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bluebirdvision
Top Member
USA
1081 Posts |
 Posted - 12/15/2010 : 09:28:12 AM
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| Something I've always wondered.... What do they use for gears in school buses? I know its all in the specs.... But If I wanted to take a bus on the thruway and do 65mph, what type of gears would be used? I've seen bus ads that say "highway gears" |
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bwest
Administrator
United States
3820 Posts |
Posted - 12/15/2010 : 09:39:39 AM
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Most of my Chevys are 4.11. I have at least one 4.63 but it is slow as pond water. I'm not sure what my newer ones have in them I just took the recomendation of the salesman. I try to find out if I get the time later.
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Bryan |
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tigger2
Advanced Member
USA
470 Posts |
Posted - 12/15/2010 : 11:12:00 AM
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Our old Navistars w/ at545 were geared at 4.44 could run 65 or so clipped at 60 w/ecm.
The Allison 2000's had 5.57 rears with o/d they ran about 70 mph.RSL to 60 mph
The new Allison 2500PTS o/d run 5.13 gears not sure where top is on these all ecm specs are set at factory now. |
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JustinB
Advanced Member
United States
490 Posts |
Posted - 12/15/2010 : 1:04:24 PM
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Most of the Allison 2500PTS trannys are licked to 5 of the 6 available ratios.
- 5th Gear is appx .87:1
- 6th Gear is appx .64:1
The 6 speed programming is a sweetheart for 65mph cruising in the 5.13:1 rear axle & 11R22.5 tires. The tach will register @ 1600rpm @ 65mph. Any hill will switch it down to 5th @ 62mph. |
I may not know the answer but I can usually find who does. |
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bluebirdvision
Top Member
USA
1081 Posts |
Posted - 12/15/2010 : 2:00:06 PM
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I had a driver in my district that complained about his Vision because he said it didn't stay in over drive long enough when attempting to climb a hill. I told him to shift out of over drive if it bothered him that much.
This particular individual complains about every bus he gets until he gets his new one, then the bus he was complaining about was the best bus and the new one is a piece of crap.
I personally think the 2500/6.7 Cummins combo does great on hills. |
Facebook Page: Blue Bird Corporation Fans
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Edited by - bluebirdvision on 12/15/2010 2:01:10 PM |
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matts4290
Advanced Member
224 Posts |
Posted - 12/15/2010 : 6:58:17 PM
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Shane, my AA has a 5.38 rear end. It has the MD3060 and 5th gear is 1:1 ratio. It runs approx. 1,900 RPMs at 55.
My TC has a 4.33 rear end and the AT545 has a 1:1 ratio in 4th gear. It runs approximately 21-2200 RPMs at 55mph.
You would think with the ratios that the TC would run lower RPMs, and it would if it had a locking torque converter clutch like the MD3060, but it does not. I would consider 4.33 highway gears, however my AA runs lower rpms which would be closer to highway gears. Both have 11R22.5s. |
We can't all be conventional!
http://www.youtube.com/user/matts4290 |
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BBInt.10
Top Member
USA
1042 Posts |
Posted - 12/15/2010 : 7:20:56 PM
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quote:
Originally posted by bluebirdvision
This particular individual complains about every bus he gets until he gets his new one, then the bus he was complaining about was the best bus and the new one is a piece of crap.
Unfortunately, sometimes you don't appreciate fully what you have until it is taken away from you. I've been driving my Vision for 1.5 years now and still haven't warmed up to it, so I don't think it's going to happen at this point. I miss my IC. I miss the large windshield with overlapping huge wipers. I miss the Euro-style mirrors. I miss the lamp check feature.
My Vision had an issue about a week ago where the door wouldn't open, and I had one of our IC spares brought to me on route. It felt nothing less than LIBERATING going from the Vision cockpit to the IC cockpit. Everything from the seat, to the angle of the pedals, to the steering wheel, shifter, parking brake, and switches is just more comfortable. It's nice being able to utilize the sides of the windshield without trying to look through distorted curved glass.
The Cummins engine is nice, it pulls up hills great, as you said, and is reliable. Plus it blows good heat, and the hand vents in the dash of the Vision are great. But overall, I'd rather brave the cold in an IC than drive a Vision. It's a shame you can't order an IC with the Cummins under the hood.
