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Old 03-17-2018, 11:51 AM   #1
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Allison MD3060 unlock tutorial

This is how the process to unlock 6th gear in the Allison MD3060 transmission unfolded for us:

1. Call the technical service department at your OEM and tell them you'd like to unlock 6th gear.
2. The OEM will make a determination based on review of the mechanical specs from the build of your bus. You will also need to send a picture and make/model description of your tires so they can verify the static load rating. If you do this in advance, it could save some time. Their engineering department will then make a decision as to whether the bus can handle the added stresses and speed. This can be a lengthy process and I might add doesn't contribute to their profits in any way so be patient!
3. If approval is granted, the bus then needs to be brought to a certified Allison service center to perform the work. Liability waivers will need to be signed.
4. The service center will contact Allison and request a 6th gear unlock code. If Allison is satisfied with the paperwork, they will generate an unlock code specific to that transmission and you're good to go.

This isn't an expensive thing to do but it is difficult. I wish good luck to anyone looking to try this.

If all else fails, you can always replace the rear axle with one that has a lower gear ratio. If you're handy and resourceful this can be a good option.
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Old 03-17-2018, 12:01 PM   #2
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Good info.

I think that there are at least two members here with Thomas buses that have been successful with this process.

Unfortunately, those of us with Bluebirds have not had any success getting Bluebird to cooperate.

Anyone here with Amtran or other manufacturers have any experience with this process?
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Old 03-17-2018, 12:16 PM   #3
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For what it's worth, we also have a Thomas. In my experience, they provided great customer support and a very friendly and helpful attitude throughout this process. We did have to find a creative solution when Allison first denied the unlock code though. After some brainstorming, Thomas rewrote their authorization letter to include a condition that the bus be electronically governed to 75mph (so as not to exceed the tire's SLR). We were then granted the passcode.
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Old 03-17-2018, 12:16 PM   #4
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I am hearing that Thomas have a cut-off at a maximum calculated speed of 75 mph.

I do not know if this is true or not.

So far I have heard of Saf-T-Liners being authorised with a FD Ratio of around 6.0.

Engineering has my request for unlocking with an FD Ratio of 5.38. With the smallest diameter tires available on their OEM fitment chart, that would give a top speed of fractionally under 75 mph.

I'll let the forum know when I get a decision, but I was told it could take a few weeks to a few months. I'm in no hurry.
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Old 03-17-2018, 01:43 PM   #5
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you can also replace the TCM with an aftermarket TCM. if your engine is electronic, you will need a TCM that has J1939 throttle input, mechanical engines likely used an analog throttle box attached to the TCMs analog input pin.. CAT developed the throttle for their engines.. I believe all of the cummins 8.3's that got MD-3060s are of the electronic variant..

I only mention this option as its a possibility for those who get turned down by their OEM and still want 6 gears...

NOTE: - this procedure is not applicable to allison 1000/2000 series transmissions in model years earlier than 2006. 2006 was the first year the 1000/2000 series was sold as a 6 speed.. while the actual gears exist in earlier years, the valve body assembly and TCM are different...

if you have a 2006 or newer Bus you can try and get this procedure done on your 1000/2000 series allison.. they are 6 speed capable but were 5 speeds in school bus applications.. however the hardware exists to unlock 6th like the MD3060s
-Christopher
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Old 03-17-2018, 01:55 PM   #6
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Quote:
Originally Posted by cadillackid View Post
I believe all of the cummins 8.3's that got MD-3060s are of the electronic variant..


-Christopher
Nope.

I have a 6CTA8.3-250 with the Allison MD3060.

Unless you mean the throttle not the engine.
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Old 03-17-2018, 02:17 PM   #7
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Didn't they add a throttle position sensor to the mechanical engines that were equipped with the 3060?
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Old 03-17-2018, 04:13 PM   #8
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Quote:
Originally Posted by Twigg View Post
Nope.

I have a 6CTA8.3-250 with the Allison MD3060.

Unless you mean the throttle not the engine.
If it were electronic, it would be cool if you could meet the speed governing requirement by reprogramming an electronically controlled throttle positioning sensor.

That is, if your throttle positioning sensor could be reprogrammed.
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Old 03-17-2018, 04:22 PM   #9
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sorry - by electronic I mean the TPS.. it will be a box with a cable on it. coming from the throttle..

the speed limiter on electronic engines is limited by the ECM.. the ECM knows the speed from the transmission speed sensor..

on mechanical engines its simply an RPM limiter and not a vehicle speed limiter.
the TPS for the allison only affects transmission operation/./. it doesnt affect the engine.

on electronic engines a data link is established between the ewngine and the transmission.. that datalink contains throttle data for the allison.. on mechanical engines they had a box which I believe was a logarythmic resistance sent to the TCM.. the TCM could be programmed to look for a voltage signal..

someone demonstrating a mechanical engine on an electronic allison.

-Christopher
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Old 03-18-2018, 03:13 AM   #10
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Good stuff. Now waiting on auction to buy the bus. Will want to get this done before engine reflash. Then just fiz the mph govenor. Has anyone figured up mpg differences with 6th gear unlock?
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