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The NV4500 transmission is found in some Dodge and Chevy trucks and is known to have issues with the 5th gear retention nut to back off over time..........here is one fix as a last ditch effort.

yesterday I had the pleasure to work on a friends 97 Cummins with the famous NV4500 5th gear issues

It has been a problem for years of the retention nut on the mainshaft to back off allowing the 5th gear to slide out of place

My friends 97 had this happen once so he purchased a new 5th gear and modified retention nut with 3 set screws in place to secure after the jam nut was fully torqued ..................needless to say I aint real impressed with how well it worked as it only lasted 2 years till he had no the gear again

So after consulting with my friend he opted not to but the new upgraded mainshaft , 5th gear and retention nut but reather went for a new gear and nut with set screws and had me tack weld the jam nut after torquing it down inplace

First thing we did was to pull the truck into my nice heated garage since it was -3 outside....had a couple cups of coffee then dove in with both feet

we removed both drivelines, then drained the oil from the t-case and transmission.....pulled the t-case out and set it out of the way then removed the tailhousing from the NV4500 to expose a retention nut backed off all the way and a real sloppy 5th gear ........removed that and installed the new gear and nut then with a special socket to fit the mainshaft and a 2 foot breaker bar and a 3 jaw socket to fit the nut we torqued the new nut down to as much as we could ...............then run the 3 setscrews into place ..................cleaned up the area real good to be be free of oil residue and built a cardboard backer plate to shield the welding splatter........I tacked the nut to the mainshaft in 3 places .....the nut aint backin off and the heat exposure was mimiumal since it was with a MIG wire feed and very quick............I quenched the final product with oil and we buttoned up the truck so it could hit the road.

Do I recommend this proceedure................NO

however I spose it will buy my friend some time so he can build funds to purchase a new mainsaft and do this right.................in other words this time when the 5th geasr fails it only has one fix...........I simply hope that when it does fail it doesnt damage anything else in there in the process

here are some pics of the final result as well as a pic of the new gear, washer and nut





 

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I'm really baffled as to how many times it has to be explained on this website that 5th gear nut has never, ever in the history of the NV4500 backed off. The nut does not turn! The material where the gear and shaft and gear and nut meat fretts away in use and the gear becomes loose along with the mainshaft bearing clearance and reverse gear gets to slam back and forth on the mainshaft.

Welding the nut accomplishes less than nothing, it just makes it harder to take apart when it does let loose.
 

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Discussion Starter #3
what can I say....the nut was backed off all the way to the end and the gear was allowed to just slop around

I guess I was seein thing then
 

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Discussion Starter #4
Another friend of mine has had luck here

I doubt he'll ever have a problem with that again. My buddy brought his NV over to me a few years ago ad I did the same thing. 140k miles later at about 520rwhp and he's still goin strong.
 

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With the setscrew nuts you don't have much by way of reference point, but many NV4500 shafts have a keyway and nut with a peen-in locking collar.

It's pretty clear when you take them apart and you have .080"+ of 5th gear movement and the nut(s) are still peened in the factory position that the silly nut didn't loosen whatsoever.

What kind of nut design did you have that was loose on the shaft? The early single nut with set screw?
 

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Discussion Starter #6
the nut I took of was the latest and greatest with the 3 set screws.........exactly like the new one I put back on


that pic of the nut gear and washer is actually the old ones I took off..........you can see on the inside of the nut one of the retention screws
 

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There are dozens of new venture and aftermarket nut designs. The single nut with set screws can move on the shaft once the gear comes loose and starts banging back and forth into the nut. Transmission mainshafts are case hardened to the high 50's. Tiny little set screws don't do much in comparison to the forces slamming 5th gear fore and aft.

Quality 5th gear, mainshaft and nut sets have double or triple nuts, typically with peen-in locking collars. The only time I've got a single nut/set screw setup is with buying the cheap chinese mainshaft/gear/nut sets.
 

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I'm really baffled as to how many times it has to be explained on this website that 5th gear nut has never, ever in the history of the NV4500 backed off. The nut does not turn! The material where the gear and shaft and gear and nut meat fretts away in use and the gear becomes loose along with the mainshaft bearing clearance and reverse gear gets to slam back and forth on the mainshaft.

Welding the nut accomplishes less than nothing, it just makes it harder to take apart when it does let loose.
The nut does back off, it is caused mainly from lugging it in fith gear, I have seen close to 100 of them. The nut will be backed completely off the threads, that's why Dodge started making the nut with a split and a screw to tighten it on the shaft for better thread contact. Welding the shaft can cause it to break if not done correctly. The only true fix would be to make a shaft with left handed threads. I don't know where you got the idea the nut doesn't back off but that is completely incorrect. My sons 97 has done it, the nut was replaced by the factory the first time with the split nut at 120,000 miles and I had to tighten it back up yesterday when he lost 5th at 230,000 miles. There is no play in the gear so I tightened it back up and used "loc-tite" to help hold the nut. I am a welder but will not weld nut until I have time to tig it in 4 spots letting it cool between welds.
 

