Bus Conversions dot Com Bulletin Board
July 30, 2014, 08:09:07 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
News: If you had an E-Mag Subscription: It will not turn yellow, get musty, dusty, and mildewed or fade.
   Home   Help Forum Rules Search Calendar Login Register BCM Home Page Contact BCM  
Pages: [1]   Go Down
  Print  
Author Topic: allison B500  (Read 3291 times)
ruthi
Hero Member
*****
Offline Offline

Posts: 1080




Ignore
« on: January 21, 2011, 04:02:11 PM »

Is there a reason that someone would block out the 6th gear in a Allison B500 transmission? Would it not really be needed if the gear ratio on rear end is high? I think the gear ration is 4. 25.
Logged

Mixed up Dina, ready for the road as of 12/25/2010
Home in middle Georgia, located somewhere in the
southeast most of the time.
FIRST RALLY ATTENDED: BUSSIN 2011!
HB of CJ
Hero Member
*****
Offline Offline

Posts: 1233




Ignore
« Reply #1 on: January 21, 2011, 04:42:01 PM »

The first reason is that 6th gear would drop the engine rpm down too low for efficient operation at the envisioned practical maximum legal cruising speed.

Another reason is that the existing engine doesn't have enough power to pull 6th gear, which is almost the same as the first reason, but different also.

Another reason is that for legality, city fathers don't want high powered fire apparatus capable of going 110 miles per hour, which they might be able to.

The limiting top speed seems to be the tires which nowadays are limited to around 75 mph.  Tires blowing out from heat failure is a bad business practice.

Finally, some say 6th gear on this tranny is somewhat weak and the factory will not warrant the Allision if 6th gear is used in some applications.

The fix is a bigger, more $expensive$ Allision transmission.  I for one would want all 6 gears that are available, but this is not always possible.

Some time ago, my brother took his fire engine down to the Detroit Diesel dealer ship and asked the computed guy what he could do to increase power.

The computer guy said he could give the 8V92TA something over 600 hp AND 6th gear, but he would would have to kill himself first.  Smog laws.
Logged
belfert
Hero Member
*****
Offline Offline

Posts: 5396




Ignore
« Reply #2 on: January 21, 2011, 04:54:58 PM »

If my 1995 and your 1998 are the same the gear ratio should be 4.10.  I was told the reason that 6th gear is locked out is because the RPM could drop too low and the B500 would just downshift to 5th.  6th gear should just be unlocked for those times when it can be used.  So what if it downshifts when it can't be used?

I talked to my local Detroit Allison dealer about unlocking 6th gear and they said it would take $600 plus a letter from an engineer at the original manufacturer.  Even if I could get the letter from MCI it didn't seem worth $600 for this.  If I gained anything on mileage it would porbably take a long time to pay back $600 for me at least.
Logged

Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
Hard Headed Ken
Sr. Member
****
Offline Offline

Posts: 307


1988 Prevost Angola Conversion Repowered With 14L Series 60 & Eaton Ultrashift


WWW

Ignore
« Reply #3 on: January 21, 2011, 07:55:53 PM »

Ruth,
 I'm reasonably sure that when we checked the information in your ECM it had the differential ratio listed at 4.1. 

Ken
Logged

Link to my engine swap slide show

https://www.youtube.com/watch?v=oxAFFBcoTQI
TomC
Hero Member
*****
Offline Offline

Posts: 6682





Ignore
« Reply #4 on: January 22, 2011, 08:33:04 AM »

Figuring you have 12R-22.5 that are 485rpm tires (in general) and with the 4.1 ratio, with the B500, 4th gear direct your engine speed will be 1822 @ 55, 1988 @ 60, 2154 @ 65.  In 5th gear, which is a .74 overdrive, your engine speed will be 1349 @ 55, 1471 @ 60, 1594 @ 65, 1716 @ 70, 1839 @ 75, 1962 @ 80. In 6th gear, which is a .64 overdrive. your engine speed will be 1272 @ 60, 1378 @ 65, 1484 @ 70, 1590 @ 75, 1696 @ 80, 1802 @ 85, 1908 @ 90, 2015 @ 95, 2121 @ 100.  If you have an electronic 8V-92TA, you could probably use the 6th gear, but otherwise, I wouldn't worry about it.  At least your drive train speed will be OK.  At Freightliner, we figure a maximum driveline speed of 3,200rpm, which is at 96mph.  Using the 6th speed would be perfect for a 4 stroke engine.

