Cummins 4BT & Diesel Conversions Forums banner
801 - 813 of 813 Posts

·
Registered
Joined
·
79 Posts
EVIguy, I am not sure. I see on the 4bt wiring diagram an input for torque limit control switch and analog torque transmission interface. If you look at the allison info it looks like torque management goes thought the J1939 (data) bus (for SEM). None of those are the same language so to speak.

131314


131315
 

·
Registered
Joined
·
219 Posts
Yes, I did see that on the wiring info but on the stock wiring between my 5 speed MD Allison and ISB there is just the shielded J1939 which leads me to believe that its done via CAN.
There are no wires in locations 36 and 40 on my ECM.
 

·
Registered
1989 Coachman Catalina
Joined
·
2 Posts
Hi Guys,

Been lurking in this thread for a while.
Have read thru all 41 pages multiple times.
I'm brain fried.
Making a wiring harness scares me and can't seem to make sense of what TCM I should buy.
If I'm posting in the wrong thread apologies in advance.

My project is to put an '06 Allison 6 speed in a 1989 Coachman Catalina Motorhome. Currently has a Carb'ed 454 gas motor. i.e. no electronics & a THM400 tranny. Am looking to buy a wiring harness & a Allison MD TCM that will accept an analog TPS input. Or somebody that can re-flash an Allison MD TCM to those specs & tell me what TCM I should buy from a local salvage yard.

I'm a retired Navy Submarine ET living on a fixed income so while I have some money I'm not a rich guy.
I'm electronically competent & digital savy with strong mechanical skills.
I have access to a competent driveline shop who can cut & balance a drive shaft.
The 454 has headers (smog deleted) & will upgrade to EFI (prolly the Holley system).
Would like to have the Allison tap shift so I can lock it out of 5th or 6th cuz' i don't think the 454 will pull a hill in overdrive.
Intention is to use a rocker switch on the dashboard for gear selection when in "M", else operate in "D" w/ shift points suitable to a gas motor limited to ~4500 RPM (when on flat roads).

Any help or a pointer to an affordable dealer/seller would be much appreciated.
Thanks in advance & PM's are solicited & desirable.

BTW, I have a '05 4WD 5 speed Allison & torque converter & a A40 TCM which came out of a '05 GMC Duramax which I bought as a spares for my '05 which I'm willing to sell. Will post pic's if desired.
 

·
Registered
1989 Coachman Catalina
Joined
·
2 Posts
I suggest talking/corresponding with Jason at transmissiontuner.com. He knows his stuff and has quite a bit of info on the website as well. Good luck!
Thanks for the post, wasn't sure this thread was still active.

I'm in Jason's build queue & I WILL buy a TCM & harness from him because:
1) He is, hands down, the most knowledgeable, most open w/ information, & most ethical individual/company I've talked to to date. A real class act.
2) His labor rates & pricing are very affordable & prolly too low for the market given the service/quality rendered.
3) I need a stable functional transmission that is as close to "plug 'n' play" as is possible.

My issue(s) is/are:
1) I'm an old fart whose physical capabilities are failing,
2) I live in Northern MN & have concerns about surviving another -50F winter (frost bite 2 years running & almost lost my left foot last winter, diabetes sucks).,
3) I don't have a tall door/ceiling shop to do the work in,
3) At the risk of releasing too much personal info, he's recovering from COVID,
4) He's overworked & backlogged till Sept.,
5) The MH was built & geared in the era of the 55 mph National speed limit so the 454 is screaming @ 60 mph & at 70 is way above it's peak torque curve. @ 80 mph (the unofficial speed limit in the right hand lane on Hwy 29) it sounds like it's gonna' throw pistons out the side.
6) Motor swap in a puller MH will be a B.....
7) Towing on a MH isn't just expensive it's F'ing expensive.

i.e. I have a limited time window to do the swap or be condemned to staying off the National Hwy system.

