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My NV4500 swap

shotty

Active member
211
55
28
Location
Northern VA :(
Earlier this year I started work on swapping an NV4500 into my M1008. I found that there was a lot of threads about this but very few went into all the details with the info I needed. This thread will not really go into details either, as erasedhammer already did an amazing write up in his thread here. Instead, I will document the things I did differently and the issues I faced. His thread wasn't a thing when I started and I only discovered it towards the end of my swap. It's an excellent resource and I highly recommend you check it out and then continue here.

Truck Stuff

So we ripped out the auto trans, as well as the vacuum pump and the vacuum lines that go to and from the injection pump for controlling the transmission and the cooling lines that go between the transmission and radiator. I installed a GM 6.5 engine speed sensor in place of the vacuum pump, and I modified the old vacuum pump into an engine oil priming tool. I removed the steering column and cut the shifter arm off right at the base. I left the bottom of the arm in place so that it would lock itself in park and not rattle around like it will do if you completely remove the arm. I also cut the tab off at the bottom of the column that would operate the shift linkage and remove all the linkage too of course.

For the pedals, I bought a set of hydraulic clutch/hydro boost brake pedals from ebay and paid way too much. Erasedhammer says you can swap your hydroboost brake pedal from your stock assembly onto a set of vacuum assist pedals from a manual truck. That can save you a couple hundred dollars, so do that. The clutch pin on my pedals had almost a 1/4" notch worn in it, so I welded that up and filed it smooth. I also got new bushings for the pedal assembly (gm #346381) and a new rubber bumper ( GM #12338127), cleaned and painted everything , and put it back together. They look brand new.

I was able to find the two dimples in the firewall on the engine side for the clutch master cylinder support rods. My wife made a template for the clutch master cylinder so I knew where to drill the center hole. She used some paper and the master cylinder to make what was basically a gasket for it, and then using the dimples in the firewall I positioned the template and marked for the center hole, then drilled all three holes. Everything lined up great. Took a bit of fighting to get the pedal assembly in but eventually it went.

I used the stock clutch master cylinder, slave cylinder, and even the clutch line for an 84 Chevy. Erasedhammer used the same master and slave setup but used a braided stainless line with AN fittings on it and AN adapters for the cylinders. I recommend you do that as the stock line is kind of a pain in the butt to get in there. Unrelated but I plan on doing this for all the lines/hoses on the truck as it's a lot easier to find or make an AN hose than it is to deal with custom oil or power steering lines.

I had to unbolt the master cylinder to get the clutch line threaded in and just generally mess with it a bunch to get everything connected. A braided line would be a lot easier and not cost much more, if at all. For the master cylinder reservoir I just snagged some random one off ebay, I think its for an 83 to 93 S10. Not real critical, just get something you can mount somewhere with a host that isn't very big.

To bleed the system, i put some fluid in the reservoir, then unbolted the slave cylinder from its mount and let it hang with the bleeder cracked. After a few minutes fluid started flowing out so I closed the bleeder. Then, with the cap off the reservoir but the reservoir full of fluid, I pushed the rod on the slave cylinder all the way in, forcing the air up the line. Slowly let the rod back out and add fluid up top if needed. Do this a few times and you will have a perfect bled clutch without any pedal pumping/bleeder cracking shenanigans.

Trans Stuff

I used a 1993 NV4500, which requires a different bell housing from advance adapters. I needed the 712577 kit to work with the early style (low first gear) transmissions. Also get the hydraulic clutch kit for the bell housing from advance adapters.

Rebuilding the transmission was.. expensive. I had to replace the input shaft, counter shaft, and main shaft. I also replaced a few gears due to chipped teeth. Being an early model trans there isn't many options for replacement gears and you need specific parts just for it. The later models used different shaft(s) so pay attention when ordering. I got a full rebuild kit as well, with new bearings seals, spacers, etc. This all came from torque king and I used their manual to rebuild it. I also snagged the damper that goes on the main shaft, its a big round weight with some rubber in it. GM started using these in later models to fix vibration issues so i wanted to try and find one (gm #15635329). I was successful and also installed that.

While I had the transmission apart, I did few modifications/upgrades. I removed the shift interlocks on 1st and 2nd gear. These prevent you from shifting into those gears at too high of a speed. I was concerned that the springs may break one day, locking me out of those gears entirely, and as GM eliminated these in later model transmissions they must not be too critical. My solution is to just not downshift into those gears.... To eliminate them you just leave out the springs and weights, easy peasy. I also added a synchronized reverse gear. This required a new main shaft gear, a synchro, reverse gear clutch, and the struts/springs for the clutch. It's the same as dealing with the struts and clutches on the other gears, you just swap in the new parts when reassembling.

I topped it off with a new late model top cover. The early model trans has an integral shift tower which is a pain to deal with. It gets in the way when installing the trans and the late model has a removable cover which you can use to peek in the trans, add oil, install the trans without it getting in the way, etc. There's also more parts available for the later top covers. While there are a lot of different internal differences for the various year models, you can swap one complete top cover for another without issue. In my case I bought a 96 and up Chevy top cover and it went on no issues. When I installed the trans I put a few layers of tape over the shifter opening in the top cover and left it there until the hole in the truck was cut so I could be sure it was perfect. Instead of the factory vent tube setup, I tapped the hole in the top cover for 1/8 NPT to 1/4" hose barb and used some cheap 1/4" fuel line run up into the engine compartment. I did the same for the breather on the transfer case.

