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Author Topic: Model of differential  (Read 4201 times)
prevost82
82 Prevost 8V92ta 6 speed
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« on: August 29, 2007, 11:37:35 AM »

Hi all ... I have a Rockwell diff in my 82 Prevost. I am looking at going to a 3.30 : 1 and I have a 3.70 : 1  now. Does anyone know a model number of the diff?
Ron
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tekebird
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« Reply #1 on: August 29, 2007, 02:46:11 PM »

crawl under...should have a tag.  or a call to prevost with your serial number will get you what it was sent out of the factory with
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TomC
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« Reply #2 on: August 29, 2007, 04:08:30 PM »

Ron- if you have 12R-22.5 at 485rpm and Allison transmission with direct as high, your present 3.70 will net you a top speed of 70mph @ 2100rpm.  Switching to the 3.30 will raise the top speed to almost 79mph.  I think you should ask yourself, is all that money for a new rear end and the trouble to change it worth the extra 9mph you're going to gain?  Personally I don't think so.

What would be most effective would be to get rid of the HT740 and get either the B500 or HD4060 with low profile oil pan (B500 is the HD4060 or 4000HS with a low profile oil pan).  Using your present 3.70 gear ratio, your top speed with the .74 (5th gear) and .64 (6th gear) overdrives in the B500 will increase to 95mph in 5th and 109mph in 6th.  Or to get more realistic, your 75 mph cruising rpm will be 1660rpm in 5th and 1435rpm in 6th-of which it might not even get into 6th until more closer to 80mph!  The B500 is about the same size as the HT740. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
prevost82
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« Reply #3 on: August 29, 2007, 04:39:49 PM »

Tom ... I running an 8V92ta @ 475 hp and a 6 speed stick tranny. I trying to get my RPM's down at cruising speed (60 MPH). I'm not trying to go faster. With a 3.3:1 ratio I'd be doing around 62 at 1600 RPM, instead of 1750 RMP and that should improve my fuel mileage a bit.

I live in the mountains and need all the gears I can get, there's not a 6% grade out of this town, on 3 highways, and not just one 6% grade either. The other option is to put a 10 speed in with 10th gear as an overdrive. Putting 4060 or B500 wouldn't work for me because I'd still have to change the diff ratio, to use 6th gear. So that option would be WAY more money.
Ron
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luvrbus
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« Reply #4 on: August 29, 2007, 05:42:05 PM »

My 8v92 loves the new gear switch from 370s to 336 ratio and i do too
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rdbishop
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'68 MCI-7 892T, 740 Richard & Missy - Texas




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« Reply #5 on: August 29, 2007, 06:18:32 PM »

Say luvrbus,

What was your top speed with the 3.70 ? Mine was 74 mph at 2250 rpm. I want to go to 336 also, but I have to find a good pumpkin housing first. I really liked the 370's in the mountains.

Richard
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luvrbus
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« Reply #6 on: August 29, 2007, 06:28:53 PM »

Richard, thats about where i ran i can not see any difference in the mountains but i can see a little difference in the braking power of Jake brake
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rdbishop
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« Reply #7 on: August 29, 2007, 06:36:27 PM »

luverbus,

Does that mean the jakes won't be as strong.

Richard
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luvrbus
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« Reply #8 on: August 29, 2007, 06:45:43 PM »

mine seem as strong just not in 4th gear it might just be me
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rdbishop
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« Reply #9 on: August 29, 2007, 06:49:20 PM »

Maybe they can be adjusted to compensate. (hopefully)

Richard
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luvrbus
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« Reply #10 on: August 29, 2007, 07:11:36 PM »

Richard, you will love the extra rpms you have when you need it
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rdbishop
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« Reply #11 on: August 29, 2007, 07:19:51 PM »

luverbus,

Sounds good!! I'm trying to get mine done before the Texas round-up. My pumpkin housing is all mess up,so I need to find one and get the 336 installed at the same time.....which is getting short.

