Swapping 700R4 to SM465 Question

[sarasotausmc]

I've been searching for days and haven't really found the answer to what I am looking for. This one comes close, but not close enough;

http://coloradok5.com/forums/showthread.php?t=104090&highlight=700r4+sm465+swap+ecm


Swapping the tranny in an 87 Jimmy, 350 TBI stock motor and ECM. Is there anything I need to do either with my ECM or Park/Neutral Switch? How will this swap affect either of those?

Got all the other bells, whistles and little things covered.

 

[sweetk30]

my computer has auto chip no real problems yet.

down on bottom of colum is the 2 half switch for nural and reverse.

reverse is on tranny top cover. and nutral is a safty switch on pedel assembly.

 

[dyeager535]

You can probably run it. ECM does look for the speed signal for certain things though, grounding the P/N switch, which is unfortunately quite common, is the wrong way to do it however.

One of the things I notice with the stock GM EFI and manual trans, GM built in a "shift delay" into the engine RPM. When shifting, the setup doesn't just drop RPM's. You've got a bit of a delay, which I can imagine would be very handy when doing something technical (or mud) before the RPM's start to drop significantly.

I can't comment on how the manual trans performs with the auto trans PROM in that regard, although I could try it with a bit of work. But since the manual trans PROM works right with the manual trans, I'm not going to waste my time on it.

Even if you did want to get under there and jury-rig the P/N switch, from what I saw in that linked post, you could get the "right" PROM for $25, which if stock, is not only the better option, it's probably just about the same difficulty.

 

[B_to_C]

I have played the "ground the P/N switch and cross your fingers" game. It didn't work for me. The truck RAN, it just didn't run as well as I knew it could. As soon as I popped in the stock PROM for a manual transmission truck ($50 from TBIchips.com) it ran a lot better.

Good luck!

 

[sarasotausmc]

Thanks for the answers Dorian and Nick. Those answers are exactly what I was looking for. Guess I'll try my hand at a tech article when it comes time to cover the TBI rigs.

George

 

[sarasotausmc]

So reading this and more, I've come up with:

Mechanical swap is straight forward. Go buy the manual prom (chip) for the tranny I am installing and remove the column park lock to allow the truck to start. The manual ECM PROM will carry those issues and with the proper ECM (manual) chip, that will take care of all engine performance issues I can think of.

Please correct me if I am wrong.

 

[CB77GMC]

Sounds like the way to go.

 

[sarasotausmc]

CB, this is the one we couldn't figure out. I guess I am ordering a chip for the ECM and running right.

 

[cabledawg]

To tell you the honest truth, I never changed anything on my ECM and aside from the "check engine" light periodically coming on, I've have gone almost a year with no issues after the swap.

 

[TruckNutzDude]

To tell you the honest truth, I never changed anything on my ECM and aside from the "check engine" light periodically coming on, I've have gone almost a year with no issues after the swap.

The check engine light is not supposed to come on.

I got a superchip from another member here for my manual trans swap and my rig ran great afterwards. No more high idle, no more check engine light and a little more power from the timing changes the chip was programmed for. If you're going to do something, do it right.