Retarder Settings/Allison Transmission

While I was at Prevost Car in Jacksonville last week I mentioned to John Kincaid the service manager that when I am running down the road or worse running down long grades and take my foot off of the gas pedal I do not feel the full affects of the engine retarder in either position one or two until I am below certain speeds but certainly not at highway speeds in six gear.

John said that my Allison was set at a factory default setting for six gear and that he would make the change in a few minutes with his computer. He did it in about 5 minutes time and set the default to 4th gear, what a difference now.

When I take my foot off the gas it actually does something and really helps me stay off the brake pedal in occasions when our friendly truckers (not picking on Truckers all future Nascar drivers qualify) decide to turn their rigs into NASCAR's and pull out from nowhere to get around slower cars in their lanes.

What I like most is that I can either allow the full force of the retarder to kick in, use the 1st setting or simply turn it off. I cannot wait until I get out West as I was finding myself using too much braking action to get the bus down to speeds where the retarder could actually work efficiently.

I am sure this is old news for you pros but it was a cheap date for me and a great solution to a old problem.

There are no free lunches. Heat is the enemy of all things mechanical.

Monitor the transmission temp and do your best to keep it as cool as possible. At best that extra heat developed by the retarder is just cooking your fluid (which is why just the simple fact that towing a car is treated by Allison in the maintenance shedule as severe duty and cuts the maintenance interval time in half).

The faster you slow down using the retarder only the greater the temperature developed. Mine drops a single gear which is excellent and on steeper declines I manage temps by selecting speeds and gear manually, along with retarder selector switch settings. My target maximum temp is 230. For no other reason than I am anal.

I had been warned about this as well. My plan is to use the 2nd detent setting in heavy close in traffic at highway speeds or when descending steep grades put otherwise use the 1st setting or turn it off as I do in towns and neighborhood driving to avoid noise.

I did change my transmission fluid and filters over to Transynd last week and have seen a noticeable difference in temps already.

I also replaced my Detroit with synthetic oil and have seen a drop in engine temps. Prevost said it was best to wait until I had at least 40K on the engine before changing over to synthetic.

Bruce, does your Marathon have an actual Transmission Retarder or a Jake Brake?

The way you were mentioning you could use stage 1 or stage 2 it sounded like you were talking about what I have which is a Jake Brake.

I am not real happy about how my Jake is functioning either, so I was hoping it would be just a computer hook up to adjust it, BUT PROBABLY NOT that simple for me?

MY BUS IS STILL IN PREVOST, but they tell me maybe I can get her in a week or more? :confused: :(

Gary S.

I call everything by my own naming conventions barely know what I am talking about, i guess it is a 2 stage Jake Brake, and it is 5 minute change with the computer from default 6th gear to 4th gear, Jon set his at 5th I think he said, but I really like my setting at least for now in 4th, and can adjust the amount of braking action with the first or second detent on the toggle switch or non at all.

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Originally Posted by 0533

I call everything by my own naming conventions barely know what I am talking about, i guess it is a 2 stage Jake Brake, and it is 5 minute change with the computer from default 6th gear to 4th gear, Jon set his at 5th I think he said, but I really like my setting at least for now in 4th, and can adjust the amount of braking action with the first or second detent on the toggle switch or non at all.

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Bruce, I wanted clarification in your terms, because apparently you and I have the Jake Brake, and Jon in his Liberty has the Transmission Retarder, which is a completely separate braking system. We have talked about the differences in them numerous times on this board.

I do hope I can also get the increased stopping power with my Jake brake with a mere computer adjustment, like you got? :)

Gary S.

If it is a Jake don't worry about transmission temps. There is no downside to a jake mechanically.

However, unless gearing is different from bus to bus my transmission will not drop into 4th above 55 which is at the rev limits for the engine. Setting it up for fourth may only allow it to drop to 5th until the bus slows to 55.

I'll check that out on the next ride. I ran mostly on cruise control on 95 on the way back from Prevost at about 72 mph 1850 RPM . I did however notice that when I was going over overpasses coming down the inclines on the other side I could feel the braking action on the cruise control better than before, does the jake play any role in this process??

I'm with Gary and don't know if you have a retarder or Jake.

You mention Allison in the first post, but talk about turning it off to avoid noise, a characteristic of a jake. You are talking about 2 completely different types of engine or transmission braking.

I am further confused because I was unaware a jake would engage when using a cruise control, but i know a retarder will engage. If you have a retarder (small stick with six or seven positions on the right side of the steering column opposite of the turn signal) and a rocker switch to engage it, along with an amber lighton the dash to indicate it is functioning then I at least understand what you have. You will not drop into forth at 72 miles per hour.

On my jake equipped bus downshifts had to be done manually to keep the revs up so the jake would work efficiently. Its effect was minimal at lower revs, but it was very effective at the higher RPMs.

Well I guess i need to spend some time at the bus with the documents. I feel based on what you have said that I have a Jake Brake. I do however have a rocker switch on the panel in aft of the Allison shift pad at the drivers window. I certainly have no small stick with six or seven positions on the right side of the steering column opposite of the turn signal, but you sure have me wondering about what you are saying. I am pretty sure its a jake as it is a Prevost item that was original equipment. It does not offer much resistance at slower speeds your right, but with the computer gear change it works much better at highway speeds.

Jon,

My CC would activate the Jake with the cruise on, it sucked. It also defaulted to 4th gear depending on speed.

Your forth gear is one down. In the six speed as you know dropping from cruise in 6th to 4th would be like hitting a wall.

Bruce, no sense looking. You must have a jake. Apparently as Truk pointed out the jake does function with the cruise on.

