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4L80E driving me crazy

I'm doing a little better so maybe I can get this done in the morning. I'm as curious as you are. Oh yeah, the oil cooling lines are factory, I can promise you all that much. They are front and rear with all O.E.M.passenger side retainers and clamps with factory bends. Richard
 
They made tcm's that didn't need the output speed sensor in the trans for 4x4's, it was just the one's used in the 91-93 trucks that also received a different valve body and an extra accumulator.
 
Richard Grant said:
I'm doing a little better so maybe I can get this done in the morning. I'm as curious as you are. Oh yeah, the oil cooling lines are factory, I can promise you all that much. They are front and rear with all O.E.M.passenger side retainers and clamps with factory bends. Richard
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Just because they're factory, it doesn't mean they were factory to that truck. For all you know, somebody could have swapped the engine, trans, and radiator out of a different truck into it. Who knows when you're dealing with a 20+ year old truck thats had who knows how many hands on it through the years. Just like my burb, it sure didn't leave the factory with a duramax and allison it, but it has one now. All you can do is to try and sort it out, and make it work.
 
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I have just finished a nice meal of crow! The truck is a 1996 K2500 special order for fleet service. That might be the only part I've gotten right. The coolant lines are not fore aft as my son in law reported but are both front connect. I should have checked behind him. I do apologize with sincerity for this mistake gentlemen. It does have the two V.S.S. on the transmission case and one on the transfere case as we discussed.
The wiring through out the truck is probably the root cause of the failure but I will repair. I was able to get better pictures with my tablet, now if I can only upload them. My service here is really bad. Thank you all very much for your time and knowledge. Richard
 
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The first picture is of the rear vss located just above the round blue connection on the transmission case. We had left it unplugged while trouble shooting The second picture is the front vss, if I can load it one time.
 

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Have you physically removed the rear speed sensor and looked inside and seen a square 40 tooth reluctor wheel? My 95 4l80e also has that same speed sensor in the rear, but theres no reluctor for it inside. Doesn't matter what it was ordered for, it should not use that rear speed sensor. There should be a jumper harness that plugs in at the rear of the trans, and routes it back to the speed sensor in the rear of the transfer case. Many a person has seen that plug and swore it was an actual OSS just to find out it's a dummy plug.
 
I know on my 98 K2500 Burb the back hole doesn't even have a "dummy plug", it just has a block off plate with a plastic cylinder into the port that holds the O-ring seal in place. It's flush on the outside without any sort of electrical plug or anything that even hints to plug the rear harness into it.
 
The plug on the donor transmission is plastic and is over flush to the case. The pictures here are of the OEM transmission that is in the truck now. I'm hoping with the help of the pro guys here I'll know exactly what I need to do so to make this sucker work. They are kinda saying it doesn't take a lot to change.
 
THEFERMANATOR said:
Have you physically removed the rear speed sensor and looked inside and seen a square 40 tooth reluctor wheel? My 95 4l80e also has that same speed sensor in the rear, but theres no reluctor for it inside. Doesn't matter what it was ordered for, it should not use that rear speed sensor. There should be a jumper harness that plugs in at the rear of the trans, and routes it back to the speed sensor in the rear of the transfer case. Many a person has seen that plug and swore it was an actual OSS just to find out it's a dummy plug.
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No sir I have not removed the sensor to verify. I will get this done this weekend. Sorry about the delay but I have doctors appointments for the next two days. These bits of information are what I'm looking for. As I said earlier I am not up to speed on the electrical system. I am a body construction engineer. Please keep the info coming as I learn and research. Thanks to all, Richard
 
It's been awhile since I said I would get the trannie out but a few health issues forced a work storage.
I listened to everyone's advice and everything is good to go. We only got the transmission out yesterday. I removed the rear vss on the removed transmission and compared it to the replacement. They are identical!!! The rear vss acts only as a mag-pickup to read and transmit speed data. I'm sure everyone but me knew this already.
I purchased 2 very good G.M. year specific 4L80 shop books for the electrical and mechanical cut sheets. Being they are real manufacturer books they have been on the mark so far.
I hope this research will help someone that is replacing an older unit with a later model one. I will be more than happy to e-mail anyone cut sheets should there be a need. Maybe I can save them money and not need to wait to receive books by mail. AGAIN, THANK YOU ALL FOR YOUR HELP AND PATIENCE. Richard
 
Richard Grant said:
It's been awhile since I said I would get the trannie out but a few health issues forced a work storage.
I listened to everyone's advice and everything is good to go. We only got the transmission out yesterday. I removed the rear vss on the removed transmission and compared it to the replacement. They are identical!!! The rear vss acts only as a mag-pickup to read and transmit speed data. I'm sure everyone but me knew this already.
I purchased 2 very good G.M. year specific 4L80 shop books for the electrical and mechanical cut sheets. Being they are real manufacturer books they have been on the mark so far.
I hope this research will help someone that is replacing an older unit with a later model one. I will be more than happy to e-mail anyone cut sheets should there be a need. Maybe I can save them money and not need to wait to receive books by mail. AGAIN, THANK YOU ALL FOR YOUR HELP AND PATIENCE. Richard
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Please excuse me for taking so long to update. We finally got back on the truck wiring harness this past Saturday so installing the transmission is next. We found several areas that could cause problems like chafing, incorrect harness routing and a general mess overall. Now after son finished his inspection, retaping and installing new split loom it looks better than new. He installed new Deutch seals on all connections after cleaning the connectors with cleaner. We did find some connections broken and glued back together. That was a first for me! He spent 6 hours doing this. He was not messing around either. He stayed at it. We'll deal with the inside wiring before we see how the replacement transmission works. I found a couple of other wires that I have no idea what they are underneath the body. If I can't determine what they are I'll post pictures and yell for help. One in particular looks factory one way and not another way. I will make new coolant lines this week for the later model trannie and get the cooler installed, that is if I can walk. Oh yeah, just a word of advice , when checking the sharpness of a circular saw blade DON'T STICK YOUR FINGER IN IT WHILE RUNNING!!! Thanks to all, Richard.
 
Glad to hear of progress!! That is about how my projects go as well........ two steps forward....long pause...one step back and three steps forward....etc.
 
Hey man, I wasn't kidding about the circular saw advice. That happened during the truck project so I was even more crippled up than normal. Thanks for letting me know that I am not alo
 
Be glad you weren't trying to put your ear up to it to listen to hear if it was running!
 
Wow, you just had to put that in so I'll cut my stupid ear off. Now I'll look like Van Gough , like I needed help hurting myself. Can't wait for the next bodyly adventure. Richard
 
Now this is a little weird, I just purchased 2 new paint guns today to use on my truck. One for priming and the other for finish coating. Lol, I'll probably wind up painting my ear. Funny.
 
Richard Grant said:
Now this is a little weird, I just purchased 2 new paint guns today to use on my truck. One for priming and the other for finish coating. Lol, I'll probably wind up painting my ear. Funny.
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Paint guns to paint the rig? Hey, might be able to paint my hummer myself! I would love to see someone actually do that!
 
Hey Will, just being willing to tackle something new is a huge part of the equation. I have always lived by the saying "YOU CAN'T BE SCARED ALL YOUR LIFE". This is what I tell myself and no one else. When my maintenance guys were hesitate about one of my unproven projects I would tell them the only people that didn’t make mistakes are the ones that don't do anything!
I'm only saying what works for me, not preaching to anyone. Richard
 
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