83 to 91 engine and trans compatibility

[dmmotes]

I just swapped the good engine and trans from my rusty ugly 83 sub into my beautiful 91 sub with a fried engine and tranny. The wiring on the 83 700r4 is different than the plug on the 91 sub that had a 700r4 can anybody tell me if I can do some rearranging to make the wiring happy???? Also how can I get rid of some of the wiring, hoses, and ecm to make this thing easier to work on. Thanks Don

[john8662]

EEK!

I don't think that you're going to be able to get the '91 wiring to work with the 83 tranny, the 83 will only have the one wire for TCC lockup. The 91 tranny had more wires going into it and more active wires inside the valve body on the transmission. The TPS on the injection pump on the 91 was also different than the one that the 83 had.

So you blew the engine and the tranny?

You can get the 83 tranny lockup to work in the 91, but probably by using your own manual lockup switch in the cab.

My advice, use the 83 engine and use the 91 model transmission behind the engine (the 91 case is a better tranny anyways). Just swap EVERYTHING from the 91 model engine onto the 83 block and heads. Use all the accessory brackets off the 91 model and all the wiring harness for the 91 vehicle, you'll be ALOT happier with it in the long run.

[20050420|7|006071|000022|69.19.2.78]

When you are swapping al the accessory`s on the `83 block don forget the waterpump from the `91, i think the `91 one waterpump turns the other way around because of the serpetine belt. :rolleyes:

[john8662]

Just a note to add on the waterpump hint. Since the 91 engine came out of a suburban then it's got V-belts. If it's got v-belts, then the waterpump and accessories are just like the 83 in rotation.

The trucks with the New body style (88+) use the serpentine setup. But the Suburbans and Blazers from 88-91 still had the body style of the 81-87 model trucks did, except for an updated headlight and grill assembly.

[dmmotes]

Thanks guys. What do I need to do to wire the converter to lock up via manual switch??. Also if I want to convert from v-drive to serpentine can I just find a 88 or newer 6.2 truck to use as a donor for my sub???? I would like to have just one belt. Thanks

[john8662]

Don't know on the lockup of the tranny specifically, so others on here will probably chime in on wiring it up. But I'd assume that all you need to do is make a switch that will supply power to the one lonely wire going to the transmission. You'll need the connector off your 83 model harness to make this happen. The harness on the 83 is seperate from the complete engine harness for the tranny.

To go serpentine you'll have to find a donor vehicle. But anything from an 88-92 model 6.2 would work, or use the accessories off a 92-95 model 6.5TD, those brackets and accessories will work. But then you'll have to swap out the waterpump as previously mentioned to do this swap. My opinion, way too much trouble for just the one belt!

Is there still any way to use your tranny from the 91?