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Old 06-26-2004, 10:50 AM   #1
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better gear ratio cheap

I've been discussing the topic of changing the final drive ratio of the skoolie on another site. There are some good options that were mentioned, but they were not cheap.
Two of the best ideas:
Install a manual transmission with double overdrive
or
Install a 2 speed rear end with a 4:10 final drive

Neither of these options are cheap.
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Old 06-26-2004, 10:54 AM   #2
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Last nite while i was laying in bed, i came up with a cheap idea......

Why not install a standard transmission backwards behind my existing allison automatic?

If the "new" trans was a 4 speed, placing the trans in 3rd gear would significantly lower the engine rpm's at any given speed.

In the unfortunate event that the skoolie engine could not handle the new gear ratio, the aux trans could always be put back into high gear which would give a 1:1 gear ratio and act as if there were no modification at all.


What are YOUR thoughts on this project??

I found a 4 speed manual trans from a big truck for $100 at the bone yard.
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Old 06-26-2004, 10:31 PM   #3
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Connecting your driveshaft to the input shaft of the second transmission will interesting. I've them do things like this on junkyard wars but never on a real passenger vehicle.
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Old 06-27-2004, 02:39 AM   #4
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I really don't believe that the input shaft ( now the output shaft ) is supported nearly enough to take the load, it is a very short shaft with inadequate bearing to take the torque you are going to throw at it .
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Old 06-28-2004, 05:30 PM   #5
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What are you trying to do, get better go faster or get better mpg? Even my 72 international with only 182 hp can do 70 on the interstate.
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Old 06-29-2004, 01:11 PM   #6
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"what are you trying to do? go faster or get better fuel economy?"

The answer is YES.

My primary focus is to increase ground speed. I have plenty of engine, but not enough gear ratio to reach decend highway speeds. The bus cruises between 57-61 mph on flat ground fighting the rpm govenor all the time. On the x-pressway, big trucks run you over at that speed!There's the possibility of better fuel economy if i were to keep the bus at 55-60 mph, that would be a nice bonus, but that's not the main motivation behind the change in gear ratio.

After talking to a few mechanics, and reading quite a few posts, I think the inverted transmission idea is not a no go. Perhaps i'll start diligently searching for a 2 speed rear axle with a 4.10 final drive. If I find one at the junk yard, i can probably bring it home for $100 bucks. The problem is finding what i'm looking for. Most of the axles i've looked at are not clearly marked with the ratio. That requires jacking up one set of duals, and counting the number of revs of the drive shaft it takes to turn the wheels one complete revolution (then multiplying the number by 2) It sound easy, but most axles are on really big trucks that are on dirt or mud in the middle of the bone yard which makes jacking quite difficult.
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Old 06-29-2004, 08:57 PM   #7
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My '91 with the 7.8L diesel and 5-speed can get up to 65+ without much difficulty. I don't like to run that fast just because it seems like the engine is turning at a pretty high RPM for my taste.

Anyway, are you sure you are hitting the RPM limiter, or a speed governor? The buses I drove for Laidlaw all had speed governors on them and were set between 55-60 mph. Which made it nice on the highway, just peg the throttle and the bus would keep it at the speed limit. Granted they are all newer than my bus and automatics....
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Old 06-30-2004, 12:43 AM   #8
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I'm not certian if there is a speed govenor on my bus....but it seems unlikely. The getleman i spoke with at the transmission shop today believed that the bus was running against the govenor. He sais the bus engine speed is set far below redline and could be "bumped up" without any detriment to the engine. To which i replied: "my bus already has over 265 thousand miles, i would prefer not to do anything that would significantly reduce what's left of my engine life"

I drive my bus with the accelerator all the way to the floor. I really only need two throttle positions: idle and full speed. I've joked about putting a brick on the gas pedal when i'm going down the expressway.
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Old 06-30-2004, 12:53 AM   #9
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I made a new friend today. I took my bus to the transmission shop to talk about options for increased highway speed. The owner of the shop really liked my bus. We talked about a standard transmission with double OD.....way to pricy! Also talked about replacing the axle with a 2 speed. He thinks that a 3.83?:1 gear ratio would be an ideal final ratio with a 2 speed rear end.

I asked him about the backwards transmission idea.....He said it's been done before. The only thing it requires is a bearing on what is now the output shaft. He said it would work, but there's a lot of labor and fabrication involved in making it work properly. Then he mentioned that they make auxilliary transmissions that would work perfectly with no modification and they can be install it backwards to get my desired effect. Even better, he found a scrap guy that had an old Ford with the same size driveshafts as my bus that has such a trans already installed. It's an old grain truck, and was on it's way to be crushed as soon as the fields dry out. (apparently it's stuck in the mud in some farmers field)

He's sais gonna get back with me soon, but it sounds like this is my ticket....and should even be in my price range WE talked about "bus stuff" for more than an hour.
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Old 07-20-2004, 01:55 AM   #10
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just outta curiosity... what size engine do you have in your skoolie ??
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