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I picked up a remanned GM 4t65hd that was in a 97 Regal GS but later found out that I need an internal range type trans for my swap. I picked up an 03 monte trans and was just going to take the diff from the hd unit and use it in the monte trans, but when I pulled the diff and the bottom trans pan off I found that this trans looks brand new on the inside....i mean it looks like it had just been rebuilt before the engine blew. My question is can i open up the side cover and just swap over all the electronics and wiring harnesses from the internal range transmission over to the external one and work, or would I be better off swapping all of the internal over basically as if I were rebuilding it? I've never dug into one of these other than swapping diffs and filters so I'm a little nervous about swapping all the main components as if I were doing a rebuild. I really hate the thought of totally ditching this fresh trans.Any advice would be appreciated. I'm doing a L32 swap in a Oldsmobile Silhouette with a northstar tb using a 2003 impala wiring harness and pcm if that helps.
 

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Might be better to just use a 98-99 PCM and leave the fresh GS transmission buttoned up (plus running an L67 tune from an earlier car will be a bit nicer to deal with in a custom swap). You'll just have to look into the difference between the harness ends for the PCM and transmission, and adapt it (you can get the range switch connectors online or at a local yard).

I can dig up the pin-outs if you want to go that route. Otherwise, look up 4t65e info on Google, as I've found a few sources that list the bunch of differences between models that might help.

Sidenote for those unfamiliar with HD diff swaps: you also need to use the HD diff cover, bearings, and output shaft... Possibly sun/park gears as well, it's been a few years since I was regularly doing them. See ZZP's sale page for HD diffs for a picture to help.
 

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I would use an older pcm but Mike from milzy motorsports suggested I use the impala pcm and harness so that my gauges would work as they should so I'm taking his advice. I've done a few diff swaps already so I've got that taken care of. The monte trans is a 35/35 sprocket and I already installed a 3.29 hd diff from an impala ss, I was just pulling the diff from the older one to keep back even though it's a 3.05. It's really not a big deal to use the newer one I have, I just thought that since I opened the older one up and saw how clean it was that maybe there was a way to swap the electronics over. I guess I'll just turn it in for the core.
 

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I can look at the Olds' schematics for what signals the dash needs (most likely standard VSS, ECT, RPM, etc.), but Chevy's are very stingy on their serial bus line, which is why people have issues tuning them, even in their original form/vehicle without some fuse pulling.

I'm in favor of you using that fresh transmission, but if you don't want to go the pcm matching route, do the research to swap the newer electronics/VB in. I know it's discussed in the decades of history here and elsewhere online.
 

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Thanks for the info., I'm still a couple of weeks from starting on this project so maybe I can find a way to still use the fresh one
 
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