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We test drove an 01 Liberty Classic Lady when we were in Florida last week, and it had the Alison 6 Speed Transmission Retarder. I just loved it.
What is better, Jake Brake, Tranny Retarder and why?
Can you guys give me the pros and cons of having one or the other, please so I can either rule out trying to find a used bus with one or the other in it?
Gary:confused:
Well, you'd never have to worry about the dreaded 'no engine brake' signs with the trans retarder.... I've always had Pac or Jacobs exhaust braking on my diesel coaches and it has worked well, plus I like the noise they make. I understand that the fluid temperatures need more monitoring with the retarder because of how it works.
Gary,
I have the retarder on the Liberty and it works fine, although you really have to pay attention to the transmission fluid temperature as it's easy to exceed 230 on some hills. You'll probably fine the concesus being the jake is better. That being said it would be pretty far down my list of considerations for the "perfect" bus.
Mike
I was temporarily brain dead and pricing a new Liberty
earlier this year. Was told all new buses come standard with retarders and a Jake would lower the price by 6 grand! I can't understand why anyone would pay an extra 6K to boil their tranny oil. Jakes have been around forever, work great and are just about bullet proof. My old used bus came w/the retarder, works ok, but I can't help feeling there's a plot involved to sell transmissions.
We had a Jake on the first coach and have a retarder on our current coach.
This is strictly an opinion so take it for what it is worth. We would never again want a coach with a retarder. Our reasons are fairly simple. The Jake does not have an adverse affect on anything. It does not raise temperatures so using it at its full setting constantly does not require anything of the driver.
The retarder seems to have more holding power. It has a broader range of retarding power than a Jake so you can select a retarding force suited for the hill, and if the retarder is on, applying the brakes also adds retarder force to assist with braking. When using brakes heavily with the retarder on will drive the temperature up rapidly.
As Mike points out, it heats up the transmission. Heat will damage the transmission fluid and the transmission, so for those who have a coach with a retarder and a transmission temperature gauge you have to monitor the temperatures. For those with newer coaches, Prevost allows you to monitor the transmission temperatures, but you have to go through some gyrations to get at that information through the Pro-Driver. Maybe Prevost feels ignorance is bliss so they eliminated the temperature gauge on the new dash.
I have no clue what a safe transmission oil temperature is because there are no limits that I can find defined anywhere. I arbitrarily use 230 degrees just because the red line for oil on my plane is 240. If someone knows what the real limit should be please post it.
This is an observation but with all the sensors and computer power now in place it seems to me that if the temperatures get too high, the computer could reduce the retarding force until temperatures return to a normal range, but the flip side of that is that Allison and Prevost will spend a lot of time in court because any time braking or retarding force is reduced it could have dire consequences.
Ditto Jon's comment.. I've had both and with a previous Foretravel running out west in the real mountains, the trans temps where a real concern with the retarder. Go with the Jake, it's bullet proof!
Retarder Operation -- How Does It Work?
The retarder is at the output of the transmission and consists of a vaned cavity and a vaned rotor which is splined to and driven by the output shaft. When the retarder is activated, fluid is directed into the retarder cavity. The interaction of the fluid with the rotating and stationary vanes causes the retarder rotor speed, and the output shaft, to decrease and slow the vehicle.
When the retarder is deactivated, the retarder cavity is evacuated.
Additional retarder information can be obtained by ordering our free Motor Home video, "Operating the Allison MH Series Transmission" (VI3424EN). Click on this link for ordering details.
Motor Home Video
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That is not a misprint, I meant retarded. I too have the retarder and I can not go anywhere unless I am up and down the hillls because of the area I live in. I have to use it constantly. I believe it was designed for flat areas. Not only can you cook the tranny oil, the tranny then will shift very hard and feels like it will jerk something loose until it has gone thru enough shifts to wash the retarder from its memory.
If I was in the process of evaluating a new to me coach purchase the retarded would not prevent me from purchasing it, but would definitely get a check on or in the minus column.
We have had similar discussions on one these forums before about this, and we have yet to come across anyone who truly understands the benefits of the retarded over the jake.
I am in agreement with Jon and Toms remarks.:cool:
That is why I am glad I joined this group, especially before I purchased a bus. The information you guys spew ( a good thing ) forth is just fantastic.
I learn so much from reading all of your posts, I just can't stand it.
Thanks again for all of the invaluable information. :)
Any of you going to be at the Tampa RV Show? Are you in your bus, or staying at a Hotel. :confused:
Peg and I are flying in Friday night the 19th, and staying at the Red Roof Inn, which I believe is next to the fairgrounds, and checking out all the bus's, Saturday and Sunday.
