GM's fix for Allison "shift busyness"

[Heavy Duty Neil]

Scroll down to the bottom for the Allison articles:

http://service.gm.com/techlink/html_en/c200207.html

Also notice the Steering rattle fix, under Tech tips.

[hoot]

Excellent post. Thanks!

[TXMAX]

HDN,

I got to the site but when I clicked on the listings I get a blank screen. Any ideas or am I just holding my lip wrong?

Thanks,

Abe

[DMAXDiva]

Hey TXMax,
I'm having the same problem. Getting this "no preview available" message in the center of a blank screen. :confused: :confused: :confused:

[FirstDiesel]

Works fine for me with IE 6.0. What browser are you using and do you have Adobe Reader 5.0 installed??

[FirstDiesel]

Works fine for me with IE 6.0. What browser are you using and do you have Adobe Reader 5.0 installed??

[2K2AD]

Great post! For those with trouble, it describes the updates that have been spoken about for some time here. It also has instructions for an OD lockout switch. Here are the cut and pasted instructions. Hope this helps!

Kevin

FOR VEHICLES WITH AIRBAG DISABLE SWITCH
Parts needed
- Momentary push button switch (normally open), qty 1 – obtain locally
- LED and 10k resistor wired in series, (if an indicator is desired), qty 1 – obtain locally
- 18 gauge wire (bulk) – obtain locally
- 3 Micro-Pack 100 W Terminals, P/N 12084912

Installation Instructions
Install the switch (and LED / resistor in series if desired) in the small, blank panel to the left of the passenger airbag shutoff switch. Using the bulk wire, route the wires from the switch through the cowl to the TCM, using approved methods. Connect one lead of the switch to TCM connector C1 pin 12 and the other to TCM connector C1 pin 28, using the Micro-Pack 100 W Terminals. If an LED / resistor is used, connect one lead to TCM connector C1 pin 20, using the Micro-Pack 100 W Terminal and the other lead to a 12 volt switched power source.

OPERATION, ALL VEHICLES
Depress the momentary switch once to inhibit 5th gear operation. Depress the momentary switch again to allow 5th gear operation. The system defaults to allow 5th gear operation with a key cycle.

Thanks to GM Technical Assistances

[Heavy Duty Neil]

For those who don't have Acrobat, I'll try to cut & paste the info. It may be a little messy, so I'll edit as necessary.
-------------------------------------------------

Allison LCT1000 M74
Automatic Transmission 5/4/5 Shift ?Busyness?

CONDITION/CONCERN:
Allison LCT1000 (M74) may experience a condition of shift ?busyness? or frequent shifting from 5th to 4th to 5th while towing or under heavy loads.

RECOMMENDATION/INSTRUCTIONS
A new TCM calibration has been released to improve the shift busyness. The TCM calibration is available on TIS 2000 version 3.50 or later released 3/24/02). The calibration also contains a feature which allows 5th gear to be disabled/inhibited if desired. To make this feature operable, the following items must be obtained and steps performed:

FOR VEHICLES WITHOUT AIRBAG DISABLE SWITCH
Parts needed:

~Momentary push button switch (normally open), qty 1 ? obtain locally.
~LED and 10k resistor wired in series,(if an indicator is desired), qty 1 ? obtain locally.
~Accessory switch opening cover, P/N 15734687, qty 2.
~Accessory switch housing, P/N 15040483, qty 1.
~18 gauge wire (bulk) ? obtain locally.
~3 Micro-Pack 100 W Terminals, P/N 12084912.

Installation Instructions:
~Install the switch (and LED / resistor in series if desired) in the accessory switch opening cover.
~Using the bulk wire, route the wires from the switch through the cowl to the TCM, using approved methods.
~Connect one lead of the switch to TCM connector C1 pin 12 and the other to TCM connector C1 pin 28, using the Micro-Pack 100 W Terminals.
~If an LED / resistor is used, connect one lead to TCM connector C1 pin 20, using the Micro-Pack 100 W Terminal and the other lead to a 12-volt switched
power source.
~Install the accessory switch cover and accessory switch housing into the dash.

FOR VEHICLES WITH AIRBAG DISABLE SWITCH
Parts needed:
~Momentary push button switch(normally open), qty 1 ? obtain locally.
~LED and 10k resistor wired in series,(if an indicator is desired), qty 1 ? obtain locally.
~18 gauge wire (bulk) ? obtain locally.
~3 Micro-Pack 100 W Terminals, P/N 12084912.

Installation Instructions:
Install the switch (and LED / resistor in series if desired) in the small, blank panel to the left of the passenger airbag shutoff switch. Using the bulk wire, route the wires from the switch through
the cowl to the TCM, using approved methods.
~Connect one lead of the switch to TCM connector C1 pin 12 and the other to TCM connector C1 pin 28, using the Micro-Pack 100 W Terminals.
~If an LED / resistor is used, connect one lead to TCM connector C1 pin 20, using the Micro-Pack 100 W Terminal and the other lead to a 12 volt switched
power source.

OPERATION, ALL VEHICLES:
~Depress the momentary switch once to inhibit 5th gear operation.
~Depress the momentary switch again to allow 5th gear operation.
~The system defaults to allow 5th gear operation with a key cycle.

? Thanks to GM
Technical Assistances
_________________________________________________

That's it. Hope it helps! smile.gif

[Heavy Duty Neil]

Oops! 2K2AD got a head start on me. It's all good! :D

[NutNbutGMC]

^...Damn, is that Service Stealer gonna' be surprised in the AM, as soon as I get there.... LMAO..

"You want what?....... Read this where?...."

[TXMAX]

Thanks for the cut and paste. This is good to go because I have been wondering about whether my "early" 02 needed the update. I can now go to the dealer and say "Here's what we gonna do!"

Thanks again,

Abe

[sonofagun]

HD Neil,

Thanks for the info. For those who looked drop the c200207.html and you get the GM Techlink site for future reference.

Regards,

Bob

[ryeguy]

Great!

I've been wanting a 5th gear lockout for a while now!

This is the type of thing why I love this site!

--Rob

[zrone]

I went to my dealer today about the overdrive lockout and computer update. He checked and told me it's not in the pipeline yet. They don't know if it will be a campaign or a TSB. He told me to wait awile until they get all the information from GM. I hope this is something they will do for anyone who wants it under warranty or not.

[77TransAm]

zrone, your dealer is behind the times. Several people on the board have already had the updates and installed the OD disable switch.

[TBC]

http://www.gmtcny.com/tech_tips.htm

The above site is a tech training school site. Some may find something they can use on it. Thanks for the tech link.

[RWHP]

I want an OD LOCKIN, not lock out. If I wanted a truck with 4 speeds it would have been a Dodge.

[01_Duramax_Dually]

I am with RWHP..I want 5 to LOCK IN not LOCK it out...
5th gear should hold longer....Period.

The other thing from time to time and I am not sure why is when it jumps right out of 5th into 3rd..Does not happen often but always an eye opener when it does...

Regardless, Still One Happy Camper with My Dmax.. :D :D

[Mic]

Is this article correct?

Do we tap into the 'TCM' mounted up near the intercooler?


Whereas for the high idle we tapped into the PCM down by the battery.....Just don't want to screw it up.


Any one attempt it and succeed? :confused:

[SoMnDMAX]

Mic, you hook into the TCM, located on the backside of the fan shoud.

Follow the directions, and the feature will work. I've had it successfully installed on my truck for a month now, and use it quite a bit.