I have a quick question that I had researched the answer to a while back....but forgot where I put the paper where I wrote down the info.

I have an '86 that came with the 2.8 auto. I just swapped in a 4 speed standard that came from an '85 2.8. I took the PROM out of the '85 ECM and put it in place of the auto PROM in my '86 ECM. Is there a problem doing this? The ECMs have different numbers, are the PROMs compatible or should I put the entire '85 ECM in?

Seems to me all the research I did pointed to just swapping the PROMs. The car seems to run fine.

Anybody know for sure?

thanks!

The 85 ecm prom mask is a lot different then the 86 and later proms. I'm not sure but I don't think it will work very well if at all.

You can't use an 85 prom in and 86-88 nor vice-versa. GM changed the location of the calibrations in the prom in 86 (I won't go into why.) You can swap in an 85 ECM but you can't mix proms across those years. You can use any 86-88 prom in any 86-88 car.

The 85 used a 1226869 and the 86-88 used a 1227170.

You need an 86-88 prom from a 1227170 ECM for your 86 car.

TK

[This message has been edited by TK (edited 05-02-2013).]

Hey thanks for the replies.
I pulled the console out this evening and had a look at what I am running. It is an '86 4 speed PROM in my '86 ECM. I have '85 and '86 parts cars and for some reason thought it was the '85 I pulled the PROM from.
I guess that explains why it's running fine.

thanks guys!