NV 5600 Failure

[jelag]

OK here goes... ... . 04 3500 dually pulling a trailer that is 15-20K lbs most of time... . truck now has 216K miles and has never gone through a full tank of fuel with out a load.....



On the way back from Missoula MT yesterday..... 70 mph on the interstate... . heard a bad pounding sound from under the truck..... and had to limp into a small town off the interstate..... 2-3 miles or so... .



Called the shop and had another truck come with a flat deck trailer to haul the truck home on... . and a local logger on the way to Spokane hauled my trailer back for us..... Gave him a 100 buck tip for the trouble.....



Pulled the transmission this morning..... Pile of metal in the bottom of the case... Closest exhange unit is in Boise and is $2800. 00



No clue on the cause..... we've changed the tranmission fluid our self every 50K or so... and did it about 3 or 4 weeks ago... . We've always used and approved fluid... .



The stage 1 clutch we installed at 100K miles looks almost new... but we're changing the release bearing and pilot bearing to be on the safe side...

 

[betterthanstock]

I'd like to know if it's just 6 th gear that sheared off the teeth, or a shaft broke, or where the pile of metal comes from. How did you limp to town? What gear(s)?

Did you remove PTO covers to look inside?



216K towing is the end of its design life. They are designed for 150K towing at capacity with stock engine power.

 

[Gary - K7GLD]

AS I asked in your other thread on the same subject - how many of those loads/miles were run in overdrive?

 

[DGamelin]

What gears do you have in it?



04. 5 3500 6x6 quad cab 6 speed 373 25k

93 250 2wd xcab auto 355 240k

 

[NIsaacs]

216K towing is the end of its design life. They are designed for 150K towing at capacity with stock engine power. [/QUOTE]





Where did you find this info? This seems kinda low for the NV5600. They have been installed in Dodge pickups with power from 235hp/460tq to 325hp/600tq. Which stock engine power are you referring to?





"NICK"

 

[BarlowCummins]

I have never had a problem with my NV5600. My 02 and my current truck both have the NV5600. I am very interested what it ends up to be, I tow about that same weight, maybe more every weekend. Please let us know what the results are. If you need any help with the new one, let me know. I live in Boise and don't mind helping another TDR member out.



Corey

 

[Diesel Power]

it must be an isolated problem, im sorry to hear you have problems, i do know of a few who have put over 300k on there nv5600 with out issue and they tow max load allowed, hope you get it resolved.

 

[betterthanstock]

I just took the time to study the gear layout of the NV5600, and 6th gear is super weak. It is at the front end of the shaft, and it is one third the size of the secondary shaft gear that meshes to it. It generates a lot of side thrust on the input shaft bearing, and the front bearing of the output shaft (the tiny one inside the input shaft) and on the thinned out front end of the output shaft. I think it is a mistake to tow heavy in 6th with this transmission, and DC certainly has the wrong final drive available for it.

What will eventually happen, is that the output shaft front bearing will go, causing the output shaft to move, and the gears to jump. The small end of the output shaft may even break off. It will total all three shafts, and possibly even bend the housing and shift forks.

All towing should take place in 5th. So the rpms in 5th should be about . 8 of the current rpm in 6th. This means availble gears should be 0. 8x3. 73=2. 98, and 4. 10x. 8=3. 28. This would also work great for the G56.

Sixth is BY FAR the weakest gear, and the one that we put the most miles on. If someone has a cutaway of the g56, I'd like to take a look at it too.



Given the lack of available proper gearing, I think all who tow heavy and fast, should either get an auxiliary OD transmission, and tow in 5th plus external OD,

or if you want to avoid catastrophic failure, you have the option of replacing the input shaft bearing, and the front output shaft bearing, and possibly 6th gear every 100-150K (or whenever you feel comfortable to do so). It may be possible to replace those two bearings thru the input shaft cover, without taking everything apart.

Oh, and the pilot bearing is part of this system also, and its failure can cause the whole transmission to go, so it too should be replaced. I would definitely change the other two bearings (mentioned above) whenever a bad pilot bearing is found.

The next time I tow, it's going to be 5th gear on all hills. (I have 3. 73 and 315 tires, so it can do 70 mph in 5th at 2640 rpm, so that's not bad at all!)

 

[Gary - K7GLD]

I just took the time to study the gear layout of the NV5600, and 6th gear is super weak. It is at the front end of the shaft, and it is one third the size of the secondary shaft gear that meshes to it. It generates a lot of side thrust on the input shaft bearing, and the front bearing of the output shaft (the tiny one inside the input shaft) and on the thinned out front end of the output shaft. I think it is a mistake to tow heavy in 6th with this transmission, and DC certainly has the wrong final drive available for it.

What will eventually happen, is that the output shaft front bearing will go, causing the output shaft to move, and the gears to jump. The small end of the output shaft may even break off. It will total all three shafts, and possibly even bend the housing and shift forks.

All towing should take place in 5th. So the rpms in 5th should be about . 8 of the current rpm in 6th. This means availble gears should be 0. 8x3. 73=2. 98, and 4. 10x. 8=3. 28. This would also work great for the G56.

