I have test driven my truck with this mod and it works great.
The lockup now functions with the lockup engaging 100% at about 42 mph.
It unlocks on deceleration, re-locks 100% after you get back on the throttle,
and unlocks under heavy throttle, just like an 80's-early 90's model GM would.

I also installed a Sonnax pinless 1-2 accumulator piston and pinless forward
accumulator piston.
The 1-2 piston was easy, but the forward piston was a bit of a chore with the 4wd
tranny crossmember in close proximity, but with a bit of enginuity it can be done
with the crossmember still in place.
And of course, a new filter and Type F fluid...
My pan hasn't been off for over 20K miles, and the Inside of the pan was spotless.
So clean I didn't even bother wiping it down...

 

I should also point out that this mod isn't really intended to cure a
P01870 code and/or vave body wear, but just to get rid of the PWM function
In a tranny that's not having problems with this yet, and possibly prevent
these issues from eventually occuring.

 

I should also point out that this mod isn't really intended to cure a P01870 code and/or vave body wear, but just to get rid of the PWM function In a tranny that's not having problems with this yet, and possibly prevent these issues from eventually occuring.

For anyone considering this modification, you may wish to read the following article from MOTOR magazine June 2006, an industry tech mag for mechanics/ dealer shops. I suppose that whether or not there would be a problem, would depend upon the model and year of your own vehicle. Too bad the OP has not stated his own vehicle specs.

http://www.motor.com/article.asp?article_ID=1039

The article says:
Should anyone modify the PWM or ECCC strategy to function as an ON/OFF apply while using a converter with a damper plate designed for PWM or ECCC, a tail end bump on the apply of the clutch would be felt, possibly resulting in a customer complaint. In some cases, a code for Converter Clutch Stuck On may also occur as a result of this modification to ECCC strategy vehicles.

 

So this just allows the TC to lock up on acceleration pretty much? I may try this. seems simple enough.

 

no it makes lockup more of an ON/OFF style like the older trucks ran.

the newer trucks run PWM (pulse width modulation) to slip the convertor into lockup. the lockup is so quick and crisp it can be mistaken for another gear change.

you can do something similar with just a tune.

 

The lockup still works as usual, following the PCM's programming table for the main TCC solenoid
Engagement and release points, just without the PWM slip function.

 

Modifying the PWM solenoid is adifferent approach than the usual
Stake the TCC isolator valve, or replace it with a Teckpac "fixed" position valve.

Bypassing the solenoid still allows AFL pressure to act on the isolator valve as
It normally would, just without being bled down by the PWM solenoid.
So it probably doesn't nail converter apply pressure to excessively high levels
like staking it does.

As for the "tail bump" from the soft clutch damper, I haven't noticed it being a problem
on my truck.
But I have bypassed my main TCC lockup solenoid to full manual control temporarilly,
to see how it reacts to full lockup at lower vehicle speeds. Applying it as low as early 2nd gear
Isn't bad, but applying it in 1st does create a rather annoying "tail end bump" on the shift to 2nd gear.
2-3 and 3-4 aren't objectionable, in fact, it feels pretty nice to me having it locked while driving around
town...
It can produce a 200-400 rpm drop when locked even under fairly light throttle.
And there could be noticeable fuel economy gains to be had by locking it when the torque converter
is in its least efficient rpm range.
As for the "converter stuck on" code, its normally only set if the PCM detects a voltage drop on the main
TCC solenoid ground circuit when its not being commanded on by the PCM.

The PCM is looking for batt. voltage on this circuit when its not being commanded on, and a voltage drop
when its commanded on...
Again, I used a 30K ohm resistor to satisfy the PCM's circuit voltage expectaions while I have it bypassed
to manual control.
And just about any resistance rating resistor will work, as long as the resistance is at least as high as the
solenoid in question. Say, 30 ohms minimum. Lower than the solenoids resistance, and there's a chance
of burning out the circuit driver in the PCM.

 

I've never drove a older Gm vehicle so I dont really know what you mean by that. Wondering if this would be worth doing.

 

Well you can test it for yourself with temporary wiring alterations at the PCM.
That's what I did before I pulled the pan for more permanent mods.
Who knows, just wiring PWM for full time current might hold up long-term.

Having a few extra PCM wires/pins is handy for this, as it allows you to test
things without having to cut up your wiring, especially before you decide you
like the mod or not.

 

Another update.
Still driving with the 3-2 solenoid disabled. Still can't tell any difference.
Monitoring MPG with my Torqe app, I've been observing changes in fuel
economy from early torque converter clutch engagement, and it looks quite
promising.
At a steady 35-36 mph on a slight uphill grade, I've seen gains
Of 4 mpg in most cases, and level ground gains of 2-3 mpg at speeds as low
as 25 mph.
So it looks like early TCC engagement could deliver significant economy
improvements with in-town and lower speed back road driving.

 

Transmission tuning is where I see the most mpg gains when I do my tunes. I have played with early lockup and saw good results. I personally dont care for it in my truck.

