71K5 - BP71K5's Just for fun build

[bp71k5]

bp71k5 submitted a new Build:

71K5 - BP71K5's Just for fun build

My buddy machining my custom radio parts was taking too long and I got bored without anything to tinker with on my truck so I decided a new tranny was in order. The trip to Moab was too painful in a 3-speed on the freeway.

I've always driven manual trannys and I like the idea of more controlled crawling over obstacles. In addition, I still have 3.07 gears in the axles and I plan on running those till they break. Plus manuals just seem like more fun and that is what a convertible k5 is all about!

I at first started ordering parts for a sm465 but learned that without overdrive, it wouldn't be much different than the th350 I had in it. So I sold the 465 stuff and started researching the nv4500 a few people had referred to.

The nv4500 is pretty expensive compared to the sm465, but not enough to discourage me. Somehow I think I only added all the costs up in my mind and not on paper. This allowed me to "forget" lots of stuff so it didn't seem as expensive as it is now turning out to be. I'm not sure I would have done it if I really did ALL the math beforehand. Oh well, this truck is just a reason to have fun getting filthy wrenching on something than for any real practical reasons.

And since I had a case of the "might as well's" I decided a doubler might as well be added since I'd have to mod the driveshafts anyway! This would give me a better crawl ratio to help make up for the fact I'm still running 3.07 d44 axle ( and I need it to have good freeway manners.)

It's a pretty stock 71 with a 4" lift.

View attachment 50599

Read more about this build here...

 

[bp71k5]

I started out by trying to find a used nv4500 on ebay or locally. It seems the west coast is full of auto drivers cause NO-ONE, I mean noone had even heard of a nv4500 and if they did, laughed when I said I wanted one used.

So I found a specialty tranny shop that had a guy who said he knew what I wanted and would build me one. He worked in the gear shop of this place so I figured I could trust him. He said he'd build it and then tell me what it would cost me. I called him every week for a month and he always said, "I'm still working on putting it together, try back next week". The last time I called his answering machine said, and I quote "I'm not home and don't want to be home. I'm hog hunting for the next month!". So I gave up on that guy.

Next, I found a used one with 200k miles on it in Maine on ebay. Turns out a guy in Norway beat me out of it at the last minute for $800. Shipping would have put this tranny at $1000 anyway so I just picked up a rebuilt one instead for not much more.

It's the early version with the extra low granny first gear.

 

[bp71k5]

I also bought a bellhousing from K5MonsterChev with an entire clutch system, and tranny adaptor. The only problem was that after I removed the tranny and test fit it with my small lift, the driveshaft was too close to the clutch fork area. I didn't want to go through all this work and time to have to pull it all out to fix a busted driveshaft later on. Damn!

So I put up the bellhousing on ebay and the guy who beat me out of the tranny (from Norway) bought it for more than I paid for it. Cool! I'd like to see what he's building over there. The clutch parts are good, but with all the money I've got into this now, I'm figuring I'll use new stuff to make sure everything is solid. I'll put the clutch pressure plate/disc up for sale in the parts section later.

 

[bp71k5]

Then I ordered a ORD doubler and while I was waiting for it, I bought a np203 rangebox from 1-tonmudder with the sm465 adaptor that I eventually sold to someone else. I tore it down, cleaned up the case, and painted it with some hi-heat engine enamel.

The picture is of the 203, 205 and tranny adaptor in the back of my 2001 VW storage container. They are waiting to go to 4x4high to machine the 203 to accept the nv4500 adaptor and to have the 205 input bearing bore enlarged for the 32spline input.

 

[bp71k5]

I figured it was time to pull the tranny out since I needed to rebuild the 205 to accept the 32spline input before I could do much else.

Now, I've never pulled anything as big as a GM tranny or engine before and all I have is a floor jack. I used to rebuild old VW motors a lot so thought I had some practice manuvering big objects on a little jack plate. Turns out I needed more practice cause I practically dropped the 205 onto the ground after I tried lowering it down. Luckily nothing was under it except a wood board I placed there to "catch" it if it did fall. No damage at all.

The tranny was much easier since it is long. I just put a big 2x6 under it and lowered it down while spilling a bunch of tranny fluid from the convertor.

I braced the motor with a piece of metal and some wood under the oil pan. I hope it holds!

 

[bp71k5]

I also got a clutch pedal assembly from Vintage Chevy Trucks up in Fremont. He can be kinda expensive depending on what you're looking for. But he has almost everything you could want. I ended up having to take the steering column out to replace the pedals. Big pain in the butt, but not complicated.

 

[bp71k5]

Then I disassembled the 205 so I could get all the machining done at the same time. I took pictures and bagged all the parts to keep everything organized. I didn't want to mix up any of the 203 and 205 parts which are all over the place.

I also got the ORD doubler and 205 32spline conversion kit a week after ordering it. Pretty cool! Stephan even called me before cutting the doubler to verify I ordered exactly what I needed and to give me some tips. I like buying stuff from a place that actually runs the stuff they sell on the kind of truck I have.

ORD also provided a template to use for drilling the 203 to accept the nv4500 adaptor. This was unexpected, but is really useful especially if I did not have an extra adaptor. The template will make it easier to ensure the hole pattern is right on.

