| Author | Message | ||
| Craig MC7 Rating: N/A |
What is the difference in operation of an auto with or without a retarder. What do you notice on a downhill in each case? | ||
| Kevin Allen, Nebus (91flyer)
Rating: N/A |
The retarder slows you down, kindof like a jake... but from what I've read, you really have to watch your temps, as it will quickly and easily overheat your transmission if it's overused. My new bus has a retarder, but since I haven't driven it yet... I can't describe how well it works, or how it feels... the other guys here can tell you that though.  -Kevin | ||
| FAST FRED Rating: N/A |
Had a Wonderodge with a retarder , built into the Allison. Its merly the torque converter to He**. Half a torque converter spins on the output shaft , the facing half IS the housing . When a simple valve is opened presurized oil fills the chamber , the spinning torus ring pumps oil that just gets hot , eating energy. The Ford 391 Truck engine had a large enough radiator to get the RV up the hill ., and with no engine cooling loads was of enough size to cool the tranny fluid going down hill. With less cooling capacity in the tranny circuits , I'm told that some caution is required out west while descending. On East coast tiny speed bump like hilly spots the Overheat light for the tranny fluid never came on. There QUIET and add only one small valve and a temp sensor to the tranny , so have no maint issues like Jake's. Worked fine, FAST FRED | ||
| Don/TX
Rating: N/A |
I rode directly behind the driver on an MCI Renaissance with a retarder. It also had a gradulated control on the drivers left console. In showing it off to me the driver showed me how he could even use it as total braking. Watching as he never moved his right foot to the brake, we would come up to a stop light or sign, stopping where he wanted. I also watched the tranny temp, you could see a noticeable heat up in just a normal stop,and down hills it heated things up in a big hurry. This was in KS, MO, and AR hills. | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
What are the maintenance issues with Jake's? Since the majority of the board members are doing a complete conversion, servicing or maintaining Jakes should be a breeze. After initial adjustment, I can not think of anything that should cause problems. Even the valve clearance has several thousants of leeway, so it should not be a problem. Richard | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
My bird does not have a retarder, I've never felt like I've needed ones, I've pulled all the biggest hills in the west, fully loaded. I'm careful about downhils though, I never go faster than the trucks. Gary | ||
| BrianMCI Rating: N/A |
Very often when Fred makes a declaration you have to be very careful in gleaning the proper information from it. In this case, Fred mentions that automatic trany retarders have no maintenance issues. In this he is dead wrong. I'd certainly have maintenance concerns regarding the tranny fluid, I would probably reduce the scheduled maintenace intervals on the transmission by half, and at that I'd be checking the condition of the tranny fluid constantly. Heat is the #1 destroyer of transmissions and retarders add tons of heat. Exessive heat can quickly degrade the quality of the tranny fluid. IMHO most transmissions are not properly cooled to begin with, adding a cooler to any tranny will extend it's life, and if I were running a retarder I'd CERTAINLY want to be sure that there was additional tranny cooling added over a non-retarder application. Adding a retarder to a component that aready has problems with heat will shorten it's life-span... add to that the additional stresses involved in the operation of the retarder and, simply put, your transmission will not last as long. BUT making sure your tranny fluid is in top condition with the addition of adequate cooling will help significantly and at least reduce the detrimental effects of a retarder. Brian | ||
| FAST FRED Rating: N/A |
I guess I should have said, Properly Engineered Factory installed retarders in auto trannies built for Skool bus service are seamless. YES, anytime one ruins the tranny fluid by overheating it , it should be changed out & the tranny flushed. However the safty light on BB comes on at 275F , not a great temp to operate fluid going up hill , but as it never lit , the temp was never reached just retarding downhill. For Jakes REQUIRED service ., the Jake folks put all the tune up and service info into a free booklet one simply has to ask for. By DA Book there IS a maint requirement ,but they seem fine when ignored for a long time, kinda like foundation brakes, or electric heaters. FAST FRED | ||
| Craig MC7 Rating: N/A |
Thanks. It sounds like there would be an additional driver control added to control the retarder. Interesting. Thanks for the education. | ||
| Derek (Derek_l)
Rating: N/A |
Gary; Rarely do you need the retarder *pulling* the hill, as you said, you usually use them going *downhill*. *chuckles* | ||
| FAST FRED Rating: N/A |
Most folks only need a retarder on a hill steep enough that climbing was not done in 6th. In all slushpumps the HEAT produced is far higher in indirect gears , 3 4 or 5. The tranny temp is harder to controll going up hills , as the engine which shares the same radiator is working hard. The tranny fluid can be ruined going up or down from heat but going down at least the engine is cooler. The Wanderlodge came with a "clutch pedal" that was the variable retarder controll. FAST FRED | ||
| Gary McFarland (Gearheadgary)
Rating: N/A |
Derek, You have obviously never experienced the power of a caterpillar Gary | ||
| Johnny Rating: N/A |
