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Transmission retarder & Jake Brakes
Folks, I looked at 2 coaches today. One was a 99 Liberty with the transmission retarder..The other was a 96 Royale with the Jake brake. I’m familiar with the Jake as that is on my Wanderlodge. Are there any heating issues on the transmission fluid with the 6 position retarder? Thanks
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67 Replies
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Yes.
But there are two things to keep in mind. If you plan your mountain descents and are in the correct gear at the right speeds you literally can control the retarder temperature easily, while never touching the brakes.
If you choose to place the control of your coach on the retarder it will do a great job and if somehow you run the temperature up to its limit of 300 degrees it will reduce the retarder effectiveness until the temps are within the allowable range.
I have had both and by far the retarder is more effective.
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Thanks Jon, I appreciate the reply. I had the transmssion retarder in another Wanderlodge and had to really pay attention to the temperature elevation.
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Ernie I have had both and like the trans retarder better all pulling a trailer never once has it got hot using the trans retarder never over 230
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I like my retarder very much. If temps rise, gear down to increase coolant flow and slow down works for me
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Part of the problem is the location of the temperature sensor, the size of the intercooler, and the driver.
I arbitrarily chose to use 230 as my upper transmission temperature limit and by planning descents of grades as steep as 8% I could go down them in 4th, with a target speed of 50, moving the stalk between the 2nd and 3rd position as required to stay within my speed range and never exceed 230.
I always drove with the master switch on so I always had help from the retarder in panic stops if necessary, and in those situations I wasn’t monitoring the temperature, nor did I care.
The sensor on my XL was at the retarder output, just ahead of the intercooler and at the highest temperature. The intercooler was more than adequate because as soon as I wasn’t using the retarder the transmission temp went down to the engine coolant temp quickly. I never had the retarder drive the engine temp up.
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Moving 50,000+ pounds up and down a mountain, I have used this parameter: whichever gear you did on the ascent, use the same on descent. This has worked many times and has resulted in no soiled clothing.
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You are right on Ernie , I do the same, gear you go up in come down in
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So Peter,
Those with Jake Brakes, can you control your descent gear, since it seems like my Jake Brake engages automatically, and I really don’t control the actually gear for the tranmission as I would in “downshifting” in a car or manual transmission.
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Tim you can push the arrows to down shift or up shift , try it push D then push the down arrow it should go down as many times you push the arrow button until in first gear drive it you will see how fast it will go then push arrow for up shift fourth should go up to about 50 mph and if you down shift too soon for the gear it will not shift until it is safe I always go down a big hill in fourth if it gets to gaining ground I push on brake pedal firm and slow down then let off brake you can over speed the gear going down hill so don’t let it gain over 2100 rpm I use 2000 rpm if it does I gear down after I slow down then down one gear more
Most of the time they are set up so when on cruise control or your foot comes of the throttle the jake will come on in sixth, then down shift from there when safe , you can get allison to change that setting easy so when you let your foot of the throttle it will hunt to go to fifth gear or fourth and so on down to I think second , I have try them all and I liked sixth the best , but fifth gear was ok to until you use cruise and it tries to shift down to fifth on a little rolling hill and when the cruise goes back on it shifts again back to sixth , so I liked it to come on in sixth and then down from there with the brakes or the jake slowing it down, I tried it so when your foot came of the throttle or you touched the brake in cruise it would try and go to fourth gear when safe but I was driving in the hills at about 55 and if I touched the brake or let the coach slow down with the jake or pushed the decelerate button it would get to about 50 then shift from sixth down to fourth I did not like it , I had it set back to sixth. That was many many years ago I am smarter now!!!!!
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Tim,
We just got our coach back from engine and transmission service. I had them reprogram the target gear to second from sixth when the Jake is engaged. This way you don’t have to manually downshift; the transmission will automatically select the lowest gear that won’t overspeed the engine. -
Per I doubt you will like that because when on cruise and you are doing about 55 and and a little hill comes up and it drops a little speed about 50 mph it will shift to fourth and be at high rpm not over but high then when the cruise kicks back on it will shift back to sixth, It won’t be bad if you are not on cruise and you let you foot off the throttle and want to slow right down on a off ramp or a quick stop , but when on cruise it will be up and down with the cruise on , depends on the speed you are going and the road but if you are in the 45 to 55 mph it won’t be smooth it keeps trying to go to fourth then back to sixth
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Per,
Why on earth would you do that rather than just manually downshift as needed? I think you’re going to have some hard shifts and the potential to overspend your engine. I realize they tell you the engine/tranny won’t let an over speed happen, but on the right hill, it’s going to exceed your safe RPM momentarily not to mention the stress on the drive gear.
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I agree Tom it’s bad news it will over speed the engine if going down hill for a bit then it might shift up if it’s on cruise or you push down on the throttle ,but it’s not for me . I always liked sixth to be the gear then I could do it l
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Thanks again … It was a rookie question but I’m glad to know it now…
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Tom,
Why on earth would you want to downshift manually when you have an automatic transmission? You just keep an eye on the RPMs, and the downshifts are just not that hard. I have every confidence in the Prevost drivetrain being able to handle the downshifts.
Peter,
I’m not sure I understand. I don’t turn the Jake on until I need it, and don’t usually leave it on with the cruise engaged. Any downhill in a heavy coach is just a matter of managing your speed
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