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01-29-2018, 08:22 PM
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#1
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Bus Crazy
Join Date: Jun 2016
Location: N.C.
Posts: 1,136
Year: 1997
Coachwork: Bluebird
Engine: DT466E
Rated Cap: 34
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Need some help with differential math
So.....I've decided to swap my differential gearing....it's currently a 4.78
Engine is DT466E, 175HP@2300rpm, 430ft-lbs@1500 rpm (had the road speed limiter removed Friday).
Will be putting 11Rs (41") on the rears.
My Spicer ES43-5D 5 speed manual ratios are as follows....1st 7.25, 2nd 3.98, 3rd 2.23, 4th 1.29, 5th 1.00
1st and 2nd are next to worthless.....I can only roll about 10 feet in first b/4 having to shift, and 2nd is about another 30 feet.
Ideally, I'd like to cruise at 62-65mph at 1600-1800rpm, and have 72-75mph available for passing/merging.
Am I right in thinking that I'll need 3.73s or 3.91s to get me where I want to be? And is there a formula to tell me top speed in each gear at a given rpm?
I'd appreciate any help to shed some light on this for me.
Don
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01-29-2018, 08:28 PM
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#2
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Bus Geek
Join Date: Sep 2017
Location: Owasso, OK
Posts: 2,627
Year: 1999
Coachwork: Thomas
Chassis: Saf-T-Liner MVP ER
Engine: Cummins 6CTA8.3 Mechanical MD3060
Rated Cap: 46 Coach Seats, 40 foot
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Quote:
Originally Posted by plfking
So.....I've decided to swap my differential gearing....it's currently a 4.78
Engine is DT466E, 175HP@2300rpm, 430ft-lbs@1500 rpm (had the road speed limiter removed Friday).
Will be putting 11Rs (41") on the rears.
My Spicer ES43-5D 5 speed manual ratios are as follows....1st 7.25, 2nd 3.98, 3rd 2.23, 4th 1.29, 5th 1.00
1st and 2nd are next to worthless.....I can only roll about 10 feet in first b/4 having to shift, and 2nd is about another 30 feet.
Ideally, I'd like to cruise at 62-65mph at 1600-1800rpm, and have 72-75mph available for passing/merging.
Am I right in thinking that I'll need 3.73s or 3.91s to get me where I want to be? And is there a formula to tell me top speed in each gear at a given rpm?
I'd appreciate any help to shed some light on this for me.
Don
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Plug your numbers in here and play to your heart's content
Gear Ratio Calculator
That page has a tire diameter calculator at the bottom too.
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01-29-2018, 08:39 PM
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#3
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Bus Geek
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 23,764
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
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Quote:
Originally Posted by plfking
So.....I've decided to swap my differential gearing....it's currently a 4.78
Engine is DT466E, 175HP@2300rpm, 430ft-lbs@1500 rpm (had the road speed limiter removed Friday).
Will be putting 11Rs (41") on the rears.
My Spicer ES43-5D 5 speed manual ratios are as follows....1st 7.25, 2nd 3.98, 3rd 2.23, 4th 1.29, 5th 1.00
1st and 2nd are next to worthless.....I can only roll about 10 feet in first b/4 having to shift, and 2nd is about another 30 feet.
Ideally, I'd like to cruise at 62-65mph at 1600-1800rpm, and have 72-75mph available for passing/merging.
Am I right in thinking that I'll need 3.73s or 3.91s to get me where I want to be? And is there a formula to tell me top speed in each gear at a given rpm?
I'd appreciate any help to shed some light on this for me.
Don
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A 4.78 will only have you doing around 65 at redline with 11R's.
4.10 would be about PERFECT for you. It would give you 76-77 at redline and 60 mph at 2000 rpm.
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01-29-2018, 11:57 PM
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#4
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Traveling
Join Date: Nov 2015
Location: Midwest
Posts: 2,573
Year: 2003
Coachwork: BlueBird
Chassis: TC2000
Engine: 5.9L Cummins
Rated Cap: '00
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ohhh, whew. My heart missed a beat- I thought you needed diff eq help.
shoutout for Randy's Rears
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01-30-2018, 01:16 AM
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#5
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Skoolie
Join Date: Dec 2017
Location: southern maine
Posts: 114
Year: 2010
Coachwork: Coach & Equipment MFG
Chassis: ford E350 superduty
Engine: 5.4 liter v8
Rated Cap: 7 passenger
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4.10 or 3.73 either is a viable option. and will make that 1st gear a lot more usable.
