If I change out my rear gears would I have to change the PROM for a 89 TPI ECM? The car is close to factory setup but has wimpy highway gears looking to change them to 3.42s or somthing close to that.

 

Im no expert at cars but I would say no, simply because there aren't any electrical hookups or sensors going to the rearend. But I could be wrong.

 

Im buying a new PROM for my ECM the ECm I have is for a 305 TPI so I need ot buy one for a 350 TPI but theres only like 4 options auto and manual trans and then the 2 different gear sets the cars came with for '89 camaros. I wouldn't think it makes a difference just want to give myself the best shot at getting this swap done right the first time.

 

You need to change the speedo gears in the trans. Takes some effort, but can be done for under $35

http://sethirdgen.org/vss.htm

http://sethirdgen.org/t5speedo.htm

-jason

 

All the memcals (any different ratio) will read the same. It was for different spark timing not the rear gears. I have tested 2.56, 2.73, 3.07, and 3.27.

 

thanks guys for the quick response. is there a specific prom i should be looking for, its a 350 TPI 88 ecm but im eliminating the cold start injector so i was going to buy the prom for a 89 ecm. is there specific differences for options like air conditioning?