I am sick of the way my 99 shifts, and I want it to shift like an 01 where it locks in 3rd and then stays locked thru 4th instead of only locking up in 4th unless i hit the lockout switch, can I install a PCM/TCM from an 01 into my 99, or reflash my 99 PCM with 01 software? I have access to a DRBIII and the necessary tools to do the swap or reflash. Please, and help? Thanks

 

You're on your own. BTW a 2000 also shifts as the 2001 does FUI. How about upgrading the valve body to a HD unit and give tranny a big performance upgrade?
If you presist on desire, check pinout of the two computers. If they are exactlly the same and you don't have overhead console and duuuhhh. It just got overwhelming again. Different protocols. Maybe a 2000.

 

Ive got a good HTS valve body and a suncoast overhaul with a goerend converter, but I dont like the way the pre-00 trans shifts compared to the 00 and up and thats what i am wondering, i do have an overhead console.

 

Well i swapped my pcm with brother in laws 01 for the heck of it, and what do you know?? it didnt work...

It would shift 1-2 and 2-3 WAY to early and would not shift into OD, i checked the pinouts and they are exactly the same between years, there HAS to be a way, now im determined, probably have to change some sensors or something, anyone have any ideas?

 

Did the spedo work normaly with the newer PCM?
The speed signal goes through the anti-lock module. Could be different.
Try the tranny relay bypass trick. The way it gets activated changed some over the years. My 99 works off of an alternator happy signal so the transmission is powered up only when engine running.

 

Hmmm, my truck does not have front wheel abs, does it run through the pcm then for rwal? my brothers does have an abs module, the pcm made my abs light come on

the speedo worked correctly

for the relay bypass trick, u mean the one for the mystery switch?

 

The speed comes from the abs sensor in the rear diff. those wires go to the abs module then out of the abs to the pcm.

Yes, the relay bypass is like described in the mystery switch.
If it doesn't turn on its will act like limp mode.

You will probably need wiring diagrams for both trucks to figure it all out.
A lot can change in two years difference.