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Old 06-16-2017, 06:34 AM   #21
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Join Date: May 2009
Location: Columbus Ohio
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Year: 1991
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Chassis: International S3800
Engine: DT360
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Quote:
Originally Posted by Tango View Post
Found a pic of the tranny mounts. They are the same on each side. Just your basic Volvo rubber hockey puck engine mount in between.




And do you know off hand where your engine mounts are located? Front, middle, rear? That can make a big difference in how the trans gets loaded.
Tango - I looked after you mentioned it.. my engine is Tri-mounted. there are 2 mounts at the rear of the engine going into the sides of the frame.. they look Stout with large bolts, then there is a cradle mount in front that goes across the bottom of the engine and then has a very llarge bolt in the center with a rubber mount that goes through the front frame support cross member. that looks like a 9/16 or 5/8 thread bolt..

so im thinking i should be fine?

-Christopher
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Old 06-16-2017, 07:40 AM   #22
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Location: Essex, MD
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Year: 1999
Chassis: Blue Bird TC RE 3904, Flat Nose, 40', 277" wh base
Engine: 8.3L Cummins ISC 260hp, AT643, 4.44 rear
Rated Cap: 84 pax or 1 RV; 33,000lbs
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Originally Posted by cadillackid View Post
an 8.3 with a 643's most costr effective way to improve is to regear the rear and turn up the smoke on the 8.3. you have the power and a good transmission you just need to lower the RPMs a bit..
-Christopher
Can I? I think I read that the 643 was good for 250hp or something hp. My build sheet says I have the 260hp variant of the ISC. The engine may be capable but is the tranny?

Second question part 1 ... How do I go about finding what rear ends are available? Since it's an RE bus I have a really tiny driveshaft. It's also coming from the wrong direction so the pumpkin looks funny.

Part 2 ... Is there a way to calculate UPHILL speed? I currently have 1:1 final tranny, 4.44 rear, 11R22.5 tires, and 2500 rpms. I don't remember the exact number but it equals near enough to 65mph top speed. Normally I stick at 60 and call it good. On the 8~9% grades, I'll drop from 65 to 38mph and into 3rd gear. If I change the rear to a 2.86 (totally made up number) I'll be able to do 157mph downhill but what would the uphill speed be?

Component Number Description
01-594 MT643/647/653
10-594 MT643/653
14-694 MT643 2200 3000
16-1265 643 2400 RM/FL/L3-4
17-508 6881461 GOVERNOR ASSY
21-738 TC378
22-552 MT643 16T SPEEDO (FOR MAG
23-894 MT643 W/O SHIPPING SACKS
37-583 5.1 DEEP W/1ST CL FD TUBE

I have no idea what this governor assembly is or if it's adjustable.
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Old 06-16-2017, 08:46 AM   #23
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if you are losing uphill speed then you would likely lose speed worse on long grades.. 8-9% grade is pretty tough grade to maintain high speed on.. I look at a build that takes care comfortably of 90% of my driving characteristics.. ie yes slowing down on a grade sucks but if im on a road trip and im only on a grade like that once ever yday or couple days then id deal with the slow uphill speeds..

for some reason I thought the 643 was good for 300+ HP.. makes me wonder if there were different variants of it.. this is great info.
-Christopher
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Old 06-16-2017, 08:52 AM   #24
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Chassis: Blue Bird TC RE 3904, Flat Nose, 40', 277" wh base
Engine: 8.3L Cummins ISC 260hp, AT643, 4.44 rear
Rated Cap: 84 pax or 1 RV; 33,000lbs
Quote:
Originally Posted by cadillackid View Post
if you are losing uphill speed then you would likely lose speed worse on long grades.. 8-9% grade is pretty tough grade to maintain high speed on.. I look at a build that takes care comfortably of 90% of my driving characteristics.. ie yes slowing down on a grade sucks but if im on a road trip and im only on a grade like that once ever yday or couple days then id deal with the slow uphill speeds..
I fully agree but if I do something stupid (i.e. 4.44 to 1.44) then what is my uphill speed? From 38 mph to 35mph done and done; let's do this!! But from 38mph to 3mph, ummmm .... don't think so.

