Adding J1939 to a 3 box for allison swap

[nikitis]

Just saw your video. Informative for me. I'm going to look for that transmission data link line on mine.

So when I go to upgrade my transmission, I just need to T into those two lines into the AU Device, and then the Purple and Brown lines into the J1708 A and B ports, which becomes my new data line.

[nikitis]

So after watching your video I looked for my transmission data line. Pic shows a dual purple and white'ish possibly faded brown two wire coming from the engine harness, but not connected to anything and a 3 white wire plug that is cut. No idea what that is.

Is it possible that my transmission data link could be hooked up to another part of the J1708 network elsewhere? I don't think I've been driving my bus this whole time with a disconnected transmission.

[Bouje bus]

The 545 is mechanical in nature. It has electronic output, but no computer to receive input, just the modulator.

The random twisted pairs are what got me confused thinking my truck had a 1939 network.

I'm at where cadilackid was with the 1939 unplugged. New trans made it around the block but it is struggling.

My plan is to update the 6 pin deutsch connector to a 9 pin by adding the 1939 lines from the trans computer. Hopefully this will allow me to see the 1939 signals on my scanguage.

I didn't order the AU data center, hoping that once I get it working I can just monitor temps with the scanguage.

Really looking forward to seeing what caddy sees coming out of the AU box.

[nikitis]

My ECM does know about my Transmission, I've seen it in the computer so it would have to be connected on some level and telling it how to shift. What is this modulator you speak of?

And do you have similar pictures to what I have? I'm so confused because I get to where I think I understand how it works then to only find out the damn t444e documentation is telling me 12V circuits are 5V when that isn't true, verified by multimeter.

How is my AT545 connected to my ECM because it's not the same path as Cadillackids wiring in his video. I understand his is a J1939 using 3 wires and he explained it well in his video, but how are the J1708 transmissions hooked up electronically because mine isn't connected to the harness there in his location?

[Bouje bus]

Following cadilac's example, I downloaded the teraterminal and set the settings per Chris and AU.



I got the following data

[nikitis]

I've ordered my AU device.

So doing more research. I guess there really isn't any electronics on my AT545 communicating with the ECM. The ECM just knows it's an AT545 from programming I guess and knows how and what RPM's to shift with it and is all mechanical. I'm assuming my ECM is smart enough for this AU device since there is a J1708 Network I can tap into, and It could make use of a more modern Transmission if I can get the translations working which the AU Device does. I'll plug in the device once I get it and see if I'm getting the same values as you guys once it arrives.

[cadillackid]

Originally Posted by nikitis

I've ordered my AU device.

So doing more research. I guess there really isn't any electronics on my AT545 communicating with the ECM. The ECM just knows it's an AT545 from programming I guess and knows how and what RPM's to shift with it and is all mechanical. I'm assuming my ECM is smart enough for this AU device since there is a J1708 Network I can tap into, and It could make use of a more modern Transmission if I can get the translations working which the AU Device does. I'll plug in the device once I get it and see if I'm getting the same values as you guys once it arrives.

the ECM knows about your allison to handle the speedometer and also to operate the electric on / off modulator..



allison AT/MT requires a hardwired speedometer sensor and will read from both wires an AC voltage signal from it for the speedo to work..



it also enables the electric modulator wires foir the kickdown function of your AT545


those things are present on the 3 box computer...



on the 3 box there is likely a J1708 link someplace that the "world series" WTEC-II transmission may have connected... im not sure if they simply wired in an additional harness to the interface box thats on the firewall inside the cab or if there was an actual connector..


from what I understand J1939 did not exist anywhere on the 3 box systems..


as for your allison , Bouje is 100% right.. its mechanical.. except for the electric modulator.. there is no TCM or data link..


the valve body controls the shifting.. (this is the way every automatic transmission was before about 1990).. the springs and spacers in the valve boidy bores set the base shift schedule.. and then shiofts can be "trimmed" by adjusting the trim wheels in the front of the valve body.. it essentially adjusts the spring pressures on the valves.. pressure goes up and down with RPM thus moving the valves against the springs.. opening other ports on the valve bidy which trigger a shift.. its all hydraulic.



the modulator controls a pressure adjustment valve which raises and lowers the shift points .. on a true modulated 545 (or 643) .. the modulation was progesssive based on engine load (gasoline models using a vacuum modulator) or on throttle position (diesels)..


they lost the ability for true modulation when the drive-by-wire engines came out with no more throttle cables.. so they created an electric modulator which is on / off (no one was doing PWM then).. the ECM is supposed to take a mix of RPM, engine load, and pedal position to decide when to turn it on or off.. it sort of works..



it worked so "good" that WW williams (major allison dealer) developed a mod (redybyrd got it). where they over-rode the ECM and turned the modulator on anytime the pedal was over 65-70%.. it was in hopes to help from burning up so ,many 545s that werent shifting modulated when they should..