It is interesting to note that in an effort to get more MPG out of the engines, Allison on the 4000 series truck transmissions used with the DD engines have them shifting at 1600rpm and into 6th gear dropping to 1100rpm on light throttle.  Allison is slowly getting more confident with their transmissions.  I remember when the HD4060 first came out-it was restricted to 430hp and 1450lb/ft torque.  Now the 4000HS has a 560hp rating and 1850lb/ft torque (in gears 3-6).  Good Luck, TomC
Logged

Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
ruthi
Hero Member
*****
Offline Offline

Posts: 1080




Ignore
« Reply #5 on: January 22, 2011, 09:20:52 AM »

Thanks Ya'll  Grin
Logged

Mixed up Dina, ready for the road as of 12/25/2010
Home in middle Georgia, located somewhere in the
southeast most of the time.
FIRST RALLY ATTENDED: BUSSIN 2011!
blue_goose
Sr. Member
****
Offline Offline

Posts: 275





Ignore
« Reply #6 on: January 23, 2011, 07:38:08 AM »

There is no reason that you can't change it to the 6 speed.  YOu will be fine with the 4.10 rear, if it needs 5th it will go there.  Give Ted Keating a call at 267-716-7332 or 800-997-4858.  He is the man to talk with about your world trans.  Ted will reprogram your transmission for a lot less than anyone with Detroit.
Jack
Logged

Data used in this document is made from 100% recycled electrons and magnetic particles. No electrons were harmed in the creation of this document.
buswarrior
Hero Member
*****
Offline Offline

Posts: 3571


'75 MC8 8V71 HT740




Ignore
« Reply #7 on: January 23, 2011, 08:23:28 PM »

Minimum input RPM for 6th gear for that specific model year of B500?

They were often paired up with 4.56 gears.

Somebody knows....

happy coaching!
buswarrior

Logged

Frozen North, Greater Toronto Area
TomC
Hero Member
*****
Offline Offline

Posts: 6682





Ignore
« Reply #8 on: January 23, 2011, 08:43:11 PM »

On the older B500 and HD4060, 1400rpm was typically the lowest rpm allowed in 6th gear-which with your 4.56 gear ratio and 485rpm 12R-22.5 tires works out to be 59mph.  Good Luck, TomC
Logged

Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
ruthi
Hero Member
*****
Offline Offline

Posts: 1080




Ignore
« Reply #9 on: January 24, 2011, 08:30:48 AM »

Actually, 4.1 is the ratio.
Logged

Mixed up Dina, ready for the road as of 12/25/2010
Home in middle Georgia, located somewhere in the
southeast most of the time.
FIRST RALLY ATTENDED: BUSSIN 2011!
TomC
Hero Member
*****
Offline Offline

Posts: 6682





Ignore
« Reply #10 on: January 24, 2011, 02:07:06 PM »

That works out to be 65.5mph at 1400rpm.  Good Luck, TomC
Logged

Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
Hard Headed Ken
Sr. Member
****
Offline Offline

Posts: 307


1988 Prevost Angola Conversion Repowered With 14L Series 60 & Eaton Ultrashift


WWW

Ignore
« Reply #11 on: January 24, 2011, 03:15:26 PM »

Tomc, do you think 6th gear unlocked will be of any value on Ruthi's Dina? I remember reading somewhere that the fuel efficiency peak for the 12.7 is at 1400 RPM. It looks like peak torque is at 1200 and remains reasonably flat to about 1550. I have another reason for asking. The transmission gear set I'm using should put's me about the same. .74 top gear ratio, 3.36 final drive and 315/80 22.5 tires. I come up with about 1400 RPM at 70 MPH. Is that close?

Thanks,
Ken
« Last Edit: January 24, 2011, 08:12:49 PM by Hard Headed Ken » Logged

Link to my engine swap slide show

https://www.youtube.com/watch?v=oxAFFBcoTQI
belfert
Hero Member
*****
Offline Offline

Posts: 5396




Ignore
« Reply #12 on: January 24, 2011, 07:02:20 PM »

That works out to be 65.5mph at 1400rpm.  Good Luck, TomC

My tires are 11R24.5 480 RPM and I have a 4.10 rear end.  Would I still be around 1400 RPM at 65 MPH with a B500?  It might be worth giving Ted Keating a call if that is the case.
Logged

Brian Elfert - 1995 Dina Viaggio 1000 Series 60/B500 - 75% done but usable - Minneapolis, MN
TomC
Hero Member
*****
Offline Offline

Posts: 6682





Ignore
« Reply #13 on: January 25, 2011, 02:30:05 PM »

Personally-I would just leave the 5th gear top in place-I don't think there will be much of an improvement using 6th gear.

As to using 315/80R-22.5 tires that are 492rpm with 3.36 gearing.  In 4th direct you'll be at 1653 @ 60, 1790 @ 65, 1928 @ 70, 2066 @ 75. In 5th overdrive of .74, you'll be at 1427 @ 70, 1529 @ 75.  I don't think 6th would work.

11R24.5 tires at 479rpm and 4.1 ratio works out to be-1963 @ 60-which is very close to the prementioned speed figurings.  Good Luck, TomC
Logged

Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
NEO/Russ
NEO/Russ
Jr. Member
**
Offline Offline

Posts: 83




Ignore
« Reply #14 on: January 27, 2011, 09:22:56 AM »

If anyone needs a new ECU for a B500 I have one.  I had it for a repower I was doing, but sold the chassis.  New in '03, never used.  Contact me direct through my email on my profile if you need one, or a new accumulator, used oil to oil cooler all for S60 and B500 and we can talk.

Russ
Logged

Well no longer a bus nut, but over the years I learned a lot here and still come back to see what I can apply to the conversion of my KW T2000 for hauling my Teton fifth wheeler.
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.18 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!