Call if you are in the neighboorhood. 713-252-2599 :D
Gary,
I'll take a 180 turn here.
If you find a coach you like don't make the decision to walk away from it because of the retarder.
You see how most of us feel, but it does not have to be a show stopper. First of all a retarder works. It assists in braking and it will help control speed going down hill. A Jake allows the driver to be less attentive, but to make a retarder work effectively and not overheat you as the driver has to plan ahead and that is not a bad thing. I get the best compromise by leaving it in the second position and slowing down slightly just before the steep downhill. That keeps the bus going downhill at a reasonable speed and it keeps the temperatures very low.
With a Jake you can be going fairly fast, and put it in the high setting and downshift and it will do a great job and you don't have to worry about it, but these buses are more than just retarders.
Information on the Allison Transmission and retarder can be found here by opening the PDF file.
http://www.allisontransmission.com/p...s/OM3349EN.jsp
Here are some highlights that may prove of interest. With a retarder service intervals are cut in half. If you use Dextron you need to change fluids every year or 12,000 miles instead of 25,000. Transynd is impacted similarly, but has longer oil change intervals, depending on some other factors such as flilter types.
The retarder force will be reduced if the fluid overheats. I mispoke earlier. It appears that the computer will eliminate the need to worry about temperatures.
Speaking of temperatures: they vary depending on where the temperature reading is taken. The sump oil temperature maximum is 250 degrees F. More details are available at the link above.
Instead of having to take the bus to Allison to deal with harsh shifting, it appears by using the correct inputs we can clear it so the transmission can reprogram (self teach) itself.
The file is 94 pages with lots of good information.
Same experience here. Last two buses had jake brakes... two cycle detroit 8-92 engines. Current bus has retarder... four cycle detroit. I think the jake was idiot proof as far as operation. The retarder took a few trips over the Rockies before I was comfortable with it's operation. Today, I really don't have a preference.
On my way out to Santa Fe, it was brought to my attention that I was riding my brakes and black smoke kept poping from my exhaust. Well, it was the Trans. retarder. I had left it on and any time I let my foot of the gas, it would slow the Coach down and then I would apply the gas. So, you have to be more aware of what you are doing. I was told you could raise the temp up to 290 degrees no problem. But I can not remember who at POG II told me. It is great for slowing down coming off the freeway, or having to make a rapid deceleration. I have to watch it on long down hill slopes.
My Country Coach Lexa has a 3 stage Jake and I liked that a lot also.
Finally, I really like my Liberty . Gary
RVbus01 The link did not come through for the Allison Tranny video, please send it to me again. From your information you apparently know your transmission, wow, great description of retarder action.
Gary
That entire text on the retarder plus a whole lot more is on the link on my previous post. I learned a lot when I read it because it gives some good indepth information.
While at DDA recently I was informed that the transmission temperature using the retarder can go as high as 280F to 290F but not for extended periods of time.
John
I have owned both systems and favor the retarder. It gives you much more control over braking and temps are not an issue that people make them to be. Running Transynd solves the temp question and the noise that the Jake makes shake small town tempers.
If they can number the Superbowl in Roman numerals surely we can handle them.
There is something classy about triple XXX.
A quick review:
The bus is moving at some speed and you want to slow down. There are 3 common ways to do this:
A. The service brakes convert the kinetic energy to heat into the brake hardware by friction of the pads or shoes against the discs or drums.
B. A Jake brake uses the kinetic energy to compress air, which is then "wasted" out the exhaust system. No heat is generated.
C. A transmission retarder converts the kinetic energy to heat inside the transmission. The heat must then be removed by the transmission oil cooler. The cooler is a small "radiator" mounted in front of the big radiator and the transmission fluid needs to pass through here a time or two to cool off the transmission, which will take a few minutes or more depending on the outside temperatures and heat load on the transmission.
All three methods do slow down the bus. Method A and C will eventually reach the point where the heat added by slowing is greater than the heat dissipated by airflow. For a single stop in traffic all will work well. For lots of stops in traffic all will work well for a while, but eventually A and C will begin to reach their limits. For descending a long grade eventually A and C will overheat. B will just keep on working, leaving the service brakes fresh and cool.
For these reasons I prefer the Jake Brake. Especially if you live and travel mostly in the western states, almost anywhere you go you encounter mountain roads and passes. Knowing the Jake is ready to manage downhill speeds without needing the service brakes at all times is very comforting. You can select most any downhill speed by choosing the gear and setting the Jake on high or low. It is easy, effective, and the system has been trouble free.
