Reply
 
Thread Tools Display Modes
 
Old 06-13-2019, 08:36 AM   #1
Mini-Skoolie
 
Join Date: Jun 2018
Location: NH
Posts: 39
Year: 2007
Chassis: 3500
Engine: 6.6L
Gear ratio

I know many are looking at diff gear ratios for speed im looking to get our engine speed down 2002 fs65 3126 cat with a at545 the gear ratio is a 5.57 the bus will do 60-65 but is pretty much topped out im looking to get the rpms down a little bit to get slightly better economy im not certain what the sweet spot for this engine rpm wise is but im sure its not sitting on red line any thoughts would be great on gear ratios for lower rpm and what the sweet spot is on the 3126 thanks
MIKE N STEPH is offline   Reply With Quote
Old 06-13-2019, 09:44 AM   #2
Bus Geek
 
EastCoastCB's Avatar
 
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 19,056
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
My bus has the same drivetrain. My rear is 3.42 or close to that. Thing FLIES on the interstate and gets great mpg's but its a 5 window shorty.
I'd probably go with something around 4.00-4.50.
You want 1800-2000 rpm at cruising speed.
__________________
.
Roll Your Own Build Thread
EastCoastCB is offline   Reply With Quote
Old 06-13-2019, 09:51 AM   #3
Mini-Skoolie
 
Join Date: Jun 2018
Location: NH
Posts: 39
Year: 2007
Chassis: 3500
Engine: 6.6L
Quote:
Originally Posted by eastcoastcb View Post
my bus has the same drivetrain. My rear is 3.42 or close to that. Thing flies on the interstate and gets great mpg's but its a 5 window shorty.
I'd probably go with something around 4.00-4.50.
You want 1800-2000 rpm at cruising speed.
nice .. Speed is not my primary concern but any extra is good im just hoping for a little more mpg ... Mine is a 9 window 32ft so not full size but not a shorty what are you getting mpg out of yours and how is it taking off the line ?
MIKE N STEPH is offline   Reply With Quote
Old 06-13-2019, 10:17 AM   #4
Bus Geek
 
EastCoastCB's Avatar
 
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 19,056
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
Quote:
Originally Posted by MIKE N STEPH View Post
nice .. Speed is not my primary concern but any extra is good im just hoping for a little more mpg ... Mine is a 9 window 32ft so not full size but not a shorty what are you getting mpg out of yours and how is it taking off the line ?
I'm not as into data tracking as other folks. Gets better than 10 far as I can tell. Does much better on fuel than any of my previous buses.
In your bus I'd go for a 4.10-ish ratio. Maybe even as high as 3.73-ish.

With 3.42 mine takes off just fine. Can't tell any much difference from the other buses I've had I just know the high gearing is awesome and I'm happy as a clam with it.
The torque of the Cat gets the bus up to speed VERY nicely by bus standards. Another benefit of the higher gearing is its a LOT quieter in the bus going down the road. Normal conversation is possible without even yelling to the rear passengers. Much less stressful and frantic than buzzing down the interstate at redline.
I mostly cruise at 45-55 but on the interstate I do 65 steady at around 1800 rpm. If I want to the bus will do 80.
__________________
.
Roll Your Own Build Thread
EastCoastCB is offline   Reply With Quote
Old 06-14-2019, 05:23 AM   #5
Bus Crazy
 
Join Date: May 2014
Location: West Ohio
Posts: 1,247
Year: 1984
Coachwork: Bluebird
Chassis: International 1753
Engine: 6.9 International
Rated Cap: 65
Great idea! But I wouldn't recommend doing it with an at545 as your transmission. You'll burn it up quick by doing that. The reason is because the stall speed of the converter is really high in the at545, almost too high to be used in an inline 6 diesel engine. Above stall speed, you'll have a few % torque converter slippage, run it below stall speed and your slippage# goes way up. Slipping like that builds a bunch of heat and loses a lot of efficiency.

So, if you had a trans with a lockup torque converter, I'd be all for it. But you don't, so I'd recommend against any changes.
Booyah45828 is offline   Reply With Quote
Old 06-14-2019, 05:51 AM   #6
Bus Geek
 
EastCoastCB's Avatar
 
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 19,056
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
Quote:
Originally Posted by Booyah45828 View Post
Great idea! But I wouldn't recommend doing it with an at545 as your transmission. You'll burn it up quick by doing that. The reason is because the stall speed of the converter is really high in the at545, almost too high to be used in an inline 6 diesel engine. Above stall speed, you'll have a few % torque converter slippage, run it below stall speed and your slippage# goes way up. Slipping like that builds a bunch of heat and loses a lot of efficiency.

