Retard switch

[Stephen_W]

My neighbor just bought a new 2013 Fleetwood Expedition 40X with a 360HP Cummings and Allison transmission on a Freightliner chassis. We were talking about the "Retard" button and he said the owners manual is vague about when to use it going down grades. Does anyone here have the same driveline? He'd like some do's & don'ts and what gear the tranny needs to be in when using the retard button vs grade, how it works, etc. Thanks in advance for the responses, just trying to help a friend out before he heads to the mountains.

[noteven]

My DW thinks I must have a retard switch that gets bumped "on" some days ...:E

[We_Cant_Wait]

I mine turned on ONLY when I want to use it to help manage speeds going down a steep hill. A lot of towns have laws/ordinances against the use of Jake Brakes within the city limits. I've never seen the NEED to use it at speed less then 50MPH unless on a long steep grade.

[et2]

wolfe10 wrote:
Getting lots of contradictory information here.

If this is on a Freightliner chassis, here is the build sheet for the 2013 Fleetwood Expedition:

http://freightlinerchassis.com/images/pdf/Fleetwood/Expedition%202013.pdf

It states "Engine braking: VGT"

It says nothing about a retarder (transmission number would end with capital "R").

If on some other chassis, please let us know what it is so we can get the facts.

Page 4-11 2013 Expedition.It is the same as the dash in mine. The switch is marked retarder. Not exhaust brake.I've had numerous exhaust brakes in the past. This doesn't have one.

To edit: It's probably an option as there is a sketch showing an exhaust brake switch as well. The OP referred to it as a retarder, so I would indicate it as being a retarder as mine is.

http://fleetwoodrv.com/partsandservice/manuals/2013_DISC_EXPD_EXCR_PROV.pdf

[wolfe10]

Getting lots of contradictory information here.

If this is on a Freightliner chassis, here is the build sheet for the 2013 Fleetwood Expedition:

http://freightlinerchassis.com/images/pdf/Fleetwood/Expedition%202013.pdf

It states "Engine braking: VGT"

It says nothing about a retarder (transmission number would end with capital "R").

If on some other chassis, please let us know what it is so we can get the facts.

[et2]

randallb wrote:
It is obvious that a transmission retarder is seriously misunderstood. It is a primitive torque converter attached internally to the output shaft. When activated the transmission redirects oil into a series of enclosed vanes (thus the primitive converter analogy) and as these vanes shear the oil it acts like a brake and applies retardation to the output shaft. The ones equipped with a joy stick allow you to set the retarder's braking level, by increasing the amount of oil pumped in to the retarder, much like setting up a trailer brake controller. The ones equipped with an activation button or switch usually rely on the program in the ECM to control oil volume and pressure in to the retarder. They are a very effective way of controlling downhill speed but the "weakness" is the amount of heat absorbed by the trans fluid which is then dissipated through the engine cooling system. Why can this system be used on a diesel? A diesel cooling system is designed to move a large amount of heat which is generated when large amounts of fuel are dumped in to the engine under high load conditions. Conversely, when coasting downhill absolutely no heat is produced and dumping the retarder heat in to the cooling system works. A diesel with an open thermostat will bottom out any temperature gauge when going downhill. The downshift can be manual or controlled by the ECM but the retarder is the primary downhill speed controller. You can, with sufficient retarder size and oil volumes, control downhill speed while remaining in high gear. The only restriction to the size of the retarder is the case size of the transmission.
Randy

Of course your assuming your just coasting downhill. If your ascending hills and descending in high ambient temps one could possibly overheat the cooling system or push it close to the engines cooling limit. Adding the heat build up from the retarder is what is described to monitor as mentioned by the people who built the system.

Telling someone to just use high gear and the retarder in such a situation could get them into a whole heap of trouble real fast. IMHO using the correct gear ( usually the same as you went up in) will help keep the engine temps and trans temps in a safe zone. Shutting off the retarder in a high heat scenario and selecting proper gearing is what's suggested by the manufacturer

[randallb]

.

[et2]

Here is another neat feature your neighbor can do in the coach after a trip. Check the trans fluid level from the Allison control pad. It would be smart for him to get, find or download the manual.


