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New Burban Owner! Wiring Quirks?

77burbangirl

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First of all, this seems to be a great informational site with great members. Keep up the good work!

I just picked up an almost mint 1977 GMC Suburban K25 a couple of weeks ago in an auction for the mere price of $625. It runs perfectly; has a 305 V8 (didn't think Burbans were available with a 305) and a 3spd manual (although not sure on that, goes from L-1-2-3, technically a 4spd?). Exterior is in great condition, newer paint, custom full-length roofrack and unique custom rear bumper. Interior is in good condition also, a few cracks in the front vinyl bench and a missing window handle. It runs on a set of Wildcat EXT mud terrains which roughly size out to 32" tall, 9.5" wide (245/85R16). It's unknown whether it has 180k or 80k (280k for that matter), but it drives like new. Steering is still pretty tight and it was very quiet when I first bought it (after inspection, pipe came disconnected during a wheeling adventure and now sounds much meaner). The truck is awesome, and this is coming from a Ford addict. /forums/images/graemlins/peace.gif

It does have some quirks, one of which has gotten me pulled over three times in the past week. When using my right turn signal, my right reverse light blinks instead of my taillight. What is causing this? My left blinker works just fine.

My speedometer stopped working a couple of days ago. All of the other gauges work fine. Wasn't doing anything too rough between the time it did work and the time I noticed it not working. I did tackle and park on a rutted soft dirt hill, but I wasn't going fast enough to knock anything out of place. Any suggestions on what to look for as far as the cause?
 

mountainexplorer

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Welcome. /forums/images/graemlins/smile.gif

Would seem almost like a crossed wire or something for the turn signal problem. Sometimes past owners can mess stuff up in the process of wiring up things like trailer lights.

As far as speedometers go... none of mine work. /forums/images/graemlins/doah.gif Problems range from either stripped out plastic speedo gears in the tranny or T-case, or in my case, a melted cable laying on exhaust.
 

Grim-Reaper

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Welcome to CK5
Turn on the parking lights. if the revers light comes on then as well then the sockets managed to get swapped. They are the same saze and it would be easy to do. 8 Screws to take it apart.

Speedo...could be several things. It may not have been fully locked into the back of the gage. You can usualy worm your arm up in there and feel it.
GM uses a little box that calabrate the speedo to the gears and tires. They screw into the side of the transfer case usualy on the driver side. Those boxes are nototious for failing. Problem is they will some times lock up and snap the shaft off in the drive in the transmission/Transfercase. Sometimes this will strip the drive.

So where are the pictures of the Burb? /forums/images/graemlins/thinking.gif
 

bigburban383

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Take out you rear lenses and inspect the grounds because they may rusted. I had problems with crazy rear lights and turn signals like that, it turned out the grounds were blew out so I fixed them, which fixed the problem.

Good luck, electrical anomalys suck /forums/images/graemlins/waytogo.gif
 

pvfjr

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Sounds like you have an SM465 tranny. It is a four speed, but first is almost a 7:1, so most people just start off in second, which is why its labeled like that.

I have seen numerous trucks where the "speedometer adapter key" has a square shaft that had become round. It is a little pin that couples the speedometer adapter to the transfer case. You can also use a drill to try and isolate the problem. Pull the cable off of the speedometer adapter and clamp the end of it into the chuck of a drill (don't tighten too much). Turn on your ignintion and give it a little crank to see if it responds.
 

77burbangirl

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Thanks for your help so far guys!

Unfortunately, my wiring woes have gotten worse. Got pulled over last night because my taillights weren't even working. Today I thought I discovered why. Underneath, there are these two plugs that somehow got disconnected from their sockets. I inspected the sockets and plugs, made sure they were clean, and stuck 'em back in to see if that was my problem. My parking lights work (right side reverse light comes on when parking lights are on). When in reverse, only my left side reverse light comes on. Neither of my turn signals work (the front ones work fine). Brake lights aren't working, either.

I checked all the bulbs and they are all in working condition. Light bulb sockets were in the right place (which left me baffled as to why my reverse light was blinking before). I took off my right side taillight assembly to check my ground wire and it seems to be in working condition also, with no visible rust.

Upon inspection of the plugs underneath, my right side plug is missing a prong that could be my problem for the turn signal. However, the other plug is in good condition with no missing prongs, which leaves me confused as to why my left turn signal doesn't work now.

Any other suggestions?

Oh, and as for pics, I do have one terrible pic of it that was given to me, but it doesn't do the truck justice. After I clean it up again, I'll take some good pics of it.
 

Muddytazz

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As for the wiring, are you or do you know of anyone good at reading or understanding wiring diagrams? I have a 75 burb and my dad has a 77 burb, so I have wiring diagrams that covers burbs from 73 - 91. If your interested, email me at muddytazz@canby.com and I'll email them to you /forums/images/graemlins/thumb.gif
 

Grim-Reaper

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Was this pug up by the frame rail on the driverside? Is there a T peice there with the wires for a trailer there? I had a bunch of issues with the adaptor for the trailer harness. The T can be removed and the wires plugh into each other. Check that.

Do us a favor and fill out your Bio. There might be sombody good with electrical that might be willing to take a quick look. Hopefully your close to Skigirl....she's the resident wiring wiz. /forums/images/graemlins/laugh.gif

Ohhhh Are the gages doing anything funny when the turn signals are on?

There is a ground strap on the back of the passengerside head to the firewall. It is often left disconnected when the engine has been pulled. It will cause all sorts of crazy issues. No brake lights, bouncing gages when signals are active are the most common.
 

77burbangirl

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Muddytaz, I may take you up on your offer. It depends on just how serious my wiring situation becomes.

Grim-Reaper, nope, this plug is on the on the passenger side. Someone told me it was supposed to be only three prongs on that side, so I believe that this isn't my problem.

Gages aren't doing anything funny (other than my speedo not working, which I haven't taken a closer look at yet) when my turn signals are on.

I'll go ahead and check the ground strap as you mentioned and see if that is my problem. I'll also fill out my bio, too. /forums/images/graemlins/smile.gif

One question I do have is whether or not the wires came all wrapped up in the frame from the factory? Seems that it would short something out that way. Are there other ground wires I should take a look at other than the ones behind my taillight assembly? So far, it just looks like something shorted out somewhere.
 
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