Engine/Transmission (1994 - 1998) Mystery Switch Instructions for 47RH trans.

[ndurbin]

First let me say I am no expert at this, but this is information and instructions I have seen posted throughout the forums.



There are 2 (two) options you have between switches; a simple on/off toggle switch or a 3 (three) position toggle switch.



First off you will need to find PIN 54 and the wire attached to it (orange w/ black tracer). This pin/wire is located in the PCM connector located behind the air filter box on the passenger side of the firewall. Now heres were the 2 (two) options come in for the switch.



First is to use a simple on/off toggle switch and ground the wire w/o cutting it. This allows you to either manually lock the TCC or to let the PCM handle it.



Your second option for the switch is to use a single pole 3 (three) position toggle switch. To use this switch you cut the wire attached to PIN 54 of the PCM, attach the trans. end to the center pole, attach a ground wire to one of the outside poles, and attach the PCM end of the wire to the other outside pole. It is suggested to use different colored wires when you cut the wire going to PIN 54, so that when extending them into the cab you won't get them confused.



Nathan

 

[SSage]

I've been searching for info on the mystery switch mod and found this old post.



The TST instructions don't have the three position switch option, well I didn't see it for the 47RH. I want to delay TC lock up while pulling large loads under 55 mph or getting up to speed. I don't care much about locked shifting. I just hate locking up the TC while heading up an on ramp and lugging the engine down. I would like to stay out of lock up between 30 and 55 mph in 3rd gear when I want to keep rpms up while getting my big trailer up to speed.



The above post seems to be the best directions I've read. Any more imput out there?

 

[KOG]

I've got two of these switched by grounding the lead straight from the transmission plug, using a dimmer switch on the floor. Mounted a green LED on the dash to indicate when in unlock so I know when it's safe to shift. Work just fine. Also have manual control of OD, and have installed shift kits with modified valve body to allow second gear lockup. All of this has been helpful when towing around 26000lbs GCW, keeps transmission temperature under control.