Richard
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rdbishop
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« Reply #12 on: August 29, 2007, 07:35:34 PM »

Prevost 82,

I talked to a diff. company in ft worth, tx. today and he said he needed a number off the pinon shaft where the yoke nut is. Said I would probally have to take the driveshaft loose. Also said I would have to wirebrush it to get the numbers. The gear ratio is there also. I'm going to look for mine tomorrow as it looks like I need another pumpkin housing. I'll let you Know what I find.

Richard
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Merlin-PV
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« Reply #13 on: August 29, 2007, 08:58:19 PM »

If memory serves me correct it is"sqdd"
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TomC
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« Reply #14 on: August 30, 2007, 12:16:36 AM »

Ron- once again, I'll repeat-don't spend the money, time and effort to change from the 3.7 to 3.3 gears- it just isn't enough of a difference to make much fuel difference-probably wouldn't ever pay it off. What will really make a difference in your fuel mileage would be to change that 6 speed to a (these are all Eaton Transmissions) 7spd overdrive (with a .75 overdrive and still in one stick with no air splitter), or a 9 spd (which I personally like the best) with either a .73 or.74 overdriver, or a 10spd with a .74 or .75 overdrive (don't like the 10spd because of the U shifting from 5th to 6th).  With the .75 overdrive of the 7 speed, you'd get your cruise rpm down.  With 3.7 and 485 tires (12R-22.5) you'd be doing 1794 at 60mph-which is fine.  Go to 65 mph and you'll be at 1944-which is starting to get a bit high.  Shift into 7th and you'll drop to 1458 at 65,  1570 at 70 and 1682 at 75-all of which is not to low for the 8V-92TA.  You'll really get fuel mileage results and quite possibly cost you less since I know there is alot of transmissions around compared to bus rear ends.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #15 on: August 30, 2007, 08:11:09 AM »

Ron-two other alternatives.  You could put in the ultimate manual which is either the 13 or 18 speed which would give you the perfect gear at any speed-if you have the room.
Personally-if I were in your shoes, I'd change your trans to a 10spd Autoshift.  Same transmission as the manual, where they literally pulled the gear shift and replaced it with two motor shifters run with a computer through your motor.  If your engine is mechanical, the have whats called Autoselect where you just have to let off the accelerator to accomplish the shift.  The advantage to the Autoshift-it shifts the same every time, never misses a gear, doesn't grind gears (anyone that says they never grind gears is just a liar), so the trans will last a long time.  Several truck fleets have gone exclusively to Autoshift (you still use the clutch to start and stop) or an Ultrashift (no clutch pedal-but only works with an electronic engine).  If I were ever to get back on the road with my own truck, there wouldn't be any question what transmission I'd put in my truck-that's a 13 spd Ultrashift.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
prevost82
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« Reply #16 on: August 30, 2007, 08:11:41 AM »

Thks Tom ... After thinking about it I came to the same conclusion. It would be the best of both worlds, on the flat I would have good low RPM at cruising speed and on the hill I would have a few more gears to find the sweet spot.

As for the Autoshift ... I love to put a M11 with a 10 speed Autoshift, like Brians did, but this is a fresh ReliaBuilt 8-92 non DEC. I would never get the wife to agree to spending a bunch more money on the M11 setup, but the tranny would be cheap as I have a 13 speed /w OD that was on the back of the 8-92 when I bought the wreaked truck.
Ron
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TomC
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« Reply #17 on: August 30, 2007, 08:40:34 AM »

Now you're talking Ron!
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Brian Diehl
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« Reply #18 on: August 30, 2007, 11:09:18 AM »

So far I love the autoshift. It is a great tranny!  It shifts smoothly and reliably every time!
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HB of CJ
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« Reply #19 on: August 30, 2007, 02:28:15 PM »

