1995 4L80E vs 1998 4L80E ~ Using a '427 PMC $OE/$31

[dave w]

I'm wondering if a '427 PCM (1995 $OE/$31) can operate the electronics for a 1998 4L80E?

Some information I found on the "net" 1994 and up have the same connectors and the 614 Hz Force Motor.

dave w

[pmkls1]

AFAIK there aren't any differences in any of the 4L80E electronics from '94-up and technically any controller capable of operating a 4L60E series with pwm tcc controls should be able to operate a 4L80E and vise versa. There weren't many changes the 4L80E at all over the years really. Unlike the 4L60 lines, the 4L80 never changed bell housing depth and the flywheels and torque converters were the only differences between 4L80s mounted to LS engines and those mounted to big blocks and Gen 1 small blocks IIRC. I know it's not "solid" proof, but it is perhaps more evidence supporting what you have found thus far.

[RobertISaar]

the only significant control differences between a 4L60 and 4L80 is that the:

4L60 had the TCC + TCC PWM solenoid compared to the 4L80 TCC PWM
4L80 had an input speed sensor, 4L60 did not
4L60 had the 3-2 downshift solenoid, 4L80 did not

everything else is minor and can be accounted for in the calibration.

also, i don't see any reason why you couldn't control the newer trans with the older PCM... FMC/PCS frequency shouldn't be THAT sensitive unless you got down to some really low frequencies. the 64Hz that a P4/P6 can control should be plenty. the TCC PWM on a lot of somewhat recent stuff was still pulsed at 32Hz.

[one92rs]

not sure if this is relevant. but in my 2002 chevy silvy I was building I put a 1997 4l80e in it. I went with the 97 due to both cooling fittings being in front instead of the tube running inside. all I did was a copy a 2002 2500 truck table in my pcm and it worked fine. if it worked in my 02 I don't thing a darn thing is different.

[one92rs]

found this.

[pmkls1]

Yeah, like I said there weren't many changes made overall and was also fairly sure that most controllers were capable of operating either/or. The 4L60 vs. 4L80 stuff is irrelevant to his question though. I still have never seen or heard of any differences in the electronics of the "later" 4L80s though. Never messed with the early units, just the 93/94-later models.

[comerz1]

Good info here. I am working on a project with a 4l80e, pretty sure it's out of a 99 but not positive. Motor will end up being TBI with a 7427 ecm, which I don't have yet. Also need the wiring harness. So are the harnesses the same regardless of transmission? Did they put 4l80e in 2wd in 94-95? If no 80's in 2wd, will there be extra plugs that went to the transfer? Just need a direction on where to start looking for a wiring harness. Hopefully I can find a donor that has all of the TBI setup, harness, pcm, etc. but I may have to piece it together.

[dave w]

I found some 4L80E schematics, 1995 and 1998. The project is to convert a 1998 Diesel to Gas, using a TBI 350 engine. From what I can figure out, this should work. I'll need to figure out if the 1998 VSSB is 4K or 2K PPM?

dave w

[helo]

Aren't you going to use a TBI drac? Speedo gets 4k (right??). PCM gets 2k to F13 and 4k to F12 (tranny speed). I honestly have no idea why GM felt they needed to feed the tranny code a 4k signal, unless maybe the tranny code was developed on a TPI car PCM that was always 4k..

With F12 vs F13, I hacked a patch to use F13/2k input for ALL speed related stuff because F12 is needed for MAF input ($0d_maf), and it's silly to be switching pins to change between MAF and s/d chips. dimented told me this was a bad idea (on TGO) because tranny code "needed more precision" than 2k, but I disregarded his advice because he runs manual tranny's =).

The alternate solution for changing between MAF+s/d is to use the 8625 PCM, which supports alternate TIS/TOS inputs on F2-F5 (flag in bin, but wiring this way is PITA).

[dave w]

Aren't you going to use a TBI drac? Speedo gets 4k (right??). PCM gets 2k to F13 and 4k to F12 (tranny speed). I honestly have no idea why GM felt they needed to feed the tranny code a 4k signal, unless maybe the tranny code was developed on a TPI car PCM that was always 4k..

