Since alot of people are asking, and I've tried without success in the past. I decided to work on it a little today and figured it out. My 05 can lock the TC up in FIRST GEAR. I thought you needed a modded VB for that, guess not. It's really simple to do this. All you need is a on-off switch. Ground one side to metal anywhere in the truck. I mounted my mystery switch next to my MP-8 volume ****, just to the right.

Go under the truck and disconnect the ROUND plug. Put a tap however you like into Pin #7 and run the wire to the switch. Now go to the fuse block and find #59 relay. It's next to the fuse marked 50. Put a peice of wire between Pin #'s 30 and 87, not 87A. Your done now. It will even lockup in first. I just did a burnout (no camera ) I started it in first, got some wheelspin, hit the switch, moved to 2nd, then D and smoked them like I never have about a block long. 4wd launches are alot more fun. Just remember to ground pin#7. It's great.

 

Now it's time to see how long that tranny of yours will last.

 

Good job, I will use this info when I start looking into my lock up switch for my 04...

Thanks a bunch!!!!

 

Indeed... I had entirely too much fun with it. It seems to be great for towing, as taking off with 10-12klb behind you seems to suck a bit, but I think get rolling at 5mph in 1st gear, hit the switch, and get it going.

 

It will still lock up like normal if you don't have the switch on, right???

the switch just gives you lock up anytime you want it...

 

Now go to the fuse block and find #59 relay. It's next to the fuse marked 50. Put a peice of wire between Pin #'s 30 and 87, not 87A.


hope this works,the 7 pin ground only gave me a limp mode,how did you figure this out and exaclty how do you run the wire ,do you just mean jumper style

 

Yup. I did the same thing of grounding pin7, limp mode 3rd gear no lockup. You run a wire between the prongs of the relay from 30 to 87. I used a small peice of 16 gauge wire, with some insulation in the middle to not short out any other pins. I just wrapped the ends around the prongs and plugged it back into the socket. Works like a charm.

It locks up normally if the switch is off, but if you turn it on it stays locked. It will even kill the engine.

 

Thanks for the info John !
Does the tranny shift from 1st to 2nd and so forth with the TC locked, or does the ECM unlock it between shifts ?

 

It can't unlock it. You've MANUALLY locked the TC. It stays locked between shifts and it feels _REAL_ good. My tranny has some issues with a pressure transducer, and has since I first bought it. It will literally go into OD at 30mph. Sure is fun hitting the switch though.

 

good job, excellent post!

 

So If your sitting still idleing and flip the switch...will it lock up and stall the truck?

 

Anyone know if this will work on all of the 48re or is it just a mod for the 04.5 and up?

 

Yes, it will stall the truck if it's in D, 2, or 1. Doesn't work in reverse (heh!).

It works on all 48re's after doing some research.

 

If you are in overdrive with the tc manually locked will the truck downshift to 3rd. I tried this method on a friend of mine's truck without the relay jumper and it would not downshift out of OD if it was manually locked.

 

Not sure what method that Michael used to hook up mine, but mine will down shift from OD to 3rd even when locked up.