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Old 01-07-2018, 12:57 PM   #1
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3000 rpm

Hello all.
I recently acquired a 1967 dodge school bus that I am renovating into an rv.
My question is when driving on the highway at 60 mph it is running at 3000 rpm. Is there any way to drop the rpm’s and be easier on the engine.
I’m thinking changing the rear end gear ratio but no idea where to start.
Any info and help is appreciated
Thanks in advance
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Old 01-07-2018, 01:16 PM   #2
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Originally Posted by Nivek1972 View Post
Hello all.
I recently acquired a 1967 dodge school bus that I am renovating into an rv.
My question is when driving on the highway at 60 mph it is running at 3000 rpm. Is there any way to drop the rpm’s and be easier on the engine.
I’m thinking changing the rear end gear ratio but no idea where to start.
Any info and help is appreciated
Thanks in advance
Cool bus...idk about rearends...at least in this case...but, yeah, it's the easiest part to mod...

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Old 01-07-2018, 01:26 PM   #3
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If you've got enough space in your wheel wells, taller tires can make a difference
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Old 01-07-2018, 01:35 PM   #4
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Check the data plate on the rear axle. There should be either a plate, or a number in the actual casting that will give you the gear ratio. Call truck shops to find out if those gears can be changed to a lower ratio.

Example: my bus had a 5.29 ratio. Eaton made a now-obsolete 33233 rear axle. Chalk's Bus Parts in Houston did some digging and found they could change that ratio to a 4.11. End result was I went from a top end of 55 mph @ 2450 rpm to 72 mph @ 2400 rpm. BIG jump!

Don't take a "No" just from one shop and think they all will say that. I took over a year to find what I needed to do that change. I always asked if the person I was talking to knew if there was someone else who might have some experience with my rear axle. I never accepted a "No" answer. It may have slowed me down, but never stopped me.

Best of luck!

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Old 01-07-2018, 01:43 PM   #5
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Very cool bus ! More pictures when you get a chance.

Tires and inside the pumpkin, like they said.

Welcome ! What are your plans once you get her to spin-down a bit?
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Old 01-07-2018, 02:02 PM   #6
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Gotta ask...what engine? That many revs in some engines is a death wish...on others...OK.

If we can determine the "sweet spot" for it, that will tell the tale on where the gears and tires should be for highway speeds.
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Old 01-07-2018, 03:59 PM   #7
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Hey there. It’s a 361 b series. Getting approx 10 mpg now the way it is
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Old 01-07-2018, 04:01 PM   #8
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More pics

Here you go
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Old 01-07-2018, 04:40 PM   #9
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Here you go
How much of the exterior you keeping? I saw a really cool '58 but when it was "restored"...it was a hot rod and "lowered"...stupid...anyway, I know you gonna do a awesome job...I'm just weird...lol

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Old 01-07-2018, 04:45 PM   #10
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How much of the exterior you keeping? I saw a really cool '58 but when it was "restored"...it was a hot rod and "lowered"...stupid...anyway, I know you gonna do a awesome job...I'm just weird...lol

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great bus!!!

being a Hot-rodder myself I think slammed and unusual busses are kickass..
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Old 01-07-2018, 04:49 PM   #11
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I have pretty much ripped out most of the interior. Going to replace the insulation and rewrite the electrics to new l e d fixtures and USB power plugs.
Doing solar power, solar shower and it will have new paint all around. The engine is sound but I need to change out the rear end to get the rpms lowered so I don’t blow the engine on a long trip.
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Old 01-07-2018, 05:42 PM   #12
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if you are getting 10 mpg with the current setup, you do not want to change anything

last gas schoolbus I drove, international 345 with an auto in 1990 was doing 4500 rpm at 55 mph
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Old 01-07-2018, 05:50 PM   #13
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10mpg ?? I don't even get that in my pickup.
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Old 01-07-2018, 06:20 PM   #14
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great bus!!!

being a Hot-rodder myself I think slammed and unusual busses are kickass..
Lol...maybe this will be of interest...https://youtu.be/2Wj-__O_yK0

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Old 01-07-2018, 06:30 PM   #15
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Peak torque on that big block is390 @ 2,400 so it's preferred highway RPM should be 25-2600. Taller tires might be the easiest way to bring down the RPM's a bit.
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