For a clutch, I went with the Advance Adapter recommended Centerforce setup for clutch, throw out bearing, and pressure plate. This worked out alright but I would recommend you just use a 6.5 clutch, and I think a 6.2 clutch is basically the same as well. Our engines don't produce the kind of power that you need for an 'upgraded stage 1' clutch, but I didn't want to have issues with this install so I just used what AA said to. It works fine, but I noticed the clutch that came out of truck I got the trans from had more springs in the hub and probably plays nicer with our diesel engines. Regardless, the Centerforce clutch works so that's what I'm using now.

Important Notes

The pilot bearing does not go in flush with the crank like it would normally. Advance Adapters states that some applications may need to leave the pilot bearing 3/16" out of the hole. I did some measuring after bolting up my bell housing and decided to leave my pilot out that much as well. It could probably benefit from a little bit more but I don't want to mess with things too much. I plan on inspecting the clutch and pilot in a few years/miles so I'll adjust from there. A failed pilot bearing is probably the #1 cause of issues with these transmissions. When I got the trans the tip of the input was chewed up from a failed pilot bearing, which causes the input shaft to wobble and then destroy the gear on the counter shaft. Take care of your pilot bearing and it will take care of you.


You must use a 1" thick flywheel.
That means a 6.2 flywheel, not a 6.5 single mass. I started this adventure using a LUK replacement flywheel for a 6.5 but it was thinner than 6.2 model. The advance adapters bell housing is setup for a 1" thick flywheel and if you don't use that the clutch fork will not have enough range of motion for proper operation and will probably bottom out on the bell housing. There was a couple different flywheels for the 6.2, you want casting #14050525 that weighs close to 50lbs. I believe the LUK flywheel for the 6.2 is correct and that's what erasedhammer used. I got one from autozone based on the casting number and it was correct as well.

The push rod that comes with the Advance Adapter kit for the hydraulic clutch is too long. You can use it but you need to take 1/4 or 1/2 inch off it. It's easy to get to and mess with so take it slow until you can get the throw out bearing clearance right with the clutch disengaged, but still long enough to get full clutch disengagement. Honestly, I would just get a piece of all thread and make your own so you have more adjustability, that's what I'm going to do (eventually™). The supplied rod would be fine if the threading on it went deeper but since it doesn't you have to shorten the unthreaded end.. It's kind of a pain but that's what their tech support told me to do and it worked.

Overall

After sorting everything above we were done with the swap and took the truck for a test drive. At first, it would not shift into 3rd or 4th after shifting into 5th until I shifted into reverse. Not sure if this is just because of the aftermarket (chinese) top cover or what. Eventually I fixed it by driving it, shifting into 5th, then stopping in neutral and kinda forcing it into 4th while stopped. I did that twice and its been fine ever since.

Another potential issue is 3rd gear can be kinda picky to shift into unless the RPMs are.. not necessarily high but shifting at a low RPM (trying to keep the truck quiet in the neighborhood) it doesn't like to hit 3rd. Sometimes it shift perfect though. Also downshifting into 3rd can be a little bit of a pain sometimes. It's gotten better over time and while it may never smooth up as well as the other gears its not bad enough to warrant taking the trans apart. I suspect it may just be the way these early transmissions are, who knows. Maybe the problem is with me (this aint no sports car transmission like I'm used to).

Lastly, there is a noticeable growl at idle in neutral. This is normal from my research and just adds to the wonderful ambient sounds in these trucks...

Driving without a shift boot is LOUD. I still don't have one because I want to fabricate a transmission mounted transfer case shifter setup to move it up next to the transmission shifter, then get a custom double boot setup made. For now I just have a towel wrapped around the base of the shifter that keeps the sound down quit nicely.

I also rebuilt the NP208 transfer case while it was out. While the documentation for doing that isn't too great, theres plenty of youtube videos that show you how, and if you can rebuild the nv4500 the transfercase will seem easy. I added a synchronizer ring from a later model np208 just to eliminate any wear from engaging 4wd at speed, which should be minimal anyways but while I had it apart.. might as well, right?

All in all I'm very happy with the swap. I can now cruise at 75mph at the same RPMs I was at doing 55mph before. The truck is a little underpowered in 5th on hills but most of the time it can pull fine. I don't have a lot of pictures of the swap like erasedhammer does, but I do have a few I'll work on posting in the future or if anyone has questions.
 

SuperAwesomeDOOD

New member
20
17
3
Location
Cool, CA
I have my trans /tcase installed (96+ nv4500 w/ AA b/h and hydro clutch bracket—all clutch components are direct fitment for 85-87 per their verbal instructions). What a pita by yourself on a poor surface, lol. Everything slid together without forcing, but I feel like the throwout lever doesn’t engage the pressure plate fingers at all through the range of motion. It’s easy to move by hand without the hydraulics hooked up. I’m pulling the rubber boot to look inside with a snake cam in the morning. I’d hate to have to drop that thing again. Took me 5 hours to get in.

Fingers crossed it’s an adjustment issue.
 
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