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What did you do with your GMT400 today...or yesterday....

Husker6.5 said:
That's good. And at least you had practice partially pulling the transmission doing the clutch replacement and it was recent enough that you could remember the procedure.
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This ^^^!

I’ve got all the bolts bagged and labeled. The coolant housing on the engine was uncharted by video, but it’s only 2 nuts and 2 bolts plus another bolt on an adjacent bracket. Then it’s coolant hoses, heater hoses, accelerator flap/vane box. Rest is on videos or easily remembered. It will take a full day, maybe more, to torque to spec.
 
@Big T that's awesome news about the transmission and having located an extremely reliable shop.

As for my truck, the transmission shop called right as I got home from a reintegration briefing for family members of persons kidnapped (joke, read to the end). Everything on my 4L80E checked out great. Servos are doing servo things like they should, pan is clean, fluid clean and nothing on the magnets. A side note by the tech after the test drive, "This thing runs very strong for a 6.5." I'll take every compliment I can get.

Side note: Looky what escaped the Gulag, ran an assisted escape and evasion route through the Ukraine, snagged a DPF and made its way home!
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Not what I did today, but something I'm thinking about doing tomorrow... Ever since I installed the new to me un-cracked dashboard I still haven't gotten around to reconnecting the LED's in my tow mirrors. I want to hook them back up and then get the kick panels back in place. I have been wanting to hook them up in such a way so that the lights work when the headlights are on, but also blink when I use my turn signal.

something that GM did on our trucks is that when you use the turn signals the front lights will alternate between them and the side markers on the grille. I have been studying the diagram in the service manual trying to figure out which side of the front side marker bulb I need to tie into for this to work. I have both the left and right mirror lights wires coming out under the dash right at the steering column area. I suppose I will need to pull the main connector for the steering column down where I can use my test light probe and see which one lights up with the headlights/park lights that also blinks with the signal lights. in the diagram it seems I will need to use the dark blue for the right and light blue for the left at the main connector. at least this time I will tie into that connector on the truck harness side and not on the column side so that if I ever need to replace the column switches I don't have to deal with cutting and re-splicing wires like what I did with the alarm and then had to replace the ignition switch!

since replacing the dash, I rewired the alarm to the dash harness. I learned that mistake LOL.

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I don’t want to encourage nor discourage you from this. Just understand it before deciding what o do it. It’s your truck and you should enjoy it however you want. Think of this like adding a CB or aftermarket stereo. A feature you could enjoy that future truck owners wouldn’t even take notice of PROVIDED there is never a fault in the system.

There is good and bad to a floating ground system.
Doing this to just that circuit rather than the entire harness complicates the hiccups somewhat. Floating ground is simply the ground wire for that circuit goes from the battery all the way to the devices in that circuit and never touch the chassis/body.

In your case you would need to remember where you made that circuit float and temporarily reground it after you undo the diodes. And this is only when hunting for an open or short of something in that harness or circuit. So you’re only adding maybe 2 minutes. But if you don’t remember this detail and have a problem later it could really throw you for a loop. Even if you have an open or a short in a different circuit- because the ground is both floated and chassis grounded it could complicate finding a short in a nearby circuit that doesn’t share the same harness.

So if you do it, make it easy to temporarily unplug snd plug back in. Then have the ground wire where you attach a ground clamp easy and the other end ofnthat grounding jumper wire to the body ground for searching. You wouldn’t have to always do it hut if you are 5 minutes into not finding a problem- you then do it real quick.

A floating ground is a better system for electronics but is more expensive to make. It will probably become the standard as new cars use more and more electronics.

Hmmwvs/ Hummers (H1 style) use a floating ground for the entire truck. Currently there is a Hummer owner who was a top notch diesel mechanic for years in the military and civilian after that, now about 70ish, that isn’t as good as he was but still better than average diy guy with skills on vehicles. Electrical wasn’t his strong suit but wasn’t bad at it either. He is a week into chasing a shorted circuit and trying to avoid ripping his entire dash and ajoining harness out of the truck to find it. He has the powerprobe master kit with short finder tool in it and understands proper use. He will get it but the normal time it takes to find a short circuit in a floating ground system is about 10 times as long as a grounded negative system like most vehicles have. Granted not as spry means it’s taking longer but that is only half the headache.

Why is it hard to find? A short either connects two circuits together- like turn on the radio and the headlights come on for some reason. Well those to wire got shorted (connected) together. Or the far more common: the radio wire rubs against the body somewhere and wears a hole in the insulation which pops a fuse to the radio.
Tools like the compass trick or the short finder from power master or other manufacturers send a tone signal on that radio wire and receive it on the other tool wire you connect to the chassis ground. The detector locates where the signal is strongest and gets louder or sweeps a needle back and forth more vigorously the closer you get to the location of the short (like playing colder/ hotter /on fire with where is my shoes hidden).

But when the ground wire is just like another wire in the harness and never has a separate area- the tools can not detect where the energy goes from positive side to negative side. So instead of the kid saying cold, cold, a little warmer, warmer, warm, hot, really hot, on fire (and now you see the shoes)… the tools just say warm warm warm warm warm warm the entire time.

The fix is to go to every single point of contact between the power and ground and disconnect them, then the tool will work. For hummers this means all the grounding pins that the harnesses all connect together, and removing all light bulbs, and unplugging all electronics. So a quick 6 hours work if you are physically fit and know where they all are before being to use the tool to find the short (or open circuit because it is found using same electrical principle just different tool).

Why do hmmwvs/hummer have it? The steel frame is NOT a one piece frame it all bolts together and doesn’t carry electrical ground well. Also the body is aluminum and having electricity make electrical connection from steel to aluminum or copper to aluminum makes the already bad galvanic corrosion of dissimilar metals become a more advanced process called electrolysis. So the softer metal wears away much faster.

This is a lesson many of the ford truck owners with aluminum beds, roofs, etc are gonna have a painful lesson in. Imagine all you added is a backup light to help out your reverse light or maybe some offroad lights and you now need to repair what seems like horrible rusting in the aluminum body parts.
 
all this with the floating ground thing has now got me thinking... the way the marker light works with it is the ground essentially alternates from one side of the bulb to the other when the parking lights are on and you have the signal on. at least that is my understanding. I had stuck LED bulbs in those front marker lights a good while back, I never checked to see if they still flash with the signal. a regular filament bulb doesn't care which side the ground comes from, an LED does!
 
IMG_1086.jpegIMG_1087.jpegReplaced drivers side ABS wheel sensor on the ‘94. Poor installation by me, allowed the cable to rub against the wheel. I do not have an OBD I code reader, and I did not have my wife bring down the adapter for the GM Tech 2. Is there a work around to clear the code?
 
Husker6.5 said:
Try disconnecting the batteries for 30 minutes and see if that clears the stored codes in the PCM. Watch the game and have a cold one while waiting the 30 minutes. Can't hurt anything if that doesn't work, plus you get a break and a brew!
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Yeah that’s what I’m doing.

Should be installing the transmission.
 
Tried to replace the $22 shift position sensor on my old OEM encoder motor for the ‘99. Unfortunately, one of the TTY tamper proof Torx screws was corroded and immediately sheared off. Tried to drill it out and failed. Bit walked and when I tried an EZ Out, it sheared off. So F that POS.IMG_1090.jpegIMG_1091.jpegIMG_1092.jpegIMG_1093.jpeg
 
Guess that means we know they don’t do systems check after rebuilding. Nothing major for that trans but I would be leery of them for automatic trans work.

The difference of diy and assuming everything works vs paying a pro and them testing everything after rebuilding is supposed to mean they test it.
 
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