Back when I had an IC for my route bus, I'd love to get the '93 Blue Bird Internationals for spares. What rustic charm they had. Don't get me wrong, I'm not anti-Blue Bird... I actually bought my favorite '93 Bird and currently still own it. But I must say, the Vision is really pretty disappointing from a driver's perspective, and once you start driving buses you will probably better be able to see where some of us are coming from. |
If all your problems are behind you... you must be a school bus driver. |
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bluebirdvision
Top Member
USA
1081 Posts |
Posted - 12/15/2010 : 7:36:11 PM
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I am not sure how your complaints about your bus helped me with my gearing question... but I appreciate your input anyways
I like the newest Visions the best, much more comfortable.
I will never be able to drive a school bus.... at least legally |
Facebook Page: Blue Bird Corporation Fans
https://www.facebook.com/home.php?sk=group_212311114614&ap=1
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Edited by - bluebirdvision on 12/15/2010 7:39:58 PM |
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Wolf0r
Top Member
USA
2181 Posts |
Posted - 12/16/2010 : 09:50:31 AM
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| Most buses have the rear axle ratio on a plate or sticker inside the bus. There are several articles on "how stuff works" dot com that explain ratios and how to calculate them. |
“The good thing about science is that it's true whether or not you believe in it.”
Neil deGrasse Tyson |
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bwest
Administrator
United States
3820 Posts |
Posted - 12/16/2010 : 09:57:39 AM
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Never?
I don't want to take this thread too far off topic but as for the IC vs. BB. It's interesting to note that my drivers love their Visions. I have two Visions on the road everyday and one has over 100,000 miles on it. I put that driver in a newer IC, just for a single trip or someting like that, and she flat told me if she had to drive one everyday she would retire right then and there. Out of the four drives I have driving an IC every day I only have one who likes hers. We have had some trouble with them but I don't think that's the reason they don't like them (all my drives are real good about taking a spare it they have trouble with theirs). I think it is more of the feel that BBInt was talking about with his Vision. All in what you get used to I guess.
I would also like to add on this thread's topic that my old Chevys with the 4.11s all have 545 Allisons and 10R22.5 tires. This seems to be a real good combination for pick up and milage. I get about 7.5 to 8 mpg on a country route (3126 Cat engines) |
Bryan |
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BBInt.10
Top Member
USA
1042 Posts |
Posted - 12/16/2010 : 1:46:03 PM
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I checked my Vision today and that's got a 5.29 rear axle ratio. Two summers ago when I picked that bus up and drove it back to my lot for the first time, I took it up on the highway to see what it would do, and if it was governed. It got up to 75 with ease in overdrive, and would have kept going but I backed off. It's actually quite a nice driving bus on the highway. Unfortunately, I don't do much highway driving, and having a rear end geared like that makes it pretty slow taking off from a stop around town. My '93 Bird takes off like a jackrabbit from a stop, but doesn't want to do much more than 60 on the highway. I'm not sure the ratio on that rear end.
I guess you're right bwest, a lot of the IC vs. BB probably has to do with what I'm used to. I spent 4 years in an IC. |
If all your problems are behind you... you must be a school bus driver. |
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JustinB
Advanced Member
United States
490 Posts |
Posted - 12/17/2010 : 07:25:15 AM
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quote:
Originally posted by matts4290
Shane, my AA has a 5.38 rear end. It has the MD3060 and 5th gear is 1:1 ratio. It runs approx. 1,900 RPMs at 55.
My TC has a 4.33 rear end and the AT545 has a 1:1 ratio in 4th gear. It runs approximately 21-2200 RPMs at 55mph.
You would think with the ratios that the TC would run lower RPMs, and it would if it had a locking torque converter clutch like the MD3060, but it does not. I would consider 4.33 highway gears, however my AA runs lower rpms which would be closer to highway gears. Both have 11R22.5s.
5th gear in the MD3060P is a .75:1 overdrive. Direct 1:1 is 4th Gear.
The product has been renamed B300
http://www.allisontransmission.com/servlet/DownloadFile?Dir=publications/pubs&FileToGet=SA3740EN.pdf |
I may not know the answer but I can usually find who does. |
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bluebirdvision
Top Member
USA
1081 Posts |
Posted - 12/17/2010 : 1:54:58 PM
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Where would I look on my Visions to find out how its geared?
bwest, I cannot obtain a CDL in NY State due to my doctor being an... umm I mean, my physical "limitations" |
Facebook Page: Blue Bird Corporation Fans
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bwest
Administrator
United States
3820 Posts |
Posted - 12/17/2010 : 2:24:25 PM
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That's too bad.