Ron....is your 6-speed manual a Spicer or a Fuller?  Reason I ask, it sounds like you have the direct 1:1 high gear.  Fuller did make an O.D. T-906 6-speed that had, if memory serves, either a 32 or 33% overdrive 6th.  This might be too tall, or it may work just fine.  First gear would be taller too.  Would be a simple R/R.  If you have the Spicer 6-speed, then I do not know.  Again, yeah, it is a matter of rpm cruising speed, not absolute top end, which our coaches may not pull for whatever reason.  Thanks.
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Merlin-PV
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« Reply #20 on: August 30, 2007, 04:54:51 PM »

Gear set(ring and pinion) close to $600.00 labor to install around $400.00 and in most cases you will need a bearing set another $200.-$300 You will never drive far enough to recoupe that kind of expense even if you live to be 100
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« Reply #21 on: August 30, 2007, 05:11:17 PM »

I think that if you spend money on your bus and can at least drive the thing around the block then you win.  No one does a conversion to make or save money.  If you want a new tranny/gear set/engine/whatever, buy it.  If that one doesn't work, buy another one.  If you don't have the means....go to the junk yard.   There is always a way to get what you need. 

The only thing that matters in this whole game is the big smile on your face when your driving down the highway.  Do whatever you have to to attain that.
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luvrbus
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« Reply #22 on: August 30, 2007, 05:29:36 PM »

Merlin these 8v92s like 1800 rpm at 65 or 70  better than 2100 rpm at the same speed i think it was worth the money myself also i wish i could buy a ring gear and pinion for a Eagle for 600.00 bucks
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TomCat
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« Reply #23 on: August 30, 2007, 06:11:53 PM »

The only thing that matters in this whole game is the big smile on your face when your driving down the highway. living your life.  Do whatever you have to to attain that.

There, I fixed it for you!

Jay
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« Reply #24 on: August 30, 2007, 06:32:29 PM »

Right on, Bro.
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prevost82
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« Reply #25 on: August 31, 2007, 10:38:51 AM »

Ron....is your 6-speed manual a Spicer or a Fuller?  Reason I ask, it sounds like you have the direct 1:1 high gear.  Fuller did make an O.D. T-906 6-speed that had, if memory serves, either a 32 or 33% overdrive 6th.  This might be too tall, or it may work just fine.  First gear would be taller too.  Would be a simple R/R.  If you have the Spicer 6-speed, then I do not know.  Again, yeah, it is a matter of rpm cruising speed, not absolute top end, which our coaches may not pull for whatever reason.  Thanks.

I have the 6 speed Spicer Tranny, with is 1:1 ratio in sixth. The thing is, I want all the gears I can get without going into OD. I have way too many grades to climb in this part of the country.

I put a lot of miles on the bus, I use it as an office / living quarters at various job sites around the counrty & RV when the wife and I go south for the winter and summer month when I'm close by, so I put on 2K to 3K per month.

I have a 13 speed with and OD, that I can shoehorn in there and should be able to do it in a weekend with minimal cost ....

Thanks for all the responses
Ron
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TomC
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« Reply #26 on: August 31, 2007, 10:17:18 PM »

Ron- you'll love the 13 spd-still think it is the best manual trans made.  What year was the trans made?  They made both a single and a double overdrive of the 13spd.  See if you can locate the tag on the side of the trans and let me know what year and model it is, then will know which gear set you have.  Are you going to get the reverser for the shifter, or are you just going to shift it backwards?  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #27 on: August 31, 2007, 10:54:19 PM »

TomC,

Will the AutoSelect work with any stick behind a 8V92?  I can't imagine opting for a 740 if I could get a stick that my wife could drive.  It seems that the only real cost effective way into this is to buy a wrecked truck that has the engine and a 13 speed with autoselect already installed.  Thanks for your comments.

