The Ultimate NV5600 Users Thread

[blacksheepdiesel]

Let's make a compilation of info regarding the NV5600. Hopefully this will make it easier for someone doing a search where most pertinent info on this transmission will be found in one thread. Please post items like:

1. Maintenance pointers

2. Fluid change interval

3. Ways to NOT abuse this transmission

4. Parts sources

5. Rebuilders

6. Upgrades

7. Oil recommendations

8. ???



The intention is to provide info, not argue about oils or who is the best rebuilder, etc.



Godspeed,

Trent

 

[blacksheepdiesel]

I'll get it started by mentioning that it is best to overfill the NV5600 by filling with a total of 7 qts of the correct oil. This helps get more oil to the rear output bearing which tends to run dry and overheat, ruining the bearing and perhaps the entire transmission.

There are 3 ways to get the oil in the transmission;
1. take off the shift tower and pour it in.
2. drive the truck on ramps on the driver side and put the oil in through the factory fill hole
3. screw a pipe extension in the fill hole high enough to allow the oil to be put in and then cap the extension.

Godspeed,
Trent

 

[AH64ID]

I am still trying to learn much of the info you are asking for, so this is a great thread.

Personally I run Amsoil Syncromesh in my NV5600 and change it every 50K miles. I also run Fast Coolers, and am overfilled by about 1 qt.

 

[TSPowell]

Rebuilder and Parts Resource:

Blumenthal mfg

Welcome to Blumenthal Manufacturing

 

[steved]

Discussion removed...

 

[GCroyle]

1. My NV5600 gets regular Pennzoil changes, Syncromesh Manual Transmission Fluid. Available most places.

2. DO NOT ASSUME IT HAS THE CORRECT AMOUNT OF FLUID! If you had your hands on it, check it, especially you professional installers, do you want to hear the clutch job you just did was in any way related to an NV5600 failure do to low or no fluid? If you ignore it, it will likely bite you, bad.

3. Put it in N at lights, don't hold it in gear with clutch released. It just consumes the limited amount of pilot bearing service life, pilot failure can lead to damaged input shaft.

4. Recommendation, don't speed shift, it ain't no 4 speed. You have one of the largest diameter discs used on diesel pick ups in it.

5. Many have commented on heavy towing up a grade, knock it down a gear, use some RPM and enjoy the climb, it ain't a race.

6. Seems to be a concensus that you should not shift w/o using clutch, trans shops speak up, urban legend or fact?

7. Take care of it. Replacements are expensive and trans is no longer made.

 

[AWeiman]

blacksheep thanks for starting this thread looking forward to being well informed. i have heard it discussed before but what about towing in 6th gear. i believe i read there is something different about 6th gear that it was not as stout as the other gears? i also believe i read in a tdr article by joe d about clutches that shifting without a clutch is not recommended. hopefully someone with alot more knowledge than myself can chim in on this.

 

[Rockranch]

Thanks for starting this thread. I wish I had something to contribute, but I am still learning.

 

[Grizzly]

I have an NV5600 on my 05 and I find this information very helpful. My friend and neighbor has an 06 with a Cummins and a G56, 6 speed. Can this information be helpful to his truck?

 

[GCroyle]

Grizzly,



The only sure carryover from my list has to do with the input shaft and pilot bearing life/span. We as drivers have a huge roll in how long these components last, put it in N at lights, wear is minimized, clock stops on pilot wear.



I bet the comments about not relying on using 6th as a hard pull tow gear would carry over also.

 

[blacksheepdiesel]

Good contributions everyone! Thanks a bunch!

Another rebuilder is Standard Transmissions & Parts: Tremec - Borg Warner - New Venture - Getrag, Cummins, 4 speed transmission, 5 speed transmission, 6 speed transmission They offer the Power Lube Package that throws oil on the mainshaft bearing and helps prevent overheating it.

About towing in 6th gear: after several hundred thousand miles of towing I recommend shifting to 5th to keep the rpm's at 2000 or higher when towing up a steep or long grade where you cannot hold steady speed in 6th. This will be a different mph and rpm for different setups.

I will say that 6th gear breakage is usually caused by sudden shock. The current 6th gear set in my '04. 5 has over 400,000 miles with no problems. The bearings did wear out and were replaced, power lube package added, synchronizers replaced, and input shaft replaced but the gears where all good.

Shifting without the clutch simply doesn't seem to be something the NV5600 can do for very long. To me it is simply not worth the risk of ruining the synchro's. Rebuilds are expensive.

Keep the info flowing!

Godspeed,
Trent

 

[RVTRKN]

Due too expensive trany repairs, use only OEM oil I know that everyone will have an opinion on this but you can't get it wrong with OEM oil. The reason people don't buy it, is its expensive so make up your own mind. It is your money, so good luck with your decisions. I can say its the best manual trans I've ever owned, although noisy, it can handle any thing the 5. 9 can handle when driven properly and maintained properly, treat your clutch with respect and don't ride it. maintenance should be sooner than recommended intervals in my opinion and again, OEM oil. Don't think your NV5600 has a problem if it is stiff when cold or going from 4th to 5th, They are very notchy, and if you have a 4X4 put the transfer case into neutral, shift into 4th gear when warming up your truck. I did just that for 50K miles of my trucks life and do the same for my G56.

