Recently finished building a 4L80. Nothing crazy just a stock rebuild with some durability upgrades etc. CK shift kit, dual feed, the usual.....

Drove it for the first time earlier and it has 2nd and reverse only. I'm thinking it's electrical. I air checked it on the stand and everything seemed to give a good solid "thunk" when applied with air.

I'm thinking electrical.... But where do I begin looking to figure it out?

 

No electrical possibly. It's in limp mode, 2nd gear only.

 

Limp mode not electrical possibly?

https://ls1tech.com/forums/automatic-transmission/1855483-rebuilt-4l80e-2nd-r-only-think-s-vehicle-wiring.html

 

I think he means it is possible. i.e., theres possibly no electrical supply to the trans so it is in limp mode which would give 2 and R

 

Yes. No 12 volts = limp mode. Or no ground, same thing.

 

My transmission, not my vehicle. The owner of the vehicle had to change the entire wiring harness due to a previous owner damaging it. After the wiring harness was changed it worked fine and has been working fine since.

 

Thanks guys, figured it's something electrical since everything air checked fine before I put it in. Any suggestions where to start looking? Solenoids?

 

I'm not familiar with what you're working on.
I would start at the transmission plug. There needs to be 12 volts and a ground there,

 

 

Opens and shorts will throw a code.
No 12 volts present won't throw a code.

Pin E is 12 volts. Ground is supplied by the computer to each solenoid when needed.

 

It's a K5 blazer so its obd1. 7427 PCM with no trans codes. I'll check those pins and report back.

 

So it's the stock application?

 

Eh, not exactly. It was originally a truck with a different stone age TBI ECM and a 4L60. I swapped the original ECM several years ago to the "better" TBI PCM the '7427 and drove it around like that until the original TBI 350 finally broke.

Built a fresh stout 355 TBI for it, using that same computer still and ditched the anemic 4Lshitty(60) in favor of the 80 that's in there now. Here's the wiring diagram for the '7427 and the 80e that was utilized in a factory application like that.

I started with what was a 4L60e trans connector and went one wire at a time and pinned in the wires individually to the TBI PCM using the wiring diagram here. I'm going to check my wires, there's a good possibility I pinned one in wrong or something.... That truck is outside and it rained here yesterday so I'm not going to mess with it for a day or two but I'm trying to prepare myself for what I need to be looking into when I do jump back on it. I reused all of the solenoids and electronics that were on the 4L80 so I don't know if they're any good and how/if I should test them.

 

Do you have an OBD I data logger or anything? I use a Moates APU1 with TunerPro RT. I use this on my '92 454/4L80E dually.

So you have two choices I think you're saying. Question the transmission electronics or question the conversion. Trust me, it's not the transmission. No offense.

If you want to determine whether it's the conversion wiring or transmission follow this: (I'm going to delete this later)

 

Ok I just caught something else.
You're using the same ECU and PROM that controlled the 4L60E? Thats not going to work.

 

I have TunerPro on my same laptop that I use to tune my turbo LQ4 truck with HPTuners. Got a Moates chip burner and a homemade ALDL interface that stays permenantly onboard with the truck. I burn my own chips.

Previously, when the truck was driving around a couple years ago before I parked it to build the new 355 and 4L80 for it, it was running on the $0D codemask which was for the 4L60e. The truck had a 4L60(700R4) so all the PCM did was control TCC lockup and nothing else......

Fast forward to today where the new 355 and 4L80 are in, I have loaded up a BIN with the $0E codemask, which was a factory application using the same 7427 computer, but with a 4L80 instead of the 4L60. The bin I'm running is BJDR which is the $0E codemask factory calibration file for a 350 4L80 application. Not sure what exactly i.e. van, truck whatever but being a 350 4L80 BIN, it ought to be close enough to use as a starting point.


I switched to this PCM several years ago becasue it can control E fans and log wideband data directly in the factory datastream in place of the EGR.... Your dually having a 4L80 likely has a PCM that can also control E fans and log wideband, if that is something you'd be interested in let me know and I can share with you my files and what I have learned as far as getting that to work.

Back to my problem:

I think I pinned in a wire in the wrong spot when I added the 10 or 11 wires to the PCM connectors for the 4L80 the other day...... Either that or the solenoids are bad on the trans but like you said, very unlikely. I probably misplaced a wire.......

Why are you going to take that picture down? I saved it so I will be checking that and I'm sure that will confirm that I need to recheck the wires I added the other day.

Here is the onboard ALDL interface that is hardwired into the truck. It enables me to simply plug a laptop into it with a USB cable instead of dragging out the ALDL cable and having it all wrapped up around your damn feet haha.

 

Gotcha. Well thank you very much for sharing it with me anyways!

I'll have to check over the other wires some more later but I did confirm switched +12v on the pink wire at the trans connector on PIN E..

Okay stupid question for you: I have not hooked up the TFT trans temp sensor to the PCM connectors. Would that cause limp mode???

 

Yes, it defaults to either max high temp or max low, I can't remember, Theres a flag in tunerpro that gives the trans temp limp mode temp. At least on mine, mask $85. Broadcast code BAMF.

 

Okay well that's good news. I bet not having the TFT pinned into the PCM connectors is causing my problem then!

I was going to look around at the BIN you have for comparison but I cannot find it.
I found the code mask $85 xdf but I cannot find BAMF??? What is the serv number on your PCM???

Here is where I source a lot of OBD1 files: XDFs ADXs BINs http://gearhead-efi.com/gearhead-efi/

I cant seem to find anything in my BIN that would be a similar setting like you describe.The closest thing I have found as of yet is something called "Force 2nd gear if in D2 and not manual"

Thanks for the input so far man, much appreciated.

 

It's been a while. I'm using a BAMM bin with the stock 7060.