speed to creat problems. So if you are going 60 and the brake applies and the tranny drops to 2nd you are going to have real problems. If so, you need to get the unit serviced imediately.

If you were exagerating, them yes the controler can be reprogrammed to almost anything you want. However, it is too expensive a unit(the engine) to risk failure. Therefore, I recommend that you have the unit checked out and if everything is to spec, leave it alone. To have this done I would suggest a CAT or Cummins facility.