 

[bp71k5]

Since I sold the old bellhousing, I ordered an Advance Adaptors bellhousing which I am told will be here in a week. Once that arrives, I can install a clutch and test fit the nv4500. It looks like it's only an inch or so longer than the th350 so it may fit pretty well. Stephen said I may be able to get away without any cutting of the body since a first gen has a little more clearance in that area. But he warned me that I might have to either use a body lift or some minor fitting. I'm trying to keep things "looking" as stock as possible in the interior so I don't want to do any major mods to the inside.

Also, just because I like to do things the hard way, I'm also trying to figure out a way to avoid using multiple shift sticks for the doubler. I'd like to fab up something to get the function of a triple stick with only the single stock 205 transfer case lever. I have some ideas, but nothing prototyped yet.

The idea is to allow the lever to be moved right and left (in addition to forward and back) just like a manual tranny. Left (+forward/back) would control the 203 hi-neutral-low. Center position (+ forward/back) would control the rear output of the 205. Right position (+forward/back) would control the front output. Anyone have any opinions on this concept? There may be something obviously wrong with the idea and everyone here seems to be pretty smart about this kinda stuff so let me hear about it if you think it's a bad idea (or good!). I know it might be difficult to know what "state" all the gears are in with this setup, but I figure if I can make everything else work, that shouldn't be too hard to deal with.

Since I'm about done with the "money spending" portion of the build, that's it for now while I wait for the bellhousing or my radio parts to get here. I'd also like to get all this done before BB07 so I can break everything on a trail!

 

[4X4HIGH]

Now would also be a good time to replace that leaking freeze plug on the driverside rear of your block. Do the passenger side plug while you're at it also.

 

[bp71k5]

Good call! I've been so busy with all this other stuff, I hadn't thought to try and figure out where the oil leak was coming from.

 

[4X4HIGH]

That is a water leak not an oil leak. If you also have an oil leak now is also the perfect time to do a rear main seal. Not too bad of a job but totally doable.

 

[bp71k5]

Errr, of course you're right. I shouldn't reply to messages when I'm still half asleep.

 

[68MUDSTUD]

*subscribing* lookin good man!

 

[sweetk30]

a simple idea for 1 stick 3 stick . you might be able to mod a 6 speed manuel shifter to work as a 3 stick possibly. or not. just a idea to look into.

 

[Yukon Jack]

Great project - I would love to get an overdrive into my K20 at some point.

 

[bp71k5]

Yea, I'm planning to tour some wrecking yards to see if I can find anything that might allow single sticking the doubler.

 

[bp71k5]

The overdrive should be a nice addition. The one quote for a rebuilt 350 was almost the same as the 5 speed. There's a bunch of other stuff you have to deal with for the 5 speed so the overall cost is more, but the trannies themselves aren't that different in cost. (Unless you buy one new).

 

[vtblazer]

That's going to be one of the best mods you'll ever do to the blazer!

Nice job and well thought out.

 

[Greg72]

Great Thread!!!

I'm always interested in topics that are a little "off the beaten path"....that radio mod definitely qualifies, and an NV4500 is a pretty obscure swap, especially in a 1st Gen!!

Couple Questions:

1. How long is the NV4500 compared to the slushbox you pulled out? Shorter?

2. Have you figured out your crawl ratio with the new setup yet? I'm imagining the NV4500 has a real deep 1st gear to help you offset those freeway flier axle gears?

3. What sort of highway RPMs are you expecting to see with this swap?


That's all, let me know when you wake up!!

 

[bp71k5]

1. How long is the NV4500 compared to the slushbox you pulled out? Shorter?

K5MonsterChev had exact numbers, but the overall length is ~ 1" longer if you are replacing a th350/np205 combo (if you don't count the doubler). Since I'm adding a doubler, the 203 adds another 6". I can measure exactly, but that's from memory.

2. Have you figured out your crawl ratio with the new setup yet? I'm imagining the NV4500 has a real deep 1st gear to help you offset those freeway flier axle gears?

Not yet. The 1st gear ratio is 6.34:1 on the version I got. I'm still on 33's but may move to 35's at some point depending on how long the axles last. I've been avoiding installing a locker to keep the axles from breaking cause once that happens, I'd need gears, 14bff, and all that stuff.

3. What sort of highway RPMs are you expecting to see with this swap?

Funny, one of the reasons I started looking at a manual was so I could have an excuse to buy a tach. I don't know what the RPM's were, but I couldn't travel faster than 70mph on the freeway without feeling like the motor was too hot. 55 mph was more like the fastest sustainable speed I could do. Faster than 70 is maybe not a good idea anyway in a lifted truck.

The parts are out for machining now, so I'm stuck fixing some oil leaks and mundane problems getting ready for them. One problem with this kind of thing is telling the parts store guy enough information to get the parts you want, but not so much that he gets confused and think's I'm an idiot. That happened when I told him I wanted a 12" clutch flywheel in a 71 blazer, but that I would be using a 95+ bellhousing. The look on his face was funny since he was trying to be polite, but obviously thought I was insane.