Chevy & GMC Vans

Aloha, I just installed a 1993 astro 4.3L engine into my 1987 4.3. All is going well except for the wiring to the interior.

1: I used the 1993 computer and left all the wiring intact on the 1993 engine.

2: There is a different set of wiring mostly in the area of the A/C and going into the firewall that is completely different. My 1987 firewall has a 24 pin plug that will accept a large plug fastened by a bolt and the corresponding wires from the 1993 engine with (about 24 wires too) and 4 smaller plugs.

**** Is there a majic adapter to convert the 4 plugs to the 24pin connector. Does anyone have a URL to a site that may have an adapter? thanks Frank

Adas, it would be nice if there were a wiring adapter for what you need, but I don't think it'll ever happen.
About the only thing I can suggest is that you get the factory wiring manuals for both the '87 and the '93 and make the wiring/component necessary.
I haven't done a swap like you are doing, and I'm assuming that you are retaining the '87 700R4 transmission, but one issue could possibly be the vehicle speed sensor (VSS) input to the '93 computer. Your '87 uses a speedometer cable and some type of conversion electronics that originally drove the '87's computer, I don't know if this VSS signal is compatible with the '93 computer. Hopefully it is, but if not you could take the speed sensor and reluctor wheel from the '93 transmission and put them into the '87 transmission. This would satisfy the the '93 computer, but the speedometer in the van would no longer work. I've seen where the aftermarket has ways around this problem, but it's not cheap. Another issue with the original transmission is the need for torque converter lockup. Lockup is accomplished on the earler vans by the ECM providing a ground to the lockup solenoid in the transmission; I'm not sure how the '93 does this. One way around this would be to use the '93's transmission, but there would still be the issue of making the speedometer work.
By the way, my van is an '89 and that's the year that the speedometer went electronic; there's no speedometer cable in my van. So, I don't like that I have to be so hazy about what you have to do to make everything work in your swap, but I'm only familiar with the '89 wiring.

Here is where I am at right now

The engine and trans were junk in the 1987, so I am swapping both engine and trans from the 93.

My plan is to now use the wiring from the 1993 up to the dash board/steering column and so the speedo whould work

The only thing I am not using from the 1993 is the ABS and I am retaining the Vacume assist brakes instead of the power steering pump brakes.
Do you think there will be an issue with the ABS and computer?

How about the cruise control? Any other things to watch for?

thanks Frank

adas wrote:Here is where I am at right now

The engine and trans were junk in the 1987, so I am swapping both engine and trans from the 93.

Great way to go, in my opinion. You'll sidestep any 700R4 torque converter lockup and PCM transmission error code issues this way. (I'm assuming that the '93s had a PCM controlled transmission, unlike my '89 which uses a TV cable from the TBI to the transmission.)

adas wrote:My plan is to now use the wiring from the 1993 up to the dash board/steering column and so the speedo whould work

Isn't the speedo in your '87 driven by a cable from the transmission? It is my understanding that '88 and earlier were cable driven. If so, how are you going to operate the mechanical speedometer?

adas wrote:The only thing I am not using from the 1993 is the ABS and I am retaining the Vacume assist brakes instead of the power steering pump brakes.
Do you think there will be an issue with the ABS and computer?

Your '87 didn't have ABS--I believe that '89s had the first ABS and that system only controlled the rear wheels (typically for no more than 18 months though as the ABS controller card didn't last very long). If the computer in 1993 was used to operate the ABS on the original van, I can see where you will get ABS error codes due to your '87 not having the wheel sensors. I wouldn't consider this a big deal, though. But then again, I don't see the need for ABS on any vehicle.
Keep in mind that I'm not familiar with exactly what the '93's computer controlled. The ECM on my '89 only controlled the engine and transmission lockup. ABS had its own module and the DRAC module conditioned the VSS signal from the transmission for use by the electric speedometer. I had to make wiring changes to operate the transmission lockup when I swapped in the carbureted 305 small block and I never tried to get the cruise control working (it didn't work when I got the van).
Did the '87 have cruise control originally? If so, there's a vacuum switch located on the brake pedal that would be reused. If not, I'm sure there must be a vacuum port on the '93's cruise servo that'll need to be plugged.

Adas, do you have the '93 van? It would be nice if you did as you could see how things were done on it and transfer the necessary parts to your '87; things like the brake pedal vacuum switch for the cruise.
I can't recommend enough that you get the factory wiring manuals for both years; it's usually the first manual I grab when I've got an issue with my '89. Bought new from Helms these manuals are expensive, but I got my used factory manuals from www. factoryautomanuals.com for low bucks. A lot of people get their manuals from ebay, though.

Rob Shaver

Aloha, Yes I have the whole 1993 van. I am now removing the dash and instruments to go into the 87. Probably will even change the steering column. I am hoping the computer will be OK if I do not have the ABS installed. There are so many small issues, but I am determined to not cut and splice any wires...
Frank

Keep us posted, adas, and get some photos. We all like to see what others are doing to their vans.

ummm why didn't you just leave eveything from the 87 when you did the swap , i put a 94 vortec motor in my wifes 88 . the only thing i had to change was the intake manifold cuz the 88 motor wasn't a balance shaft motor where the vortec was . other than that everything bolted right up to the 94 motor .just seems like alot of unnecessary headaches to swap the wiring over to the 87 , when both motors are a 4.3 .