87-91 tbi suburban wiring diagrams

[60ratrod]

Does anyone have good wiring and complete wiring diagrams for the 87-91 suburban/blazer? I did an ls swap on my 91 and think i lost my speedo signal in the process. Biggest indicator is the fact cut the twisted purple/green from the original harness and spliced it into the ls stand-alone harness, so i don't know if the factory gauge panel needs any other inputs or tagged into the stand-alone harness for the ecu to tell it what's going on

[SuburbanStevie]

Do these help? Although I don’t see a Purple/Green wire.
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[James Lamb]

Does yours have a cable driven speedometer? My '89 Suburban was, although it was a diesel so maybe it was different. I had to buy an adapter that screws onto the transfer case, gives speed signal to the 4l60e I just put in, and also allows a mechanical connection for the speedometer cable.

[SuburbanStevie]

Yikes…. A challenging question. I don’t know for sure. I remember when I had a GearVendor OD installed they had to hook connection up to new location. I can check tomorrow if needed?
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[James Lamb]

I literally just did this a week ago on my '89 Suburban. I got tired of 700R4 transmissions pooping out if I glanced at them while frowning, and had an electronically controlled and beefed up 4l60e put in. But because mine has a mechanical speedometer cable, and on a 4 wheel drive the speedo signal comes off the back of the transfer case, I needed something to send the signal to the new transmission. The good news is it was like $50, AND I can adjust it so that me speedometer finally reads correctly due to the oversize tires I run.

For a two-wheel drive I think the speed signal comes off the tail piece of the transmission. I will look tonight because I can't remember the vendor. But I called them, told them what I was doing, and they told me exactly which part # I needed. Hopefully it's that simple.

Also, my 700r4 had no electrics, so I had to buy an aftermarket controller for the new transmission.

[60ratrod]

Thanks Steve, that looks like i a good place to start looking. Now i just gotta figure out where the digital ratio adapter is and go from there. And so far my 700r4 has been solid now that i got it adjusted.

[James Lamb]

I wish you the absolute best luck with the 700R4. I know a lot of people have good experiences with them. I have not. The one in my truck was rebuilt maybe 5 times since I've owned it. I finally gave up and had a 4l60e put in, which is the exact same transmission, same gearing, same dimensions, but electronically controlled. That removes the sensitivity of the Mal-adjusted tv cable. Plus it locks up in 3rd and 4th. And you can program in shift point and firmness of shifts. So if you ever need to go that way I'm pretty happy with mine.

[60ratrod]

So this is gonna take a back burner for a bit. I got hit last night by an uninsured red light runner so now i gotta price and hunt down parts

[60ratrod]

Ok, so i took some time a month ago to swap the stereo since i hate pioneers, and figured that i'd look into getting the speedo working. All it took was taking the signal wire from the truck ecu and splicing it into the cluster harness right where the cluster harness goes into the rest and it works as good as it did before the swap. Now to tackle the oil pressure, coolant temp, and fuel gauges.