T Converter lockup switch tow haul mode - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



Welcome Enthusiast! If you already own a Chevy TrailBlazer or GMC Envoy or perhaps thinking of purchasing such a vehicle, then you have come to the best TrailBlazer and Envoy site on the net! Rainier, Bravada, Ascender, and 9-7x owners welcome too!

You are currently viewing our site as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to search and post topics, communicate privately with other members, respond to polls, upload content, and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!

If you have any problems with the registration process or your account login, please contact contact us.
Join Today!
Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > Transmission Mods

Transmission Mods Performance Transmission Modifications

TrailVoy.com is the premier GMC Envoy Forum on the internet. Registered Users do not see the above ads.
Reply
 
Thread Tools
  #1  
Old 08-08-2013, 12:56 PM
eric82930 eric82930 is offline
Junior Member
 
2004 GMC Envoy SLE XUV
Liquid Silver Metallic 4.2L I6 2WD
Join Date: Apr 2013
Location: wyoming
Posts: 16
T Converter lockup switch tow haul mode

I just installed a lockup switch on my dash for to manual lock the torque converter.I got this idea from a buddy with a dodge cummins who had a lockup switch on his dash. After searching the internet, there is plenty of info on how to do it, I just wanted to put it here for us to use.

The WHY:
I have had pcm4less reflash my pcm twice and it was way better, but it still would unlock the TC under high load conditions which is exactly opposite of what I want. Un-locking does help a 4 speed auto by making a bit more torque to the wheels and providing a fake in-between gear ratio so it acts like a gear between 3rd and 4th. If the transmission controls were smarter, I wouldn't have cared so much but even after the reflash, mine would unlock when towing into a head wind and stay unlocked for many miles which gets horrible gas mileage and makes a lot more transmission heat. I believe this is the main reason why these have such a bad rep for poor fuel economy.

The HOW:
So here is how to do it on a 2004 I6. (other years may be different)

you need a toggle switch mounted somewhere on the dash and about 4 feet of wire (two conductors). You can poke a hole through the rubber boot under the dash where the big bundle of wires passes through the firewall, just be careful not to nick any of the factory wires.

Next take the cap off the center connector on the PCM module. On the I6, the PCM is mounted right on the drivers side of the intake manifold. If you need more room to work you can disconnect the plug from the PCM. Disconnecting the battery is a good idea, (but I skipped that part).

From here there are one or two wires that will be cut and grounded through your switch depending on how you want the lockup to work. You can connect the ground side of the switch to the fat black wire in the center pin of the plug, I just cut off a bit of insulation and soldered it on.

The main lockup wire is a tan/blk wire on pin 37 (there are numbers on the back of the plug). This will be cut and connect the side going to the trans to the other wire from your switch. The remaining piece of wire from the PCM will need to go through a 100 ohm 5 watt resistor to a 12v source. I just connected it to the backup light fuse in the fuse box. This is only necessary to keep it from turning on the check engine light.

At this point the converter will lock whenever the switch is on IF the PWM solenoid is allowing it to. The PWM solenoid is controlled by another wire that lets the computer make a "softer" engagement of the converter clutch. I tried it this way and it would still be totally disengaged below 1500 RPM and the Partially slipping the TC at 1800-2000RPM.

There is a PWM solenoid valve mod which can be installed in the transmission which will make the PWM on all the time and the converter will be on or off with no slip. This is part of the Transgo shift kit.

I don't have my Transgo shift kit installed yet so I decided to switch the PWM circuit to full on as well. The PWM wire is a brown wire in pin22. I just cut it and connected the trans side to the same switch as the tc wire. Then I use another 100 ohm 5 watt resister to connect the PCM side to the 12v source on the fuse box to keep it from turning on the check engine light.

Now my converter is full locked anytime - anywhere when the switch is on. It will stall the motor if you forget to turn it of when you stop. (thats how my buddys cummins is too).

Here are some negative side effects to be discussed:

When the switch is off the TC is always un-locked. If you used a double pole switch you could probably wire it another way so the off position re-connects the PCM to control the lockup. I like it this way better but I am a control freak.....

The engine may PUSH the vehicle slightly in an emergency stop menuver that could ad a few feet to you stoping distance if you dont flip the switch off in time. This could be fixed by putting a relay in the circuit that triggers from the brake light.

There are some people saying the PWM mod is hard on the torque converter because it allows full pressure on it all the time. I am no expert but from my research, the older 4l60e and 700r4 trannys came that way from the factory so I can't see it being a big deal.

I don't have a lot of miles on it yet an I am going to install the transgo shift kit soon. But I wanted to try it on a stock tranny first. My trans has 100,000 miles on it so I will post back any pros and cons I find.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2  
Old 08-12-2013, 03:21 PM
eric82930 eric82930 is offline
Junior Member
 
2004 GMC Envoy SLE XUV
Liquid Silver Metallic 4.2L I6 2WD
Join Date: Apr 2013
Location: wyoming
Posts: 16
I put on 400 miles towing this weekend and it works great. Its amazing how much torque the little I6 has at 2000RPM. It can tow the trailer over some pretty big rollers without down shifting or loosing speed. It set a code twice when I didn't unlock it in time and the RPMs got too low. I use my android phone with an app called "Torque" that has a button to reset codes on the fly through a wireless bluetooth obd port. It's so cool. But I think I will try making the switch automatic by using a relay and possible triggering the relay with the cruise control light or something that is only active above 40MPH. Any Ideas????

