Nv4500 teardown and rebuild

[SquareRoot]

I just started the teardown and complete rebuild of my unicorn 94 nv4500. If anyone is interested in this endeavor let it be known and I will document and post pix.

 

[Juggernaut]

I rebuilt my NV4500 about 5 years ago. Used a manual from 4x4repairmanuals.com. It was one of the easiest rebuilds I have ever done. The manual was very detailed and step by step. If I had it to do over, I would have used gaskets and gasket adhesive instead of Permatex black RTV on the gasket surfaces. Even though I wiped all the surfaces down with grease and wax remover, the main housing started seeping oil soon after I started running it. Maybe I should have used a different type of RTV? Good luck with the rebuild!

 

[Vbb199]

I just started the teardown and complete rebuild of my unicorn 94 nv4500. If anyone is interested in this endeavor let it be known and I will document and post pix.

While im not a manual transmission person, i would be interested in a teardown with videos/pics. Tag me in a post if you create one so i can follow it.
I have taken apart and built some automatics enough to say "ive gotten my hands dirty and can build a decent one" but i havent ever taken apart a manual really... just popped the covers on a few to see the insides and how they work.

Is this the one you have in your truck now? Already? Or a replacement ?

 

[SquareRoot]

I rebuilt my NV4500 about 5 years ago. Used a manual from 4x4repairmanuals.com. It was one of the easiest rebuilds I have ever done. The manual was very detailed and step by step. If I had it to do over, I would have used gaskets and gasket adhesive instead of Permatex black RTV on the gasket surfaces. Even though I wiped all the surfaces down with grease and wax remover, the main housing started seeping oil soon after I started running it. Maybe I should have used a different type of RTV? Good luck with the rebuild!

Curious. Did yours have the harmonic balancer on the tailshaft? If so did you buy any "special" tools to remove/install it along with the 5th gear?
I was able to get them both off with a 3 jaw puller and part of a bearing separator tool. Putting them back on is going to be another story.

 

[SquareRoot]

While im not a manual transmission person, i would be interested in a teardown with videos/pics. Tag me in a post if you create one so i can follow it.
I have taken apart and built some automatics enough to say "ive gotten my hands dirty and can build a decent one" but i havent ever taken apart a manual really... just popped the covers on a few to see the insides and how they work.

Is this the one you have in your truck now? Already? Or a replacement ?

It's not the one currently in the truck. However, that one was used but shifted good but the bearings are starting to rattle and the syncros on the 2-3 shift are dragging a little. Fortunately, I found another one out of a 94 that is the one year only option. Unlike the 93 that's in there, the 94 has the higher 1,2 gears which I will much prefer for street driving. As it it, I start off in second-sometimes third gear and its a little annoying. The higher gear version will be better suited to the 4:56 gears. Fortunately, their both the "early" pattern and use the same bellhousing, despite the upgrade to the higher gears and the top shift tower is removable making install way easier in the floorboard.

 

[Vbb199]

Owning 2 GM nv4500's at the same time would make you a god here.... its impossible to even obtain 1

 

[Juggernaut]

Curious. Did yours have the harmonic balancer on the tailshaft? If so did you buy any "special" tools to remove/install it along with the 5th gear?
I was able to get them both off with a 3 jaw puller and part of a bearing separator tool. Putting them back on is going to be another story.

Yes, mine has the damper. I pulled it off with a cheap bearing separator from Harbor Freight. You will also need a good, heavy duty snap ring plier for removing the flat ended snap rings.

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There's a tapered roller with a race in a blind cavity you won't be able to remove with a punch. Best way to get it out is to run a weld bead around the inside of the race, let it cool and it will fall right out. Make sure to cover everything to keep weld splatter off. Aluminum foil works well for this. Only other thing I can think of is a dial indicator and base to set your end play.

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[SquareRoot]

Yes, mine has the damper. I pulled it off with a cheap bearing separator from Harbor Freight. You will also need a good, heavy duty snap ring plier for removing the flat ended snap rings.

You must be registered for see images attach

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There's a tapered roller with a race in a blind cavity you won't be able to remove with a punch. Best way to get it out is to run a weld bead around the inside of the race, let it cool and it will fall right out. Make sure to cover everything to keep weld splatter off. Aluminum foil works well for this. Only other thing I can think of is a dial indicator and base to set your end play.

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Thanks for that info. How did you install the rear bearing? I'm thinking dry ice on the shaft, heat the bearing and "tap" it on with a piece of pvc and a hammer?

 

[Juggernaut]

Ok, you asked, so I'm going to tell you. But you are not going to believe me. First, dry ice is best, but if you don't have dry ice, just put the shaft in the freezer for a day. You won't be able to freeze the countershaft because the bearing goes on after installing the shaft in the housing. So here's what you do with the cone. Soak a hand towel in water and fully wrap the wet towel around the bearing. Don't leave any exposed metal. Now here's the unbelievable part, put it in a microwave for about 1-2 minutes. If you have an infrared thermometer, you will want the bearing around 250-300 degrees. If you don't, you can do what I do, the "sting test". Slap your bare hand down on the bearing and pull it off immediately after. If your hand stings, it's hot enough. If it didn't get hot enough, nuke it a little longer. It depends on the size of the bearing. Use a good pair of welding gloves, the bearing will slide right on. Have a piece of plastic pipe ready if it's not quite hot enough. It should take only a couple light taps, but I didn't have to tap on any of them. Blow the water off with compressed air and oil it to keep it from flash rusting

 

[SquareRoot]

I like Redneck engineering. Don't underestimate my resolve to drop the whole damn trans in the deep freezer I have in the garage. Lol. I was thinking dry ice and my propane torch might get r done.

 

[Juggernaut]

I hate seeing guys heating a bearing with a torch. It heats the bearing unevenly and there's too big a chance of damaging the cage. You should only use an induction type bearing heater, but who can afford one of those! If you don't want to try the microwave trick, you would be better off hammering it on with a piece of soft tubing the same size as the inner race, or use a brass punch. It's not a super tight fit. Just my opinion, and 5 years experience rebuilding gearboxes at an electric motor shop

 

[Juggernaut]

One other tricky part to the NV4500 assembly I just thought of is the first/second synchronizer. There are 4 little springs and 4 little plates that have to be compressed and the synchronizer sleeve slid up over them. I had those springs pop out and fly off several times before I finally figured it out. The springs are tiny and can fly a long way, so keep a clean work bench so you can find them. Be patient, it may take a few tries, but you will figure it out. Or maybe you will be like me and start throwing tools and complain about engineers!

 

[SquareRoot]

Opened her up and staring at her guts. Actually, the parts in this thing are massive! However, after a few beers and an hour or so staring at it, it looks pretty straight forward.