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Early 93 4L80E harness plug to late 93 harness plug
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Post Early 93 4L80E harness plug to late 93 harness plug 
I have a 1993 2500 Suburban with a 5.7L and a 4L80E trans that went bad. I got a deal on a 1993 3500 4L80EHD trans and now my delemma is the harness plug. My old trans and my burb have the old style plug (which I read changed in May of 1993, mine is a Feb 93.) and the new trans has the larger round plug with the torx bolt holding it on. Is there a way to make this all fit?

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The old trans connector was phased out because it was a bad design. It was far too easy to bend the case terminals.
There is a part number for a retrofit, but unfortunately it includes both the external part for updating your truck's harness AND the internal complete harness. It's expensive, almost $300.
GM Part number 24200161

Here's a $30 solution:
http://www.transmissioncenter.net/4l80e.htm
Scroll down to part #2PT.
Splice in that connector and you're set.

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I have a couple of those pigtail kits collecting dust in my garage. If you're interested, shoot me a pm and I'll get one out to you for cheaper than transmissioncenter will.


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Thnks guys, I am learning more about these transmissions than I ever wanted to. It appears from both of your replies that I have it all backwards. My Suburban has the new style plug and the transmission I acquired has the old one. My burb was made in February but has the new harness... Interesting, when the change wasmadein May... Anyway, I see the solution to my problem all over the place with an new internal harness. Thanks for helpingme out, I am new to this forum but you have made a new fan.

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Well guys, I finally got the trans upgraded and installed in my Burb to find that I have no 4th gear. I installed a Transgo shift kit with an upgrade to the pump pressure. I haven't been able to get to pulling the codes as of yet but I am wondering if there is something I did wrong with the shift kit to kill only 4th gear? The transmission works great other than never shifting into 4th. I am thinking that the 4th gear solenoid is not working and will try to prove this with my snapon 2500 scan tool while driving but I need to break away from working on everyone elses cars so I can fix my own. Somehistory on the trans is that I got it from a low mileage wrecked 3500 truck. It's the HD version of the 4l80e according to the I.D. plate on the side of the case. I decided to upgrade the trans so that I would have many years of service from it, that's why I installed the shift kit. The inside of the pan was nice and clean and there was very little clutch dust on the magnet, everything looked real good and I wasexcited to have found a great trans. Now I am just a tad dissapointed becasue I need the Burb on the 26th and I have little time to work on it. Any helpyou might have to helpme fiund a speedy solution would be greatly appreciated. I am not a transmission guy, this is the first one I have ever opened up but my tech in my shop is an old time trans guy from the 80's.

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I pulled the codes this morning and it shows a code 28. Trans pressure SW Manifold problem. Any ideas for me?

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First step is to ensure there's electrical continuity from the PCM connectors that go to the manifold pressure switch to the connections at the switch itself. Use the wiring diagrams, pull the trans pan, and ohm them out.

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Finally, I have a working transmission. I replaced the A and B solenoids as well as the manifold because they didn't snap open the way I thought they should. They opened but not quick and firm. Useing my snap on scan tool, I noticed thatthere was no gear selector info getting through. It had ???? reading for what gear I was in. Now it shows exactly what gear I am in while I am in the transmission module but the engine module still shows a wandering possition. I don't get that but it's working and not setting any codes.
I do have another issue though. While driving onthe freeway, the engine cuts out for about a half a second. Probably a ignition module or something. I will figure that one out but I appreciate the help on the trans. Checking the solenolids was the ticket.

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On my cutting out issue, I installed a new distributor, not rebuilt, new, and the problem still exists. To refresh everything a bit; While driving at freeway speeds or at least above 40mph, the burb jerks like it cut out for a split second. At first, I thought that it was fuel pressure or volume cutting out the throttle body injector or something. Then, I ran into the distributor issues and so I replaced that with no improvement. My question is: I bought a used transmission and installed a Transgo shift improver kit in it with a high pressure release vale in it. I have since replaced the shift solenoids and the shift valve assembly but not the pressure switch/valve. Is that pressure switch bad and pushing too much pressure to where it hits the blow off that I installed with the shift kit? Would that cause a "jerk" in the drive train? I am thinking it is in the transmission because I have worked the engine over and I have no misfires and no running issues at all. My fuel pressure is at 15lbs and even though the volume is ambit low at 2.5, where 4 is kinda my minimum of flow. Will the throttle body cut out for a split second if it runs lowon fuel? Iknow I have a lot of questions here but I am running out of ideas. Thanks for all of your help.

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