So, if you had a trans with a lockup torque converter, I'd be all for it. But you don't, so I'd recommend against any changes.
My bus does really well out on the highway. No high temps and I don't notice crazy slipping like other 545's I've owned.
The bus was originally 4.10 but they went to 3.42 when they put in a reman 545.
I wouldn't let a 545 stop me from modding and enjoying an otherwise nice bus. You have to crack eggs to make an omelette.
__________________
.
Roll Your Own Build Thread
EastCoastCB is offline   Reply With Quote
Old 06-14-2019, 05:53 AM   #7
Bus Crazy
 
Join Date: May 2014
Location: West Ohio
Posts: 1,247
Year: 1984
Coachwork: Bluebird
Chassis: International 1753
Engine: 6.9 International
Rated Cap: 65
I thought your bus had an Allison 2000 in it?
Booyah45828 is offline   Reply With Quote
Old 06-14-2019, 06:04 AM   #8
Bus Geek
 
EastCoastCB's Avatar
 
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 19,056
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
Quote:
Originally Posted by Booyah45828 View Post
I thought your bus had an Allison 2000 in it?
nope. Its got a Cat 3126 and a 545. Has the best highway manners of any bus I've owned. Whisper quiet ride and great fuel economy.
If/When the 545 ever gives me problems a 643 will take its place.
__________________
.
Roll Your Own Build Thread
EastCoastCB is offline   Reply With Quote
Old 06-14-2019, 06:26 AM   #9
Bus Crazy
 
Join Date: May 2014
Location: West Ohio
Posts: 1,247
Year: 1984
Coachwork: Bluebird
Chassis: International 1753
Engine: 6.9 International
Rated Cap: 65
Well, I learned something new today.

I'll let them make their own decision. I wouldn't do it if it was mine personally, unless they got enough budget for a trans swap in the future as well

I was told the Allison at series was designed for medium duty gas engines back in the 70's, which is why it has a governed rpm rating of 2400 rpm minimum and the lowest stall speed available is around 2000. They couldn't make it lower because the transmission can't handle the torque at that low of an rpm. Ideal stall speed for the 3126 would be around 1200-1600 rpm.

You can run the bus below stall speed, just make sure your fluid doesn't overheat, and you're not at max load/power. You being a shorty, you'll likely never be there so you won't have problems.
Booyah45828 is offline   Reply With Quote
Old 06-14-2019, 06:48 AM   #10
Bus Geek
 
EastCoastCB's Avatar
 
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 19,056
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
Of the 4 I've had with 545's the one with highway gearing feels the best. I'm at 1800 rpm on the highway.
__________________
.
Roll Your Own Build Thread
EastCoastCB is offline   Reply With Quote
Old 06-14-2019, 08:16 AM   #11
Mini-Skoolie
 
Join Date: Jun 2018
Location: NH
Posts: 39
Year: 2007
Chassis: 3500
Engine: 6.6L
Quote:
Originally Posted by eastcoastcb View Post
of the 4 i've had with 545's the one with highway gearing feels the best. I'm at 1800 rpm on the highway.
the rpms are nice in that range .. Looks like your running a little warm though
MIKE N STEPH is offline   Reply With Quote
Old 06-14-2019, 02:09 PM   #12
Bus Geek
 
EastCoastCB's Avatar
 
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 19,056
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
Quote:
Originally Posted by MIKE N STEPH View Post
the rpms are nice in that range .. Looks like your running a little warm though
Nah they all run right up to the thermostat temp. It gets to that temp and stays there no matter what kind of driving.
If you think these run warm definitely avoid the 444E!
__________________
.
Roll Your Own Build Thread
EastCoastCB is offline   Reply With Quote
Old 06-14-2019, 02:13 PM   #13
Mini-Skoolie
 
Join Date: Jun 2018
Location: NH
Posts: 39
Year: 2007
Chassis: 3500
Engine: 6.6L
Quote:
Originally Posted by eastcoastcb View Post
nah they all run right up to the thermostat temp. It gets to that temp and stays there no matter what kind of driving.
If you think these run warm definitely avoid the 444e!
yeah no kidding mines a little under that and it stays there up hills or down the gauge is steady
MIKE N STEPH is offline   Reply With Quote
Old 06-14-2019, 02:41 PM   #14
Bus Geek
 
