Retard switch

wolfe10 wrote:
To OP: Please call your chassis maker with your VIN and ask exactly what you have. Freightliner 800 385-4357.

As an alternative, call Allison with your transmission serial number:800 252 5283


With that Freightliner chassis, I have NEVER seen a transmission retarder, NEVER.

I showed you in the owners manual. I know what a "exhaust brake" is. This is not one. The switch specifically says "retarder". Do you own this exact model? Maybe Fleetwood put the wrong switch in two MH's? I doubt it.

Please see page 4-11 thru 4-14. There are two configurations. One showing a retarder switch ( as in the model we are referencing) and one with the exhaust brake.

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

We Cant Wait wrote:
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.

It's not a Jake brake or a exhaust brake, so the ordinance wouldn't apply in this case. The whaamp clapping noise isn't associated with the transmission retarder. I use mine on exit ramps or pulling into rest stops, also when coming to a quick stop. The extra braking it provides is great for slowing down, sometimes with very little brake use.

To OP: Please call your chassis maker with your VIN and ask exactly what you have. Freightliner 800 385-4357.

As an alternative, call Allison with your transmission serial number:800 252 5283


With that Freightliner chassis, I have NEVER seen a transmission retarder, NEVER.

It states "Engine braking: VGT"

VGT stands for Variable Geometry Turbo- that is the retarder that you have in your MH. It is similar to an exhaust brake in that it affects exhaust flow to slow the vehicle down. The vanes reverse or aperture closes (depends on engine manufacturer) to create back pressure with much the same effect as an exhaust brake.

http://cumminsengines.com/vgt-turbocharger


http://cumminsengines.com/uploads/docs/4971282.pdf

Steve

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

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.

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

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.

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

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