__________________
2010 ford e350 superduty v8 7 passenger bus
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01-30-2018, 01:19 AM
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#6
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Skoolie
Join Date: Dec 2017
Location: southern maine
Posts: 114
Year: 2010
Coachwork: Coach & Equipment MFG
Chassis: ford E350 superduty
Engine: 5.4 liter v8
Rated Cap: 7 passenger
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Quote:
Originally Posted by Rusty
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yikes horrors of college just flashed back through my head.
__________________
2010 ford e350 superduty v8 7 passenger bus
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01-30-2018, 07:47 PM
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#7
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Bus Crazy
Join Date: Jun 2016
Location: N.C.
Posts: 1,136
Year: 1997
Coachwork: Bluebird
Engine: DT466E
Rated Cap: 34
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Thank you, guys, for your input and the calculator.
Food for thought.
Don
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01-30-2018, 08:24 PM
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#8
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Bus Geek
Join Date: Sep 2017
Location: Swansboro,NC
Posts: 2,987
Year: 86
Coachwork: Thomas
Chassis: Ford B700
Engine: 8.2
Rated Cap: 60 bodies
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Do you plan on towing anything?
Gearing for road speed reduces your Towing ability to even pull a car on a bar.
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01-30-2018, 10:50 PM
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#9
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Bus Crazy
Join Date: Jun 2016
Location: N.C.
Posts: 1,136
Year: 1997
Coachwork: Bluebird
Engine: DT466E
Rated Cap: 34
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MAY occasionally tow a 6x8 trailer with a couple of dirt bikes, but no plans for anything heavier.
Even if 5th gear becomes nothing but a flat-country OD gear, that would be okay with me.
Don
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01-31-2018, 06:40 AM
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#10
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Bus Geek
Join Date: May 2009
Location: Columbus Ohio
Posts: 18,830
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
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my 6th gear on my redbyrd is nothiung but a flat country gear.. has me Taching about 1550-1600 at 65 MPH.. id like to have a little lower gearing than that .. omnce I go up the least little incline I drop back to 5th which has decent power. but you may want to keep your RPMs in that 1800-1900 range in top gear at 65 or your planned cruising speeds.. seems the engines are happier there.. at least my 444E is.
-Christopher
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01-31-2018, 07:36 AM
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#11
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Bus Crazy
Join Date: Feb 2015
Location: Cincinnati, Ohio
Posts: 1,001
Year: 2000
Coachwork: Blue Bird
Chassis: International
Engine: TE 444
Rated Cap: 12
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3.90 would be good
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01-31-2018, 07:53 AM
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#12
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Bus Geek
Join Date: May 2009
Location: Columbus Ohio
Posts: 18,830
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
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Quote:
Originally Posted by Kubla
3.90 would be good
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thats probably what i need in my bus
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01-31-2018, 11:25 AM
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#13
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Bus Geek
Join Date: Dec 2016
Location: Weeki Wachee, FL
Posts: 3,056
Year: 1997
Coachwork: Bluebird
Chassis: TC2000 FE
Engine: Cummins 5.9
Rated Cap: 72
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Do folks usually swap the entire rear end or do they replace the internals of their current diff?
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01-31-2018, 11:41 AM
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#14
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Bus Crazy
Join Date: May 2016
Location: Georgia
Posts: 2,264
Year: 2001
Coachwork: Blue Bird
Chassis: IH
Engine: T444E
Rated Cap: 14
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Quote:
Originally Posted by brokedown
Do folks usually swap the entire rear end or do they replace the internals of their current diff?
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Usually it is far cheaper and easier just to swap out the "chunk" (carrier housing). The only reasons I would swap out an entire axle is:
1. The old one is damaged beyond reasonable repair (as in, I could replace it cheaper).
2. Swapping spring ride for air ride (and the old one won't work).
3. Needing a heavier duty axle.
4. Parts for the old one are no longer available.
5. Swapping Budd/Dayton style rims. This would usually include doing the same on the front axle as well.
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06-13-2018, 05:03 PM
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#15
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Mini-Skoolie
Join Date: May 2018
Location: Hager City WI
Posts: 36
Year: 1996
Chassis: International 3800
Engine: DT 466 Mechanical spicer 6+1. & 5.9 Cummins
Rated Cap: 65
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update?
Hey was wondering if you actually swapped the rear diff out, I have a 96 3800 with a DT 466 mechanical rated at 190HP with the 4.78 rear and was wondering what your speeds and RPMs are, I have a 6+1 spicer tranny. I want to go to a 4.10 as well but would like to hear about yours first
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06-13-2018, 08:56 PM
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#16
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Bus Crazy
Join Date: Jun 2016
Location: N.C.
Posts: 1,136
Year: 1997
Coachwork: Bluebird
Engine: DT466E
Rated Cap: 34
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Sent you a PM
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