96 C3500 RCLB aka Stumpy

Thanks to a suggestion from @bluex Stumpy officially has a working 4L80E. Went through the details in my NV4500 to 4L80E thread, so won't detail that again, but while I had the dash laid down, I swapped out the skinny brake pedal, for the wide brake pedal. What a pain in the ass that was, but it's done.



So happy to finally have that wrapped up, and used all factory wiring from the parts truck, including it's computer. The tune, and firm shift from Black Bear, is pretty cool too.

Got an interesting issue, since the trans swap. I hadn't been listening to the radio, because I was too busy listening to the truck. So I was ready for some tunes, and realized, I have no sound, and when I put the trans into gear, the radio loses power, and turns off.

Apparently in all the rewiring something got screwed up. Instead of trying to figure it out, I'll probably just run new wires, it has an aftermarket radio anyway.

Stumpy said:

Got an interesting issue, since the trans swap. I hadn't been listening to the radio, because I was too busy listening to the truck. So I was ready for some tunes, and realized, I have no sound, and when I put the trans into gear, the radio loses power, and turns off.

Apparently in all the rewiring something got screwed up. Instead of trying to figure it out, I'll probably just run new wires, it has an aftermarket radio anyway.

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Out of curiousity, I'd be interested if you are losing the +12V power to the radio, or is the +12V power there but you are losing the ground?
From your observations this is new behavior since the tranny swap, correct?

Interesting problem. No doubt that fresh power & ground wiring will solve the issue 100%, but if you have a multimeter handy
it would be interesting to figure out what side the loss of necessary current flow occurs when you put the truck into gear...

Road Trip said:

Out of curiousity, I'd be interested if you are losing the +12V power to the radio, or is the +12V power there but you are losing the ground?
From your observations this is new behavior since the tranny swap, correct?

Interesting problem. No doubt that fresh power & ground wiring will solve the issue 100%, but if you have a multimeter handy
it would be interesting to figure out what side the loss of necessary current flow occurs when you put the truck into gear...

Click to expand...

Yeah, would probably be a good idea to see what is turning off. I don't do a lot when the weather is cold, so might be a while before I really dig into it.

I was mulling over your problem description, and came up with a simple electrical cross-check
that you could perform on your truck to give a little further insight. In the '96 C/K Service Manual
(book 2, p.2143) Fuse 17 is identified as the one that is supposed to feed your radio.

IF you pulled Fuse 17 and the radio no longer worked, then we would know that the power
source is as designed. (ie: Powered during ACC and ON positions from the ignition switch feed
through Fuse 17.) If so, then we would turn our attention to the ground circuit side as documented
on the lower RH corner of the diagram. (ie: full, constant power on the +12V feed, and 'disappearing'
ground when auto is shifted into gear scenario.)

On the other hand, if you pull Fuse 17 and the radio continues to play, then it's time to pull fuses
one at a time until the radio quits playing and sort that out?

To recap, I fully understand not wanting to do a full electrical wiring harness troubleshooting session in
the cold, but the above is just pulling a single fuse and getting a go/no-go result. I also understand that
this isn't a high priority/safety of flight type of issue, but if a wiring harness deviates from factory behavior but we can
explain why, then we have a good handle on where you are & deferring repair until the weather warms up.

Looking forward to what you find & your eventual solution.

Cheers --

I think the radio has quit on me. Got it to maintain power, but there's still no sound. Been wanting to upgrade anyway, so I'll work that in eventually.

On another note, my son got me some lights/reflectors for the doors...



Unfortunately, they take a plug, that my truck doesn't have, so got to figure out what plug they need. My plug is a light socket. Did the older trucks have a plug?

Also got the new key fobs programmed. Another nice luxury to have.

Get ahold of your local GM Parts Guy, ask him nicley to print out a build sheet from your VIN I do it all the time. ex below

I’m looking to sell my pioneer, I plan on running an iPad if you are interested. It’s a nice stereo just bored with my truck 700shipped

QLONA said:

I’m looking to sell my pioneer, I plan on running an iPad if you are interested. It’s a nice stereo just bored with my truck 700shipped

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I appreciate it, but I won't be putting a bunch of money in the radio for this truck.

This may come as a surprise, but I'm thinking about selling Stumpy. I may have an opportunity to buy a '50 Chevy truck, which I've wanted for a very long time. I passed on one probably 20 years ago, and have regretted it ever since.