We just got back from a cruise/tour of Alaska. On the tour portion we were in several MCI coaches. I am not familiar with bus automatic transmissions, as my 4104 had a 4 speed manual and my current truck conversion has a 6 speed manual.
The MCI's seemed to have two distinctly different automatics. One shifted very smoothly, much like an automobile transmission. The other MCI shifted like an automated manual transmission. It would accelerate to the governor, pause/shift and accelerate to the governor.
Can you give me an idea what I was experiencing?
Thanks,
GaryD
MCI offers the ALLISON B500 which is the fully automatic. As you stated, it shifts as nice as a typical car or light truck automatic. They also offer the ZF ASTRONIC which is the automated manual. Think of it as the driver driving it like a fully automatic with someone else doing the shifting and clutching. The ALLSION bus will accelerate faster since the power is pretty much uninterrupted while the ASTRONIC must clutch. VAN-HOOL also offers the ASTRONIC while PREVOST has their own version in the name of VOLVO since they are part of that empire. Almost every driver I talked to prefers the ALLISON since it's much smoother and even non bus nut passengers notice the difference.
TomC could give you good perspective on this.
How did you like your trip? I took my first and only cruise in that beautiful state in 2006 at about this time. I was on PRINCESS CRUISE LINES specifically the DIAMOND PRINCESS. I rode on my first PREVOST H3-45 on the way back to Anchorage.
Not too many of those anymore.
The ZF AS Tronic uses a dry clutch that is why drivers prefer the B500 the torque converter in the B500 makes it so smooth.
Bus manufactures use the ZF AS Tronic because it has a Intarder as Germans call it same thing a retarder here and I don't think Eaton offers that option yet.FWIW the ZF is a lot smoother shifting than a Eaton Ultrashift to me, but neither can touch the smoothness of the B500 IMO.
The Allison 10 speed is a smooth transmission as it uses a torque converter it is still in the testing stages for buses though
Thank you CrabbyMilton and luvrbus for your explanations.
I thought the smooth shifting trans had to be an Allison. I wasn't sure about the other though. As far as passenger comfort the Allison "hands-down" was much more comfortable. And, yes the automated manual definitely had a retarder; good holding power on some of the down grades. The driver rarely used the service brakes on some pretty good downhill grades. There was no exhaust rumble as you get with a Jacobs Brake, but lots of retard. You could feel it. From what I read, a lot of the new class 8 tractors are using automated manual transmissions.
Our trip to Alaska was absolutely superb. This was our second trip there, and this one was a cruise/tour with Princess Cruises on the Coral Princess. Seven nights up the Inside Passage to Whittier and then on the Princess train to Talkeetna. And six nights up to Fairbanks. We had beautiful weather all the way; cold and misty on the boat and clear/scattered clouds on the land portion. We were very fortunate and saw Denali's peak above the clouds several times and once the complete mountain! 75*F in Fairbanks. Princess did everything close to perfect, with military precision and the customer in mind all the time! Alaska, a beautiful state and hardy people. The children go to school when it is -40*F to -50*F and play on the playground too in those temperatures!
Thanks again for the explanation on transmissions.
GaryD
The ZF 12 spd automated is basically a 4 spd transmission with a 3 spd planetary splitter-made as an automated transmission. Freightliner was using the ZF for a while, but when the transmissions started coming back and replacement parts were so expensive, repairs turned into an R&R affair-even though the shop had bought all the specialized tools and the mechanics had gone through ZF school to learn rebuilding. The truck version never had a retarder, relied on the Jake brakes.
Eatons Ultrashift II is a good transmission-automatic clutch with faster shifting than the old Autoshifts. They accomplish this by using the clutch at every shift along with a transmission brake-as compared to the old Autoshifts that only used the Jake brake during shifts if needed. Available in 10, 11, 13, 18spds.
Mercedes-Benz and Frieghtliner use a 12 spd automated that is drastically different than the ZF. It is a 3spd main box (single counter shaft), with a 2spd planetary splitter and a hi/lo range. The two big advantages to the Freightliner 12spd is it is available up to 600hp and 2050lb/ft torque (even Allison can't go that high). The other is hill start assist. Most other automated transmissions will hold the brake on a hill for 3 seconds after you take your foot off the brake-but you better start accelerating-if you don't the truck will release brakes and roll backwards. Frieghtliner has hill start assist. The brakes hold for three seconds-but if you don't touch the accelerator, the truck will automatically engage the clutch and get you moving-just have to hit the accelerator to speed up. Pretty nifty.
I haven't heard about the Allison TC10 in truck us-Navistar is offering it, and I believe Pete and KW are now too.
Personally-stick with the Allison torque converter/planetary gear transmission-whether it be the older MT/HT series or the newer World-you'll be quite happy with the performance. Good Luck, TomC
I should also note that many "JAKES" are muffled so your bus may have had them and not knowing it. I was on a charter trip back in 2010 thru some hilly areas in GA and NC. The J4500 had the ASTRONIC and but no loud brap ap ap ap ap AP!! I asked the driver if it had JAKES and he said yes so while I'm not saying that bus that it was or was not equipped with JAKES as opposed to a retarder, the thing is unless you ask the driver, you'll never know for sure.
While bus drivers and passengers prefer the Allison for smoothness and acceleration, bus owners prefer the automated manuals for their better fuel mileage. Good Luck, TomC
Thanks TomC and CrabbyMilton. Interesting info on what is going on in the industry. When we were in New Zealand several years ago all the buses had automated manual transmissions. What is the mileage difference between automatic and automated manual? Is it significant for operators?
GaryD
Perhaps the AM is slightly better but then again, once the B500 locks up on the highway, it should be about the same. I was heard an idea that the MPG is slightly lower due to the fact that at least around town, the drivers tend to floor it more since they are faster than a ASTRONIC. Could be and it makes sense.
Quote from: usbusin on August 23, 2016, 09:53:24 AM
Thanks TomC and CrabbyMilton. Interesting info on what is going on in the industry. When we were in New Zealand several years ago all the buses had automated manual transmissions. What is the mileage difference between automatic and automated manual? Is it significant for operators?
GaryD
The jury is out on that my friend @Arrow Stage Lines says his J's with the B500 get better fuel mileage in town and on the highway than the AS Tronic he hasn't bought a J in 4 years with a ZF AS Tronic transmission