Here I am

NV5600 Breaking gears on the hwy

Attention: TDR Forum Junkies
To the point: Click this link and check out the Front Page News story(ies) where we are tracking the introduction of the 2025 Ram HD trucks.

Thanks, TDR Staff

Hot NV5600 !!!

Tail shaft seal I thought?

Status
Not open for further replies.
This is the second time 6th gear has broken while driving 60 mph.

The first time was 19k miles ago. I'm not sure I can afford this rebuild,

but Standard Transmission in Ft Worth has my truck and I'm awaiting for the verdict.

The conclusion I have come to is that the rear wheel/wheels are coming off the ground after hitting really bad rough spots in the road. This might seem pretty far fetched, but it is a common occurrence with both instances.

The first time I was towing trailer and load 18000 lbs up hill. After hitting the bumps in the road the sound of broken teeth began. I did not recall hearing the engine revving up or did not notice the tach jumping up. The bumps came up quickly without any notice.

The second time I was towing trailer and load of 22500 lbs on flat ground. The bumps were several in a row and I did release the accelerator after the first ones. When resuming the broken teeth sound started again. O boy,:mad:I knew what this meant.



Has anyone have any other conclusion that may cause this action? I just have never heard of wheels bouncing off the ground before and I'm not sure this could even cause the gears to break. But it is a fact and a very expensive fix.



The trailer is a gooseneck 40' flat bed. The weight on the trailer neck was (guessing) 3-5k lbs. Truck tires are stock size w/80lbs air, shocks appear to be working fine, the overload springs have 2-1/2" blocks.



The highway bumps that I refer to I would call the bouncy kind not the washboard kind.



I would appreciate any responses and especially anyone with the same problem.

Thanks guys and TDR
 
Not quite the same thing, but I had to replace the rear diff on mine after pulling my trailer over some bad bumps on the highway. If there's stress on it because of acceleration at the time of the shock of the bumps, I am sure it could happen. Just sucks that you had it fail twice now.
 
All I can think of is to make sure your shocks are good, help keep tires on the ground, and pulling that much weight, just use fifth gear which is direct, no teeth to break.
 
Tom,



I pull a 5er that weighs in at about 14k, and the truck weighs 8k a grand total of 22k. I have not experienced any problems pulling in 6th gear except the egt's are hard to control. I have always thought about pulling in 5th gear at about 62mph. Did not know if this would be a good thing or not. I tried to set the cruise in 6th gear and a slight hill would kick the cruise off. It felt like something bad happened, a big jarring, so I don't set the cruise in 6th anymore. I wonder if the cruise would be able to keep up in full time 5th gear. What do you think? Is 5th gear ok to pull at 62 mph for long highway travel?



Brian
 
If I was towing heavy, I would use 5th most of the time. As long as you are not holding the engine to 3200 + all day, the Cummins is built to handle it. Your mileage will suck, but the Cummins will be fine. Stay out of 6th when you are really heavy. I have heard of loosing 6th when towing heavy due to poor lubrication of 6th gear. My 0. 02.
 
As others have said... keep the trans in 1 to 1, and let the engine spin faster. The increased RPM will be your friend in long term durability of the entire truck. TRUE diesel engines are designed to run at rated speed continiously, so its not going to hurt the engine.

I could see rear end chatter causing 6th gear breakage(is 6th gear really that pathetic in these transmissions???)

Typically, rear end chatter is termed axle hop at low speeds, and usually ends up twisting an axle shaft or spitting the driveline... . but I suppose that since youre up to speed, and all the shock is being sent futher upstream to a weak component, guess its just its time to go...

Hate to hear about your mis-fortune. .
 
A 4. 10 rear axle would have helped. I agree with others, keep it out of 6th gear when towing that heavy.



george
 
If I keep it in 5th gear, what would happen to 5th gear if I bounce on some more rough spots on the highway?

The last rebuild states they replaced "M/S 6th gear" , "c/s drive 5th" and "input 26T".

I assume there are gears with 5th too.



I just heard from Standard, $1400. 00, he said 6th gear was toast and a crack gear on something else can't remember what he called it.



I think I need a second and third job now.
 
Fifth gear is direct, ie, no power is being transmitted through gears. The input shaft is coupled directly to the output shaft, the gears are still turning but not transmitting any torque.

IMO, for the weight you are talking, you should be looking at at least a 5500 with the Aisin auto. or a true medium duty truck.
 
It's pretty hard to believe that the rear axle/wheels could be clearing the ground enough to allow the engine to rev before the wheels slam down again with that much weight on the rear axle.

Your truck should not be towing loads that heavy in sixth gear with 3. 73 gears. It would be easier on the transmission to run 62mph in fifth with the loads you are towing.
 
Is Standard installing thier 'power lube ' package ? When I hauled that heavy (or heavier) :eek: I wouldn't grab 6th till about 65-70 MPH, and that was on level ground, higher on hills . Install a trans temp gauge while its being worked on, you will be surprised how hot these 5600's run !
 
Your right Harvey, I don't really believe it either but I have nothing else to base it on but bouncing up and down on the bumps, then rattle rattle rattle of broken gears. What else could have just happened???

A couple months back I talked with a salesman from the local Dodge dealer and he said that the 4500 & 5500 had the same engine and manual transmission as the 3500. If this is true, I don't see much of a benefit from a 3500.

