40 years in the transmission business and I still cannot understand why anyone would want to do this. There are SOOO many differences Sell your truck as is and buy what you want in it,, save a LOT of time and money.

 

Hey Dan I'm doing this swap. Was it pin 20 on the block connector that goes to the transmission harness or is it pin 20 on pcm harness?

I found that pin 20 on the block connector to the transmission is the missing pin, It leads to pin 7 on the pcm harness. Is that the only pin needed?

The only way I see this being feasible is using the complete dash harness, the complete engine bay harness, pcm, gem, bcm, instrument cluster and key for anyone using this as a guide for 99-03. I'm coming across issues with using only the engine harness and pcm from the same truck the 4r100 came from to my truck. different things coming on that are pinned differently than the body harness. If you're really attempting this and want this transmission to work you need everything from a donor truck. Or buy another truck. I'm only doing this swap because I've put a 4 door 2002 cab on a different 1998 frame and didn't know the wiring needed or differences in transmission before hand. Yay me.

 

It's been so long and I've lost my wiring harness book so I don't remember exactly which pins was which. I knew I had to add 1 maybe 2 wires to the transmission harness. Of course I got a used pcm compatible with a 4r100. The main harness supports the swap but the transmission harness needed modification. Frankly every mechanic online said "YOU'RE A MORON, DON'T DO IT! IT WON'T WORK! YOU'LL GO BROKE! YOU'LL GO INSANE THINKING ABOUT EVERY LITTLE DETAIL!" My truck runs and shifts and still has a few problems, and if I had it to do again, I probably would have done things a little differently.

 

I see 2 different wires in the 4r70w harness versus the 4r100
do you know if you had to delete pats or no?

 

No, pats is in the instrument cluster in 99. I didn't actually delete anything.

 

I have a f150 99 5.4l 4r100 trans and i want to put the engine,trans, and driveshaft on a 4.6l v8 2003 and i want to know how it can make the transmission work on the 03 truck. Do i need to swap harness or is it plug and play

 

I have a f150 99 5.4l 4r100 trans and i want to put the engine,trans, and driveshaft on a 4.6l v8 2003 and i want to know how it can make the transmission work on the 03 truck. Do i need to swap harness or is it plug and play

 

Swap it, it will be easier to do that. I had to add 2 wires to the transmission harness to make it work. The connectors are different too.

 

Thank you for answering I've been looking at so much info online and getting mixed opinions. What exactly should I swap out? Only the transmission wiring harness or the engine wiring harness with the transmission harness. Would i have to swap out the cab harness aswell?