Reply
 
Thread Tools Display Modes
 
Old 09-01-2018, 10:14 PM   #1
Mini-Skoolie
 
OrionsComfortBus's Avatar
 
Join Date: Jul 2018
Location: Poteet, Tx
Posts: 39
Year: 1993
Coachwork: International - AmTran
Chassis: 3800
Engine: DTA 360
Rated Cap: 25,500 lbs
Rear Diff ratio?

Im considering lowering the rear differential ratio on my Comfort bus.
I have a DTA360 attached to a ATA545 with 10r22.5 tires. Tire circumference is about 42 inches. Trans in 4th is a 1 to 1 ratio. Id like a rear diff ratio to allow 65MPH at about 2700-2800 rpm. Can somebody help figure a good ratio? Vander Haags has Spicer N175 diffs in a variety of ratios for $650 each. I figure this would be a better investment than a MT643 which has the same 4th gear ratio. Possibly get me better mileage since I dont haul anything and drive mostly 90% or better highway miles.

www.vanderhaags.com/detailview.php?part=24648952
__________________
The price of freedom is eternal vigilance. - Thomas Jefferson
Ongoing project of maintenance and replacement of things in and on the Comfort Bus https://www.skoolie.net/forums/f9/up...bus-24772.html
OrionsComfortBus is offline   Reply With Quote
Old 09-01-2018, 11:16 PM   #2
Bus Geek
 
Tango's Avatar
 
Join Date: Mar 2011
Location: Houston, Texas
Posts: 7,983
Year: 1946
Coachwork: Chevrolet/Wayne
Chassis: 1- 1/2 ton
Engine: Cummins 4BT
Rated Cap: 15
Plug your numbers into the bottom calculator...then you can play with any of them and see the difference.


Engine RPM Calculator
Tango is offline   Reply With Quote
Old 09-02-2018, 01:45 AM   #3
Mini-Skoolie
 
OrionsComfortBus's Avatar
 
Join Date: Jul 2018
Location: Poteet, Tx
Posts: 39
Year: 1993
Coachwork: International - AmTran
Chassis: 3800
Engine: DTA 360
Rated Cap: 25,500 lbs
super easy, thanks a bunch

That was super easy. Thank You for posting that link.
I'm going to try and get a 4.44 or 4.10 ratio. good options and keeps the engine in its power band. Id rather see 2100 RPM at 60MPH than 2900RPM
Now to make the purchase and swap em out.
__________________
The price of freedom is eternal vigilance. - Thomas Jefferson
Ongoing project of maintenance and replacement of things in and on the Comfort Bus https://www.skoolie.net/forums/f9/up...bus-24772.html
OrionsComfortBus is offline   Reply With Quote
Old 09-02-2018, 09:59 AM   #4
Bus Geek
 
Tango's Avatar
 
Join Date: Mar 2011
Location: Houston, Texas
Posts: 7,983
Year: 1946
Coachwork: Chevrolet/Wayne
Chassis: 1- 1/2 ton
Engine: Cummins 4BT
Rated Cap: 15
Roger that. Many benefits to be had by keeping a diesel in or near its' "sweet spot".


And most people are surprised by the differences even small adjustments can make. Sometimes you can achieve what you want with a minor change in tire size instead of a big $$$ re-gearing.


That calculator can be fun to play with. Glad to hear it helped.
Tango is offline   Reply With Quote
Old 09-16-2018, 12:41 PM   #5
Mini-Skoolie
 
Join Date: May 2018
Posts: 10
trans lockup?

Stop me if I'm wrong, but don't you have a transmission without lockup?

Wouldn't you benefit more from the transmission swap?

http://www.skoolie.net/forums/f33/mt...nay-24142.html

I just recently saw somewhere that someone had purchased Allison's back stock of older transmissions, including MT643s which they were selling for around $650.
hyperlogos is offline   Reply With Quote
Old 09-16-2018, 03:11 PM   #6
Mini-Skoolie
 
OrionsComfortBus's Avatar
 
Join Date: Jul 2018
Location: Poteet, Tx
Posts: 39
Year: 1993
Coachwork: International - AmTran
Chassis: 3800
Engine: DTA 360
Rated Cap: 25,500 lbs
Yes, I have a AT545 in the bus. I have found a remanufactured MT643 to purchase. I have not found any of those surplus for $650. If anybody has a link to those, I'd gladly check em out.
__________________
The price of freedom is eternal vigilance. - Thomas Jefferson
Ongoing project of maintenance and replacement of things in and on the Comfort Bus https://www.skoolie.net/forums/f9/up...bus-24772.html
OrionsComfortBus is offline   Reply With Quote
Old 09-16-2018, 04:44 PM   #7
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 10,231
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
Quote:
Originally Posted by OrionsComfortBus View Post
Yes, I have a AT545 in the bus. I have found a remanufactured MT643 to purchase. I have not found any of those surplus for $650. If anybody has a link to those, I'd gladly check em out.

here is where I got mine.. im in the middle of the swap on a DTA-360 as we speak..


https://www.lkqheavytruck.com/part-d...ON&model=MT643


-Christopher
cadillackid is offline   Reply With Quote
Old 09-16-2018, 05:56 PM   #8
Mini-Skoolie
 
OrionsComfortBus's Avatar
 
Join Date: Jul 2018
Location: Poteet, Tx
Posts: 39
Year: 1993
Coachwork: International - AmTran
Chassis: 3800
Engine: DTA 360
Rated Cap: 25,500 lbs
Nice. It says it's been renewed/remanufactured by Allison. I'm going to call on Monday to find out. If it's accurate and shipping is acceptable. I may get that instead.
__________________
The price of freedom is eternal vigilance. - Thomas Jefferson
Ongoing project of maintenance and replacement of things in and on the Comfort Bus https://www.skoolie.net/forums/f9/up...bus-24772.html
OrionsComfortBus is offline   Reply With Quote
Old 09-16-2018, 07:55 PM   #9
Mini-Skoolie
 
Join Date: May 2018
Posts: 10
Yep I just found that in my web history

cadillackid beat me to it

We've got a B300R so my big goal is to get sixth unlocked... rear axle ratio is 5.38. Sadly it's in a Blue Bird, so I would realistically need to get a TCM for that.
hyperlogos is offline   Reply With Quote
Old 09-18-2018, 02:43 AM   #10
Mini-Skoolie
 
OrionsComfortBus's Avatar
 
Join Date: Jul 2018
Location: Poteet, Tx
Posts: 39
Year: 1993
Coachwork: International - AmTran
Chassis: 3800
Engine: DTA 360
Rated Cap: 25,500 lbs
I called and the price is good as well as the shipping. Sure beats $2,000 for the same thing. All that is left on my upgrade list is a DT466. Well that air disc brakes, insulation, new floor, better seats, ect.
__________________
The price of freedom is eternal vigilance. - Thomas Jefferson
Ongoing project of maintenance and replacement of things in and on the Comfort Bus https://www.skoolie.net/forums/f9/up...bus-24772.html
OrionsComfortBus is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 10:05 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2018, vBulletin Solutions, Inc.