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Old 01-16-2020, 04:15 PM   #1
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Opinions on this bus please.

Looking at a 2004 International RE3000 with a DT466e and Allison MD3000, 146,000 miles, unknown hours, 78 passenger, A/C, and tinted windows. This bus checks all my boxes except that it has 6.17 rear differential ratio and a 55MPH speed limiter. Questions that come to mind are: Would unlocking 6th gear (if possible) get me up to a 65MPH cruising speed without redlining the engine assuming I get the speed limiter removed? Or would I need to change my ring and pinion to a higher gear? Are 41" tires standard on a bus like this? Been trying to use the calculator to answer the gearing question but not sure of tire size. Any input would be appreciated.

Rhino
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Old 01-16-2020, 04:26 PM   #2
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Yes, tire diameter of ~41" is about right - sounds like 11R22.5's to me. The 10R22.5's are roughly 40" diameter. What rear axle does it have (not the ratio, but the actual axle model, such as N175 or N190?)


Assuming 41" tires, 6,17 gears, 0.74 5th gear OD, and 2500 RPM you should be running around 65 MPH. If there's a 0.65 6th gear, at the same RPM you'll get around 76 MPH. Not everyone has had luck getting 6th unlocked (easily). If you swap to a 5.38 gear ratio, it'll bring you to 76+ in 5th gear at 2500 RPM.


I have a 5.38 gear in my axle but I don't have OD (manual transmission), so I'm looking to move to a 3.91 or so. I have an N175 axle (and I may have to swap carriers for my gear change), so I'd be willing to negotiate a deal for my current setup (I'm told it will interchange with an N190).


BTW, with a gear swap you'll need to get the computer reprogrammed for the speedometer. You'll want to change the speed limiter anyway, so easy to do both these at the same time.
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Old 01-16-2020, 04:30 PM   #3
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Follow up - some have complained that 1st gear was simply too low to be of much use with a really low (high numerically) rear end ratio. Re-gearing gave a much more acceptable 1st gear range.
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Old 01-16-2020, 04:54 PM   #4
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Thanks for the reply. The build sheet shows the rear axle as a Dana Spicer 21060s with 6.17 gears.
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Old 01-16-2020, 05:24 PM   #5
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Originally Posted by Rhino View Post
Looking at a 2004 International RE3000 with a DT466e and Allison MD3000, 146,000 miles, unknown hours, 78 passenger, A/C, and tinted windows. This bus checks all my boxes except that it has 6.17 rear differential ratio and a 55MPH speed limiter. Questions that come to mind are: Would unlocking 6th gear (if possible) get me up to a 65MPH cruising speed without redlining the engine assuming I get the speed limiter removed? Or would I need to change my ring and pinion to a higher gear? Are 41" tires standard on a bus like this? Been trying to use the calculator to answer the gearing question but not sure of tire size. Any input would be appreciated.

Rhino
Yeah 11R's are around 41".
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Old 01-16-2020, 05:26 PM   #6
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Follow up - some have complained that 1st gear was simply too low to be of much use with a really low (high numerically) rear end ratio. Re-gearing gave a much more acceptable 1st gear range.
Yep. Since most school buses see low speed stop and go mostly, regearing is one of the ESSENTIAL skoolie mods, at least in my book.
I'm not picky about what buses I buy, but one thing I'm damn picky about is gearing.
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Old 01-16-2020, 05:27 PM   #7
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Quote:
Originally Posted by Rhino View Post
Looking at a 2004 International RE3000 with a DT466e and Allison MD3000, 146,000 miles, unknown hours, 78 passenger, A/C, and tinted windows. This bus checks all my boxes except that it has 6.17 rear differential ratio and a 55MPH speed limiter. Questions that come to mind are: Would unlocking 6th gear (if possible) get me up to a 65MPH cruising speed without redlining the engine assuming I get the speed limiter removed? Or would I need to change my ring and pinion to a higher gear? Are 41" tires standard on a bus like this? Been trying to use the calculator to answer the gearing question but not sure of tire size. Any input would be appreciated.

Rhino
You can get 6th gear unlocked. I'd start with that then regear if/when that's not enough.
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Old 01-16-2020, 06:01 PM   #8
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I agree, unlocking 6th gear first and trying that out seems like a first logical step. My intention isn't to go fast necessarily but to cruise comfortably at 65 and not strain the drivetrain. We do plan on traveling out west a lot and I know that if I go too high on gearing than climbing those steep grades could be a challenge especially towing a vehicle.
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Old 01-16-2020, 06:32 PM   #9
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It's worth mentioning that many Big Rigs often have gearing in the high 2's and mid 3's. Why? Many trucks don't have overdrive transmissions (some do) and larger engines often redline under 2000 RPM. Also, companies and manufacturers find that just because an engine can run at 1900 RPM all day, it's not the most efficient. Many of these engines generate the most torque in the 1400-1700 RPM range. Trucking companies are in business to make money and it's in their best interest to get the best fuel economy possible. Some example calculations:
(I'm assuming 11R22.5 tires and a 1:1 top gear for consistency, and because they are relatively "standard of the industry").

1:1 Trans top gear, 41" tires, 1800 RPM, 3.23 gears - 68 MPH
Same setup, 1900 RPM (Theoretical redline) - 71.78 MPH
1:1 Top gear, 41" tires, 1650 RPM, 2.89 gears - 69.67 MPH
Same setup, 1550 RPM - 65.45 (kinda of assuming a speed limiter on this one)
Same setup, 1900 (Theoretical redline) - 80.22 MPH
1:1 Top Gear, 41" tires, 1900 RPM, 3.54 gears - 65.49 MPH (I might expect this on a local use, vocational [mixer/dump], or heavy-haul truck.)
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Old 01-16-2020, 11:56 PM   #10
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Look through the front bumper at the passenger frame rail under the door. Crawl under the bus if you have to. Those buses like to rot there and quite a few get retired because of it. Granted being in Tennessee may mean it's perfectly fine.
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Old 01-17-2020, 08:41 AM   #11
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Thanks for the tip, I hadn't heard that. Will definitely check that out before I lay down any money. Exactly the type of help I'm looking for here!
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