[Diy_efi] Best donor vehicle for GM TBI system???

[Dustin Lof]

Mike, first if it has a 1227747 ecm it would be a good
donor anything else and it is just more work for
yourself.  Second the vss buffer piggybacked to the
ecm is there to convert the A.C. voltage produced by
the speed sensor on the back of the transmission into
a 5v D.C. square wave that the ecm can use.  It also
provides calibration for your tire size and gear
ratio.  Your 83 van should use a cable driven spedo
with an optical vss sensor mounted to the back of the
speedometer. I have seen vehiciles without the sensor
but the hole is there to mount one.  There is a buffer
attatched to that sensor.  It is there so the cruise
can opperate in your van.  All the calibration is done
by changing the speedometer gears in the transmission.
 During your retrofit you will need to splice a wire
from that vss buffer (usually yellow) to the vss wire
in your donor harness.

--- Mike <sonoma at shaw.ca> wrote:

> Hi
> 
> I was at my local auto wrecker looking for a donor
> vehicle I found a 91 2500 GMC Van, I want to
> transfer this TBI system to my 83 3500 GMC Van.
> 
> The question I have is a earlier TBI system better
> than a more recent system the ECM had a speed
> control module on the side of the ECM (think it is
> module which tells the ECM what tire size and gear
> ratio is in the vehicle) I changed this module when
> I changed the gear ratio in my 91 S10.
>  
> Can the speed module be eliminated along with the
> VSS?  Do all GM trucks (87-94TBI) use this module
> which I've seen attached to the ECM?
> 
> Will a 1227747 ECM work with all TBI wiring
> harnesses from 87 Up?
>  
> Thanks 
>                 Mike...>
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