Then there is the issue of some towns and their signs about compression brakes. I have noticed the wording of these signs varies from place to place. Some I have seen say "Unmuffled Compression Brakes Prohibited" , or " Jake Brakes Unlawful in city limits", "Use of Engine Brakes Prohibited" or some such.
I take the approach that in any kind of emergency, I will use all the braking systems I have no matter the signs in the area. Also, since the Prevost installation IS a muffled engine brake, it is not nearly so loud as what we typically heard on logging trucks, etc in the 1970's when the Jake Brakes came into common use and many of these signs sprang up. I have never heard of anyone getting stopped or ticketed for using the Jake Brake, but I would like to know if it has happened. Anyone?
Another interesting point, on my 94 the brake taillights come on when the jake brake is working, and when you step on the service brake pedal, the red light on the dash also comes on to indicate that. So, someone behind you might think you are riding the brakes all the way down a long hill when actually you might not have touched them at all. And if you are decelerating into a town that has several speed reductions as you come to the center, while the Jake is working any local policeman will see that you are slowing down and not ignoring his speed limit on purpose. SO far I have never been stopped for that either, and wear and tear on service brakes can be minimized.
One further note, I have driven both a Series 60 Detroit bus ( mine) and a 8V92 Detroit bus. The Jake effectiveness was noticably more in the Series 60 version when the setting on both was on High.
As always, comments welcome!
Peter vS
94 Marathon XLV
IMHO The transyn may have helped the temps some, but not enough for the difference in the price. The temps have concerned me enough that I am on my second dose. I don't know that I will use it again although I have had one so called mechanic tell me - once you use it, you must stay with it. I have been BSed before. Any body else heard that?
Peter,
Marathon must have changed the jake/brake light in the later years. Mine does not operate the brake light and works with cruise control as well. ;)
Tom, my brakes lights come on with the jakes, at least the light on the trailer brake controller comes on, so I assume the brake lights are on!
Thanks for the further info. My bus has the DDEC II system, and it is not sophisticated enough to allow user programming of the Jake Brake with cruise control, but the later DDEC III and IV are. You just hook up the reader box and set on or off with cruise control as you prefer.Quote:
Originally Posted by truk4u
That points out the one deficiency I see with my set up, while toolig down the interstate and you start descending a little, well, the bus just picks up speed like a ball bearing rolling down a ski jump and before you know it you are doing 85. So, you have to stay alert and kill the cruise on a big downhill. That can be a pain if you are in a place like Interstate 5 in southern Oregon where there are a long series of 10 miles up hill followed by 10 miles downhill. But, clearly, Prevost addressed that on the later busses. Not enough reason to convince me to trade up though.
Thanks again guys for all the important information about Jakes and Retarders. I can honestly say I am only half as confused as I was half a week ago. (just kidding)
Thanks for the info.
Gary
Quote:
Originally Posted by Petervs
Peter: Most of the posts I have read are pro jake. If the jake system is preferred by most, why did Prevost go the retarder route on new shells?
According to the Prevost website, both the Jake brake and the retarder are options on their shells. You can get them either way. I suspect the Jake brake costs more as a factory option.Quote:
Originally Posted by Stelan73
http://www.prevostcar.com/cgi-bin/pa...tab=powertrain
I personally also prefer the Jake brake. Might be nice to have both! The only downside would be cost.
Peter vS
94 Marathon XLV
I too question why a retarder would be used in place of a Jake.
It is abundantly clear by the maintenance schedule that Allison considers a retarder equipped transmission so hard on the fluids that change intervals are cut in half.
There is a real plus for the Jake. When our granson was little when he travelled with us and we went through tunnels he loved hearing the sound of the Jake. He thought that was great.
See my earlier post. The retarder costs more, much more.
And Peter, The Jake on my Peterbilt is hooked to the cruise. If it can't hold the set cruise speed on a down grade the 1st stage comes on, if that doesn't do the trick the second stage and then the 3rd if needed. All automatically, with no driver input. Towns put up no Jake signs cause Grandma got tired of being blasted out of the bed at 2 AM by "chicken trucks" with straight pipes. My truck has 8" pipes with no mufflers but I've never had a problem cause I know when to behave. :cool: Jacobs Engine Brakes have been around for billyuns and billyuns of miles and work, period. I'm telling you, this is all a plot cooked up by Allison to sell trannys.
Sure, I agree, but I bet your Peterbuilt is newer than my 1994 with a DDEC II. The later ones do it your way and that would be a great feature to have. But like I said, I do not think I will change coaches for just that.Quote:
Originally Posted by dreadnought
Peter VS
It seems clear we would like to have a Jake instead of a retarder, but there is a downside to the Jake that nobody has mentioned yet. A Jake works best at higher RPM.
