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K5 6.2 nv3500 or sm465?

TooManyProjects

TooManyProjects

3/4 ton FWC
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Location
Terre haute indiana
My 700r4 let go and I don’t want to put it back in so im going manual.

it is currently a ‘90 tbi 350, im toying with the idea of swapping that for a 6.2 out of an 84 that has 50k on it, would probably change head gaskets and stud it at the same time.

I have an nv3500 out of a fullsize that I would put the k5 factory 241 on.

I also have an sm 465/205 that I could put in.

I would prefer the overdrive I would get with the 5 speed but im worried about the strength of the trans mainly.

The reason for being worried about the strength of trans is I want to go to blazerbash in Moab Utah. I am not familiar with the nv3500 and dont know how it would handle the climbing and potential accidental bouncing. And also dont know if the gearing with 241 would be low enough for the climbing.

I know the sm465 could handle the power of a 350 or 6.2 fine but am then worried about gearing for highway driving, especially with the 6.2.

A gearvendor under overdrive is out of the budget and so is an nv4500.

axles are currently half ton, would maybe go 3/4 because I have some. Currently 31s and 3.73s max would probably be 33s.

if anyone has any input or experiences with nv3500s in wheeling situations that would be great. Hows it held up and is the gearing low enough for moab without a doubler?

thank you all in advance
 
I ran a late model nv3500 in a k5 on tons and 37's.
That trans will hold up just fine to 33's. There gear splits are so much more enjoyable than the 465, and a 241 is a much better tcase than the 205, unless you are planning on running a doubler.

What year is the nv3500 out of?

I was running 37's and 4:10 gears, it was awesome on the highway, and 1st and 4 low on a np208 was decent gearing for wheeling.

I'm currently running a 465, and np241 in my suburban and dislike the gearing, the highway I'm turning over 3k to keep up with traffic.

I sold my nv3500 because I was concerned it wouldn't hold up to the weight of a suburban with full interior.
For a k5 they work extremely well.
 
I second the question on what year NV3500 you have. There is a huge difference between the early HM290 getrag and the late model NV from behind LS 4.8 or 4.3L V6 trucks in the mid 2000s. Essentially anything newer than 98 is a pretty decent transmission. 96/97 is okay, but no as good. 88-95 stuff I would avoid.

I ran a 2004 NV3500 from a 4.8L LS powered half ton behind an NA 6.2L in my 85 old reg cab long box K15 on 35" boggers with an NP241 behind it. It served me very well but was seriously underpowered with 3.73 gears. 5th gear was useless. I later swapped it into my K5 with a turbocharged 6.2L on 37" boggers with 4.56 gears and found it was a very enjoyable truck to drive. It had good power and held up to a lot of abuse before I switched over to my 2 door Tahoe build.
 
From full-size chev.com

...One easy way to tell is to remove the shifter tower (4 bolts on the top of the trans) and look at the shifter ball where it goes into the socket in the transmission. If the ball protrudes from the shift tower gasket surface, you have the NV3500. If the ball is recessed into the shifter tower, you have an earlier design. The older design was much more complicated inside because it had 4 shift rails whereas the NV3500 simplified the design and made one common rail for all shift forks. This made them a little more reliable. Otherwise, I dont know what other distinguishing features there are on the casting. ".......
 
TooManyProjects said:
if anyone has any input or experiences with nv3500s in wheeling situations that would be great.
Click to expand...

I can answer some of your questions. I'm not a rock crawler, but I have taken all of my vehicles offroad. I ran a stock(ish) 6.2/700R4 for 8 years. I had a 6.5/NV4500 for a while. I took a 6.2/TH400 CUCV and swapped in an NV4500, with some mods. Played with that for 7 years. And then, as Dean mentioned, I built the turbocharged 6.2/NV3500 Suburban (6 years and counting). I detailed both of the transmission swap builds here on CK5. You can find a lot of specific answers in those two threads as well as my NV3500 and NV4500 tech threads.