John
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« Reply #28 on: September 01, 2007, 04:20:45 AM »

The 10 spd and 18 spd Autoshift, that uses a clutch pedal just to start and stop can be programmed as a Autoselect to be used on mechanical engines.  The 10 spd and 13 spd Ultrashift that has no clutch pedal has to be used with an electronic engine only. When used in Autoselect form, you have to release and push down the  accelerator at every shift.  Both the Autoshift and the Ultrashift are just like a normal automatic where you keep a constant pedal pressure where the computer turns on and off the engine for you in between shifts.

For those of you that don't know what we're talking about, Eaton (truck transmission manufacturer) has taken their Roadranger transmissions and literally pulled the manual gear shift lever off and replaced it with two electric motor shifters that are controlled with a computer that is tied into the engine computer. So driving these transmission still feel like a manual transmission with an interruption between each shift.  The main advantage is that they shift the same way everytime, don't grind gears, and maximize the shifting to get the best fuel mileage (Allison does this also, but the planetary gear and clutch setup of the Allison has built in drag that just plainly takes more power to turn and more to cool).  If I got back on the road my first choice of transmission would be the Allison 6spd.  Then it would be the 13spd Utlrashift, then the 10spd Ultrashift, then the 18spd Autoshift, then the 10 spd Autoshift, then the 18spd manual, then the 13spd manual, then a 9spd manual (don't like driving a 10spd or 15 spd).  After 1.3 million miles of driving a 13 spd, I have no love loss for shifting.  It is a big pain in the left leg and right arm and the computers these days are very much up to the task of shifting better than anyone else at all times (they don't get tired).  In a bus situation like we have for our motorhome, I would never consider any kind of manual.  It takes all the fun out of driving and if something happens to you, can anyone else drive the bus?  I thought so.  Good Luck, TomC 
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Sojourner
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« Reply #29 on: September 01, 2007, 04:45:04 AM »

  If I were ever to get back on the road with my own truck, there wouldn't be any question what transmission I'd put in my truck-that's a 13 spd Ultrashift.  Good Luck, TomC

TomC....can you skip every other shift with 13 spd Ultrashift if you want to?
Thanks Tom
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buswarrior
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« Reply #30 on: September 01, 2007, 07:40:32 AM »

The Ultrashift will skip the gears for you, as will the ZF ASTronic, the one MCI is using in the new coaches.

Under light throttle and light load, it jumps to whatever gear makes sence.

In a bus, the ASTronic 10 speed typically will start in 2 and go 4,6 8 9 10, depending on grade, headway being made, weight in the bus and your choice of throttle setting.

You may tap the control pad and ask for an early shift, or tap twice for a gear skip, or leave it alone, whatever your mood or desire.

I'm with Tom. Gear rowing, fun as it was in the beginning, is now just a chore.

These transmissions are beginning to be found in donor trucks, with everything you need to do a 4 stroke power upgrade swap at the same time. A bunch of younger tires attached, a couple of airride seats...and then sell what's left to a scrap yard with al your take-outs stuffed into and make some money back.

Or, the quicker route: Anyone have the winning lottery numbers for an upcoming draw?

happy coaching!
buswarrior
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prevost82
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« Reply #31 on: September 01, 2007, 09:22:57 AM »

Hey Tom ... I'm in the middle of nowhere right now (no cell service, only sat. internet) I will check the numbers when I get back to civilization. Prevost uses a dummy box up front and a cabover shift tower on the tranny and a drive shaft inbetween so that shouldn't be a problem ... just have to find a cabover tower for a 13 speed or maybe I will get lucky and this one will fit.

Ron
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TomC
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« Reply #32 on: September 01, 2007, 09:29:56 AM »

Actually on the 18spd and the high range of the 13spd where the overdrive splitter is working, you can skip shift manually up to four gears at a time-since with the splitter thats what it takes to actually skip a whole gear.  So example- on the 10 spd, if you want to go from 6 to 8th, you tap the up arrow twice-once onto 7th then again into 8th.  On the 13 or 18 speed if you want to go from 6th direct to 8th direct, you tap the up button once into 6th overdrive, again for 7th direct, again for 7th overdrive, then again for 8th direct.  The easiest is just to let the transmission do its' thing.  As long as you keep your foot off the accelerator and just use partial throttle during acceleration, the transmission will automatically skip shift.  During full throttle with for instance going up a hill and the rate of acceleration is low, the transmission will use all gears.

