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NV4500 rebuild

Winchested

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Holy thread necro here,


I'm currently rebuilding one of these GM NV4500s it's a 95.

The mainshaft output splines are toast as were the Np241 input splines. The 5th gear nut was loose, I used a Chevy 1/2 ton 4x4 spindle socket fits perfect. Was only $20 bucks compared to the $200-300 they want for the proper socket. But was hand tight.

This has the damper on it which I'm going to say is possibly what destroyed the output splines.

Should I re use it or cannibalize it for the center section and just run it as a spacer?

This will be going behind a 5.3 or 6.0 LS with an NWF doubler and NP205.

I plan on buying the transparts Warehouse kit. As it's the cheapest I can get into Canada for the early GM nv4500.


Someone early mention SMF? What the eff is that?


Thanks for any pointers.20220405_171229.jpg
 

MrMarty51

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Holy thread necro here,


I'm currently rebuilding one of these GM NV4500s it's a 95.

The mainshaft output splines are toast as were the Np241 input splines. The 5th gear nut was loose, I used a Chevy 1/2 ton 4x4 spindle socket fits perfect. Was only $20 bucks compared to the $200-300 they want for the proper socket. But was hand tight.

This has the damper on it which I'm going to say is possibly what destroyed the output splines.

Should I re use it or cannibalize it for the center section and just run it as a spacer?

This will be going behind a 5.3 or 6.0 LS with an NWF doubler and NP205.

I plan on buying the transparts Warehouse kit. As it's the cheapest I can get into Canada for the early GM nv4500.


Someone early mention SMF? What the eff is that?


Thanks for any pointers.View attachment 73711
I know knott one thing about transmissions, just bounced in to say welcome to the forum Winchested.
 

DieselAmateur

She ain't revved 'til the rods are thrown...
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SMF might mean Solid Mass Flywheel (as opposed to Dual Mass Flywheel)

There was another question on here about the dampener being necessary or not. I'm no expert so don't take anything I say as gospel. But I think the damper was more for diesel trucks, so if this transmission is going behind a gas engine I'd say you can let go of the damper in case you think it was problematic. They sell a spacer in its place that is way cheaper

The main shaft splines are a known weak point in these transmissions. If rebuilding the best you can do is install a new mainshaft. And get an upgraded 5th gear nut with set screws and use red loctite to hold the nut in place

Rebuild manual for the NV4500 here


good luck!
 

MrMarty51

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Thanks for the welcome Mr Marty and thanks dieselAm! I think I'm going to build it without the damper.

Ill be using an 04/05 LS flywheel and clutch. External slave and TOB.

Its all going in a 79' IH Scout SSII.
My son has two IH Scouts. 196?, one is a special built unit.
Do a search for IH Red Carpet Special. The one He has came out of the Lewistown Montana dealer.
 

Winchested

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My son has two IH Scouts. 196?, one is a special built unit.
Do a search for IH Red Carpet Special. The one He has came out of the Lewistown Montana dealer.

Awesome yes I know what the RCS very hard to find any that survived in one piece.

The later year scouts 67+ could of had a 152 196 266 or 304.

Mine has a very tired 345 that I topped with a 91' suburban TBI EFI setup. It runs great but it's not worth rebuilding.
 

ruger454

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Winchested... I am in the process of tearing down my nv4500 after it decided to start making a quick grinding noise and then slamming into 4 gear when I had shifted it there. Grind only lasted a second and then a bang but got it torn down and gears and synchro's look good. But little history on trans. Top shifter bolts had back out and shifter popped up and lost over half of it's fluid. Input shaft got hot and melted pocket bearing (plastic caged) that got into 4th gear synchro. Pulled out plastic and inspected and replaced pocket bearing and I reinstalled everything. That was 6 months ago. Now it did It's bump and grind. But during inspection, I noticed the 4th and reverse gears have a small hole down in between the teeth 120 degrees apart. Those holes on 4th gear were stopped up with the small pieces of melted plastic. Do you think this could have caused the problem with shifting into 4 gear or can you tell me what you think happens when these holes are stopped up. I need all the help on this that I can get...Thanks ahead of time...
 

