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    Driving '91 GM electronic speedometer from a US Shift Controller

    Tayto, you were exactly right. Jumping the OSS wires that came with the US Shift controller kit over to the old OSS wires that I had hanging zipped tied out of the way near the transmission allowed the speedo to work again. That, and the fact that error codes the US Shift controller were...
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    Driving '91 GM electronic speedometer from a US Shift Controller

    Hi Tayto, At this point I'm sure you're right, and I'll test that theory on the weekend. I needed to follow this guys advice first, it's their product. As it happens the US Shift controller magically, after a week of sitting, managed to clear it's error code and shift normally. It didn't...
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    Driving '91 GM electronic speedometer from a US Shift Controller

    Hi Tayto. Given I'm somewhat beholden to at least try what their tech suggested (that is if I intend to keep them linked into supporting their product, which I do) I went ahead and tried the latest wiring connection he suggested. It didn't work, no speedo output. I believe your suggestion above...
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    Driving '91 GM electronic speedometer from a US Shift Controller

    I maybe figured this out, and maybe Tayto you're right, possibly even the tech at US Shift is right. I thought all along when you guys were talking about jumpering wires you were talking about those that terminate in either of the two connectors that make up the PCM connector set, but now I'm...
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    Driving '91 GM electronic speedometer from a US Shift Controller

    Last night I got a chance to work on it again. To follow what the tech at US Shift recommended I spliced into the two wires in their loom that go from the transmission speed sensor to the port on the Quick 2 into the two they said I needed to splice into, which were wires B5 & B6 at the PCM...
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    Driving '91 GM electronic speedometer from a US Shift Controller

    I had a chance to get things apart tonight and have a look, and in the meantime the tech from US shift got back with me. Both of you are saying essentially the same thing, except he identified the 4WD wire pair as the one to jumper onto and you're identifying the 2wd pair, which oddly enough...
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    Driving '91 GM electronic speedometer from a US Shift Controller

    My Drac is integrated into the cluster for sure. I didn't cut out any of the original wiring, I just unplugged it from the transmission and zipped tied it out of the way, then used the US Shift wiring harness from the transmission up to it's mounting spot which in my case is in the glove box...
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    Driving '91 GM electronic speedometer from a US Shift Controller

    Thanks Tayto. To be specific, which wire on the printout you attached am I to connect the Quick 2 speedo output wire to? I'm not real clear which one goes to the drac. Thanks!
  9. G

    Driving '91 GM electronic speedometer from a US Shift Controller

    Hi, I recently installed a US Shift transmission controller on my 1991 GMC C3500 with 4L80E. It works great, and solved a problem 3 shops couldn't diagnose or fix. In any case, I still cannot get my stock electronic speedometer to drive. The Quick 2 controller has a speedo output wire to connect...
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    Problem with '91 4L80E

    PCM or wiring, yes, definitely.
  11. G

    Problem with '91 4L80E

    I got the Quick 2. It had all the features I needed and If I want I can still tune the shifts. It wasn't hard to install but took most of a day to get the wiring harness routed. I wound up routing it from the transmission following the same route off the main harness then popped a new hole...
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    Problem with '91 4L80E

    Hi folks, Update: The US shift stand alone controller solved all the shifting problems. I still have a couple other issues to overcome however. The US Shift talks about connecting their device to a speed sensor coming off "an" electronic speedo. Since hooking it up I have no speedo output from...
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    Problem with '91 4L80E

    Thanks Tayto, and I appreciate your sentiments, but given everything it's not a terrible idea to replace 30 year old parts with new if they're even remotely suspect. The cost is minor, especially when weighed against what the 3 shops I took it to charged me to come up with nothing. I think it's...
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    Problem with '91 4L80E

    Update: I replaced the TPS, but it made no difference. Also, it appears I may be getting both 2nd & 3rd, not just 3rd. Question to all of you: Does anyone know of a company that makes a replacement wiring harness? I called Painless wiring and they don't. I could probably create a (non color...
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    Problem with '91 4L80E

    I'm liking the pinched broken wire scenario. My '91 is in fact the same as your '88. I'm also going to resume my search for used cluster to swap in to see if it makes a difference. All excellent help, Thanks!
  16. G

    Problem with '91 4L80E

    The first bit of diagnostics are a bit above my skill level, but the TPS isn't. Thanks!
  17. G

    Problem with '91 4L80E

    I will give that a try, thank you!
  18. G

    Problem with '91 4L80E

    Hi Folks, I have a '91 C3500 GMC Sierra with a 4L80E with 70K original miles on the truck. Bought surplus from a nearby municipality at 56K. About 6 months ago I began experiencing a loss of 4th gear. I took it to 2 different reputable transmission shops. Since it was intermittent and...

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