Auto to manual conversion?

[Ian Mills]

My 4l60e is starting to show its age a bit. Not ready to condemn it yet but it occurred to me that it would not be too difficult (on the scale of trans swaps) to put a NV4500 from a GMT-800 HD truck in place of my 4l60e. 

I've done a bunch of research on which part numbers I would need and it seems mostly manageable but I have run across something I can't find the answer to online.

My NP246 transfer case has the 27 spline input shaft because it's currently hooked up to a 4l60e. The NV4500 has a 32 spline output and was never (as far as I can tell) offered with a NP246, just the NP261 it seems like. However there's a part number for a 32 spline input shaft for a NP246. If I install that input shaft, will I be able to put my NP246 behind a NV4500?
 

[Ian Mills]

Upon further research, I think it looks like the 32 spline input was installed in NP246 cases hooked up to a 4l80e in the 6.0 trucks. That means the 32 spline end would work with the NV4500 correctly but I still don't know if the planetary end of the input shaft is the same. 

NP246 cases with the 32 spline input are technically called NP246HD...

[dna9656]

I think it's much more involved than swapping transfer cases and trannys. The computeror some kind of transmission control unit is going to want to know what happened to the 4L60E. I'm sure the 80 talks a whole new language. This job was easy on a 1964 Impala, a real pain since 1986 or so.

[Ian Mills]

Well I'm not planning going to an 80. I'm scoping out going to a NV4500. 

I've seen that if you leave the PNP switch in Park, unplug the 20 pin, and seal it up with a plastic cover, the TCM basically just thinks nothing is up.

The VSS is in the transfer case so not an issue there.

The transmission temp sensor (on 4l60e only) and the reverse lamp switch on (NV4500 only) might give me some grief but I'm doing research still.

[shakenfake]

You don't have a TCM you just have a PCM. You will need a tune to tell the computer that your truck is a manual now

[Ian Mills]

Right, yeah. I used the wrong acronym. 

I do expect to eventually tune the truck (if/when I install the manual, I'm pretty tired of my 4l60e) but I've been reading other forums and it seems like other people who swap manuals into their GMT800 trucks have very few electrical problems even before the tune

[shakenfake]

Couldn't tell ya exactly about that.

[Ian Mills]

The question I actually have is about transfer case/trassmission interfacing. I was hoping to confirm that the 32 spline transfer case input shaft is a drop-in replacement for the 27 spline shaft. I'm hoping I don't also need to buy the low range planetary set but if I do, I would want to know before I had the case apart on my bench

[It's Tim]

Easier and probably less expensive to just scrap it and buy something else. 

[Ian Mills]

I'd be surprised if a whole new transfer case is cheaper than an input shaft and a set of clutches and steels. I'm sure it would be easier but I'm more budget-constrained than time-constrained

[shakenfake]

Maybe go on performancetrucks.net and ask this question or gmfullsize. 

A few dudes on those sites have swapped manuals and I would suggest try those sites and ask

[J. Rob]

If this ever gets seen I wanted to share that the few fellas I’ve seen pull this off was with stand alone ECU and the other had to incorporate a “piggyback” that also controlled the transmission parameterswhich was only done with quite a bit of custom tuning by way of some software wizardry….if you would like I can try n look for their contact info if you’d like….although its been nearly 8-9yrs back so I can’t promise much sir…