I still want to know how you can drop into 4th from 6th. Don't try to answer. Just thinking out loud about how pieces and parts will be falling from the rear if that could actually happen.

Mine would go from 6th to 4th if the speed was at a certain point. If the rpm's in 6th were low enough, it would go directly to 4th, bypassing 5th completely.

Just ask Jamie, he can confirm that....

The Jake brake on my Marathon does engage while using the cruise control.

Mike

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Originally Posted by MangoMike

The Jake brake on my Marathon does engage while using the cruise control.

Mike

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Ditto, what MM said above. My Cruise works fine even with the rocker switches turned on to engage the Jake brake when I touch the brake.

My problem is I don't ( IMO ) have much braking assistance from my Jake?

Prevost is looking into this Jake Brake deficiency for me this week since it is still up in Ft. Worth?

Bruce you would know, now if you had a Retarder or Jake. I am pretty sure you have a Jake, cause like Jon said, if you have a retarder it operates on the right side of the steering column and looks like a turn signal indicator. You pull it down 1-6 clicks to get it to offer more braking power. I wish I had one, but hey it is all good!!!! :) The jake is just a 1-2 toggle button on the dash.

Gary S.

I am sure that Bruce has a Jake brake. Incidentally, my Jake is still acting up. I replaced my Throttle Position Sensor and it made no difference. My wife, or "driver" as I call her, says we have a lazy Jake. Symptoms: in the first hour or two of driving, the jake holds strong on even the steepest downgrades. (For those of you who think you have a weak Jake, you might... or you might try to gear down to 5, 4, or even 3 depending on the grade.) Then, after we've been rolling for a while, the jake simply doesn't come on. Or it comes on for a second and then kicks back off. This can be quite a surprise when you are depending on it... which we no longer do. Actually, our driving has become much better now that we can't trust the Jake. Plus Joe yelled at me in a previous post and I figured that I didn't want him fearing for my life any more.

Now, for the kicker.... once the Jake stops working, it will not come back on again until you stop the bus for at least 20 minutes. (No, 5 minutes makes no difference.) At that point, it is back on in full force. So, you give 'er a rest and she is ready to work again. Thus the technical diagnosis by "driver" of Lazy Jake.

Of course, if I took it into Prevost or Detroit, they would charge me a fortune and tell that it was all fine.... cuz it is.... for the first two hours!

~A

I think what happens is that the computer senses the pressure removed from the throttle and starts the process of downshifting in sequence to 4th, but rather quickly, it does end up in 4th. It is not that abrupt but is hugely better than the default 6th gear.

I just want to mention how dangerous it can be to manually force a downshift into a lower gear while driving in the mountians on any declining grade. As long as you know what you are doing and remain totally aware of rpm's you will be o.k. If not, the downside is a Motor that will self destruct. Pistons will hit valves,etc,etc. When manually downshifting your Governor is unable to limit your rpm's.

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Originally Posted by JIM KELLER

I just want to mention how dangerous it can be to manually force a downshift into a lower gear while driving in the mountians on any declining grade. As long as you know what you are doing and remain totally aware of rpm's you will be o.k. If not, the downside is a Motor that will self destruct. Pistons will hit valves,etc,etc. When manually downshifting your Governor is unable to limit your rpm's.

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Really? When I try to manually down shift, the transmission won't actually shift down until I have reached a certain RPM. It will let me set the gear I want to be in, but it won't go there until I slow down enough... either by Jake or regular braking.

~A

Jim is absolutely right. When returning from Florida recently, I downshifted on a grade and momentarily saw 2500RPM. Be very careful when downshifting for compression assisted slowing. :eek:

I think if the shifting is left to the computers, such as letting the bus downshift by itself according to how it is programmed the bus will not over rev. It also will not give you the maximum performance because to be most effective with a jake for example the higher the revs the better it works.

When we were out west this spring I was manually managing the coach shifts to maximize the effectiveness of the retarder while controlling heat and to do that you must know the rev limits per each gear. On my coach for example fourth gear tops at 55 MPH at 2100 rpm. Unless I was below 55 I could not and would not select 4th. I never exceeded the 5th gear rev limits so I could always hit fifth at any time going up or down hills.

Having owned a Prevost with the more exspensive retarder, and now a Prevost with a two stage Jake brake- I have made the following conclusion.

I'll take the Jake its cheaper and I prefer it.

I had the opportunity yesterday to descend Fancy Gap and I 77 South in North Carolina and never had to touch the brakes and no concerns with Temps either engine or tranny. I consider this a significant plus for whatever it is worth.

Now having said that to everyone that is shopping for their first Prevost, I would not let the retarder or Jake be a deal breaker, but if all else is equal when considering between more than one coach, I would take the Jake.

We spent a lot of last year in the Rockies with a retarder. Steep grades are scary and it takes a lot of retarder, manual gear shifts and brakes to keep things under control. Overuse of the retarder unexpectedly and quickly got the temperature up to the alarm point of 330°. Slowing early seems the best defense. I had Allison check the transmission codes and there was no history of overheating, and from what I have read that over temperature alarm is from the retarder sump and not the transmission. Still, being in the mountains is a thrill. I don't know what is involved in a brake job, but the last check showed we have many, many miles left. Thank goodness. Since I can't do the brakes myself, I would presume that it is very expensive.

Anyone know what the expected life of brakes are?

The environment you drive in dictates the life of brakes. I have 214,000 and my drives and tag are original, the front was replaced at about 165,000. I replaced all firction material on my first coach at around 200,000. Not worn out, but cracks in the lining on a couple of shoes.

Also, if you tailgate or rely on brakes while going down a hill you will get less, and if you are easy on the brakes you should get more.