6 Speed Valve Body Question

[kidturbo]

Hi guys, here is a question for you transmission pros.

When shifting a 6spd Allison into manual mode, is there actually a different position in the valve body section??

Reason I ask, am helping a friend with a 6spd in a "no torque converter" marine conversion. Currently he only uses shiftier positions R N D, but would like to add the manual shift function as in a truck. Unfortunately there is no easy way to allow it to shift into M without changing to a 2 stick throttle/shift setup.

Wondering if we could just "electrically" change the mode to M while in D on the cable.

Thanks

-K

 

[Mike L.]

Hi guys, here is a question for you transmission pros.

When shifting a 6spd Allison into manual mode, is there actually a different position in the valve body section??

Reason I ask, am helping a friend with a 6spd in a "no torque converter" marine conversion. Currently he only uses shiftier positions R N D, but would like to add the manual shift function as in a truck. Unfortunately there is no easy way to allow it to shift into M without changing to a 2 stick throttle/shift setup.

Wondering if we could just "electrically" change the mode to M while in D on the cable.

Thanks

-K

It is all smoke and mirrors. No change in the valve body.

 

[kidturbo]

Excellent. So now I just have to find the correct pin or pins on the TCM. to activate it...

Tks

 

[THEFERMANATOR]

All of the world series trans don't change anything from d on down. All that changes is the output from the nsbu(or ims for 06+). If you look at the manual shift shaft, it does nothing once it's in d back in all forward gears. I believe they even offerred some of the 2000 series with no manual shift linkage what so ever. All they had was a push button at the drivers station, or a dummy shifter that moved a mode switch. I know the 3000+ works that way.

 

[kidturbo]

What I figured. I have seen one with pan off before, but don't have one handy I can test on today. The NSBU looks like a TPS... Which could make this harder, I was hoping for a single switch in there..

Will take a look at the TCM pinout and maybe something jumps out at me. If not, gonna need someone to work backwards from a transmission using a volt meter. If it is a 0-5v signal, possibly use a switched resistor inline I guess.

 

[THEFERMANATOR]

It's a series of switches inside of it, not a resistance strip like a tps. I piggy backed into mine to power up my 95's cluster gear display. Pretty sure it was 4 contacts, and it used a set of 2 contacts to tell it each position. I would have to dig up my swap papers to see what they were.

 

[kidturbo]

Super!!! I'll do some digging tomorrow also.

BTW, glad to see you back on the keyboard again :welcome6:

 

[THEFERMANATOR]

Super!!! I'll do some digging tomorrow also.

BTW, glad to see you back on the keyboard again :welcome6:

Been a rough 2 weeks, now my 3 year old has it. Spent last night in urgent care with him.

 

[kidturbo]

With some onsite tuning help from Nate@PPE, the boats trans is holding 5th now. However with only the A mode pattern available, it's still hunting 3/4 at low speeds when on and off the throttle in rough water. So looks like a BCM with switch for tow haul and manual mode is on the list.

He has the BCM and plugs from the truck, and I've all the diagrams to wire up tap shift and tow/haul modes. Could use a copy of the NSBU 4 wire switch positions if anyone has it handly. I saw a screenshot showing if all 4 switches are open, that is Manual mode?

Also what's the basic diff from the light duty and medium duty TCM? Tune or hardware? I know they are basically always operating in tow haul. Since 6th likely won't be used, that OS may work better in this build.

Tks

-K

 

[THEFERMANATOR]

I don't have the 6 speed IMS wiring diagrams, only 5 speed. The MD cal will work just fine with a truck, and like you said, will basically be locked in tow/haul mode. You can get one with 6th gear in it though if you want. The stock 06 cal is only a 5 speed, but the 07 cal was a 6 speed. Theres no way to select 5th as far as I know with a MD cal, and I'm pretty sure the tap shift won't work with a MD cal either. Ben I believe has a way to select tow/haul without installing a BCM.

 

[IOWA LLY]

If you were to use a medium duty calibration that was always in tow haul essentially you could simply tune 6th gear out by raising the upshift speed and rpm high enough it would never get there.

You should be able to dial in your existing calibration to keep from hunting between 3rd and 4th though I would think.

Sent from my SM-N920V using Tapatalk

 

[kidturbo]

If you were to use a medium duty calibration that was always in tow haul essentially you could simply tune 6th gear out by raising the upshift speed and rpm high enough it would never get there.

That's basically what he has set right now to lock out 6th. But the big deal with this boat has a surface piercing prop setup. It may cavitate at high speed, then hook up again. Which looks about like breaking the tires lose at 80 mph in the eyes of the TCM..

Was just thinking maybe the med duty contained some extra features or J1939 protocol to allow using the push button shifter like the Navistar versions used. That would be an easy fix since does not use park.

I also believe he would lose tap shift with the medium duty TCM. Looks like the BCM is going back in for now to allow for tap and Tow.

Thanks for all the input guys.

 

[THEFERMANATOR]

If you go with a MD calibration, it can be customized by an ALLISON dealer as those cals are not locked down due to the GM agreement. So they should have no problems switching it over to a push button shifting setup if you go with a MD cal. Then you could set up the secondary shift schedule in it to be a locked into whatever gear is selected setup. This all hinges though on finding an ALLISON dealer willing to work with you with the DOC software.

 

[kidturbo]

Yeah that's it. My GM tech buddy said the last dealership he worked at had to take all the MD trucks to an Allison dealer any time they needed a new TCM or reflash. However he did flash one OS from MD to LD using a Tech2 for a member here. Would be good to know if you can go the other way using EFIlive or something to load it.

I'll have him contact a Allison dealer and get the scoop on the push button selector and TCM options. I drove a F650 with that setup and like it. Would be a cool mod for this marine setup..

 

[THEFERMANATOR]

I'm pretty sure the 2000 series could have used the push button control setup on it since there was no parking pawl in them. Or maybe you could adapt a megasquirt setup to it for the trans shifting. PCS can be made to shift one, but the problem was supposed to be the lack of shift adaptives with it. You basically had to program each shift time to the microsecond, and there was no compensation for trans temp changes, and since there was no adapts it couldn't self compensate for clutch wear. So you had to constantly adjust the shift times and clutch volumes yourself. Megasquirt is supposed to have a new trans controller out with adaptive numerators in it if I heard correctly. For a boat it may be an option.