Allison MD3060 unlock tutorial

[Backwoods Wanderer]

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.

 

[PNW_Steve]

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?

 

[Backwoods Wanderer]

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.

 

[Twigg-SKO]

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.

 

[cadillackid]

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

 

[Twigg-SKO]

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.

 

[PNW_Steve]

Didn't they add a throttle position sensor to the mechanical engines that were equipped with the 3060?

 

[Backwoods Wanderer]

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.

 

[cadillackid]

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

 

[stixNstaples]

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?

 

[Twigg-SKO]

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?

It usually improves unless you have a heavy right foot.

Most people want the extra gear to reduce rpm at cruising speed, and not necessarily to go faster.

 

[Panoman14]

Allison range increase form

Was sent this file by my local Allison dealer to start the process of having 6th unlocked on my international 3800 blue bird bus with the MD3060 transmission.

 

[joeblack5]

Thank you panoman. Very nice to see the actual letter and reduce the amount of hearsay.
Later. J

 

[cadillackid]

great stuff!! awesome to see that letter to know exactly what we are dealing with..

-Christopher

 

[rensch26]

That is a great document. So I basically need to contact either International or now IC Bus and get the ball rolling?

 

[Panoman14]

I was told to contact Blue Bird. I think it depends on the body of the bus, and not the chassis. Also, I believe those with rear engines will have an easier time getting approval due to the shorter drive shaft being less of a concern at higher speeds. Looking at the document, however, leads me to believe you might get around that by having them speed restrict the bus through the ECM rather than locking the gear in the TCM. It all depends on the bus and what the engineers at the OEM deem a safe speed.

 

[rensch26]

I'm firing off an email to Navistar now. Will keep everyone posted on my progress.

 

[rensch26]

I'm firing off an email to Navistar now. Will keep everyone posted on my progress.

I got a response from Navistar. They instructed me to start the process at any International dealer. They will submit an iRequest for sixth gear approval in the Navistar service portal. I'm not positive you'd even need to bring your bus in, probably just need to provide the VIN and maybe the transmission serial number.

 

[Twigg-SKO]

I was told to contact Blue Bird. I think it depends on the body of the bus, and not the chassis. Also, I believe those with rear engines will have an easier time getting approval due to the shorter drive shaft being less of a concern at higher speeds. Looking at the document, however, leads me to believe you might get around that by having them speed restrict the bus through the ECM rather than locking the gear in the TCM. It all depends on the bus and what the engineers at the OEM deem a safe speed.

Please do. We need info on Blue Bird because I've yet to see an example where BB have cooperated.

Getting them to respond would be useful info for a lot of people.

As far as I know, Thomas Built are pretty good at the (my request is still waiting engineering approval), but there is little data on the other bus builders.

 

[Panoman14]

Please do. We need info on Blue Bird because I've yet to see an example where BB have cooperated.

Getting them to respond would be useful info for a lot of people.

Getting them to reply seems to be the trick! I'm working nights this week so I'm headed for bed, but I've sent both my blue bird dealer and corporate emails requesting info and help the last couple days. No response yet. I'll try calling corporate tomorrow if I don't hear anything by then. My guy at Allison says he has some contacts at Blue Bird too, so if all else fails I'll try to go through him.