MFI questions using 6.5 and 4l80e

[street_xr]

Hi All,

I'm a recent convert to the 6.2/6.5 and am replacing and repowering my motor pool to diesel power. I just bought a 1997 Chevy 3500 1 ton extended van to replace my 1995 gas 1 ton, which I may keep and repower with a diesel.

I have never been a fan of fly-by-wire systems, and combined with the notorious problems of the FSD on the DS4 pump I want to convert to mechanical injection, and would also like a fail-safe backup to control the 4l80e transmissions.

I have searched the archives without really getting a clear picture of how to make all of the little details work. It seems you put the '92-'93 4911 mechanical pump on with a throttle cable and let the PCU think it is still controlling a DS4. I am waiting for the Helm manuals to show up so I can't tell what sort of feedback connections might exist from the pump to the PCU.

That still leaves the PCU controlling the 4l80e. Are these transmissions totally non-functional without a PCU? I know Transgo makes a full manual shift kit, but I probably don't want that in a daily driver. Maybe it would be possible to build a switch matrix that could be plugged in if the PCU fails to allow manual control of the solenoids?

I'd like to hear from members with insight or experience in this conversion.

cheers, street_xr

[journeyman]

We did a transmission conversion from the TH400 to the 4L80e.
To control the 4L80e, we bought a TCI controller system. See
http://www.tciauto.com/Products/Electronics/

Here is part of the description:
The TCI® Transmission Control Unit is fully-programmable, and can be run as a standalone unit –even with a non-computer controlled engine, or in conjunction with OEM or aftermarket engine computers such as the FAST™ XFI™ system. The TCI® Transmission Control Unit will work with most GM, Ford, and Chrysler electronically-controlled automatic transmissions*, and includes a wide array of tuning options including load, gear, rpm and speed-based programming –all of which can be adjusted by simply connecting the unit to any Windows® based pc or laptop***.


A few years ago we paid something in the neighborhood of $700 for it.
It took a bit to dial in, but works well and is fully adjustable (shift points, firmness, etc.)

[journeyman]

Another question... Have you considered the Allison 1000 transmission?

Now that the used prices are down, it may be well worth it.
I have seen new units (5 speed) for as low as $2100. This is a FAR superior transmission to the 4L80e.

[street_xr]

Hi Journeyman,

Thanks for the info. In the case of the 1997, or other vehicles that already have a diesel and 4l80e I'm thinking the solution is to put the mechanical injection pump in and carry a spare PCM in case of failure. Seems like the going rate for used PCMs is around $ 100, much less than the $ 700 TCI unit. I can see the value of the TCI for standalone use though.

I really don't know anything about the Allison other than it is expensive. But it sounds like it is cheaper and better than the TH400 plus Gear Vendors overdrive units, that are $ 2500 by themselves. What does the Allison give you? The ability to keep the engine always in the powerband when towing heavy trailers? I thought I read somewhere that it needed a controller- is it capable of standalone operation?

Cheers, street_xr

[Burning Oil]

Below is a post I made on another site. This was my reply to a question.
I have swaped out the 6.5 for a Cummins 5.9, but as far as the transmission go's all the same info applies. My brother has swaped the DS4 for a DS2. Both our trucks are 1996 obdII factory. We removed the ecm or pcm and installed a TCM obdI.



"I have a 6bt in my 1996 GMC truck. It has a 4L80E in it and I used
a "TCM" not a ECM in mine. It will depend on what year you get the 4L80
from as to what TCM you will need. Up to 1993 can use a TCM up to 1993
only (common sence) but in 1994 they changed the force motors so a 1993
TCM wont work on a 1994-up. In 1994 GM trucks went to a PCM that
controls engine and trans. It is not what you would want. Luckily the
1994-up GM vans with the 6.5 were still mechanical injection and also
have the right TCM to drive the force motors in the 1994-up 4L80e's.
I was able to use my 1996 4L80E.
You will have to have considerable knowlege to complete the swap
becuase you will be combining OBD1 and OBDII systems. You will need the
pigtails from the TCM and know how to reconfigue the pins and know
which wires to use from the OBDII to plug into the TCM/OBDI. My brother
is actualy the one that has the knowlege to perform the swap, but some
of it rubed off on me. He is in the process of making a guide to do the
convertion.
In your case you would need to know how to run the wires to the pigtails
on the TCM.
I have to run, but will try to answer questions if you have them.
I could email my brothers contact info to you if I can't answer.
Later.
Leroy"

[street_xr]

Burningoil, thanks for the info. This is turning out to be a bit more complicated than I first thought. I can see why there isn't a whole lot of detail on how to do this. The electronics have crept into every nook and cranny of the powertrain.

