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Discussion Starter #1
I know there are threads on this subject, but I'm still not sure what to do. 5th gear quit on me driving up a hill last night. I drove another 80 miles home in 4th gear. One shop tells me that the nut backed off and they need to take the back of the tranny out, replace the nut and I'm good to go - for $900. Another shop tells me not to bother and that I should just replace the entire tran. What should I do and how much should it cost. Also, what kind of damage will I do if I drive the truck before it's fixed? Thanks for any advice.
 

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Rescue Tower
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Is this the first time it has fallen off? It sounds like the first transmission shop has a clue. NV4500 Rebuild and Overhaul Kits

You can drive it in 4th all day long. No damage.
You may want to consider a full rebuild if you have more than 150k miles on it though.
 

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:ditto:If you have more than 150 i would rebuild also......Had mine done I took trans out and took to shop and it cost 1400.00
 

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what causes this and is there any way to help prevent it
 

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Usually what causes it is running in fifth gear at low speeds and low RPM causing the engine to lug and put's excessive strain and vibration on the transmission. My transmission guy told me not to pull anything in fifth gear under 1500 rpm. And he also told me to change the fluid at regular intervals and only use the mopar or GM fluid
 

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Rescue Tower
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Have you used that kit? Be careful of cheap kits because a recent flood of poor Chinese parts. I hate to see a guy do a rebuild just to redo it early. If at all possible get new NV parts.
 

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Get the trans fixed up with at least a 5th gear nut. I got mine rebuilt with the nut, a bearing kit, and bigger input shaft for $7XX. I was told that the only oil to use is the MOPAR gear oil specifically for the NV4500. It's pricey though at $17 or $18 a quart. You'll need exactly 4 quarts.
 

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you can also use Amsoils version of transmission fluid for these things..the tranny shops around here offer it.. i personally like it better than the Mopar brand, but thats just my .02
 

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about 4 months ago i was going up an off ramp and got on the throttal and felt a pop i broke the splins off 5th gear the gear cost $75 and the oil cost about $90 and took about 2 hours to fix so it could be that to insted of the nut.
 

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my buddy had this happen to his 97 had the shop do a rebuild and a clutch and they welded the nut on and no more problems !
 

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heres my two cents for what its worth. What it is, as stated, the nut that holds 5th gear on backed off and allowed the gear to actually slide out where its not riding ont he counter shaft anymore. your can drive it no problemo. if your tranny is shifting fine, I wouldnt mess with a rebuild. if you have notchy shifting (like I did), then a rebuild would be nice. you get it rebuilt you'll think your driving a new truck.

as far as preventing it, Dodge actually made a revised mainshaft that fixed this problem, the only issue is that your talking about a 400+ dollar part, plus labor. Spec ont he 5th gear nut is 250-300 ft/lbs and lots of red loctite. havent seen one come back yet.
 

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Boy oh boy!!!! Every time I come on this site I find out that I have to fix something else at great expense. I have 166,000 miles on my 2500 so my transmission is supposed to lose 5th gear, right??? Do all the NV4500 lose fifth or just the ones that have done a lot of hard work or had abuse. My trans is still tight, with no slop when shifting etc. I hang on 1800 when driving and if it drops down to 1500 or so I shift down. When I do tow it's only about 7000 lbs. I don't know what the previous owner did but the truck doesn't seem to have been abused. The star wheel is in the middle and no other mods visible so it hasn't been souped up.

The Quad kit people say that they won't sell a self installable kit if the truck has 150000 or more so I would be stuck with a huge rebuild fee.

Who designs this crap anyway. The transmission is just a bunch of gears and shafts it ought to outlast the engine with proper oil changes etc.
 

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Rescue Tower
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It's a bit of a mystery. You are doing the right things to make 5th last. Hopefully it will. I woudn't worry about it untill something happens. The cost to rebuild our manuals is WAY less than what the auto guys get to pay. The 5th gear is a dumb design. It works well on a non diesel truck though.
 

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crap?? my ol lady has a kia rio, now thats crap, i love my 1 ton, even if the nut falls off my nv4500 today. LONG LIVE THE CUMMINS!!!
 

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Thanks. Yeah, I think you're right, just drive it until it comes loose. I wonder if there are any 4500's out there that have gone for 200 or 300k?? Anyone know about that??

Yeah, crap. Crap design. Bad design is bad design. Ford had a 5 speed that vibrated so bad you had to have a special clutch to compensate. Crappy design. If you like bad design then good for you. Like I said, the transmission that isn't abused should outlast even the Cummins engine. The engine, as good as it is, has some dumb problems. The vacuum pump exhausts the air it sucks in into the crankcase. Get a vacuum leak and see what happens. 7 quarts of oil blown out the crankcase breather tube in under 200 miles. The little pickup I was towing behind was totally covered in oil. These companies need to get the damn accountants out of the design equation and let the engineers get on with building good equipment.

Picks up his soap box and walks away.
 

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Mt truck has 200K miles on it. I suspect never been out of either. Shifts fine, makes a lil noise in 5th when you let off the nise gets quiter, but still there.

I don't go under 1500 rpm in 5th and don't hammer on it. Fluid is full. I might do a oil swap in the tranny, but that is it. If it ain't broke I'm not digging into it.

I don't haul much with it.
 

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simple fix, pull the drive shaft, pull the tail stock off the trans and you can see the nut and 5th gear. Put th enut back on, tq it to 200lbs and then tack weld 4 spots on it.. this is what is done to mine and no worries at all..
 

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Thanks. Yeah, I think you're right, just drive it until it comes loose. I wonder if there are any 4500's out there that have gone for 200 or 300k?? Anyone know about that??

Yeah, crap. Crap design. Bad design is bad design. Ford had a 5 speed that vibrated so bad you had to have a special clutch to compensate. Crappy design. If you like bad design then good for you. Like I said, the transmission that isn't abused should outlast even the Cummins engine. The engine, as good as it is, has some dumb problems. The vacuum pump exhausts the air it sucks in into the crankcase. Get a vacuum leak and see what happens. 7 quarts of oil blown out the crankcase breather tube in under 200 miles. The little pickup I was towing behind was totally covered in oil. These companies need to get the damn accountants out of the design equation and let the engineers get on with building good equipment.

Picks up his soap box and walks away.
i have 284xxx miles on my cummins and just lost 5th gear haha..
 
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