Not all 4L80e can be TCU'd alone??

[borneo]

I am a bit confused after fed by several friends that OBD II 4L80e that previously using PCM for its shifting (and doesn't have its own TCU originally) can't be converted to be a stand alone TCU transmission as the internal structure of this type of 4L80E is different from the generic 4L80e that coupled with originally mechanical engine (non electronic 6.5)

I wonder if this is true? :confused: :confused:

I am in the process of converting my originally electronic GM 6.5 turbo diesel engine to the DB2 mechanical set up, therefore I plan to purchase PCS TCU to hanle the 4L80e.

I do not have the original PCM nor TCU or harness of any kind for my 4L80E when I bought the GM 6.5 and I hate to invest $700 on the TCU and end up it won't work.

IS it true that just because it is 4L80e it will not be necessary compatible with the aftre market TCU?

Expert advice appreciated.

Thank you!
borneo

[DA BIG ONE]

Aside from the TPS any rig w/NP 246 AutoTrac has 3 speed sensors that sense frt driveshaft speed, rear driveshaft speed and road speed then the ABS is intergrated into that making for a PITA project going to standalone tranny control.

Reason for the 3 speed sensors, the NP246 has a clutch pack 9 clutches and 10 plates, when in autotrac everything comes into play and when slippage/or different speeds are sensed controller adjusts clutches as needed.

Any other t-case does not have the complex setup as a rig equipped w/NP246 does.

Hopes this helps ya!

[Randy H]

Should not be a problem with the trans. I think my trans is a 1996 and it works ok with the TCI computer.

Randy

[borneo]

[QUOTE=DA BIG ONE]
Reason for the 3 speed sensors, the NP246 has a clutch pack 9 clutches and 10 plates, when in autotrac everything comes into play and when slippage/or different speeds are sensed controller adjusts clutches as needed.

Any other t-case does not have the complex setup as a rig equipped w/NP246 does.
QUOTE]

If that is the case (NP 246 Vss confuses the TCU), if we just avoid tapping the VSS from the NP246 and use the VSS of the 4L80e instead. Shouldn't be this problem avoided?

My actual question is can we "divorce" the OBDII 4L80E hardware from the engine PCM (As my engine will be converted to mechanical) and wired it as stand alone using TCI tcu. Some says it can't be done as OBDII 4L80E is always needing an engine PCM.

Thank you,
borneo

[Robyn]

Here is a suggestion
Check with a local tranny parts supplier to see if there are major differences in the speed sensors in the tranny and or the inner controls.
I dont think you will have any issues as long as you stay away from the 246 electric T case.

However handy the elctric cases may seem, the complexity can be a source of issue when you need it most.

You should be able to marry almost any 4L80E box to any T case designed to handle the 4L80 shaft and flange.

Do a little snooping and I think you will find that all is not lost.

Good luck

[DA BIG ONE]

[QUOTE=DA BIG ONE]
Reason for the 3 speed sensors, the NP246 has a clutch pack 9 clutches and 10 plates, when in autotrac everything comes into play and when slippage/or different speeds are sensed controller adjusts clutches as needed.

Any other t-case does not have the complex setup as a rig equipped w/NP246 does.
QUOTE]

If that is the case (NP 246 Vss confuses the TCU), if we just avoid tapping the VSS from the NP246 and use the VSS of the 4L80e instead. Shouldn't be this problem avoided?

My actual question is can we "divorce" the OBDII 4L80E hardware from the engine PCM (As my engine will be converted to mechanical) and wired it as stand alone using TCI tcu. Some says it can't be done as OBDII 4L80E is always needing an engine PCM.

Thank you,
borneo

I'm thinking the ABS will act up then, aftermarket guys won't even do a beta unit for my evaluation "liability issue". Some have suggested to disconnect the trans harnesses and see if the truck will start and run ok? Stating if it does run ok the controller should work w/just TPS and VSS..........

I've though of doing away with autotrac and going to manual control (stick shift) for the NP246 fully engaging clutches when in 4wd.

I need to buy the wiring schematics for my rig to study it completely.

[JohnC]

The trans doesn't give a darn. The question is whether the rest of the vehicle will care or not. You may need to find a PCM from a manual trans or something like that...

[borneo]

If the tranny doesn't give a darn missing the PCM, life is beautiful as I will have the engine converted to mechanical injection using DB2 IP.

The next question is where do I suppose to get Engine RPM source to feed my TCU?

My 6.5 has a rear Turbo mounted so technically blocking my access to the back of the engine to put the Engine Speed Sensor (ESS) on the oil pump drive?

Please enlighten me as I am sratching my head as where I can get ESS for the TCU.

Thank you

Borneo

[DmaxMaverick]

The tranny (or TCM) doesn't care what the engine speed is. It only needs to see the tranny input speed (which it will already know), and the throttle position. The engine speed is relative to the TC speed, not the tranny input speed. The TCM will figure out the rest.

The tranny won't miss the PCM, but the PCM will miss the tranny, if it's an auto tranny PCM.

[Burning Oil]

It can be done, My brother has done his that way and we are in the process of making mine work.
The main thing is to have compatible TCM and force motor solinoid in trans. In 94 They changed force motor to a 614HZ and 93 down was 292HZ. The good news is you can buy a new force motor (either one) for the trans to mach the TCM. You obviously want a TCM from a DB2 truck/van. If you find one in a 94 or newer van it will match up with your 94 & new trans. You can get a TCM from a 92-93 truck, but will have to change force motor in your 94 & up trans.

That is the easy part of the whole swap you still need to know how to reconfigue the pins on the TCM. My brother is the smart one and he did his and working on mine now, but it can be done. He is planing on doing some CAD drawings and selling a guide.
His is a 96 OBDII truck converted to DB2 (just passed TX inspection also)
Mine is a 96 4x4 converting to Cummins 5.9 and 4L80E.

Hope this helps.

[Burning Oil]

As far as the ESS you will need to install it. The TCM will need it. You will have to move turbo if its in your way.

Later

[Burning Oil]

Sorry I think I may have wasted your time. Everything I posted before was using the GM TCM's. I just reread your post and see you have a "TCI" TCM.
I/we have no experience with that.

What I do know is the 4L80E can be made to work atleast 3 different ways.
A stand alone aftermarket computer like "Compushift"

A factory TCM, like I just posted.

And a full manual valve body. I have this in a 72 Chevelle, but would not use it in a daliy driver.

[More Power]

The Jet 4L80-E TCM kit I installed in 1999 needed ESS & TPS. ;)

The factory 6.5 ESS would probably work with a center-mounted turbo cuz it sits so low in the engine valley. I imagine that's how the HMMWV's do it.

Jim

[JohnC]

The TCM needs ESS to calculate TCC slip. TOO MNY TLA!

[borneo]

Thank you so much for all the advice. I do not plan to use GM TCM as it is complicated as there are a lot of conflicts and guesswork. I will purcahse aftermarket TCU, I have decided buying PCS TCU. I sent them an email and what they said was their TCU is a true stand alone and I need to just yank all the GM original wiring and use their. It is pricey though but at least there shouldn't be any guessworks and "buy and try" risk.

borneo