Full size K5 build

[Fitz4x4]

Hello all

I have a1980 K5 Blazer that I have been working on for a couple of years now. I had to take a break from it and now have restarted my efforts. What I really need is some advice from anybody who knows these trucks. I have installed a 5.3ls and am stuck on what drive train option to run listed below are what I have accumulated. I just don't know the what I should put in.

1992 nv4500 with np241c
Figure 8 sm465 with np205
700r4 with np241c
Th350 with np203

So far I have the sm465 installed with a hydraulic bell housing from a 199? Truck. I'm having a hard time finding the correct slave and clutch fork with throwout bearing. Anybody with any knowledge on this please let me know. Thanks for the help in advance.

 

[Chaentjens]

I did that same swap and used all those parts from an 87 k10.
Did the trick!

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[vwjay]

It all depends on how you want to use the truck. If you're driving long distance, often. I would suggest either an automatic or manual with overdrive. I'd personally stay away from the 700r4 and go either 4l60 or 4l80. The NV4500 is a decent transmission. In more local overdrive is not an issue. If I'm ever lucky enough to find the parts or a parts truck to do the swap for my Blazer I want an SM465/NP208 or Sm465/NP205 I like the granny gear for my driving and use. Plus I enjoy the ease of not having to remember what truck what came from when ordering parts.


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[TerryD]

I just sold my 84 K5. It was built to be a crawler and was entirely too rough to go overlanding comfortably in but I have some thoughts from my build that might help you along.

I'm a proponent of the automatic. Having grown up on a farm, I spent my fair share of time pushing a clutch. I daily drove manual transmissions for several years and as I've aged (only 34 now) I've had issues with my clutch knee, as has my Dad and younger brother. With my 98 Cherokee, when hung in traffic or in town, my knee would begin to ache. After several hours on the trail, it would ache badly and could last a few days. So a manual was out for me. Also growing up around hot rodders and drag racers, I know the value of a good automatic and that will a little work, they're just as tough as a manual transmission.

I agree with going to a computer controlled automatic. The 4L60E or 4l65E (slightly different variants of the same transmission based on the old TH700R4) would both be great for your application. You already have the computer for it, you'll just need to add the harness for the transmission and it will fit with cross members that are readily available. The 4L80E is a good transmission, but it's slow and heavy. I have one in my K2500 GMC and while I'm happy with it, I wouldn't attempt to use it in something like this. Properly tuned and built, the 4L60E will provide many many trouble free miles. The overdrive automatic also has the benefit of a longer front driveshaft, making it easier to control u-joint angles and include enough slip that you don't pull the shaft apart when fully drooped on the passenger side.

The NP241C has a lower low range than either the 203 or 205, improving off-road gearing and allowing you to use slightly higher differential gears to maintain highway mileage. (say 4.10 vs 4.56 on 35's) With it's billet planet carrier, it's stronger than the NP208 but don't discount the 208 so quickly for a vehicle you wheel mildly and aren't towing 8k with. Many of the 208s were made and they are very common. Just think about the number of military trucks that were made with the NP208 in them, plus almost every 1/2t 4x4 GM made throughout the 80's while the 241C in pass drop is a rarer case should you bust it on a trip. Both the 241 and 208 have the ability to eliminate the slip yoke for the rear output as well.

You've spent the money to have the modern engine, why go with 50's vintage tech with a 465 or TH350? I would also consider how much you like pushing the clutch for hours at a time when traveling off-road. If you use a proper shifter such as the rockgate, you can easily and quickly control your gears on the trail. Plus, a F-R-F bump to free yourself is as easy as a simple push, pull, push of the shifter with a little throttle feathering. I've wheeled both and prefer the control of the automatic off-road.

 

[Fitz4x4]

Wow Terryd you make a great case and probably the best worded advice I have seen from a reply to a post. So7nds like automatic is the way to go unfortunately I only have a 700r4 from a cyclone I think it is a 92ish. Would it be the same internally as a 4l60e just mechanical? I've done some research and it seems so.

 

[Fitz4x4]

Also I didn't mention this earlier and I don't know if it matters but the axles are d60 up front and a 14bolt out back with 4.56 gears. Also the truck has about a 6in lift. I'm not really looking to so any hardcore rock crawling with it just trails camping and maybe (maybe) some of those great trips like Moab. I have little ones 6 and 7 that need to stay right side up in the truck so nothing to crazy.

 

[vwjay]

If that 700r4 is from a V6 it may not work. Most GM V6 engines used a 60 deg bell housing vs the 90 deg v8 bell housing, they're not interchangeable and won't bolt up to the other.

 

[TerryD]

Also I didn't mention this earlier and I don't know if it matters but the axles are d60 up front and a 14bolt out back with 4.56 gears. Also the truck has about a 6in lift. I'm not really looking to so any hardcore rock crawling with it just trails camping and maybe (maybe) some of those great trips like Moab. I have little ones 6 and 7 that need to stay right side up in the truck so nothing to crazy.

Thanks for the compliment! I've spent years thinking about my setup when I had my K5. I'm having to relearn everything about the Xterra now! If I can be honest with you, if you're not looking to do really hardcore stuff, you could sell your 6" kit and one ton axles and snag a SF 14b rear, a 3/4t 10b front and a 4" lift from ORD. That'd actually give you more ground clearance on 35's than your current 14bff on 38's has and lower your center of gravity a LOT. I know it's a bunch of work but it's a thought. That cyclone 700 should do you fine. In fact, the 6cyl converter should give you a slightly higher stall speed. It should have the updated valve body. I would have the 4L60E sun shell and band put in it though, along with a Trans-Go shift kit and hardened pump ring kit. Make sure you get the converter clutch working or you'll cook the transmission first time out. A B&M stacked plate cooler for it would be good as well.

If that 700r4 is from a V6 it may not work. Most GM V6 engines used a 60 deg bell housing vs the 90 deg v8 bell housing, they're not interchangeable and won't bolt up to the other.

The Cyclone was a 4.3L which is the same bellhousing as the small block.

 

[vwjay]

That's why I said may. There's almost always an exception.

 

[TerryD]

That's why I said may. There's almost always an exception.

I wish this forum had the thumbs up smiley. I feel like without it, people take me as condescending when I don't mean to be.

 

[Fitz4x4]

I received two stall converters with it. One I believe was the stock original and a 3000 stall new in box.

 

[Fitz4x4]

I hear what your saying about the axles. When I purchased the truck it came with them installed and the 10bolt and d44 in the truck cab. I have since sold the 10 and 44. Dammit! Ha

 

[TerryD]

Lord don't run that 3k one! You'll just be turning all your power to heat. I don't know your engine specs, but for most off-road use you don't want much over stock stall. There just isn't a real need for it. A lot of guys try to run grossly overbuilt engines on the trail and that's just bad times. Some rigs, like dedicated mud or hill climb trucks need that kinda stuff. Stuff you're gonna be driving around in like what it sounds like you want to do will be find with the stock converter or "towing" converter. I think the V6 converter will provide a slight increase in stall speed but still have good manners.

 

[Fitz4x4]

Vwjay if I decide to go auto I'll let you know about the sm465 and np205

 

[vwjay]

I wish this forum had the thumbs up smiley. I feel like without it, people take me as condescending when I don't mean to be.

Not at all, I took no offense.


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[Fitz4x4]

Hey guys thanks for all the great ideas and advice