As far as Standards "power lube" kit, from the last rebuild they said there were no signs of over heating. He said that because I ran at least 1qt over filled that would have helped a lot. Plus the trans cool fins help as well. He felt that the "power lube" wasn't needed. So I run 1 to 2 qts over and deal with the minimal droplets from the rear seal.



I will heed to the warning of pulling in 6th under 63mph, that does sound logical.



Thanks guys for your'e great advice.

The TDR is my #1 source for information and you guys make it the best.

Ron
 
I could see the rear end coming off the ground in the right bump scenario. But the impact being transmitted to the 6th gear... nope. Someone told me once that towing heavy in 6th was bad for the gear and that it wouldn't hold up. I couldn't get a reason why. I don't know how the gears are made or what they are made of. I suppose in theory... It could be possible to crack / break a cast gear from to much impact between the gears as a result of the harmonics from the engine and drivetrain. Likely hood... twice even... doubtful. It would be nice to know what the gear is made of, and what process was used to make it.
 
Dave,



Your post brings up an interesting question that's been nagging me. Where is Standard Transmission sourcing their parts for the NV5600 rebuilds? Maybe the gears they are using aren't as robust as the originals.



I towed at a GCW of about 23,500 lbs with my NV5600-equipped 2002 dually for quite a few miles and never had any transmission problems at all. With the 4. 10 rear axle, almost all of those miles were in 6th gear.



Rusty
 
Your right Harvey, I don't really believe it either but I have nothing else to base it on but bouncing up and down on the bumps, then rattle rattle rattle of broken gears. What else could have just happened???
A couple months back I talked with a salesman from the local Dodge dealer and he said that the 4500 & 5500 had the same engine and manual transmission as the 3500. If this is true, I don't see much of a benefit from a 3500.
As far as Standards "power lube" kit, from the last rebuild they said there were no signs of over heating. He said that because I ran at least 1qt over filled that would have helped a lot. Plus the trans cool fins help as well. He felt that the "power lube" wasn't needed. So I run 1 to 2 qts over and deal with the minimal droplets from the rear seal.

I will heed to the warning of pulling in 6th under 63mph, that does sound logical.

Thanks guys for your'e great advice.
The TDR is my #1 source for information and you guys make it the best.
Ron

Ron,

The salesman's statement that the 3500/4500/5500 Rams all use the same tranmission whether G-56 manual six speed or Aisin automatic six speed is correct but I don't understand the connection to your situation.

Your opening post indicated you have an '05 with a NV-5600 manual six speed which hasn't been installed in new Rams since late '05.

One of the significant differences between 3500/4500/5500 cab and chassis trucks is differential gearing. A 3500 set up for heavy towing will have a 4. 10 differential, a 4500 offers a 4. 44, and a 5500 offers a 4. 88. The lower rear end gears allow the heavier rated trucks to tow heavier loads and reduce driveline stress.
 
Dave,



Your post brings up an interesting question that's been nagging me. Where is Standard Transmission sourcing their parts for the NV5600 rebuilds? Maybe the gears they are using aren't as robust as the originals.



I towed at a GCW of about 23,500 lbs with my NV5600-equipped 2002 dually for quite a few miles and never had any transmission problems at all. With the 4. 10 rear axle, almost all of those miles were in 6th gear.



Rusty



Seeing as how NV ceased production of these units ... what 5. 5-6 years ago, that only leaves one other place to get parts ! :{ Anyone gets a chance (zzman) ask to see what 6th gear looks like , not too much to see, and when I think of how I tow, even with my puny little 20 ' race trailer, its amazing that gear holds up like they do ... . sometimes . :eek: Wish someone would come out with a 10 speed Roadranger swap !:D
 
After NV went out of business a certain remanufacturer of 5600's began having new internal parts machined to their specs which means there is at least one brand of new parts available.

For what it's worth I have also broken 6th gear teeth off at the root, which is caused by sudden shock. I managed to also break a nearly new main shaft in two on another reman 5600. In both instances I was towing heavy 5th wheel campers up a grade in 6th gear with cruise control set at 65 mph. Both times the vacuum cruise control "dropped out" and then decided the truck wasn't going fast enough so it applied considerable right pedal to compensate and "wham". The situation was compounded by the fact that the 5th wheel hitch had some "slop" in it and the rear pinion needed to be tighter. I really think the culprit was a bad APPS because after I replaced it I never broke another transmission due to shock loading.

I highly recommend the Power Lube Package from Standard Transmission in Ft Worth. Although I don't have a lot of miles yet on the 5600 I had them rebuild with said package it does seem that there is considerably less drive line noise than I have had from any of my previous 5600 remans. It simply cannot hurt and most certainly helps to have additional lube flow to that rear output bearing.

Godspeed,
Trent
 
Last edited:
You need to be in 5th when towing heavy with the 3:73 rear, but I would do the same with 4:10, if I was set up with it. I use 6th gear when heavy on flat roads, but as soon as there is an incline I drop to 5th. I've towed heavy with both, the NV5600 and the G56 with the same rear (3:73) and have not had any issues.
 
I thought about it some more and I agree that the shock being increased by the truck bouncing could cause the breakage. However, I also think that there could be an issue with the gears being substandard. This is all supposing that this was a singular or initial sitiuation on each gear. Continual stress scenarios as well as repeated sudden stress will cause everything to break. This is supported by every material having a "Yield". I would try to find out if the gear had been replaced in each of the transmissions. If it had... Where it came from and so on.
 
Status
Not open for further replies.
Back
Top