With F12 vs F13, I hacked a patch to use F13/2k input for ALL speed related stuff because F12 is needed for MAF input ($0d_maf), and it's silly to be switching pins to change between MAF and s/d chips. dimented told me this was a bad idea (on TGO) because tranny code "needed more precision" than 2k, but I disregarded his advice because he runs manual tranny's =).

The alternate solution for changing between MAF+s/d is to use the 8625 PCM, which supports alternate TIS/TOS inputs on F2-F5 (flag in bin, but wiring this way is PITA).

I'm converting a 1998 diesel vehicle to a TBI gas engine. I'm thinking I should use the 1998 TISS outputs to F2 / F3 on the '7427 PCM, and the 1998 VSSB outputs to F12 / F13 on the '7427 PCM.

dave w

[pmkls1]

I only had time to glance at the schematics, but I THINK you are on the right track. I hate that I am always overloaded with responsibilities when somebody that has taken the time to help me needs a little help. But honestly, you're better at this stuff than I am anyways dave. If nothing else, you can count on me for moral support lol.

[1project2many]

There are some notable 4L80E differences over the years. These occur with the force motor and TCC.

After '93 the force motor frequency was changed from 293Hz to 614Hz to reduce electrical interference. There were also some changes to how the motor was actuated with the old system having a cleaning cycle sent to the force motor 6 times per minute.

TCC control strategy and the actual clutch material should be matched up. Pre 95 transmissions used an "on/off" apply strategy while later units added a PWM solenoid to gradually increase pressure and smooth TCC application. 98+ TCC calibration may allow much more slip* and in fact may never fully lock. Clutch materials change with TCC apply strategy. Early converters used a carbon material, next was Kevlar. High slip strategy rewuires woven carbon graphite. On/off type clutch should not be used with slip controls but slip materials may work with on/off. Possible side effects are clunky, bangy aply/release of TCC when using on/off with clutch designed for slipping.

Reference info:
http://www.msgpio.com/manuals/mshift/4L80E/4L80e.html
http://www.chevyavalanchefanclub.com...ic=5072.0;wap2

* I have only found a few indirect references to the 4L80E using the same slip strategy as the 4L60E from 98+ so don't take it as gospel.

[pmkls1]

You are correct about the TCC strategy for 98+ transmissions and that applies to multiple if not all GM transmissions of the era. But, the 4L80E always used a PWM TCC solenoid and only had 1 TCC solenoid. The 4L60E is the transmission that added a PWM solenoid later and it was actually around 96-97 that a PWM solenoid was added to the valve body. The TCC strategy you are talking about was called the EC3 or ECCC and it didn't require any different components in the trans other than a clutch lining in the converter that could handle the constant slipping as you stated. The rest of the "strategy" was basically calibration differences to set a pre-determined amount of converter slip. All of that crap was to serve 2 purposes. First it gave the TCC operation a smooth seamless feel to quell customer complaints about the clunk sometimes felt with an on/off TCC and also because a full lockup transmits more driveline noise and feel to the driver. Second, the constant slipping could be varied to improve economy and performance by sustaining just enough load on the engine at all times to keep RPM's in the best range for power and economy. It is also no coincidence that the later vehicles have exponentially more converter issues than older vehicles because a lot of heat and stress is placed on the converters. Using the '95 427 PCM with a '98 4L80E shouldn't have any issues with the converter and will probably extend it's life. Although the engagement may be more harsh, I don't think it would be all that noticeable just from my experience seeing trans techs disable the PWM TCC solenoids on 4L60E transmissions for select individuals.

[EagleMark]

Couple facts I can verify on 4L60E. 1995 4L60E went to PWM TCC, plays havoc when you use a 1994 bin. This is same on LT1 F and B cars as well as trucks.

My 1998 4L60e has a max TCC lockup setting of 98%... I've always want to go 100% to stop slip, reduce heat. Just spooked on some trans tuning...