 

[MickeyMiller]

I've been changing the NV5600 oil every 25K. Tried OEM, RP, REDLINE, Amsoil and a trick racing trans oil that was recommended in TDR. I don't notice any big difference in shifting regardless of brand. Oil looks and smells like new at 25K changes. Pilot bearing failure necessitated a clutch change at 155K. Went to SB DD. With the trans out noticed syncro wear so had the box rebuilt at the same time. BTW, I also have one of Gino's splash trans oil filters so I fill with 7. 5 qts. Running Redline MTL right now. Both Redline and Amsoil claim to meet Dodge specs.



Clutchless shifting? Are you kidding... I shift this thing slow and delibertly. If in a hurry just start in 3rd and avoid the firt 2 shifts!



BTW, on level ground I always start in 2nd.

 

[Grizzly]

For heavy hauling in the Rocky Mountains, is the 400# cast iron NV5600 any better than the aluminum housing G56?

 

[blacksheepdiesel]

Good point Mickey, I also shift slow and deliberate. My technique is to push in the clutch, pull shifter out of gear and hold it with slight pressure in the next notch until it drops in. To me the less pressure used in going into the next gear (whether upshifting or downshifting) equals less wear on the synchronizers. Don't know if it is true but I have gone 350,000 miles on one NV5600 before the bearings wore out and the synchro's were still working good. Had them replaced anyway just because it was already torn apart.

Godspeed,
Trent

 

[blacksheepdiesel]

RVTRKN: you are correct that you can't go wrong using OEM oil. You are also correct that it is very expensive compared to other oils. To say it is the only oil safe to use is not true and I say this from much experience. It seems the NV 5600 is a very finicky creature and some 5600's shift better with one brand of oil better than others. Every owner will have their own preference.

The most important thing concerning oil was stated by steved above that the correct specification of oil is used. Never gear oil! If you are going to have a shop change oil in the 5600 then take the oil to them that you want put in it and tell them how many quarts to put in.

Godspeed,
Trent

 

[blacksheepdiesel]

Grizzly,

Great question. It can be safely said that the 5600 is safe for heavy mountain towing as long as you downshift on steep or long pulls to keep engine speed up. I believe this also keeps heat down in the transmission and reduces stress on components. The engine is stout in stock form and then adding power modifiers that add power low in the rpm band can give a false sense of security to the driver. While the engine might be able to pull the grade it may do so to the detriment of transmission components.

I have never heard of a 5600 or G56 housing break because of heavy mountain hauling. If someone has, please chime in here. Someone's bad experience can be wisdom for the rest of us.

Godspeed,
Trent

 

[NIsaacs]

I remember when the '01 HO/6-speeds hit the showroom. I slobbered for two years I wanted one so bad. In '03 I bought one and love it. It and my '91 have been mostly daily drivers with some personal towing so I can't comment on heavy duty use.



Back in 1990 when I did the Ford conversion not much was known about the trq. of the Cummins. All the four-wheeler magazines suggested the Clark 280 VO was bullet proof so I went with one. WRONG! I have used this truck for heavy loads and have lost 5th twice and 3rd once.



I use 15/40 engine oil in all three trucks with good results, I change at 36,000 miles. "Disclaimer" not a recommendation, just that I use it



Over the years I have rebuilt numerous gear boxes and have found that the small bearing surface of the pocket bearing (where the input shaft and main/output shaft couple, is a weak point in all gear boxes that have this setup. I think it is mostly due to the physical size and lubrication. Water weight oils and heavy weight gear oil might be less then ideal. It turns in every gear except direct. Direct is straight through so no stress or heat is generated.



Nick

 

[Buffalo]

Regarding heavy towing, uphill, with the NV-5600 in fifth gear, the reason that that gear is the best choice is that it is direct drive & is a much larger gear than the overdrive, 6th gear. I've heard that it will hold up to much more abuse than 6th gear.



I'm not a transmission expert, in any way but, this is what I've heard & read. Lots of good points in this thread. I appreciate the sharing of information from you guys. For example, steved mentioned that using LSD additive didn't do much for his trans. shifting over a period of time. I had heard that it was a good fix for notchy shifting & was wondering if any of you guys had tried it & what your results were?



I called Standard Transmission in TX to have them confirm what I had read about their recommendation of Amsoil's product for use in the NV-5600. The guy I spoke with said that they had the best results with Amsoil. Interesting!!!



At the last trans service, I installed a trans filter & over-filled the trans. At the next service, I'm going to install a Trans-Cool cooler on the other side of the trans. Steved made another good recommendation to use neversieze on the bolts of the cooler (aluminum). I would have never thought of that. THANKS, Steved!!!!!



So far, my NV-5600 works great for towing in the mountainous West. I just completed a 3362 mile trip towing my travel trailer in the mountains. This trans provides the proper gear in all conditions. I can't imagine how anything could be better for towing.



Joe F.

 

[ILIANBG]

Thanks for starting that thread. One thing I want to warn everyone is to be careful when installing a new clutch. I had a reputable shop in my area do this and now I have noise and vibrations I did not have before. I am saving to have it rebuilt. The oil has been changed every 20000 miles, sometimes earlier.
The Pennzoil seems to work very well, even a bit better then OEM. I tried the Amsoil, and I had to change it earlier then the other fluids. It became harder to shift earlier then with the other two did.
So, how much extra do you guys add without fast coolers? I have seem very different opinions. A mechanic at a local Dodge dealer said that over filling has caused more failures. I do not know what to do for best protection. I do a lot of stop and go driving- city traffic.
Thanks and looking forward to learn more from everyone here.
Ilian