Seems like if you can't mix and match electronic components the way we swap mechanical components the project becomes too complicated to be worth doing. There is a whole subculture in the gasser crowd that spends huge amounts of their time reverse engineering the software in the computers to get control over the fuel and spark programs, but apparently few people have torn into the code for the diesel versions.

One possibility for my situation is that the vans from 1992 to 1995 were apparently all mechanical injection and non turbo, with a separate transmission control unit. So the PCM doesn't expect to control the injection pump and so on. I need the PCM to run the speedo and other stuff, and it probably talks to the TCM also. This still leaves me with more electronics in the loop than I would like, But I think I can come up with a homebrew trans controller for emergency use if the PCM or TCM die on the road.

I will start looking for the pieces in the junkyards to see what I can come up with.

Cheers, street_xr

[Burning Oil]

In my post above I said my brother swaped out the DS4 for a DS2 I meant
DB2 the mechanical pump.

In the 94-95 vans there is no PCM its a TCM and will work with 4L80E's from trucks 1994-up.
I think The speed buffer drives the speedo and the speed buffer gets a signal from the TCM so you will be fine there.
I have another 1996 truck and it is have IP problems. I might convert it to a DB2 also, but I have another Cummins 6bt just waiting to go in to
Let me know if I can help.

[EWC]

Transgo is also offering a vacuum modulator? kit that does away with the TCM . I have not used this but would like to hear from anyone that has . Supposed to be able to use vaccum to make the trans shift .

[Burning Oil]

That would work on a gas motor, but off hand I don't think so on a diesel. I don't know how you would regulate the vaccum off the vac pump??
I have a Trans Go full manual shift on my 72 Chevelle with 4L80E. I would not want it on a daily driver.

[EWC]

VRV valve on the side of the injection pump that's used for the TH400 .

[Burning Oil]

VRV valve on the side of the injection pump that's used for the TH400 .

That would be cool. Never heard of one. What is VRV? (guessing vaccum regulator valve??) what applications were they on? were they on the DB2 style IP's.
My full manual 4L80E has a vac modulator, but that just cotrols line pressure. I would think you would need some kind of electric kit along with a vac modulator on a 4L80E. Seems like that would be expensive retail.

Thanks.

[DA BIG ONE]

Hi Journeyman,

Thanks for the info. In the case of the 1997, or other vehicles that already have a diesel and 4l80e I'm thinking the solution is to put the mechanical injection pump in and carry a spare PCM in case of failure. Seems like the going rate for used PCMs is around $ 100, much less than the $ 700 TCI unit. I can see the value of the TCI for standalone use though. Cheers, street_xr

Yes, best to use what you have w/TPS mounted to DB2, or DB4. T-stat housing can stay by making throttle cable bracket that mounts to top right (drivers side) bolt of stat housing. TPS and throttle cable bracket mods can be found in members area.

[EWC]

Transgo 48-MOD is the kit number . I did a goggle search and came up with a few hits . I'd like to hear from someone who has used this . Supposed to replace the EPC motor with a vac regulator .

[street_xr]

Thanks All, I'm starting to get the picture. You need the TCU from a 1994 or 1995 to control the trans because they changed the solenoids/force motors between 1993 and 1994-later. You also need a vehicle speed sensor buffer to run the speedo and maybe other stuff. This should make the trans behave like a non-electronic trans that doesn't need any outside control.

This basically turns the vehicle into an OBD-I type setup I think. I may have to deal with needing the SES and other instrument cluster lights to appear to work normally to keep the smog police happy, I'm not sure what runs those on a diesel. My gas 1995 definitely has an ECU/PCM or whatever you want to call the computer, that definitely runs everything. I am waiting for the 1995 electrical and emissions volume of the shop manual to arrive, also the transmission unit repair manual.

In the meantime I'm going to dig out my manuals an the turbo 400 to refresh my memory on how it makes shift decisions.

I'm curious how "smart" the TCM is as to how it decides how to make gear select decisions. It looks like there are only three electrical controls on a 4l80-e ; the TCC lockup solenoid and two gear select solenoids. The two gear selects give you only four possible combinations, so I think the forward reverse decision must be made mechanically inside the trans by the selector lever, although it is possible there could be some hardwired logic built into the switch on the trans. I guess the books will answer these questions


P.S. Oilburner, what truck did you put the 6bt Cummins in? I'm thinking it must be a conventional cab rather than a van, but what about the weight of the cummins compared to the GM motor?

Cheers, street_xr

[Burning Oil]

I put the Cummins 6BT in a 1996 crew cab dually 4x4. I don't remember exact #'s but seem to remember it being about 200lbs more than a 6.5. Im not sure if a big block gas motor is more than a 6.5, but either way it handles it just fine.

[diodow]

im too in the same problem ,to control the 4l80e i guess the computer from a 94-95 van is a good option its kinda simple.