None of the '93 -'97 4L60E's are directly interchangeable, except '93 and '94!!!
Here's a list of yearly differences that will show you why. Yes, some years will
fit in others and may not even throw a code, but there will be an issue in the
long run. The big issues become forced 3-2 downshifts, and converter lock up
issues and burnt lock up clutches. When a converter cluych cause it to lose lock
up, the 3-4 clutches, in the transmission will soon follow because the 3-4's
need lock up to keep them cool while cruising in overdrive.

1993: These
were used in trucks only. Not available in F-Bodies, B-Bodies, or
Vettes

1994: Interchangeable with '93 4L60E with no modifications. The
'93-'94 is a NON PWM transmission. This means that the lock up apply strategy is
an on /off arrangement. It has an 11 pin case connector. Does not have PWM cast
into front pump. 1 piece TCC control valve in the valve body. Plate has holes in
plate, marked in diagram below. 1st design 3-2 valve

1995: Stand alone
year! Will not interchange with any other year. This is a PWM transmission. An
extra solenoid was added to the valve body to control the pulsed lock up
strategy of the conerter clutch. It has a 12 pin case connector, extra wire in
the transmission to computer harness and different computer to control the new
PWM circuit. Has PWM cast in front pump. Front pump internal passages different
to match new TCC strategy. 2 piece TCC control valve in valve body. Has holes in
plate, marked in diagram below. 1st design 3-2 valve. 12 pin case connector. '94
computer won't recognise new TCC strategy., and will burn lock-up clutch and 3-4
clutches up. '96 computer isn't compatible with '96 3-2 control solenoid.


1996: The 3-2 downshift strategy was changed to an on /off arrangement.
The TCC control solenoid was changed to a 20-31 OHM solenoid, from the previous
10-15 OHM solenoid. The 3-2 control valve was changed to the second design
valve. The easiest way to identify the valve is, the second design valve will
fall out as soon as the solenoid is removed. The first design has a plug and
retaining clip. TCC solenoid remains 10-15 OHMs, which is the same as the '95
arrangement. Has PWM stamped cast in pump. pump is the same as '95. Will not
interchange with '95 unless changing 3-2 solenoid, valvebody casting, and
seperator plate. Has holes in plate marked in diagram. '94 or '95 computer will
not accept the 20-31 OHM 3-2 solenoid and will throw an SES light and throw the
transmission into limp mode. Some less knowledgeable builders will swap the
solenoid so the computer will see the correct resistance, but the valve itself
then causes downshift issues. If only the solenoid is changed, it will result in
a 3-2 downshift cut loose. In other words...3-neutral-2 downshift. Speedo moved
to passenger side of tail housing, but easily changed.

1997: Basically
the same as '96.

[helo]

On/off type clutch should not be used with slip controls but slip materials may work with on/off. Possible side effects are clunky, bangy aply/release of TCC when using on/off with clutch designed for slipping.

True. You can adjust a few 7427 tranny tables and constants to soften TCC application for the kevlar clutches if it's a problem (mostly if you play with 2nd gear lockup, in my experience).

I'm converting a 1998 diesel vehicle to a TBI gas engine. I'm thinking I should use the 1998 TISS outputs to F2 / F3 on the '7427 PCM, and the 1998 VSSB outputs to F12 / F13 on the '7427 PCM.

Yup, forgot about TIS; I don't use it ($0d/4l80e). One caveat, I do believe the polarity is supposed to be wired a certain way?

Only reason 7427 wants TIS is for TCC slip calculations, and with a kevlar TCC the only reason you should ever get excessive slip is a valve body problem, not worn clutch material, and at that point there's truly no sense in releasing TCC because of detected slip. For the pre-kevlar design, releasing on slip can save the TC from certain destruction.


(edit, as next post says, yeah, there is code segment to detect 'other' slippage, but it's fawqing useless IMO, I'm not pulling my 4l80e for slippage SES code, I'm driving it 'til something actually breaks.)