Sixth is BY FAR the weakest gear, and the one that we put the most miles on. If someone has a cutaway of the g56, I'd like to take a look at it too.



Given the lack of available proper gearing, I think all who tow heavy and fast, should either get an auxiliary OD transmission, and tow in 5th plus external OD,

or if you want to avoid catastrophic failure, you have the option of replacing the input shaft and the front output shaft bearings, and possibly 6th gear every 100-150K (or whenever you feel comfortable to do so). It may be possible to replace those two bearings thru the input shaft cover, without taking everything apart.

The next time I tow, it's going to be 5th gear on all hills.

BINGO!



And *exactly* why I kept asking about miles towing in OD! The OD is a great feature in the NV-5600 - but the mistake of applying the available torque of the Cummins to the 5600 OD in heavy towing situations is very likely to shorten the lifespan of the transmission. Guys see that the engine has the power to apparently handle 6th gear - and assume the rest of the drivetrain is also up to the task - it might do well on the short term, or for occasional heavy use - but is at risk in situations where regular heavy use is involved.



Perhaps yet another wakeup call for getting ENOUGH truck for the intended work?



Personally, for RV towing in the hills, I have installed new TOYO 285's for the OD *they* provide in the 45-65 MPH range, and use 5th gear for the grades. OD is reserved for flatland towing and driving empty - our 5er is a relatively light 24 footer weighing about 6500 lbs loaded. As a side benefit, my EGTs are far lower, and the flexibility of power in this arrangement makes mountain driving far less stressful on ME as well as the transmission! :-laf

 

[klenger]

It's starting to look like the dreaded G56 may be in fact be the better transmission, especially given the lower 6 gear ratio.

 

[Gary - K7GLD]

It's starting to look like the dreaded G56 may be in fact be the better transmission, especially given the lower 6 gear ratio.

Perhaps - but I'll wait for the reports after substantial G56 OD heavy hauling as reported in this thread.

 

[JamesSimpson]

This may be a dumb question and some of you may say why but, could you replace the nv 5600 with a beefy 4500??? I seem to me that one of the problems with the 5600 is finding a replacement or parts. I would think a beefed up 4500 would work just as well and you could run an OD unit with it.





Just a thought and question

 

[betterthanstock]

This may be a dumb question and some of you may say why but, could you replace the nv 5600 with a beefy 4500??? I seem to me that one of the problems with the 5600 is finding a replacement or parts. I would think a beefed up 4500 would work just as well and you could run an OD unit with it.

The idea is to prevent failure by towing in 5th uphill, or even against very strong headwinds with a large frontal area trailer. The rest of the nv5600 is much stronger, and can easily go a million miles. It has much better gearing than the 4500. For anyone who does not know, 5th is direct coupled, so no gears or bearings carry any loads.

 

[JamesSimpson]

But in theroy would the 4500 work?

 

[Cattletrkr]

Mark me down as one destined for a failure then. 130K of heavy towing, way past "design" when loaded... about double the trailer weight actually. I run in OD a lot. Can't do it in 5th, not enough top end. With my taller 19. 5's I run 60mph at 2500rpm. That's fine, but 70mph is screamin' a little too much. '



Yes, I should have more truck for what I tow. Problem is, such a truck does not exist... yet. I need 4wd. I can't afford two trucks and then use one of them a mere 10% of the time. That's why I have a 1 ton to tow what a FL80 should tow instead. For now, those of us who tow absurdly heavy and at freeway speeds just have to plan on trading more often or replacing blown up parts. It's just the way it is.



If I ever, errr when I shell out a rear end I'll replace it with 3. 73's. I told myself after I bought my last truck I'd never get 4. 10's again. What did I do? Yep, 4. 10's. I blame DC, it's all their fault.



How much of the problems with towing in 6th are heat related?

 

[Vaughn MacKenzie]

livingez on NW Bombers is on his 3rd NV5600, which went in around 190k on his '04. 5. He tows 6th all the time, and is well aware of the transmission's weakness as betterthanstock explained.



He had a '97 before this truck, he replaced the original NV4500 at 360,000, and transmission #2 was still doing fine when sold the truck at 602,000.

 

[Swamp Donkey]

Or you can be like me... ... about 1000 miles towing around 7,000 lbs and nv5600 failure. Over 6 weeks in the shop with no nv5600 available through dc's warranty.

 

[jelag]

Gary K7GDL



When we're on the open road in UT, AZ, MT, ID, NV and the speed limit is 75 mph we're traveling at 70-75 in 6th... . coasting down the interstate in OR, WA, and northern CA on straight and level 55 we're also in 6th... its only when we are in those hills that the transmission stays in 5th... . its got the 4:10 rear end... and it just won't go fast enough in 5th on the open road... .



Maybe I should have bought the other rear end, and left it in 5th... . But i'm going to buy a 5500 as soon as they come out... .



Jim

 

[Bigd6.6]

My local dealer can have one in a 2weeks.