C3500 - SM465 to NV4500 swap questions..

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DerekTheGreat

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Good morning. I'm sure this has been beaten to death but I can't exactly find the information I need...

Looking to swap our clunky SM465 for a NV4500.

Heard that the 92-95 transmissions have RPO code MT8 and would be a direct swap. GM bellhousing to engine is the same regardless of V8 small or big block or diesel.

Heard that the 96+ transmissions have RPO code MW3 and would also swap in but would require changing the slave cylinder stuff over but you also gain better gearing, smoother shifts and synchronized Low & reverse. GM bellhousing to engine is same regardless of V8 small or big block or diesel.

Question is, are these correct statements and what would you run with?

Our truck is an '88 C3500 with a 454 and the SM trans. Currently looking at buying either a '92 or '96 parts truck. Help us decide!
 

Biggershaft96

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Good morning. I'm sure this has been beaten to death but I can't exactly find the information I need...

Looking to swap our clunky SM465 for a NV4500.

Heard that the 92-95 transmissions have RPO code MT8 and would be a direct swap. GM bellhousing to engine is the same regardless of V8 small or big block or diesel.

Heard that the 96+ transmissions have RPO code MW3 and would also swap in but would require changing the slave cylinder stuff over but you also gain better gearing, smoother shifts and synchronized Low & reverse. GM bellhousing to engine is same regardless of V8 small or big block or diesel.

Question is, are these correct statements and what would you run with?

Our truck is an '88 C3500 with a 454 and the SM trans. Currently looking at buying either a '92 or '96 parts truck. Help us decide!
Other then having to have a different drive shaft i think your on the right track. Finally someone who does their research lol.
 

DerekTheGreat

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Haha thanks. I've been researching the swap ever since we got the truck and well, I didn't think it would be so hard or expensive to get ahold of one. If I had known what I know now then, I'd have just bought a later model truck.

Anyway, I heard the swap is a direct swap with a 92-94 (maybe 95) trans and that you could reuse the driveshaft, clutch and even the metal lines for the slave cylinder, even the hole for the shifter is the same. There's a member on here that's done it and that's where I got the most useful info. Forget his name though. I'd really like to hear from someone who has done the swap.

About 7 months ago I test drove a 99 or 98 2500 HD with an NV4500 in it and it shifted very smoothly and the ratios weren't so wide like the SM465's. I was even able to use "Low" although this truck had the more modern shift knob that read 1-5 instead of L,1,2,3,OD. Engine was smoked, trans had noises and so we just couldn't agree on the price. Didn't help that some fat Wilfred Bremley look-a-like showed up in a Hummer offering asking price without even driving it. Schmuck.

Anyway, would an earlier NV4500 with the different ratios & unsynchronized low & reverse still shift like the later ones? If not I'd rather get a later one and go through the pains of converting the slave cylinder set-up as all I'd be gaining is OD but would still have a slow shifting, clunky transmission.
 

Chewy1576

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I did this exact swap, but it was a 4WD application and I used the earlier model with external slave. I reused the flywheel, clutch, master and slave cylinders (although I have since swapped them for the NV4500 ones, still direct bolt in though), transmission crossmember and mount, transfer case, and drive shafts. No cutting or drilling required.

It shifts much more smoothly than the SM465 and the overdrive is invaluable.
 

Justin S

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I did this exact swap, but it was a 4WD application and I used the earlier model with external slave. I reused the flywheel, clutch, master and slave cylinders (although I have since swapped them for the NV4500 ones, still direct bolt in though), transmission crossmember and mount, transfer case, and drive shafts. No cutting or drilling required.

It shifts much more smoothly than the SM465 and the overdrive is invaluable.
That's awesome that the driveshafts are the same. Did it come up through the floor in the same spot as well?
 

DerekTheGreat

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You're the dude I was talking about! I recognize the truck in your profile.

Awesome, thanks for the information. Hmm, I wonder though if the 2wd's are just as easy. Also, I heard with the SM465 it has a switch that signals to the ECM to run lean in top gear. What happens with this when I go to the NV4500? What did you do? What about the shifter hole, was that the same too? Did you reuse the big ugly cover that the SM has or did you use one from a donor truck? How is the gear spread? Is it just as wide and crappy like the SM? I really hate the SM trans, only thing it's good for IMO is getting the truck to move. Mine is in perfect shape though, doesn't pop out of 2nd like everyone says they're prone too and the shifter itself is nice & tight. Pics of before & after of your truck would be nice.
 

DerekTheGreat

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Also, How hard would it be to convert to the 96+ set up with the internal slave? What's involved? I'm pretty much a bolt on kinda guy, fabrication really isn't my thing. Reason I ask is I've got a line on a 96 3500 with the same configuration my truck has minus the 454. Best deal & lowest mileage I've seen yet.
 

Chewy1576

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See if you can find bellhousing to yoke measurements for both transmission in the 2WD applicatoin to see if the driveshaft can be reused. In my case, the difference from bell housing to transfercase flange was 0.125" and they both had the same transfer case. This meant driveshafts could be reused without modification.

The only switch I was aware of was the reverse switch for the lights. Same with the NV4500. The 5th gear switch to enable lean cruise may only be in the later model NV4500. Also, look into the speed sensor.

The shift tower for the early model NV4500 is roughly in the same location as the SM465, so no cutting of the floor and I reused the SM floor cover and boot because it was still better to look at than the ugly, old carpet underneath it. I believe the later model NV4500 shift tower is in a different location because of a newer design of the top cover, so cutting the floor would be needed.

The gearing is similar to the SM465, but includes 5th gear OD. I hardly ever use L gear with the NV4500 and hardly used it with the SM465 as well. I was never really looking for close ratio gearing to slam through though, I'm building this truck as more of a workhorse than racer.

I believe it's possible to convert to the internal slave cylinder, but I haven't looked into it. I wanted the early model to stay with the external slave like the SM465 for ease of install. The SM465 slave cylinder will bolt on to the bell housing and function, but I was having trouble shifting reliably. I looked into bore sizes of the SM465 Master/Slave and the NV4500 Master/Slave and there are differences, also differences in length of slave travel. I put in the NV4500 Master/Slave and the clutch now fully disengages and the pedal feel is a lot better.
 

Chewy1576

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The only pic of the project that I have is the one after I took the NV4500 out of the donor truck. After that, I loaded it in the bed of my truck, drove it to a transmission shop, and they did the R&R for me.
 
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