To access oil level information (refer to Figure 13):
1. Park the vehicle on a level surface, shift to N (Neutral), and apply the parking brake.
2. Pushbutton shift selector—simultaneously press the ? (Up) and ? (Down) Arrow buttons once.
3. Lever shift selector—press the DISPLAY MODE/DIAGNOSTIC button one time.
The fluid level check may be delayed until the following conditions have been met:
• The fluid temperature is above 60°C (140°F) and below 104°C (220°F).
• The transmission is in N (Neutral).
• The engine is at idle.
• The transmission output shaft is stopped.
• The vehicle has been stationary for approximately two minutes to allow the fluid to settle.
A delayed fluid level check is indicated by a “—” in each of the digital displays (SELECT and MONITOR) followed by a numerical countdown. The countdown, from 8 to 1, indicates the time remaining in the two minute waiting period.
A numerical display (alphabetical for MY08) is a fault code and indicates conditions are not proper to receive the fluid level information, or that there is a system malfunction.
• Correct Fluid Level—“o, L” is displayed (represents Fluid (Oil) Level Check Mode), followed by “o, K”. The “o, K” display indicates the fluid is within the correct fluid level zone. The sensor display and the transmission dipstick may not agree exactly because the oil level sensor compensates for fluid temperature.
• Low Fluid Level—“o, L” is displayed (represents Fluid (Oil) Level Check Mode) and the number of quarts the transmission fluid is low. Example: “2” indicates 2 additional quarts will bring the fluid level within the middle of the “o, K” zone.
• High Fluid Level—“o, L” is displayed (represents Fluid (Oil) Level Check Mode), followed by “HI” (represents High Oil Level) and the number of quarts the transmission is overfilled. Example: “1” indicates 1 quart of fluid above the full transmission level.
• Invalid For Display—“o, L” (represents Fluid (Oil) Level Check Mode), followed by “—” and a numerical display (alphabetical for MY08 and newer). The numerical display (alphabetical for MY08 and newer) is a fault code and indicates conditions are not proper to receive the fluid level information, or there is a system malfunction. The fault codes that may be encountered are shown in Table 3, Fluid Level Fault Codes, below.

[et2]

CAUTION: Observe the following cautions when driving a vehicle equipped with a retarder:
• THE RETARDER WORKS ONLY WHEN THE ENGINE IS AT CLOSED THROTTLE.
• OBSERVE TRANSMISSION AND ENGINE TEMPERATURE LIMITS AT ALL TIMES. Select the lowest possible transmission range to increase the cooling system capacity and total retardation available.
• In the event of OVERHEATING, DECREASE THE USE OF THE RETARDER; USE THE SERVICE BRAKES TO SLOW THE VEHICLE.
• OBSERVE THE RETARDER/SUMP “OVERTEMP” LIGHT to be sure it responds properly to retarder temperature.
NOTE: The transmission retarder is configured as either a low, medium, or high capacity retarder. Retarder capacity configuration is determined by the vehicle OEM. Allison Transmission requires vehicle OEM approval before a service outlet increases the retarder capacity at customer request. This vehicle qualification is to make sure existing vehicle drivelines, differentials, axles, and cooling system are designed for the additional retarder torque generated in a higher capacity retarder configuration. Additionally, WTEC III Controls will require a retarder charging spring change and possibly an ECU re-calibration as well. Allison 4th Generation retarder requires only a TCM re-calibration with the OEM approval for a higher capacity retarder. Cost incurred to modify retarder capacity is the responsibility of the customer.
NOTE: Allison 4th Generation and WTEC III retarder activation, response, and driver requested retarder amount are characteristically similar but not identical. Refer to the Types of Retarder Control Table in this section to see how retarder modulation request (RMR) can be changed if desired to increase or decrease retarder percentage apply. These controls are also OEM determined and installed. Cost incurred to modify a RMR is the responsibility of the customer.
NOTE: Transmission fluid level must be set correctly for highest retarder effectiveness. As much as 2 liters (2 quarts) too high or too low can reduce retarder effectiveness and increase transmission temperature.

[et2]

wolfe10 wrote:

oldmattb wrote:
Aren't we talking about a transmission retarder and not an exhaust brake?

Matt B

NOPE. Not on the OP's coach.

To the OP. I have exactly the same model and year in your post. It's not a "exhaust brake". It's a transmission retarder. Just set whatever gear you need to head down the hill and engage the retarder switch. If you need to slow down more then take your foot off the gas, the retarder will take over and downshift the trans to slow you down.Giving it gas will release the retarder until you remove your foot from the gas again. If you keep building speed drop another gear using the selector pad.

I use the economy mode on the Allison selection pad while on the freeway. It will give you better fuel economy ( but less performance). It would probably be a good idea to turn that off when going up and down the hills as the shift pattern & power would be more desirable.

DO REMEMBER TO SHUT IT OFF IF YOUR NOT USING IT. In high temps it will add stress to your transmission and build up the trans temperature. It's all spelled out in the owners information packet that came with the motor home. Perhaps your friend needs to look a little better. If not, it can be downloaded off the web. I have it on my ipad for easy reference if I need it. I always have it with me up front in the cab area when traveling.

Hope that helps

[ScottG]

BTW, you have a CUMMINS - no G.

[wolfe10]

oldmattb wrote:
Aren't we talking about a transmission retarder and not an exhaust brake?

Matt B

NOPE. Not on the OP's coach.

[oldmattb]

http://www.beamalarm.com/Documents/transmission_retarder_operation.html

[oldmattb]

Aren't we talking about a transmission retarder and not an exhaust brake?

Right-on about the Isuzu NPR. We had a NPR-based motorhome, and the exhaust brake would drag it to a stop on a 15 percent grade, with no brakes. Just amazing.

Matt B

[PAThwacker]

I had a 1986 Isuzu NPR 4 cyl stick. Exhaust brake equipped and never needed to use the brakes.

[dakdave]

I turn mine on ,leave trans in drive,it downshifts trans to slow down if rpms low enough to overspeed engine.Is not an exhaust brake or a jake brake,but they work great.My understanding is they use a combo of trans,engine,vgt turbo.
Turn it on and let ecm operate on its own.