Maybe you can work on them and be able to drive them with no students on them or maybe you can deliver them from the factory. That would be fun. |
Bryan |
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BBInt.10
Top Member
USA
1042 Posts |
Posted - 12/17/2010 : 6:33:21 PM
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quote:
Originally posted by bluebirdvision
Where would I look on my Visions to find out how its geared?
bwest, I cannot obtain a CDL in NY State due to my doctor being an... umm I mean, my physical "limitations"
There should be a sticker stuck up on the panel above the windshield on the passenger side, above the manufacturer plate. |
If all your problems are behind you... you must be a school bus driver. |
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bluebirdvision
Top Member
USA
1081 Posts |
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matts4290
Advanced Member
224 Posts |
Posted - 12/17/2010 : 7:41:27 PM
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quote:
5th gear in the MD3060P is a .75:1 overdrive. Direct 1:1 is 4th Gear.
The product has been renamed B300
http://www.allisontransmission.com/servlet/DownloadFile?Dir=publications/pubs&FileToGet=SA3740EN.pdf
I'm sorry! Thanks. I don't know what I was thinking. I did all the math once to see if it would be feasible to have the sixth gear unlocked (double overdrive), and calculated that 55MPH would take the engine down to 1,600 RPMS, which sounds too low to me, but might be appropriate for highway application. Sixth gear is .65:1.
Shane, heres some pics. This is the data plate above the main bluebird plate with the model year on the front top right above the service door.
Notice "rear axel ratio" bottom left
Notice "axel ratio" bottom left |
We can't all be conventional!
http://www.youtube.com/user/matts4290 |
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bluebirdvision
Top Member
USA
1081 Posts |
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08 Thomas EF
Top Member
533 Posts |
Posted - 12/18/2010 : 7:23:18 PM
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| Justin, would the 6th gear be unlocked on, say, an activity bus (whether it's an EF, CE, whatever)? With that 5.13 ratio, how's the acceleration? Is there any ratio that stands out as being more common than others in school (or activity) buses? |
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JustinB
Advanced Member
United States
490 Posts |
Posted - 12/19/2010 : 05:55:47 AM
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Assuming that the rear axle ratio remains unchanged @ 5.13:1, unlocking 6th gear will have no bearing on accelleration.
Most buses in MI bounce between 2 axle ratios depending on the district's operation.
Roughly speaking = 5.13:1(600-660lb/ft) or 5.73:1(500-605lb/ft)
5 years back 6.14:1 was common. (UGH!!)
These were with the 5 speed programming on the 3000 srs & 2000 srs Allisons.
Over the past year or so, with the opening up of speed limits for buses on the interstates & major state rural highways, districts are beginning to see the benefit of having a "Highway Gear" & getting the cruise RPMs down for line-haul situations.
I like the 5.13:1-ish ratio because it seems to keep the Allison from "Hunting" between 2&3 gear ratios that can overlap in the available 2500rpm rev band of a 6L-8L engine. This also forces the transmission to do two things. First, the upshifts are forced to grab the gear at an rpm closer to the peak torque curve, not above it. Second, on the downshift, it forces the transmission to lug deeper into the torque curve for efficient hill pulling. In short, a bit of "progressive shifting" forced onto an Allison that always seems to seek the rev limiter under power demand. Banging off the rev-limiter is poor practice reserved for V-8s & 2-strokes, not modern 4-stroke L6 engines.
Some of the Plains States are delivering 6-speed buses with 4.88:1 & 4.56:1 gearing. It takes a good 640lb/ft to move a 33k#+ bus comfortably at 65-70mph & 1600rpm. Definitely not a high density stop/start route spec.
edit: bolded by JB |
I may not know the answer but I can usually find who does. |
Edited by - JustinB on 12/20/2010 06:40:03 AM |
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08 Thomas EF
Top Member
533 Posts |
Posted - 12/19/2010 : 3:42:51 PM
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| Thanks, Justin! |
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JustinB
Advanced Member
United States
490 Posts |
Posted - 12/20/2010 : 06:34:18 AM
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quote:
Originally posted by JustinB
Some of the Plains States are delivering 6-speed buses with 4.88:1 & 4.56:1 gearing. It takes a good 640lb/ft to move a 33k#+ bus comfortably at 65-70mph & 1600rpm. Definitely NOT a high density stop/start route spec.
Doh?! I missed a very important word in that post - Post edited. |
I may not know the answer but I can usually find who does. |
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Wolf0r
Top Member
USA
2181 Posts |
Posted - 12/20/2010 : 08:53:12 AM
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| Great Info! |
“The good thing about science is that it's true whether or not you believe in it.”
Neil deGrasse Tyson |
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Topic |
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Gearing