Quote:
for some reason I thought the 643 was good for 300+ HP.. makes me wonder if there were different variants of it.. this is great info.
-Christopher
I dunno; could be. Right now I'm looking for info on the governor. Can't find squat. I'll see if I can't find something on hp.
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Old 06-16-2017, 08:58 AM   #25
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Chassis: Blue Bird TC RE 3904, Flat Nose, 40', 277" wh base
Engine: 8.3L Cummins ISC 260hp, AT643, 4.44 rear
Rated Cap: 84 pax or 1 RV; 33,000lbs
https://www.google.com/url?sa=t&rct=...Mei-dw&cad=rja

This says 250 even tho my engine is 260.

https://www.google.com/url?sa=t&rct=...sbrP9VlmYajS3Q

This one says 235-275hp. Also says 2200-3000 rpm. I've not gone above 2700. I try to make sure it doesn't go above 2500.
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Old 06-16-2017, 09:07 AM   #26
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The double engine mounts should prevent the engine from trying to rotate which should lessen any forces on the tranny. And from what I understand, the new gen Allies have cases that were significantly strengthened over the older units. I could have probably gotten away with just moving my motor mounts back to the center (balance) position, but I figured what the heck...why not bolt it all down with rubber pads.
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Old 06-16-2017, 11:25 AM   #27
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Quote:
Originally Posted by cadillackid View Post
an 8.3 with a 643's most costr effective way to improve is to regear the rear and turn up the smoke on the 8.3. you have the power and a good transmission you just need to lower the RPMs a bit..
-Christopher
lol in the skoolie world complaining about an 8.3 with a 643 is SOOOO a first world problem!
My 195hp DT466 with 643 and 4.44 rear rides out pretty nice. Sure it tops out at 63mph, but that's alright. Pulls like a mule!
Could probably fit larger tires and get it to 65 mph, but this thing will forever be cruising the slow lanes, even with a NICE powertrain.
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Old 06-16-2017, 11:47 AM   #28
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Take advantage of the fact that people expect buses to be slow. Don't disappoint them.
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Old 06-16-2017, 11:57 AM   #29
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Join Date: Oct 2016
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Year: 1999
Chassis: Blue Bird TC RE 3904, Flat Nose, 40', 277" wh base
Engine: 8.3L Cummins ISC 260hp, AT643, 4.44 rear
Rated Cap: 84 pax or 1 RV; 33,000lbs
Quote:
Originally Posted by EastCoastCB View Post
lol in the skoolie world complaining about an 8.3 with a 643 is SOOOO a first world problem!
My 195hp DT466 with 643 and 4.44 rear rides out pretty nice. Sure it tops out at 63mph, but that's alright. Pulls like a mule!
Could probably fit larger tires and get it to 65 mph, but this thing will forever be cruising the slow lanes, even with a NICE powertrain.
My problem with it is NOT top speed tho I will admit I'm jealous of the coach buses blowing by at 80mph. My "problem" with it is staying power. If I could give up 65mph on level ground for a 55mph bus uphill, I'd do it in a heartbeat.

With a good run at the grade, I'll drop to 3rd and 38mph up a hill. If there's a stoplight at the bottom of the hill, I'm lucky if I can hit 25mph.
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Old 06-16-2017, 11:59 AM   #30
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Join Date: May 2009
Location: Columbus Ohio
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Year: 1991
Coachwork: Carpenter
Chassis: International S3800
Engine: DT360
Rated Cap: 7 Row Handicap
The Aim in my build is for a bus that shifts like it supposed to, efficiency, a Temp gauge that stays left of center on the highway, cool-factor (new electronic trany means another digital screen!!)... and the ability to cruise through cities in traffic..
-Christopher
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