My thoughts:

I would not install an SM465. I can understand the case for building an NV4500 rig (very similar gear ratios), but life is too short for a 3.5-speed transmission with gaping wide gear gaps. There's just not enough gears to keep the engine happy at all speeds. Definitely keep the NP241 if you're offroading. Since you mentioned them together, I'm assuming you have a short SM465 with a figure-8 adapter. This swap would require you to redo driveshafts. Over the course of the '80s, GM standardized the sizes of their truck transmissions (until the 4L80 came out in 1991). So both the NV4500 and NV3500 can be easily substituted for your 700R4. Same length and same bolt patterns (though you will need a 32-spline input shaft in your transfer case, as 700R4 trucks came with 27-spline inputs). Your truck is late enough to use the same crossmember offsets as the GMT400 trucks, so you can bolt your NV3500 directly to your crossmember and you shouldn't even need to drill new bolt holes.


I wouldn't worry about strength. Anyone can break a transmission with enough abuse. But neither your TBI 350 nor your 6.2 will produce as much power or torque (more important) as the stock 350 Vortec that a 1995 NV3500 would have come with. And your rig will almost certainly be lighter than a loaded pickup, so the gears won't be carrying as much torque loading on average. It's not a license to be stupid with the gas pedal, but you have more safety margin than someone wheeling a 1995 truck.

Gear-wise, I ran 3.73 and 0.73:1 overdrive with 31s and with 33s. They're both fine, but the 6.2 is slightly happier with the 33s. I think I have enough gearing to handle 35s, but I haven't tried it. YMMV.
 
Wes Harden said:
From full-size chev.com

...One easy way to tell is to remove the shifter tower (4 bolts on the top of the trans) and look at the shifter ball where it goes into the socket in the transmission. If the ball protrudes from the shift tower gasket surface, you have the NV3500. If the ball is recessed into the shifter tower, you have an earlier design. The older design was much more complicated inside because it had 4 shift rails whereas the NV3500 simplified the design and made one common rail for all shift forks. This made them a little more reliable. Otherwise, I dont know what other distinguishing features there are on the casting. ".......
Click to expand...

The front case casting is also quite different on the LS-era NV3500s, in addition to the shift rail changes.
 
83ChevyK5Blazer said:
I sold my nv3500 because I was concerned it wouldn't hold up to the weight of a suburban with full interior.
Click to expand...


You might be right, but I don't think that's a huge problem. The 700R4 is more famous for early failures. Even if you have shift rail problems (like the early models), you will probably make it home. A dead 700R4 leaves you stranded.

My Burb isn't a hardcore crawling rig, but it's not like this truck is on parade duty, either. Rocky trails, hill climbs, water crossings, beach sand spinning, stamp sand bouncing, and mud (when I can't arrange to avoid it). High speed and low speed obstacles, with a little trailer duty thrown on the side. Plus that time I pulled a 12,000 pound RV stuck in loose sand (with help from Luke). The transmission is getting a workout. I've only had mine on the road for a couple of years, but it hasn't shown any signs of degradation yet. You guys will hear about it when it does fail, but I don't consider it to be my truck's weak spot. At this point I can recommend it with a clear conscience. :waytogo:

Great Smaug in the berm


View media item 37265
 
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If the TBI 350 is in good condition and runs well I see no reason to swap a 6.2 oil burner in place of it. But that's just me.

Now for the trans, my DD S10 has the nv3500 and I can say it's a great shifting, smooth transmission. These guys here have paved the way for the swap so I'd follow along with what they have done since I haven't swapped one. Where you live you'd make better use not having the deep granny gear of the bigger brother nv4500. I've got a 4500 for mine, but I have different needs. One mine truck is one heavy pig with the camper. Two, mine has been known to see rocks and very steep downhill descents. Mine currently has a 700r4 and even with the nice 2.72:1 low range I really miss going downhill with the granny gear I had in my old K5 with the 465. As far as the gear splits go on the 4500, with a torquey 8.1 in front of it, there won't be a problem.

Getting back to a 3500, I think the gear splits are pretty well set up. I think with your gearing and minimal tire size it would work well in a K5.
 
Wonder if this will upload. Kinda selfish numbers, cherry picked the RPM's I generally care about in each gear. Didn't know there was a wide ratio and close ratio unit. Apparently the S10 version has a different exterior. Found a place online selling them rebuilt for $900, can't recall the core cost.

Seems a pretty decent option with ease of shifting, OD, and closer gear spacing. Wish search was working, I'm assuming a 3500/241 combo is same length as any other combo that came stock with a 241. Also a given that the shifter is further back than the 465...

full
 
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