I may have to temporarily, for this winter run south, swap in a 700R4 w/ lock up & baby it (BIG cooler & watch tranny temps).
Was hoping for an affordable temporary Allison 6 speed solution while Jason catches up on his work backlog.
Like maybe somebody started a Jason conversion & for whatever reason gave up on it & has parts for sale (wiring harness &/or Allison MD TCM). This option would simplify Jason's workload, get me on the road sooner, & free up $$$ for the seller at what he/she paid for it.

BTW, his advice/document on TPS's was immensely helpful. And after a little pricing research, it resulted in an optimal ease of installation solution @ the lowest cost. The TCM6000 - Remote Mount TPS Adapter Kit (A-TCM6000) from Pace Performance @ $100.80 + $13.32 (shipping) = $114.12 delivered to my door. Sweet.

Also looking for a EFI Live Flashscan or Autocal V2 as it seems EFI Live screwed up the V3.

Be safe folks & thanks for the response.
 

·
Registered
Joined
·
2 Posts
Success!!!! I hooked the TPS to the TCM, using a diode to prevent the 8V output of the TPS from being applied to the 5V input of the TCM. Worked like a charm. Here's a little video I made showing what it does:


Like I mentioned, I used a diode to block the 8V from being applied to the inputs on the TCM. The inputs have weak 5V pullups, and putting 8V to them could cause damage. Here's a schematic of the TPS to TCM connection:



I only connected it to the "Managed Input" pin for testing, but I am about 99% positive that it needs to be connected to the "Unmanaged Input" pin as well, otherwise the TCM will throw a code and inhibit TC lockup :rasta:

From what I understand, the Unmanaged Torque is the torque being requested by the driver (basically equal to throttle position), while Managed Torque is the torque actually being delivered by the engine. If no torque reduction is enabled they should track each other. Torque reduction on a computer controlled engine could come from a request from the TCM, or from the traction control system, or from the ECM itself due to certain conditions. When that is the case, the torque requested by the driver may be quite different from what is actually being delivered. Since shift speed is dependent on throttle position (unmanaged torque) and shift firmness, trans pressures, and TCC operation are dependent on actual engine output torque, the trans would need to know both for proper operation.

I mentioned in the video that I wasn't sure why the torque readings went negative. Well, thinking about it, this is the actual torque being delivered by the engine. If you are cruising and let off the throttle, the engine torque is now negative - the transmission is driving the engine, rather than the other way around. With that in mind, the readings make sense. Obviously those are not real values. They are just numbers programmed into the TCM to equate to a certain input pulse width.

In the case of a mechanically controlled engine (or an electronic engine with no torque reduction enabled), unmanaged torque and managed torque should always track each other. By connecting the TPS output to both inputs, were faking it. The TCM shoudln't care - it's going to base it's shift firmness off of the managed torque value and adapt to the rest. All that should matter is that the inputs are consistent, which they will be. The only thing we need to do is disable torque management in the TCM, otherwise it will request torque reduction for shifts, and when that doesn't happen it will throw yet another code. Luckily, EFI Live lets us disable TR :D
Max, great work! I'm a member here but I can not see this video or use the link in post 89 for 06 schematics. Any idea?
 

·
Registered
Joined
·
1,399 Posts
Discussion Starter · #809 ·
Max, great work! I'm a member here but I can not see this video or use the link in post 89 for 06 schematics. Any idea?
The link was broken. Its fixed now (y)
 

·
Registered
Joined
·
25 Posts
MaxPF,
Post #94 you posted a schematic for the TPS - TCM connection. The pic/link isn’t viewable for me. Just trying to make sure there’s no specific way to wire it to both managed/unmanaged inputs besides the 5v limited diode. Both inputs are run in parallel to the TPS?
 

·
Registered
Joined
·
1,399 Posts
Discussion Starter · #812 ·
MaxPF,
Post #94 you posted a schematic for the TPS - TCM connection. The pic/link isn’t viewable for me. Just trying to make sure there’s no specific way to wire it to both managed/unmanaged inputs besides the 5v limited diode. Both inputs are run in parallel to the TPS?
That's actually post #95. Took me a while rummaging through my HD to find that one. It's fixed now.
 
801 - 813 of 813 Posts
Top