Hey everyone. My friend did a swap from a 4.6 to a 5.4 over the summer in his truck. He installed a 98 5.4L computer and harness and the truck started and ran fine. Problem is the transmission will slip in first and second, once it gets rolling it runs fine. He took it to a tranny shop and was told the computer is trying to communicate with a 4R100 not the 4R70W. Eric at innovative diesel said he should run the 5.4 computer to run the engine and the 4.6 computer to run the tranny. Can anyone else shed some light on this? I have never run two computers in parallel before.

Thanks!

Erik

 

How do you/we know the shop is right?
If they are let them tell you how it's done.
Are there any transmission codes telling this?

I can tell you a lot about this but it won't do you any good.
Good luck.

 

well I'm getting all this info second hand, but here goes. The tranny guy pulled the tranny, said it looked very clean but at my friend's request he rebuilt it anyway. Put it back in with the same problem. Dropped it again and replaced the torque converter. The problem persisted. He rechecked all his work and when he reached the point of pulling his hair out he called my friend and asked what the hell he did. After he told him it made sense, he did some checks and said the 98 F150 w/5.4 came with the 4R100 not the 4R70w so the TCM is trying to communicate with a 4R100. I have an 04 Powerstroke and my SCT tuner programs the engine and then the transmission. I figured I'd shoot my tuner (Eric @ Innovative Diesel Performance) an email asking if he could program a transmission only tune to solve this. He replied talking about using the old and new computers in parallel. The best way I can describe what's going on is it almost sounds like the truck has a 4,000RPM stall converter. I didn't do the build, just trying to help him out.

 

The 98 5.4 came with a E40D in it. Witch is the earlier tranny before they come out with a 4R100 to replace it!
The 98 4.6 has,or had in this case a 4R70 in it.
If the truck has the 5.4 in it now and still has the 4R70 tranny in it. All he needs to do is put the 4.6 computer back in and have it tuned to run the 5.4!
In other-words, he needs a custom tune on the computer to run the 5.4 and the tranny will be fine.
When doing a motor swap, the computer must match the tranny,not the motor.
You can tune the computer to run the motor but can not tune the computer to work the tranny.
That is why when I put the 4R100 in my truck,(that had the 4R70 originally) I had to put a Lightning computer in it to get the tranny to work properly.

 

I'm not sure about your slippage issue but i was doing some research into swapping my own 4.6 to a 5.4 and I found this post: 4.6 to 5.4 Swap Notes - F150online Forums
Its basically the bible on this project and explains how many drivetrain problems can be remedied as well as tuning and wiring. Good luck!!