Fast Shifting

[ScottR65]

So I'm going to post this and hopefully wont get bashed to hard. First off I'm a super green rookie with HP tuners and tuning in general.
[ATTACH=CONFIG]137922
I'm trying to narrow down why the tranny is short shifting through the gears and dumping into OD.
It was a 4wd transmission at one time. When I did the swap I had the tail housing and output shaft swapped to a 2wd.
Can the previous 4wd programing cause this condition? It acts like its in 4wd low.
There's more to it but lets see if I have the current file attached right?

[TheMechanic]

Screenshot 2023-10-03 194253.png
Shifting pretty short.
Use BlueCat.

[ScottR65]

I was able to make a couple of short scanner files.
This is a LS swap into my 65 Nova. I'm looking for help!
It's a long story so I'll keep it short. Had it to a tuner to sort out the shift points. He loaded up a tune and it worked flawlessly we stopped to make an adjustment key off key back on start, drive and right back to short shifting. He said I'll rewrite it, key off key back on start and drive. No change. Two or so mile drive back to his shop no change after rewrite still short shifting dumping into OD. We stop at a stop sign take off and it snaps out of it. Trailer it home take it for a drive and same thing short shifting.
I've been reading there could be a conflict because of it being a 4wd TCM and my need to be rewrote to a 2wd. i had the transmission converted from 4wd to 2wd by changing the output shaft and tail housing.

[TheMechanic]

Do you actually have a measured 25" tall rear tire with a diff gear of 3.90?

[ScottR65]

Ahhh no I don’t believe that’s correct. I’m pretty sure it’s 26 or26.5

[ScottR65]

Confirmed 25" tall tire and diff is a 3.90. I can see the relevance to this question but its kinda off of what the original topic was.
Which is dose anyone think there is a problem with this being a 4wd TCM and should it be changed to 2wd OS or are they basically the same?
I've read on this form were some have experienced this key on key off issue, but as usual they never follow up on how they fixed it. Did it work did it not? I have yet been able to reproduce what had happened.

[gtstorey]

Does the VSS pull from different location on he 2wd vs 4wd?

[ScottR65]

It's the same thing just that the output shaft on 2wd is longer than a 4wd same thing just longer no transfer case. It's just a mechanical adjustment same thing but different. Output shaft is longer. Programing not sure?

[gtstorey]

I thought it pulled a speed from the transfer case on the 4wd.

[ScottR65]

That’s what I’m trying to find out?
Would it be advisable to rewrite the TCM to a 2wd OS? Not sure? You would think that could be the problem. Maybe? Someone has had to run across this.

[edcmat-l1]

How would a 2wd OS differ from a 4wd OS? The transfer case is separate and requires no programming. The location of the VSS is irrelevant. It's the same signal.

Edit: Is this a 4L80? If so, are you using an input speed sensor?

Really would help overall if people posting looking for help would include build specifics, so people that know don't have to guess.

[ScottR65]

I don’t know how it would differ that’s why I’ve asked for help.
I thought the Editor file would give the specifics of my configuration.
It’s a 5.3 backed by 4i65e. It was a complete pullout from a 2008 gmc pickup 4wd.
ECM, Tcm, drive by wire pedal are all matching.
I’m trying not to get into a super long explanation of what has brought me to this point of posting in these forums. Trying to keep it simple as not to offend.

[edcmat-l1]

I don’t know how it would differ that’s why I’ve asked for help.
I thought the Editor file would give the specifics of my configuration.
It’s a 5.3 backed by 4i65e. It was a complete pullout from a 2008 gmc pickup 4wd.
ECM, Tcm, drive by wire pedal are all matching.
I’m trying not to get into a super long explanation of what has brought me to this point of posting in these forums. Trying to keep it simple as not to offend.

Super long explanations are sometimes needed especially on swap vehicles.

That being said, you have some interesting settings if it's not an 80. It has the ISS enabled. Do you have one? I'd maybe change some of the settings under configuration and see if that has any effect.

[edcmat-l1]

I don't know if this is your answer, you may indeed need a different OS, but this seems like the logical changes to me.

Edit: Need to PM Alvin on here. He's really sharp on trans swaps, different OSs, that kinda stuff.

[gtstorey]

Maybe I was thinking about the OSS not VSS.

[ScottR65]

Ok thanks super appreciated! I will give it a try.
It does have an ISS.

I will report back on this! Hopefully it will get resolved so some can learn from my mistakes or what to do if this happens to them on there ls swaps!

I have to edit something here. I noticed the OSS after 4wd transfer case and thought that was kinda odd. Sry I'm still crawling here but would OSS stand for the outside speed sensor I guess? Would that be the one that's located by the tail shaft?

[2xLS1]

Does logged mph agree with gps mph when driving? And a 08 15 pin plug 4l65e will have an ISS.
Any codes when the shifting acts up?

[GHuggins]

I could be wrong, but I'm pretty sure it depends on whether or not it originally had an auto or manual transfer case and what range inputs it's looking for. If I remember right it just looks for a switch ground to know if it's in 4lo. It sounds like it "thinks" it's in 4lo and going off of that shift pattern. The tcm can be completely reflashed to a 2wd. I would advise using tis2web and using a 2wd vin and then flashing both the ecm and tcm both to a 2wd configuration as there are background changes that correlate to both modules.

[ScottR65]

Does logged mph agree with gps mph when driving? And a 08 15 pin plug 4l65e will have an ISS.
Any codes when the shifting acts up?

No I didn't not think of the gps thing and No there are no codes.

[ScottR65]

I could be wrong, but I'm pretty sure it depends on whether or not it originally had an auto or manual transfer case and what range inputs it's looking for. If I remember right it just looks for a switch ground to know if it's in 4lo. It sounds like it "thinks" it's in 4lo and going off of that shift pattern. The tcm can be completely reflashed to a 2wd. I would advise using tis2web and using a 2wd vin and then flashing both the ecm and tcm both to a 2wd configuration as there are background changes that correlate to both modules.

I deleted all of the 4wd stuff from the harness so there is no way for it communicate that information between the ECM and TCM.
So this thing has been doing this for a couple of years now and I've just been dealing with it.
We I say, my wife and I have just been enjoying the car. Taking it to shows and cruse in's and what not.
It took me a decade to build to the dam thing!
I can manually shift it and it runs like a scalded dog.
For what ever reason when a rewrite is thrown at it, it works until it is keyed off and then keyed back on.

edit: I would agree its a OS issue