NV4500 5 speed 3rd gear synchro going out? 1994 K3500

[jrsavoie]

NV4500 5 speed 3rd gear synchro going out? 1994 K3500

It seems the 3rd gear synchro is going out in the 1994 K3500. That is a NV4500, correct?

I've never torn into a transmission or differential before.

The trans is grinding going into 3rd gear. If you don't rev up to normal speeds in 2nd and shift excrutiatingly slowly the grinding can be avoided.

Can anybody give me advice or parts numbers for what will be needed?

How big a job is this? Is this best left to a guy that knows trannys well?

Any advice would be appreciated.

If there is a better place to post this or a link to a how to, I would much appreciate a heads up.
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[tRustyK5]

Mainshaft assembly will need to come completely out. Then dis-assembled part by part from the rear until you can get to the 2-3 synchro and replace it. Frankly you're best off to replace all the synchro's, seals and bearings at that point.

I rebuilt my NV4500 after getting it as a grenaded basket case. I replaced a sh1t ton of parts with the exception of the very synchro you are having issues with. It looked 100% A-OK unlike the rest. I have a very slight grind going into 3rd gear...not bad and it may get a bit better with some more miles on it bit it is there and I had to shift a little slower into that gear for the 200 or so miles I put on it. For obvious reasons I never tore it back down to deal with it.


Rene

 

[jrsavoie]

Thanks

Can you give me a heads up on what to buy and where?

Do they make a master rebuild kit?

Do they make aftermarket kits that are better than OEM?

 

[tRustyK5]

Check www.quad4x4.com

This page will get you closer. http://quad4x4.com/NV4500_Parts.html

Factory the synchros have a kevlar lining, but they also make all brass synchros which is what i used for the ones I replaced. I got all my NV4500 parts through Northwest Fab. They were able to match or beat pricing I could find online and got me the parts pretty fast. Quad 4x4 has a good visual of the parts available.

Rene

 

[DEMON44]

the upgrade aftermarket nv4500 kits have a fully splined mainshaft.

 

[jrsavoie]

Great link. Thanks a bunch

We keep our vehicles forever. I only want to do this once. Any ideas for better chances of longevity are appreciated.

This trans only has 240,000 miles.

The trans in my International has 500,000 & the Getrag 5 speed in my 89 had 800,000 miles on it.

I am pretty disappointed in the performance of this transmission

 

[tRustyK5]

the upgrade aftermarket nv4500 kits have a fully splined mainshaft.

I'd have a look at whether the original was showing any signs of fretting before laying out the money for that...unless the intended application included a big torque powerplant and a lot of towing. Big tq, heavy load being towed in 5th is the recipe for fretting against the 5th gear nut and having it loosen off.

I went with a stock nut, but my NV4500 also has the vibration damper between 5th gear and the nut so gear fret is much less of a possibility. I was also running a NA 6.2 and didn't tow.

Rene

 

[jrsavoie]

I run about 9100 GVW almost always. The truck is usually loaded with tools

 

[tRustyK5]

Dis-assembly will tell you what you need. I did mine at home with basic tools other than a pair of burly snap ring pliers i had to buy. Pretty much everything else was straight forward.

Rene

 

[DEMON44]

I didn't suggest he needed it, just that this is about the only upgrade worth a damn.

 

[tRustyK5]

I know, and I wasn't saying he didn't need it either. There are a lot of aftermarket 5th gear nuts, but none address the actual problem like the replacement mainshaft with full splines.

rene