C3500 - SM465 to NV4500 swap questions..

Found some good info about dimensions of all kinds of transmissions here:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=32506.0

Then went here for more detailed NV4500 info: (Gotta scroll down & click on dimensions)
http://www.high-impact.net/transmission_and_gear/nv4500.htm#NV4500: General Information:

In summary:

2WD SM465 Dimensions:
Bellhousing= 6.5"
Case= 11.875"
Tailshaft= 5.625"
Bellhousing to yoke= 24"

2WD NV4500 Dimensions:
Bellhousing= 6.875"
Case= 12.375"
Tailshaft= 6"
Bellhousing to yoke= 25.25"

Difference= +1.25"

So based on this information I would need a different driveshaft or a donor vehicle. I did a quick calculation based on what setup you had and what you went to, With your SM465 & NP241 the length was ~36.875" but with the NV4500 & NP241 it should be ~37.75", (Difference= +0.875") based on the websites I pulled information from. So that almost suggests you wouldn't have been able to run your original driveshaft but you did. Getting confused a bit.. How much wiggle room is there? Seems if I could use the SM465's bellhousing I'll be ok but that's not possible.

Also, could not find any information about the location of the shifter for either NV4500 or SM465. None of the websites I came across mentioned any dimensional differences between 92-95 NV4500's or 96+ NV's.

As for the lean cruise thing I only see the speed sensor wires going to the trans. We've dealt with that already. Must be a switch for reverse but I didn't see anything which could sense it was in 1:1 to initiate a lean cruise mode. My GM service manual doesn't say anything about that either, only source for that info is the web. Shift light doesn't work and never has. Lit up when I was playing around with ECM's once (IIRC). When I had the scanner hooked up to it there was something in it that would tell me if the shift light was on or off and it was always "off."

Looks like the '96 parts truck I'm looking into will be sold by the weekend. Only time I have to look at **** when it's 50+ miles away.

You're right on the dimensions. The input shaft difference was 0.125", not overall length. I chose to let the slip yoke on the transfer case end of the driveshaft take up the difference in overall length instead of having the driveshaft shortened. I haven't had any issues with it bottoming out.

Maybe my claim about shifter location is unwarranted. There are a lot of people out there that have swapped the older style too cover for the new one with no mods so it's possible they are close enough. I can tell you though the late SM465 and early NV4500 shifters are close enough that the shifter hole needs no cutting.

My shift light didn't worked either. I swapped a PCM from the 94/95 trucks for tuning, and can get it to work with that but I leave it off.


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Oh, so the 94/95 trucks have the shift light programmed into the prom or PCM? I noticed with those the wire routing on the harness is different along with some of the wire colors from my 88. If I went with one of those newer PCM'S would I have to change those around and what would I gain? Thought my PROM chip was dicked so I bought a JET stage 1 chip for it.

Didn't know that about the top cover on the transmission, there was a NV4500 at a yard awhile back but it was a 4x4 and didn't know there were differences in covers. Anyone have any pics?

Sent from mah phonic while eating biscuits & mustard with French-fried taters mm-hmm.

I hang out at Gearhead-EFI.com too. Used the info there to swap from a 1228747 to 16197427 PCM. A lot better data transfer rates and more tuneability with the newer PCMs. All I had to do was move wires into the new connectors and plug it in. It fired on the first try.

Here's a pic of the top covers. People say the newer, square cover shifts better.




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Thanks for all the info dude! This is certainly helping to clear the fog. Looks like the newer cover would fit too, never had the plastic cover and boot off of my trans for a peek though. So the covers would swap over?

Do you have link to something that shows which wires to swap? I might not bother with it if all it gains are tuning options. Pretty much going to leave it stock.

Sent from mah phonic while eating biscuits & mustard with French-fried taters mm-hmm.

Yeah I use cover and boot from the SM465.

Here's a link to the pin maps (http://www.gearhead-efi.com/Fuel-In...ersion-PCM-Swap-with-Wiring-Pinout-Directions!). It only took about 30 min. You probably won't gain any more than you already have with the Jet chip. I threw in a 383 crate to replace my old, worn out 350 so tuning was needed to get it running right.


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Cool. Do you remember what was under that huge plastic cover? I know 1987-1996 F-150's have a huge cover for the floor pan that changed depending on drivetrain combinations, so even if you had to modify one it wasn't like you were destroying something that would be hard to return back to factory appearance.

Nice. What mods were done to the 383 in terms of Cam, intake, heads & exhaust manifold? How does it run now?

Just carpet with a hole in it!

Blueprint Engines built the engine. 4 bolt main block bored .40 over, some machine work on the heads, and the Edelbrock TBI intake. It was meant to be a direct replacement for a 350 TBI. Swap everything over, swap out the chip for the one that comes with the engine, and run it. I swapped in larger injectors and bumped fuel pressure to increase fuel flow to feed the beast. Had to retune for that and some spark table adjustments. I think it runs fairly well.


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Oh, so there wasn't a steel cover under that like the F series trucks have? Basically what I'm trying to figure out is if any trimming has to be done if it means trimming a cover or the actual floor pan.

Sweet, they supply the chip too?

Been communicating with a owner of a potential donor truck. Just like mine, regular cab long box 2wd. Sent me a pic of the RPO sticker and it's got MW3 on it. He's asking 1400. I was hoping to get it for 1000. Should have a Vortec 350 in it too but don't know what the RPO is for that and he says the motor was swapped before he got it. I'll try to attach the pic but what do you think? Truck doesn't appear rusty but it's crappy CL photos and he probably sprayed paint over the crusty spots.


Sent from mah phonic while eating biscuits & mustard with French-fried taters mm-hmm.

No steel cover. I was worried about cutting and trimming when I did my swap, but neither was needed. I was impressed well the NV4500 fit right in place.

Yeah they supplied a chip and it ran ok on the stock TBI system, but I wanted to try to get more out of it and plan for future upgrades.

If it's a 95 or later, it should be a Vortec engine. I did the same thing and bought a donor truck for my swap. It was the same K2500, same RCLB, even the same color but it had an NV4500 and 4.10 gears. I still have the front diff and rear axle to swap with mine that have 3.42's but that shouldn't be hard.


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