R tuerck

I need some help. I have the NV 5600 in my truck. I'm towing a 48 foot tow car hauler with two race cars and parts. My tranny has been rebuilt three times already this year. I'm getting sick of spending all this crazy money on this thing. I'm in a Edit position where I can't upgrade to a 03 04 model because i don't have the money. I've looked into doing an 03 04 auto swap but its to involved and to much money. I have also looked into the G56 tranny swap but can't buy one from dodge since they don't sell them unless you have a vin# to go with it. I want to get a G56 tranny. let me know what you guys can do.

torquefan

I'm thinking the NV5600 is plenty strong enough to do what you want it to do, so maybe there's an underlying problem here. Perhaps the rebuilder is making an error in assembly or there may even be a factory problem with how the transmission is lined up with the engine. What type of failure have you been experiencing? I know this isn't really the type of help you were looking for, but I think you already have the perfect combination for heavy towing and I hate to see you spend time and $$ to end up worse off.

dodgezilla04

r tuerck, you posted a word inappropriate for this forum. please edit your post and fix it. thanks

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blackdiesel

Well I have to agree with TF, I don't think it's the 5600 that's bad it's YOUR 5600 that is. (or your rebuilder). I had mine go out had a guy that rebiulds big rig trannys go though it. And it didn't last. I took it to a shop that does it all the time, and they put in new input, out put,and main shafts, and that's seemed to do the trick. If I were you I might look at a different 5600, before going to the $$$ of a conplete switch to a g56 (IMO) it's not as strong as the 5600

R tuerck

thanks guys for the help. You've made me feel a little more confident in this transmission. It's still being rebuilt as of right now. I'm going to add the fast coolers to it and go as far as mounting a pump on a switch to run the fluid through an externally mounted tranny cooler.

DryCreek

You need to post your model year of the truck.
That makes a bit of a difference for the NV5600. The early models had a smaller input shaft and were known to have problems. Around the 2000 or 2001 MY Dodge went to a larger input shaft with beefier splines. That could be your whole problem. The upgrade is realtively simple, but you will need to change your clutch when you change the input shaft. You know, larger friction plate, and pressure plate, stronger throw-out (release) bearing and upgraded pilot bushing.

Dry Creek

gmctd

The input shaft size doesn't have much to do with gearbox failure - Dodge upgraded the shaft diameter due to breakage at some severe 20000lb towing tests, where the go-pedal was pushed-released-pushed-released-etc, heavy accell - heavy decel, etc - which would eventually break any input shaft.

The 1.250" input shaft was for 1-ton trucks, the 1.3750" shaft was for 2-ton trucks, which did not pan out when NVG decided to scrap the trans - the 1.3750" shaft was then used in the 305-350hp trucks.

Need more details on your failure(s), but failure is usually traced to the lubricant type and quantity - NV5600 won't survive on 90wt gear oil, nor on ATF Dexron III or IV.

R tuerck

I have a 2001 2500 HO model. I am towing roughly 20,000 pounds with a southbend clutch, helper springs, rickson truck 19.5's single rears with bridgestone commercial tires. I think the tranny failure had alot to do with the tranny being overheated. I didn't have a gauge but about an hour after it broke the tranny was still abut 160 degrees.

PourinDiesel

01 and up have the 1.3750" shaft...that is only a 245hp motor.

NVG never scrapped the trans. NVG (MTM facility) was a joint venture with GM and Chrysler with GM as the operating partner building NV4500 and NV5600 transmissions....DC was the sole customer (after a certain point). When DC decided they wanted to use their own cheaper Mercedes trannies there was no demand for the NVG trannies anymore and the plant along with all of its machinery, spare parts and transmissions complete and incomplete was shut down, dissolved and sold.

I would take my NV5600 any day over the G56.

The NV5600 is stout but if rebuilt incorrectly you can have some real issues.

gmctd

Good input - right around '01 and the shaft upgrade, the synchro assemblies were revised for better oiling to handle the power increase, so the trans in the 305-350 trucks were fully-suited for that HD application.

Should be no probs if the type and quantity of lube is maintained - I use the full 10pts of synthetic rather than the suggested 9.5

cgraham

Found a NV5600 on craigslist. Guy said 6th gear "locked up". I'm not sure what that means, mechanically or as far as $$$$ goes. Any ideas? Thanks!

mudwisr2

There is a company here in Memphis, TN called High Gear transmissions. The NV5600 is one of their specialties. They correct all the old problems. My factory NV5600 (2000 model) failed at 76K miles. The original owner that I bought it from changed the fluid and put Lucas oil in it b/c "it's the best oil out there" and the trans failed about 10K miles later. High Gear builds them to 2004 specs, they redrill the case to improve fluid flow, and raise the fill plug to allow for a higher fluid capacity. I think they sell for $3200 if you give them a rebuildable core. They ship all over the U.S. Hope this helps.

Homestead

First thing you do is knock the shift tower off and dump in 6 quarts of quality synthetic...MTL or MTF. Why?, the 5600 has a rear bearing lubrication problem and running the stock fill of lube will accelerate the issue. 6 quarts will submerge this bearing. Don't worry about heat with to much fluid, it's not an issue.

Second thing, change your oil on a very regular basis, 20,000 miles for me and don't skimp on the changes. Oil is cheap.

Third thing, weld a bung into the drivers side PTO plate and run a temp guage. Yes you can buzz down the highway in 6th pulling your load but 6th gear runs a lot hotter than 5th, watch your guage, when it climbs, downshift for a bit. Don't pull hills in 6th if 5th will work.

Coolers, finned PTO plates, whatever works to keep the heat down or at a minimum is worth it. Trust me, I've seen 260/270 plus degrees trans oil temps pulling loads through the hills. Smartening up and driving it a little more human, brings them down in a real hurry.

These trannies are so big, they don't get a whole lot of air flow around them to pull some of the heat away from them, then you stuff a mighty Cummins in to a hole in front of it and make bacon, the heat climbs and climbs fast when your puffing hard.

Jeff

dozer12216

Good job Homestead. Running in 6th gear because it will pull doesn't mean it is not being overloaded causing overheating failures. Poor choices in lubes will make a difference also. The tranny is not easy to overhaul and not everyone is capable. A quart overfilled and a cooler is a definite improvement.

mgvia

I need some real help.Is the nv5600 6 speed really junk and why didn't dodge recall the transmission and fix the problem.I'm not even pulling anything and mine gets hot running 70 mph in 6th gear.