We have 2 small buses at work (1998 Freightliner chassis, 19K GVWR, Goshen bodies, Cummins 6BT/AT545 Allison) with retarders. The control is a "trolley handle", with 5 detents: off, & settings 1-4. It will go up to setting 2 automatically, when the brakes are used. It's a pretty good setup. I do wish for a trans temp gauge and bigger cooler, though, especially on the non-lockup AT545. | ||
| WA David (Wacoastmci)
Rating: N/A |
Our 102D has Allison HD4060R with DD Series 60. Great combo. Retarder has joystick control with 4 positions. Normal tranny temp around 200 degrees. Sensible downshifting on steep grades (like the Grapevine), coupled with retarder application and periodic braking keeps temp at around 250-260 degrees and coach speed easily under control. I am told that DD/Allison electronic controls will moderate retarder if trans temp reaches 300 degrees but have never reached that temp in actual operation over lots of steep grades. Retarder is coupled to brakes which helps slow coach even on flat ground, so leave it on in normal driving. I use synthetic transmission fluid on advice of MCI. No complaints at all about this setup. Works great. Hard to imagine something better (unless it would be jake and retarder combo) | ||
| Don/TX
Rating: N/A |
Great idea, how simple, and effective. Never thought about BOTH, has anybody seen or heard of Jakes and Retarder together on any vehicle? Should be an ideal setup. | ||
| Jack Conrad (Jackconrad)
Rating: N/A |
A couple of our fire engines have both. Our engines rarely travel far enough to really worry about overheating the transmission(we average less than a 10 minute response time). Jack | ||
| Buswarrior (Buswarrior)
Rating: N/A |
Hello retarders! More cooling is relatively simple to install. WA David, you want to be careful, the 102D were notorious for overheating the tranny fluid, due to insufficient cooling for the tranny. To maintain tranny warranty, Allison demanded that the fleets change synthetic fluid as often as engine oil until a fix was retrofitted!!! Don't expect MCI to tell you... Back to tranny cooling: Select a Hydraulic cooler sized to mount to the side engine access door of your coach. Construction equipment offer a large variety of shapes and sizes. Replace skin on the door with expanded steel screen to match your radiator screens, find a couple of surplus electric auto radiator fans, and an adjustable thermostatic control. Plumb the coolant lines direct to the new cooler from the transmission, and then through the stock cooler. No worries about over-cooling if you route the tranny juice back through the stock cooler, the engine coolant will warm it back up! Good for your total cooling strategy, you can set the auxiliary cooler to take all the heat out of the tranny fluid, relieving that duty from your engine radiators, leaving more room for engine heat, if you will. I have seen these and will be doing my own when the time comes. happy coaching! buswarrior | ||
| Macgyver (91flyer)
Rating: N/A |
Hmmm... BW, since my bus has a retarder built in... I think I'll be doing that as well. -Kevin | ||
| Henry R. Bergman, Jr. (Henryofcj)
Rating: N/A |
Or...how about the type one triple (fire engine) returning to the nameless pretty city from down south in LA land coming down the Ridge Route north at 75 mph in position 5 in the retarder and almost (but not quite) burned up the entire fire engine. Melted just about everything. Anyway...that little stunt cost the taxpayers about $15,000 for a new Allision along with hoses, a radiator, etc.. When asked (somewhat politely) by the Fire Chief just what was he thinking about... ...coming down a 6% grade with a 38,000 pound fire engine AT 75MPH!!! the Engineer just said that was how he drove his car and that he did not see any difference between the two. Anyway, he got some unpaid vacation time to reconsider. The point being that safety systems need to be more foolproof. With a Jake Brake, one just adjusts to setting to the needs, then just concentrates upon his driving. About 70% of the heat generated just goes out the exhaust pipe, the rest into the radiator and is NOT dumped into a marginal tranny cooling system. Thank you. | ||
| Tom Caffrey (Pvcces)
Rating: N/A |
Henry, the more foolproof you make these systems, the more careless that people get, which might translate to more fools on the road. I don't know if we gain or lose by making them more foolproof. Do you think we gain anything? Tom Caffrey PD4106-2576 Suncatcher | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
It would seem to me that the heat generated by a Jake would be inconsequential. There would be no fuel being burned. Other than the air being compressed and then blown out of the exhaust, I can see no other source of heat. I know that when I was on a long downgrade, using the Jakes, the engine temperature would often drop below the 180 degree thermostats. Richard | ||
| Henry R. Bergman, Jr. (Henryofcj)
Rating: N/A |
Tom and Richard both raise excellent points. Just how much are we (society collectly) supposed to protect the likes of all of us? Do we have any individual responsibility left? Hummmgh. I may have the percentages on the Jake Brake energy dispersal backwards. Been quite awhile since talking to the Jake Brake Engineers on the phone. Very nice people. Richard, yeah, sometimes with a 2-stroke Detroit, the engine still loses heat on downgrades riding the Jake. One would think thermostates would work in both directions. Oh well. Jakes forever!! | ||
| FAST FRED Rating: N/A |
"One would think thermostates would work in both directions. " The thermostat IS working , just a DD not under load can not keep it self at operating temp. That's EFFICENCY ! and also why ideling a DD is poor practice. FAST FRED | ||
| Henry R. Bergman, Jr. (Henryofcj)
Rating: N/A |
I was trying to make a little joke Fred. |