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Yea mine backed all the way off put it back on and used loctite green been good for 3 yrs now
 

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yeah, af250 is out in left feild with that statment.

ill tell you right here and now that they will back off/unthread and it is exactly like 63chevies said, lugging the motor low on the rpm.


it rattles the trans and the whole nine yards. with the way most modern drivers want their rigs now is to get the lowest possible rpm at maximum speed. 1400rpm @70/75/80.

i dont do tranny work and ive fixed one.
 

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nuts

2 guys garage did a show on how to weld the nut on as a last ditch fix---they said when you do the upgrade you throw away the old shaft and old nut anyway--there have now been 3 upgrades done now for the shaft and nut retention---it sounds like the chevy version doesnt have the dodge problem----can it be true?
 

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I'm really baffled as to how many times it has to be explained on this website that 5th gear nut has never, ever in the history of the NV4500 backed off. The nut does not turn! The material where the gear and shaft and gear and nut meat fretts away in use and the gear becomes loose along with the mainshaft bearing clearance and reverse gear gets to slam back and forth on the mainshaft.

Welding the nut accomplishes less than nothing, it just makes it harder to take apart when it does let loose.
Here's the link I posted on different thread a little while back:
http://quad4x4.com/NV4500 5th Gear Failures and Solutions.htm
 

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I coupled all 3 patches together when mine backed off. And it definitely backed off: it was a couple turns loose and then half the threads were pulled out. It still threaded right back on, though. The 5th gear is not fully splined, so it only had to slide off about 3/4" and the shaft splines were in a smooth part of the gear.

To patch it for a long duration, I applied sleeve bearing retaining Loctite to the gear's splines and the retaining nut's threads, replaced the nut with the 2-piece clamp down version, and then had a guy come over and put 3 tig welds between the nut and shaft to make sure it won't move. Like savoy64 said, the next best solution is the full shaft replacement where you throw away the old shaft and old nut anyway. Now they will just need to be cut off if that happens.
 

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the main key is to not lug it in 5th. my buddy works at a trans shop and has done several on chevys, its not just dodges.
when I built my trans it got a new chevy mainshaft and nut, with a good used 5th. drove it for several years til I wrecked it, and bent the mainshaft. I had to press 5th off the shaft, so obviously not lugging it is the key, cause I tow in 5th with trailers all the time, and have enough power I can spin the tires even with a trailer attached.
I have seen one slick setup though, that involves a splined section welded to the end of a socket that fits the nut, that locks it to the shaft splines.
 

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I have a Dodge gasser NV4500 version. None of the "super nuts" will fit my app. Different size shaft? Is this because it doesn't happen with the gasser version? Yeah, right. What's a poor boy to do when this happens to me? I'm sure the double OD is helping.:rolleyes: 1800 somewhere around 81 mph so I do lug when traffic slowes me down to the 70's. Saving Grace is I'm not making much power. Have no noises from my trans as of yet, but I know I'm working with a recipe for disaster.
Will the upgrade shaft/nut fit my tranny if she let's loose?
 

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2 guys garage did a show on how to weld the nut on as a last ditch fix---they said when you do the upgrade you throw away the old shaft and old nut anyway--there have now been 3 upgrades done now for the shaft and nut retention---it sounds like the chevy version doesnt have the dodge problem----can it be true?
seeing as how the chevy versions dont see the excessive torque, lugging and vibration like the dodge ones do i wouldnt expect them to have issues as often.

it cal also be considerd a numbers game. for arguments sake lets say 1 in 50 nv4500 trans have a 5th gear failure. let also say that since the chevy nv4500 equiped truck is also considerably rarer than a dodge [again, for arguments sake] 50 dodge to every 1 chevy.


for every 5000 dodges out there you only find 100 chevys.
you will also see 100 dodge failures and 2 chevy failure.


im just sayin.......
 

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On my 99 dodge at 150,000 I lost 5th for the 2nd time and i had the nut with the 3 set screws. Garbage, as they cant grip the hardened shaft. I finally welded the nut to the 5th gear. Weld the nut, washer and gear together in 3 places. I used a stick welder with E308H rod and it has held up for 45,000miles under mostly heavy towing loads long distances. Protect everything with several layers of tin foil, it will conform nicely to the parts and no fire hazard as I welded another tranny and lite a fire inside the gear box, this was all while tranny was installed under truck. This has worked for both of these trannies for several years
 
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