DieselAmateur

She ain't revved 'til the rods are thrown...
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If it's grinding between gears, then the synchros were/ are most likely shot. Especially if it ran low on fluid and got hot enough to melt the pocket bearing. Also if you don't know the history on the trans then it's very likely that at some point in its life the incorrect gear oil was used which also leads to premature synchro wear

If it were me I'd replace everything I can while I'm in there, do it once do it right. It's a pain to pull the trans any way you slice it so as my old man used to say the more you do now the less you do later...

With regards to the small holes in the gears, do some looking around on the Torque King 4x4 website, they have tech articles specific to this transmission. Or give them a call, the few times I've called with questions about parts they were very helpful in terms of taking time to discuss how everything works and whatnot.

finally make sure you use the correct fluid for this transmission, GM part # 12346190
 

ruger454

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Will, this trans was put in brand new quite a few years back but has less than 25,000 miles on it. The synchros are brass and still look great but after pulling top shaft and getting a better look at the gears, I have some roughness on 4th gear and bottom shaft large gear up front is rough also. So looks like I will be replacing 4th and the bottom shaft and I think that will take care of it. That isn't going to be cheap by any means. I think with those holes being stopped up that is what caused some oiling issues and that is what happened to 4th gear and the counter shaft. This trans worked so great up until that top loader decided to pop loose and lower my fluid amount but I just hope I can get things going quick. I am supposed to be moving down to Arkansas within the next week or so. Just sold my house and now I have to move. 500 miles down to a new start.
 

DieselAmateur

She ain't revved 'til the rods are thrown...
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The synchros have a friction material on the inside of the brass ring that can wear out quicker than the teeth themselves. This is what slows the input shaft down and allows for smooth shifts. This is why the correct fluid is so critical. Incorrect fluids will cause premature wear and failure of this material.

I also highly recommend a transmission temperature gauge. I use PTO cooling fins on mine which come with a port for a trans temp probe.

Good luck with the move and best wishes for your new start :)
 

ruger454

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I had to order a counter shaft and input shaft so the money is flowing out now... lol. I am closing on my house in 3 days on the 10th. and just hope that the guy buying it will allow me to finish my truck up and then move all this stuff out of my 51 x 30 shop and its a heck of a lot in here. So thanks for thinking of me and may God bless us all. In this time we are in right now everyone needs some help from our economy and gas prices..
 

smokymtn65

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The synchros have a friction material on the inside of the brass ring that can wear out quicker than the teeth themselves. This is what slows the input shaft down and allows for smooth shifts. This is why the correct fluid is so critical. Incorrect fluids will cause premature wear and failure of this material.

I also highly recommend a transmission temperature gauge. I use PTO cooling fins on mine which come with a port for a trans temp probe.

Good luck with the move and best wishes for your new start :)
More on the PTO cooling fins?
 

DieselAmateur

She ain't revved 'til the rods are thrown...
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@smokymtn65 here's a link to what I have on my NV4500. As noted in my sig you have to shave down the fins a tad on the driver side so the driveshaft clears as these were meant for Dodge NV4500 trucks


These coolers are also for the NV4500 and as far as I know will fit without having to do any modification. The link is for just the coolers where you re-use your existing PTO covers. They sell a more expensive kit with a sight glass and matching covers.


I went went with the first option because the fin design appeared to be more efficient in cooling, a sentiment also echoed in this thread where I came across them in the first place

 
Last edited:

smokymtn65

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@smokymtn65 here's a link to what I have on my NV4500. As noted in my sig you have to shave down the fins a tad on the driver side so the driveshaft clears as these were meant for Dodge NV4500 trucks


These coolers are also for the NV4500 and as far as I know will fit without having to do any modification. The link is for just the coolers where you re-use your existing PTO covers. They sell a more expensive kit with a sight glass and matching covers.


I went went with the first option because the fin design appeared to be more efficient in cooling, a sentiment also echoed in this thread where I came across them in the first place

Thanks
 
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