Transmission Retarder

[dale farley]

This article gives a simplified explanation of how to effectively use your Transmission Retarder. The Prevosts I've had used a Jake; so I have not used a transmission retarder before, but I assume the transmission retarder has advantages and disadvantages over the Jake Brake or Exhaust Brake.

http://rvdailyreport.com/owner/things-to-consider-when-using-a-motorhome-retarder/

[garyde]

I have the Transmission retarder. It is very effective on down hill slopes. It does heat the transmission up to about 230 degrees on long downhill runs but quickly lowers as you level off. I find it very helpful in freeway traffic as well, limiting the braking in slow and start-stop traffic. In getting off an off ramp, it reduces the amount of braking required to come to a full stop.
I rely on it quite a bit. Additionally, it makes no sound unlike the Jake brakes.

[dale farley]

Gary, It sounds as though you have used both the retarder and Jake. If everything else was exactly the same on two Prevosts, would you choose one over the other based on this system alone.

[Gil_J]

I'm pretty sure the newer engines all have variable pitch turbos. This allows the pitch to actually be reversed, creating a drag on the engine. This doesn't have the resistance a Jake does, so it's augmented with a transmission retarder. I've had both, although the turbo/transmission retarder coach I had was a lighter 42-foot Beaver, I'd say the Jake in Lo is comparable. The Jake on HIGH seems better than the retarder setup on that CAT powered Beaver.

One thing I didn't like with both setups is that the transmission downshifted to 4th when either was activated. I've since had my current coach's transmission reprogrammed. When the Jake is activated now the transmission down shifts to 5th. I manually down shift as needed. Frankly, I seldom use the Jake on the east coast.

[Pete]

I had an 85 Prevost with the Jake, and now have a 95 Prevost with a retarder, and while both have advantages, I prefer the Jake. Primarily because of the heat generated by the retarder. One must be very careful with the retarder on long downgrades, and use the service brakes and downshifting in concert with the retarder. Having said that, the newer Prevost coaches have increased cooling capacity for the transmission and I think have pretty much solved the heating situation in the transmission. The retarder has no noise effect which is better in some cities where a Jake is restricted.
In addition, the use of Transynd in the transmission has also been a plus, in that Transynd allows higher temps for longer periods in a retarder application.

[jack14r]

I have used the retarder on Black Mountain in North Carolina with a Gross Weight of 71,000 which included a stacker loaded and the highest temperature was 224 degrees,I never touched the brakes and ran from 35-45 MPH all the way down.I have had both and there is no comparison,the jake is just inadequate compared to the retarder.Allison states that the retarder has 500 brake horse power and I believe that their statement is accurate.

[jbchevy3]

I agree with Jack on the retarder, I have had 6 Coaches with the Jake brake. Compared to the retarder I have now, they were all noisy, and not as smooth to operate as the retarder. Both stop well, but the retarder has more settings, and with the stalk control, it makes it easy to apply as needed. The trans temp has never went over 228 degrees in mine, even in the Summer. I hardly ever use my brakes except in town.

[garyde]

My previous Coach was a Lexa 42 ft. Country Coach. It had 3 settings for the Jake brake. I liked it. When I purchased my Liberty with the Retarder, I found more flexibility and a much quicker response . It has 5 settings and it will work well going just 15 or 25 MPH.
This makes it more effective than a Jake brake and gives me more control of my Coach.

[Gary Carmichael]

Just came down Fancy gap Tranny in fifth gear retarder on second notch never touched the brakes, actually had to speed up a couple times speed at 50mph, I am pulling a Tahoe with Airforce one brakeing system, I love the retarder just have to watch the temps on say a 10 mile grade. Gary

[dogbone]

My coach is somewhat unusual in that I have both systems installed and operational. I find the retarder is quite effective in creeping rush-hour traffic, urban areas, or other noise sensitive locations. Though I've used the retarder in the mountains, I much prefer the Jake in this type of terrain mainly to avoid the higher tranny oil temperatures and from a driving perspective I feel the Jake offers a certain performance predictability or expectation. Operationally, I select which system will be active; the two systems are never simultaneously in operation.
I recall reading an Allison manual sometime past where a suggestion is made, for those tranny's with retarders, to shorten the tranny oil change interval due to the frequent higher oil temps affecting oil life.