Ron- KW and Freightliner on their latest cabovers used a very successful 2 cable shifting method, one for the X shifting (side to side) and the other for the Y shifting (for and back).  You'd have to have for instance Johnston controls make some long cables for you, but then would be the easiest installation-rather than using and trying to align up a long driveshaft.  The other advantage to the cables is that you could install them to get a normal shift pattern up front, compared to the direct drive shaft that most likely would be backwards.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
prevost82
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« Reply #33 on: September 01, 2007, 09:56:25 AM »

Tom The way the dummy box up front work is it reverses the shift pattern to normal. I think I'll stick with the drive shafts for shifting, but thks for the suggesting.
Ron
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Sojourner
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« Reply #34 on: September 01, 2007, 06:04:49 PM »

TomC & Buswarrior...........Thanks you so much to update me. I can now go looking for a futrue wreck class 8 truck with the Ultrashift or ZF ASTronic with ISM or DD 12.7 which is more common than RV burnout Spartan Mountain equips motorhome with B500. I always prefer slider shift trans over sun-gear type trans. So this is well waiting for the right time to get the latest upgrade.

Thanks to all for good supports.

Sojourn for Christ, Jerry
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« Reply #35 on: September 01, 2007, 10:32:00 PM »

Sojourner- Highly recommend you stay away from the ZF Astronic transmission.  While they are a good design, work well, shift smoothly, they use a very expensive 17" single plate clutch.  And if the transmission ever goofs up, they are so expensive to repair usually you just exchange it for a newly rebuilt one.  Personally-look for a truck with the Eaton Ultrashift in it-much easier to get service on it since the basic transmission is a standard truck transmission with electronic controls added, they use standard clutch linings, and they have been around long enough to be proven.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #36 on: September 01, 2007, 11:49:25 PM »

An interesting note is that MCI is offering to replace B500 trannies with a new ZF Astronic for the same cost as replacing a B500 with a rebuilt B500.  I am guessing this only applies to true MCI buses and not my Dina.  (Not that I ever intend to replace my B500.)

Posters here have reported that the ZF Astronic in new buses is not nearly as smooth for passengers due to the many shifts needed to get to highway speed compared to the B500.
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« Reply #37 on: September 02, 2007, 07:08:04 AM »

On the ride quality issue:

Allsion is now heavily using this in their marketing. The clear detection and break in power delivery for every shift of the automated trannies, and the related complaints from little old ladies, and other discerning customers about their heads bobbing in the hands of a thug driver versus the seamless power delivery of a proper torque converter equipped Allision.

And in the city, in stop and go, the Allsion will be out of sight, the automated are much slower to get motivated down the road.

Not necessarily issues for a busnut, as the automated may be driven smoothly in the hands of a caring driver, just not at any great rate of acceleration without an increase in notice by the passengers.

happy coaching!
buswarrior
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« Reply #38 on: September 02, 2007, 09:57:56 AM »

With proper driving techniques- meaning easing out of a signal and not just flooring it all the time (although it is alot of fun) the Allison will get very close to the Automated transmission in fuel mileage.  With the smoothness and great acceleration from a stop, and hill starting capabilities, I'm sold on Allison.  I drove a truck with 76,000lb with the wide ration Allison 4500RDS in it, and it was truly eye opening the acceleration it had compared to a stick transmission, or even an automated.  I firmly believe, for our use, the Allison is the best choice-anyone can drive it, it is smooth on acceleration, fast from a stop, and most any trans shop can work on them that are Allison trained-compared to the ZF that gets alot of head scratching.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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