One thing I have noticed with the retarder is that when it is on and I hit the brakes the retarder aids in stopping power to a noticeable degree. With the Jake, when we got down below about 20 it dropped out and while it wasn't like the coach accelerated, there was a noticeable loss of stopping assistance.
I guess if it could be done Perter's idea of having both would be the ideal.
I really don't know what I am talking about (as usual) so bear that in mind.
However, our Angola had a retarder which was almost useless. That bus just did NOT want to stop. Witness the knuckle-marks on the steering column and my footprint on the brake pedal!
The Vogue had a Jake Brake on it and it sounded kinda cool (now we are Series 60 land), but I didn't see any big difference in stopping power with it.
Our new camper has kind of a neat deal. On the right hand side of the steering column there is a lever with a 4-position adjustable retarder. I was goofing around with it the last few days and as the tranny downshifts and you change the range of effect on the retarder, you slow down mighty quick.
I wasn't looking at the temperatures as I try to watch the road, mostly.
So that's my 2 cents worth.
This may be a rather difficult concept for a postal worker to grasp, but since he is alone and presumably desirous of avoiding trouble, and with the lady of the house tending to the welfare of New England, maybe he might want to spend spare time with a good book, like the owner's manual.
That unknown device to the right of the steering column is not the RH turn signal switch, but a supplement to your braking power. Since you may be driving that rig in close proximity to mine, please read what neat things like that thing does. It just may keep you from bumping into me.
Jon:
Thanks for the good idea.
However, I don't see very well, so the manual is a problem.
I use the 'Audio Parking Method.'
When you hear it crash, step on the brake. That's the one left of the GO pedal, right?
Whoa......That's all I say and it stops. Whoops, that is one of Deb ponies. I don't know how to stop the bus. I haven't gotten that far in training.
They told me that was why there are those little rubber bumpers on the Prevost Car Chassis now, for supplimental braking while operating or parking close to other vehicles.
I am still on the fence with my Trans. Retarder. I was not using it correctly to begin with, and then when i knew more about it and the Heat issue , I became more frugel.
Troy at Liberty said I would really enjoy having the Retarder, and I can say it works great on off Ramps, Stop Signs, and Stop and Go Traffic, and emergency stops.
On down grades, I brake to about 55 or 50 MPH and then apply the Trans Retarder to the 1st or 2nd position. I then cruise until the speed exceeds 60 to 62 MPH , then I brake again and start the process over agan.
I leave it off most of the time except on grades.
The temperature climbs to 290 on long downhill grades.
Gary,
When we first got ours I was reluctant to really engage it because I could see the transmission temperature gauge racing upward.
But....I think I have a good compromise the way I use it now. First I leave the switch on, but do not put the lever in any of the "on" positions. What this does for me is it brings the retarder into play if I have to do any braking.
When I encounter hills and want the retarder to help hold me back I put the lever in the second position. That seems close to the help I got from the Jake on our first coach, and unless I get on the brakes temperatures range up to about 210 to 220. If the hills require braking, I just watch the gauge and try to limit it to 230. That is just my limit because I know high oil temps are hard on the transmission and the oil. Allison proves this with their reduced oil change intervals when a retarder is used.
BTW, I do not wait until I need the retarder. In hilly country I leave it in the second position as soon as I see I will need it and it manages temps nicely. It also downshifts by itself to make the retarder more effective.
The only thing besides temps I dislike is the brakes lights come on and that must drive anyone following me nuts.
The brake lights coming on when the retarder slows the bus down, seems like the proper thing to do, I mean the guys behind you got to know your slowing that animal down?Quote:
Originally Posted by Jon Wehrenberg
You wouldn't want anybody running up behind you and kissing your rear end, cause they didn't know you were slowing down.:D
Thanks Jon, and everyone else for the information on the Retarder, and Jake brake.
I can honestly say now, when we find the right bus, it won't sway me one way or the other if it has the Retarder or not, but I still kind of like the Retarder idea over the Jake. :cool:
Gary S.
The brake lights are annoying at night to those following. With the retarder on simply lifting your foot from the accelerator with the retarder on lights the lights, and even with them on you may actually be accelerating down the hill.
Day or night with them constantly coming on when the retarder is engaging (cruise control on or off) eventually a vehicle following treats them as meaningless and when you really have to get on the brakes what will alert those drivers other than the brake lights that have previously been meaningless?
Thanks Jon, now I understand.