-
Teton Pass
We are heading to the Tetons in a couple days and Natalie started getting nervous about the 10% grades someone told her about. Have you done it? Any hints other than “go slow”?
-
29 Replies
-
Go down the same speeds and same gears used when going up. That is the general rule. Don’t pump your brakes. Set your target speed, use the retarder to maintain it, and if brakes are needed apply them firmly and steady to bring your speed to well below the target speed then release them until speed builds again.
Ignore anyone behind you that thinks you should be going faster. Don’t be intimidated into pushing the speeds.
-
Did that trip early May of this year. It is doable without any problem as long as you follow Jon’s advice. Good think to remember is that the speed you climb should be your target speed going down.
Beautiful area, have fun.
-
Drove it daily in the winter as well as summer in tour/ski busses, with manual trannies. We’ve even done it recently in several of our Prevost MH over the years including the current coach with 8V. Do as Jon and others said, or even better not using the brakes going down,We always follow rule, whatever gear used going up, use the next gear lower going down. Just remember to use 4 way blinkers
-
Thx guys. What is target speed, as fast as gravity will allow while going up?
do you even bother with the transmission retarder? -
Karl: That’s a truly scary post. the transmission retarder (assuming you do not have a jake brake) is the PRIMARY means of controlling downhill speed!
Overuse of the retarder, however, can destroy the transmission due to overheat. Generally speaking (YMMV), if I feel safe at 60 mph I can use gear 5 and level 3 of the retarder—any more use of the retarder will cause trans overheating over 250F. To hold 52mph I can use gear 4 and up to level 4. On a 10% grade, I would guess you would not want to go over 40…gear 3, level 4. I do not use levels 5 or 6 on my retarder except briefly in extreme cases. Find your trans fluid temp display somewhere and practice a bit BEFORE you get there.
You may find your numbers a bit different based on weights (I’m usually 65,000 to 70,000 #), gear ratios, etc.
-
Karl,
I don’t disagree with Joel except to say your coach and his have different intercoolers fo rthe transmission fluid and my XL heated up transmission fluid quickly whereas the current one has much better temp control. Even if you are no paying attention the computer is going to limit the temp anyway.
I would use 4th gear and 55 MPH as the absolute upper limit on the downhill. My target speed would be between 45 and 50. You can likely hold that speed with the 2nd or 3rd retarder position. I would monitor the tranmission temp on the message center and as a personal limit I would let 230 be the top. As it goes up to that point use the brakes and drop the retarder to a lower position. Keep in mind with the retarder master on using the brakes regardless of the retarder stalk position engages the retarder so if the temps climb you may have to turn off the master. At the speed and gear mentioned above you should be OK.
-
Best advise I read here so far was don’t let anyone behind you force into thinking you should be going faster. That is the only reason anyone would want to go faster anyway. Stay with the advise here and you should be fine.
One Thought: If you haven’t used the manual shifting methods before, you might practice or get a feel for it before you hit the 10%. That is a beast. Most I have had our bus on is 7% in CO.
Have a safe trip.
-
Just recently we have done some down shifting in the mountains of California and New Mexico. I appreciate the gear and retarder suggestions. That helps a lot.
I guess I don’t understand how the retarder works though. I thought it just caused you to downshift and that if you had done so manually it wasn’t doing anything. Enlighten me?
-
Not to hi-jack Karl’s post, but I definitely want a coach with a retarder and most coaches I’ve looked at do have one. However, there is the occasion coach which has a jake brake.
Did Prevost switch around using a jake brake at some point in history or could it be that the customer wanted a jake brake and Prevost built it to that spec? Or, did Prevost put a jake brake on some coaches in a certain year group?
-
Karl,
Make your owners manual your best friend. 50,000 to 60,000 pounds on 10% grades has the potential to get exciting.
The retarder is exactly as the name suggests. The transmission becomes a brake when the retarder is engaged, and as a driver you control how much retarding force is applied by the retarder. Work it in concert with the gear shift and it is very effective. But like your brakes, if you over work it you generate heat so you have to balance speed, gear, retarder control position and application of brakes to maintain control of the bus while keeping the systems well within their operating limits.
-
Tim,The retarder or jake is an option that the converter could choose,I have had both and the retarder is much more effective,I have read that it has 500 brake horse power.
-
T&C, don’t let a jake or retarder be a deciding factor in looking for the right bus. While the retarder is more effective it also has a downside. A Jake will work quite well with the right gear selection. I really think there are (though I don’t know for sure) are more busses out there with a Jake than a retarder, but it would not be a factor for me in choosing any particular bus. FWIW Geo.
-
I agree, I’ve had both. I also think the retarder is somewhat more effective but I would not let it become a deciding factor in coach selection.
-
Jon, I guess more specifically what I was asking was how does the retarder retard? Downshifting or some other mechanism?
Log in to reply.