[cadillackid]

Originally Posted by Bouje bus

Following cadilac's example, I downloaded the teraterminal and set the settings per Chris and AU.



I got the following data

YES!!! yours is talking J1708 now


I had hoped to work on this yesterday but my work got busy.. maybe today hopefully

[nikitis]

Originally Posted by cadillackid

allison AT/MT requires a hardwired speedometer sensor and will read from both wires an AC voltage signal from it for the speedo to work..

Yes, I understood that about the speedometer as I got it to work by replacing the sensor at the transmission already. I've done past work on that. And I understand the dip switch systems pretty well for the gauge cluster.

Originally Posted by cadillackid

it also enables the electric modulator wires foir the kickdown function of your AT545


those things are present on the 3 box computer...

This is something I have no clue about. I don't know what it looks like or fully what it does. Is this a device that should have wires coming from my transmission to a box device somewhere or is it a part of the transmission itself and then wires come from it to T into the J1708 somewhere?

Originally Posted by cadillackid

on the 3 box there is likely a J1708 link someplace that the "world series" WTEC-II transmission may have connected... im not sure if they simply wired in an additional harness to the interface box thats on the firewall inside the cab or if there was an actual connector..

from what I understand J1939 did not exist anywhere on the 3 box systems..

Got it, I knew J1939 didn't exist on 3 box. The reason i'm confused is because on my Engine harness, at the same exact place you have your Transmission datalink plug, I have one as well, but my wires are 3 white wires unlabled, not green or yellow, nor purple or brown. However there is a Purple and maybe faded brown one also next to it on the engine harness. Makes me wonder if that is a J1708 Datalink I could tap into.

I'm also confused and don't know what is connected between transmission and ECM physically if anything at all or are there even any wires from transmission to ECM. This electronic modulator, is it the ECM itself or a separate box?

Does it go like Transmission -> Electronic Modulator -> ECM?
Or Transmission -> ECM (cause it's the modulator?)
Or ? What's the order of operations? Or do we not know for certain? I've tried to trace it physically but all of the wires are in wire coverings and difficult to trace.

Originally Posted by cadillackid

as for your allison , Bouje is 100% right.. its mechanical.. except for the electric modulator.. there is no TCM or data link..

No data link. This is fantastic! This was what I was confused about. But is the electronic modulator a device on the J1708 network? If so wouldn't that technically be a data link?

Originally Posted by cadillackid

the valve body controls the shifting.. (this is the way every automatic transmission was before about 1990).. the springs and spacers in the valve boidy bores set the base shift schedule.. and then shiofts can be "trimmed" by adjusting the trim wheels in the front of the valve body.. it essentially adjusts the spring pressures on the valves.. pressure goes up and down with RPM thus moving the valves against the springs.. opening other ports on the valve bidy which trigger a shift.. its all hydraulic.

So I understand hydraulics a bit. Does the valve body work like it would on say an Excavator with slide valves that have holes in them and as they shift they allow hydraulic pressure to pass through thus enabling the device or pistons? If so then I get how it works then on the transmission.

Originally Posted by cadillackid

the modulator controls a pressure adjustment valve which raises and lowers the shift points .. on a true modulated 545 (or 643) .. the modulation was progesssive based on engine load (gasoline models using a vacuum modulator) or on throttle position (diesels)..


they lost the ability for true modulation when the drive-by-wire engines came out with no more throttle cables.. so they created an electric modulator which is on / off (no one was doing PWM then).. the ECM is supposed to take a mix of RPM, engine load, and pedal position to decide when to turn it on or off.. it sort of works..



it worked so "good" that WW williams (major allison dealer) developed a mod (redybyrd got it). where they over-rode the ECM and turned the modulator on anytime the pedal was over 65-70%.. it was in hopes to help from burning up so ,many 545s that werent shifting modulated when they should..

So I have this issue with switching from 1st to 2nd, sometimes 2nd to 3rd, 3rd to 4th is okay. You mentioned a trim wheel. I may need to adjust this some, or can one purchase one of these mods from WW williams and install it?

[cadillackid]

theres youtube videos with the ins and outs of the valve body.. but essentially yes the valves allow and block fluid flow to various components of the transmission..


im not sure what your shifting issue is? too early? too late? not at all?


so the modulator is a cylinder device hanging off the side of the transmission aboiut halfway back with a 2 pin wire coming from it..



when you apply +12 VDC to it, it turns on (bench testing it will result in a definite "CLick!". it pushes a plunger rod out which activates the modulation valve in the valve body.. essentially putting all of the shifts into their maximum RPM (full throttle) mode.. "kickdown"..



if you ever used a GM TH-400 it had an electric kickdown connected to the gas pedal on the car.. this works similar..



if the modulator dies and you keep driving (like I did not realizing it was bad).. then you eventually ruin the transmission.. I replaced my modulator but the damage was already done.. alas what started my quest for the allison 1000 swap back in 2017..



