My 91 GV 6v92 D-Troit has a transmission retarder button. and there is a retarder on the transmission as far as I can tell. The button on the dash has power but the light does not come on when I flip the switch.
How does this work?
Stump, Does it have a 6 speed Allison ? The older four speeds did not usually have retarders. Some had Exhaust brakes though.
Gary B
My 93, U300 has a 6V92 Detroit and a button that says Retarder on the dash. However that button activates my Jake Brake. I have a two position Jake. The first detent of the button kicks in 3 cylinders of the Jake and when I fully depress the button all 6 cylinders of the Jake are activated. I typically leave my button pushed all of the way in all of the time. The Jake is only activated when you take all pressure off of the accelerator pedal and will not engage when the Cruise Control is active. I'm betting you have he same setup as my coach.
The Jake Brake is not as powerful as the transmission retarder but now that I have one I like it just fine. The Jake will not heat up the transmission on long down hill runs and is not so effective at braking the coach that I neglect using my service brakes. I have read that some members use their transmission retarders so frequently and effectively that components of their service brakes become corroded and damaged from lack of use.
The light bulb in the switch is a "seed" type and can be replaced but I'm afraid of breaking the switch trying to get it out of the dash so I choose to go without a light. Mine light does work some of the time however.
Stump,
Check the date of mfg on the data plate below the driver's window. Late 1991s will have 1992 specs. A 1991 U300 should have a MTB648 transmission with a retarder rather than a Jake. The late 1991 had a HT746 with a Jake. Several ways to tell. Open the engine compartment and look at the valve covers. If they say "Detroit Diesel" in big letters, it's a '91 without Jake. Look under and if it looks like the transmission here: http://www.utxchange.com/pdfs/MechanicsTips/MT1997EN.pdf (http://www.utxchange.com/pdfs/MechanicsTips/MT1997EN.pdf)
it has a transmission retarder. The horsepower is 300 compared to 350 in the 1992. As I recall, the 648 is not rated for the additional 50 HP.
Think the 1991 had a rear radiator rather than the side radiator on the later models.
If you have a Jake, you can just open the driver's window and with the switch turned on and your foot off the accelerator, you can hear the exhaust note change. Not loud like a lot of big trucks but a nice, satisfying purr.
Pierce
I have power everywere. On the relay there is a blue wire and the schematic says goes to pin 213 on the ATEC interface when I ground this the relay closes and when pushing the brake pedal the light on the switch comes on release brake light goes off.
The schematic says see allison drawing AS00-138. Now i'm looking for that.
My 1991 U300 has a retarder with the toggle switch. Leave the toggle switch on all the time unless you have a specific reason to turn the retarder off. An example of an excellent reason to turn it off would be if you're driving on ice. When you step on the brake pedal the switch should light up red indicating the retarder is applying braking pressure. You'll feel it slowing the coach down suddenly if you hold your foot on the brake pedal long enough. If you let off the brake pedal a little bit the retarder will reduce braking pressure. It's similar to what an electric trailer brake controller feels like if you know what I mean. Even if the bulb in the switch is burned out and you don't know what the retarder feels like, you can still tell it's working by watching your transmission temperature gauge climb when you step on the brake pedal. Don't let your transmission temperature go over 250 except in an emergency stopping situation. If it does get too hot check your transmission fluid and change it if it's discolored... A very small price to pay for saving your life in an emergency. :) ...You're gonna love the retarder, and the rest of the coach too. You bought exactly the finest coach ever built, in every detail, right down to the best model and best year. You'll learn why as you go along.
My light only comes on when the retarder is engaged, either by me using the joystick or by applying the brakes.
I think you will have to be moving (and maybe more than about 30) before the retarder engages and the light comes on.
HTH
Thanks ya'll,I checked it out today on my way to get hew tires and it's working great!
I'm loving this thing,
So which is it, a transmission retarder or a Jake Brake?
It is a transmission retarder.