EastCoastCB's Avatar
 
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 19,056
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
Quote:
Originally Posted by MIKE N STEPH View Post
yeah no kidding mines a little under that and it stays there up hills or down the gauge is steady
Yeah that's what you want a steady gauge. Long as its working lol.
Modern engines run a lot hotter than older ones. gotta keep that in mind. With an at545 bus you want a FULL radiator. A lot of the Internationals had wimpy little half radiators and at speed they're struggling to keep up.
A good rad, a nice add on trans cooler, some highway gears... I'm happy with this bus. Its crazy how smooth and quiet this thing is compared to other buses I've had.
My old shorty had a 444E and a 545 with a split radiator and 4.10 rear. It was a nice cruiser but the temps would start to climb over 60. It was annoying cause I HAD to watch the gauge a lot. This one I only have check periodically for peace of mind.
__________________
.
Roll Your Own Build Thread
EastCoastCB is offline   Reply With Quote
Old 06-14-2019, 02:49 PM   #15
Mini-Skoolie
 
Join Date: Jun 2018
Location: NH
Posts: 39
Year: 2007
Chassis: 3500
Engine: 6.6L
Quote:
Originally Posted by eastcoastcb View Post
yeah that's what you want a steady gauge. Long as its working lol.
Modern engines run a lot hotter than older ones. Gotta keep that in mind. With an at545 bus you want a full radiator. A lot of the internationals had wimpy little half radiators and at speed they're struggling to keep up.
A good rad, a nice add on trans cooler, some highway gears... I'm happy with this bus. Its crazy how smooth and quiet this thing is compared to other buses i've had.
My old shorty had a 444e and a 545 with a split radiator and 4.10 rear. It was a nice cruiser but the temps would start to climb over 60. It was annoying cause i had to watch the gauge a lot. This one i only have check periodically for peace of mind.
i have no idea what type of person would put a split rad on a diesel engine but thats dumb ... Thats a good thing of the freightliner chassis full rad and inter-cooler
MIKE N STEPH is offline   Reply With Quote
Old 06-14-2019, 02:58 PM   #16
Bus Geek
 
EastCoastCB's Avatar
 
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 19,056
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
Quote:
Originally Posted by MIKE N STEPH View Post
i have no idea what type of person would put a split rad on a diesel engine but thats dumb ... Thats a good thing of the freightliner chassis full rad and inter-cooler
Yep. I like the way the Freightliner/Cat/Thomas is put together.
For those with an IC wanting a full rad the CE300 parts are what you want. Its got a full rad and CAC on a 3800 chassis setup for a DT466E. Nice big improvement over the split setup!
__________________
.
Roll Your Own Build Thread
EastCoastCB is offline   Reply With Quote
Old 06-15-2019, 06:23 PM   #17
Skoolie
 
WARGEAR's Avatar
 
Join Date: Mar 2018
Location: Fingerlakes region NY
Posts: 195
Year: 1999
Coachwork: AmTran/Wolfington
Chassis: 3800
Engine: International DT466E 190HP variant
Rated Cap: 72 pax 29500 GVWR
Quote:
Originally Posted by MIKE N STEPH View Post
I know many are looking at diff gear ratios for speed im looking to get our engine speed down 2002 fs65 3126 cat with a at545 the gear ratio is a 5.57 the bus will do 60-65 but is pretty much topped out im looking to get the rpms down a little bit to get slightly better economy im not certain what the sweet spot for this engine rpm wise is but im sure its not sitting on red line any thoughts would be great on gear ratios for lower rpm and what the sweet spot is on the 3126 thanks
Am I missing something here? How are you pulling that high a top end speed with a 1:1 top gear and 5.57 rear end?
WARGEAR is offline   Reply With Quote
Old 06-17-2019, 07:57 AM   #18
Mini-Skoolie
 
Join Date: Jun 2018
Location: NH
Posts: 39
Year: 2007
Chassis: 3500
Engine: 6.6L
Quote:
Originally Posted by wargear View Post
am i missing something here? How are you pulling that high a top end speed with a 1:1 top gear and 5.57 rear end?
i hate to say but i dont know .. I called freightliner so they told me what my axle is and i had the bus on the road for a few miles with your questioning maybe ill start counting how many time the driveshaft goes round
MIKE N STEPH is offline   Reply With Quote
Old 06-17-2019, 12:15 PM   #19
Bus Geek
 
EastCoastCB's Avatar
 
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 19,056
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
Ok, lets figure it out.
What's your tire size and your RPM at top speed?
__________________
.
Roll Your Own Build Thread
EastCoastCB is offline   Reply With Quote
Old 06-17-2019, 12:57 PM   #20
Mini-Skoolie
 
Join Date: Jun 2018
Location: NH
Posts: 39
Year: 2007
Chassis: 3500
Engine: 6.6L
Quote:
Originally Posted by eastcoastcb View Post
ok, lets figure it out.
What's your tire size and your rpm at top speed?
10r22.5 tire so thats 40 inch
2300rpm at 60
2500rmp held to the floor 65
MIKE N STEPH 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 04:57 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
×