I doubt WW williams probably even knows what the mod is anymore.. after all the AT545 was discontinued in 2003... if you really want one, I can pull the one off of my bus .. it essentially was a microswitch activated by the accelerator pedal asnd was wired in parallel with the transmisison relay up on the firewall (in that relay bank of 3 or 4).. the only reason I knew thats where it came from was an old-timer bus mechanic in one of my enthusiast groups helped to develop it at the WW williams here in columbus.. he talked about how many 545s were dying when electronic engines came out compared to previously on the mechanical and gas engines..

[Bouje bus]

two different troubleshooting guides have said 2 120 ohm resistances in parallel to generate a 60 ohm load across yellow/green.

i measured and got 2.5v on high side, 1.79 on low side.
physically i think the network is solid.

is the address request going unanswered from the AU box, or the TCM?

[Bouje bus]

i stumbled across this thread searching for address assignment.
unfortunately the link on page 2 now takes me to a stigmatism website????

https://www.skoolie.net/forums/f37/j...diy-37196.html

[cadillackid]

I was trying to figure out what address the AU claims .. I’m guessing the claim not complete error is due to no response from any other devices .

I regret I didn’t make it over today to work on the bus .. I’m partner and main tech guy in a few companies to my work tends to be really busy all the time .. and I’m the type to pick up work stuff 24 hrs a day if need be so didn’t get over.
Hopefullly things are quieter tomorrow and I can try this out on my Allison .

I’d expect the AU to claim 0 or 1 unless it’s claiming as a scan tool ..

[cadillackid]

OK so I finally hooked this up to my transmission.. and it talks..



termination resistors. I looked and I bought the AU device with built in TERM resistor so if you got one without then you are correct in installing a term resistor.. this would be consistent with the factory setup which has 1 single Term resistor in the network..


from what I understand the allison TCM's have an internal resistor on the J1939 port.



it was as simple for me as connecting the yellow and green wires from my AU device to the CAN high and CAN low going to my allison.



the AU claimed address zero and the teraterm display showed the J1939 link on.


I had no check trans light and my digital dash display connected to the allison showed TPS as I moved the throttle..



I had thought there was some AT commands you could use to view more debug from the serial port but doesnt seem to be...



I havent driven the bus yet but it does show throttle so we shall see in a few

[Bouje bus]

Ok, I surrender my multimeter and admit I am the dumbest monkey in the zoo.


While troubleshooting I pulled the Fuse to the TCM, so I didn't unplug the cable with power applied.
I put the Fuse back in the adjacent slot. I've been trying to diagnose a computer with no power.



Ugh.


With Fuse in place I get 1939 on. Address claimed.



Now to clean up and take it for a test run.

[cadillackid]

Originally Posted by Bouje bus

Ok, I surrender my multimeter and admit I am the dumbest monkey in the zoo.


While troubleshooting I pulled the Fuse to the TCM, so I didn't unplug the cable with power applied.
I put the Fuse back in the adjacent slot. I've been trying to diagnose a computer with no power.



Ugh.


With Fuse in place I get 1939 on. Address claimed.



Now to clean up and take it for a test run.

yes!!!!!!!!! thats awesome!!!!

[Bouje bus]

Successful test drive!!! Feels like a Tacoma, slow but smooth. Shifts easy.



Got home to new issue.

It's leaking between trans and engine.

[cadillackid]

Originally Posted by Bouje bus

Successful test drive!!! Feels like a Tacoma, slow but smooth. Shifts easy.



Got home to new issue.

It's leaking between trans and engine.

great news o nthe test drive!!..


I cant tell what engine you have but if its a T444E.. look to the valley before you assume its a rear main seal.. (looks like engine oil and not trans fluid)..


HPOP lines, or turbo pedestal area leaks often mistake themselves as rear mean leaks.. oil runs down and gets between the flywheel housing and the block... ends up on the converter and flung.. or leaks from around..



so id look in the valley of the motor for any oil first and around the turbo pedestal..


this isnt applicable if you are a different engine...

[Bouje bus]

You are 100% again. T444e. Wetness in the valley.

Not red like trans fluid, but thin and honey colored. Not like oil in pan.

[nikitis]

Nicely done gentleman. I now have a solution for when my AT545 dies. I'm waiting on the device to arrive and I have the know how, at least electronically now from your tests.

Did you guys install the transmission yourselves? And if so which ones did you add?