 

Wow, very interesting and impressive gains!

 

i need to do some more homework on exactly what this does before i think about going any further. I miss my built up trans that thing screwed compared to this shitty stock one

 

Can't say I'd notice the difference between a stock and built trans on a 2.2. Only reason I'd be interested is for consistent RPM and better MPG.

 

I'd say 2.2l trucks could see considerable economy gains too
considering their high stall speed coverters.

 

Like I said, all you have to is pull the PWM and TCC wires at the PCM
then connect them to a grounded momentary switch for testing, then
connect a couple resistors between a swtched battery source and the
terminals in the PCM to fool it into thinking those solenoids are still
connected to it to see if you like it or not.

 

Im sure it is simpler then it sounds but electrical is not one of my better points. You should post some pics! Also which resistors do you use?

 

I used 33K ohm resistors, but just about anything above 30 ohms
Up to and maybe even over 100K ohms should work.
All the resistors do is fool the PCM into thinking the circuit to the
solenoids is good so it doesn't set codes and and possibly inhibit
4th gear and force max line pressure.

And Merry Christmas to everyone.

 

Just another update.
I had previously wired the main TCC solenoid to a hand held momentary switch,
for full manual control. This became a bit bothersome with extended driving, as
ignoring it at higher road speeds would force the PCM to perceive the slippage
as a TCC fault, and inhibit 4th gear and max line pressure which would persist
until the engine was re-started.

But I didn't want to just re-install the TCC pin back into the PCM harness and not
be able to manually engage it at speeds below the programmed 40 mph minimum.

So I decided to devise an auto/manual dual control capability, by wiring up a relay
that the PCM can control to to operate the lockup in normal fashion, but still me the
ability to manually override it whenever I want without triggering any fault codes.

The relays 83 ohm coil is connected to a switched positive on one side, and is grounded
by the PCM on the other side. The TCC solenoid wire attaches to one of the switched
contacs of the relay. this terminal also taps into the momentary switch in the cab,
then to ground.
the other switched relay contact is attached to ground.

Works great. I have normal PCM controlled lockup, with an override control to engage
lockup at will with no trouble codes.

 

BTW, still seeing considerable in-town and under 40 mph
back road driving economy gains,
and the 3-2 solenoid is still disconnected with no significant
difference in 3-2 shift feel that I can detect.

 

Just read through all your posts. Sounds like a good way to make my Blazer on 42s feel a little more "responsive" Would you care to sketch up a basic diagram for your testing and relay mods?

Sent from AutoGuide.com Free App

 

Well I'm not really good at making diagrams, but its actually pretty easy to visualize.
Basically, a switched 12V feed connects to one of the relay coil terminals, say, #85.
(I tapped into the pink EVAP purge solenoid wire to get my 12V feed.)
And #86 will connect to the PCM terminal that the TCC solenoid normally connects to.

On 98-00 models, the TCC solenoid goes to the blue (C1) PCM plug, pin #10.
the wire is tan with black stripe.
This wire will now connect to relay terminal #30. the override switch will also
connect to this terminal, then go into the cab and attach the a momentary switch.
The other side of this switch connects to chassis ground.

The last terminal on the relay (#87) also connects to ground.
So the PCM now controls the relay, which now provides the ground
path for the TCC solenoid, or the override switch inside the truck can also
ground it.

If you get a 5 terminal relay, the 5th terminal will be marked as "87a", that terminal
will be unused.
actually, now that I think about it, you could just connect your "override" wire
to that terminal instead, but I still think it would be a bit better to just tee it in
to terminial 30 as I originally described.

Hope this makes sense....

Also, I'm not sure this qualifies as making the truck "more responsive".
If anything, it could be percieved as less responsive during lockup.
The real goal of this mod is improved in-town fuel economy, and
to that end, its definetly helping my truck.

 

I was under the impression that 95 was a stand alone year with PWM, and 93-94 then 96-99 were either on or off. Did they reintroduce PWM at a later date or were they all basicly PWM? When I had my 95 transmission rebuilt the guy made it just straight lock the converter, rather then the PWM. When it locks its a right now kind of thing. I do get some exhaust drone, but I also have loud mud tires, and leaky door seals to listen to too lol.

 

No, TCC PWM has existed from 95-up.
What made the 95 4L60's unique was that it was the first year for TCC PWM,
and the last year for a PWM'ed 3-2 solenoid and control programing in the computer.
96-up 3-2 solenoids switched to on/off control.
95 was also the last year for integral case and bellhousing, in the S-series at least.
96-up S-series, and other 4.3L equipped trucks and vans used bolt-on bellhousing,
and six bolt tail housing.

 

hey crew cab Sonoma, I was wondering if you would take a look at my post on the blazer forum. im having issues with lockup. I put a switch in and deleted the pwm like you did here but still nothing. so heres the link thanks http://blazerforum.com/forum/2nd-ge.../forum/2nd-gen-s-series-1995-2005-tech-41/95-blazer-no-lockup-86863/#post632746