I could still override the relay with the switch but probably wouldn't need to do it very often. Locking the converter in second gear seems to work better on really big hills instead of unlocked in third....I won't get to that project for a while, I'll post back when I do.
Reply With Quote Quick reply to this message
  #3  
Old 09-17-2013, 12:05 PM
eric82930 eric82930 is offline
Junior Member
 
2004 GMC Envoy SLE XUV
Liquid Silver Metallic 4.2L I6 2WD
Join Date: Apr 2013
Location: wyoming
Posts: 16
I am nearing my final stage of this mod. I have since installed the transgo shift kit that includes the PWM valve mod so I no longer have to wire the pwm solenoid to full on anymore. So my current set-up only grounds the tcc lockup solenoid and the pwm solenoid is hooked back up to the pcm. It is grounding the solenoide through a double pole relay controled by my dash switch that way the other poles on the relay connects a a 75 ohm resistor to the pcm when in "manual mode" so the pcm still thinks its hooked up to the solenoid and doesn't set a code.

I also added a nice bonus feature to cut the ground to the injectors when the brake switch is on and tcc is manual locked. It acts as a jake brake for towing.
It sets a pending fault code but doesn't turn on the cel light.

The only negative so far is if you forget to shut it of and it bogs the motor too low in second gear, it sets a pending fault and the cruise won't work until its reset. I will eventually hook up a speed trigger so the relay will be automatic on above 35 mph. Then it will be foolproof.
Reply With Quote Quick reply to this message
 
  #4  
Old 01-13-2014, 06:25 PM
Chewy1576's Avatar
Chewy1576 Chewy1576 is offline
Member
 
2005 Chevy TrailBlazer LS
Graystone Metallic 4.2L I6 4X4
Join Date: Mar 2009
Location: North Ogden, UT
Posts: 343
Any updates on your mod? My transmission/TC behaves the same way yours did before you added the lock switch. I don't like how easily the TC unlocks in 4th gear and I feel it's unnecessary. I'm looking at doing this mod as opposed to sending my PCM back to have it reprogrammed. Any luck with a speed trigger? I was also thinking about an input that will disengage the TC lockup when the brake pedal is pressed, similar to how the cruise control disengages.
Reply With Quote Quick reply to this message
  #5  
Old 01-14-2014, 10:54 AM
eric82930 eric82930 is offline
Junior Member
 
2004 GMC Envoy SLE XUV
Liquid Silver Metallic 4.2L I6 2WD
Join Date: Apr 2013
Location: wyoming
Posts: 16
I still didn't figure out a speed trigger. There is a wire for one of the trans solenoids that is only grounded in 3 and 4th and I tried using that to trigger the lockup relay, but since my pcm was reprogrammed it stays in 3rd until almost a complete stop when decelerating. so its still tripped a code sometimes. If your pcm is stock you might want to try it that way. I think the error code is set below 30mph or so. I wouldn't care about just the light being on but it disables the cruise control when the error code is set.I have just made it a manual switch and only lock it when I'm towing or if there is a bad head wind. I have a permanent bluetooth obd plugged in all the time and I use software on my phone to reset the code if it occasionally happens.
Reply With Quote Quick reply to this message
  #6  
Old 01-14-2014, 11:44 AM
Chewy1576's Avatar
Chewy1576 Chewy1576 is offline
Member
 
2005 Chevy TrailBlazer LS
Graystone Metallic 4.2L I6 4X4
Join Date: Mar 2009
Location: North Ogden, UT
Posts: 343
My PCM has been tuned so I'm sure I have a similar program to you. I had sent mine back a few times to try to correct the speedometer because I was running larger tires at the time but it never quite displayed correctly. I was looking into latching relays that activate on a button press and deactivate when I presses the button again or the brake pedal. That would seem to function more like a stock Tow/Haul button to me. Check out the DEI 611T and let me know what you think.
Reply With Quote Quick reply to this message
  #7  
Old 01-14-2014, 10:12 PM
eric82930 eric82930 is offline
Junior Member
 
2004 GMC Envoy SLE XUV
Liquid Silver Metallic 4.2L I6 2WD
Join Date: Apr 2013
Location: wyoming
Posts: 16
That dei relay is pretty cool.my brain is smoking.I will figure out a good use for one even if its not my envoy.

Sent from AutoGuide.com Free App
Reply With Quote Quick reply to this message
  #8  
Old 01-18-2014, 11:48 PM
the builder the builder is offline
Junior Member
 
2006 GMC TrailBlazer LS
Carbon Metallic 4.2L I6 4X4
Join Date: Jan 2014
Location: leola pa
Posts: 1
I have been building these converters for awhile now and the clutch plates are a major problem in them. The rivets holing the dampener to the plate are bad from factory and are weak. The heads snap off and wipe the lining off. Just my input if you throw the switch all the time be prepared to purchase another converter. I weld the dampened cage to the plate and weld the rivets to the plate on them. So if you get another one have a local converter shop hook you up also ask for a raybestos pt lining. Other than that they are bullet proof converters
Reply With Quote Quick reply to this message
  #9  
Old 05-21-2019, 07:23 PM
greg1290's Avatar
greg1290 greg1290 is offline
Junior Member
 
2005 Chevy TrailBlazer LT EXT
Summit White 4.2L I6 2WD
Join Date: May 2019
Location: Tennessee
Posts: 8
Could I cut the tan/black wire from the connector at the pcm and leave it at that and not have lockup at all?
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum forums, you must first register.

Please enter your desired user name, your email address and other required details in the form below.
(Only letters, numbers, dashes and underscores are permitted for user names)
The user name that you choose is permanent and can never be changed.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


» Sponsors

Advertising Info

All times are GMT -4. The time now is 05:08 PM.


Chevy TrailBlazer and GMC Envoy Enthusiasts - Copyright 2004 - 2009 All Rights Reserved.
All trademarks referenced herein are property of their respective owners.
RSS Feed