A Living Resource
I get lots of PM's and thread questions about NV5600's and I also see lots of threads on this topic. This will develop more as I have time and get more details of my current trans buildup. Please note, these are my experiences and personal opinions. I am hoping for this to be a living resource. If you have something to add or disagree with please pipe up and I will add that info or attempt to alter the existing info to be more accurate. Some people will not need all of this stuff to get an NV to live a long life. Others are more ham fisted... Like myself... and need all the help we can get. All posters who say stuff like "swap to a built auto" will be deleted from this thread.
First and foremost is... Use a well versed builder. I recommend SuperStick Transmissions AKA: Cody Albrecht. Easiest to contact him via Facebook. https://www.facebook.com/SuperStickTransmissions/
Just a quick look at the page and you'll know you've come to the right place. Very reasonable prices and great guy to work with. If you get a reman from an unknown company you may have a dead unit on your hands 15,000 miles later. Ask me how I know...
I have heard that Blumenthals, Midwest Transmission and Highgear are competent with these units but have no first hand experience and I would never personally go to these shops. For shipping your NV strap it to a pallet and call Fastenal 3PL or ask Superstick to take care of that for you. Expect to pay $200-350 one way depending on location in US. The shipping is well worth it to send it to the only guy that will warranty a manual against gear breakage.
I've been told by a member Chuck's Gear in Spokane, WA did a successful rebuild for him. Thread this was discussed on page 11.
Companies to avoid: Standard Transmission in DFW.
Good replacement parts are very important. Cody seems to have a good source on these. There was a time in ~2007-2008 when good parts became hard to come by. New Venture ceased production on the NV5600 in 05 and the stock of "OEM" parts became depleted. If you read around, you'll see many tales of crappy chinese parts. I believe most of that is behind us now if you go to reputable parts suppliers like Enterprise Engine.
There has also been some discussion on page 15 by Monkey Brain that many of the good quality parts may be coming Transstar.
Any "AT" brand parts are garbage and should be avoided at all costs.
1 3/8" input shaft. All common rail NV's came with the bigger input. HO 2nd gens had the 1 3/8". SO 2nd gens had the 1 1/4. Do not even bother beefing up an NV if you are keeping the 1 1/4 input. That is your weak link. Even then, some of the the internal components are weaker on the 1 1/4 units so if you are hunting cores, avoid the small inputs.
This info applies to the G56 as well. Keep the plate load low on the pressure plate. The lower the plate load the less the shock on the gears if you have a "whoopsie" moment. I strongly recommend triple disc clutches with the 3250# diaphragm style pressure plate. Valair offers the 3250 ceramic as "standard" configuration. IIRC, feramic and organic are available upon request for non comp situations. SB makes similar options as well. If you must have a sintered iron clutch, be prepared to be snapping some shafts if launching on pavement or power shifting. I feel, sintered should only be used on sled pullers, dirt draggers or street driven trucks with very mature drivers.
If you must do a DD ceramic for cost savings, I strongly recommend staying away from the 3800# plate. Yes you will have less holding power with a 3250 DD but thats the price you pay to keep the trans happy.
The lever plate is also and option but from my trials with both styles I like the diaphragm better for street use.
When your OEM hydraulics fail get a set from one of the clutch vendors. Both Valair and SB sell the same 3rd party aftermarket hydraulic kit so don't worry about where to get it. Adjust to your liking. I like mine set very high because I slip it like a snowmobile all the time. The hydraulic instructions say to set engagement 2" off the floor. Thats a good baseline but I like it looser.
Overfill by at least one qt. Nothing special needs to be done to do this. Simply dump in the extra lube through the shifter hole. You can fill more at the risk of it weeping from the output shaft. The fast coolers add ~1.5qts of capacity. I tried to stuff 9 qts in it and its been weeping out of the ouput shaft seal from being overfull. 8.5-8.75 qts would probably work very well with the Fast coolers.
Edit: I have successfully stuffed 7.25 qts in without PTO coolers and no weeping. Try not to park on a hill with the rear facing downward or you may get weeping out of the output seal.
I feel the best shifting is with Pennzoil Synchromesh. I've tried Royal purple synchromax and Valvoline synchromesh. My favorite is by far the Pennzoil. Only brand I haven't tried personally is Redline. A member here posted about using both Amsoil and Pennzoil and he preferred the Penzoil for smoothness. Some members in this thread have had good results with Redline MTF in mixed weights(Page 14) Cody recommends straight 50w Gear lube like Delvac or Syngaurd.
There are many brands of this stuff so you should be able to find some at your local parts store. I believe it helps with speeding up the shifting. I use about 1/2 qt of this stuff. I've tried other hyper lubes with similar results.
. There are several variants. This is strongly recommended especially in hot climates. I'm using the FAST coolers. The benefits of these coolers are obvious. Extra lube volume and cooling. If towing I would recommend a standalone temp gauge. Seems temp has a high impact on the longevity of 6th gear. If towing heavy I would say pto coolers are essentially mandatory.
If you do nothing else. Put a magnet in. It takes no time at all and has huge impact on longevity. In OEM form these things have nothing to catch debris. Do yourself a favor and get a magnet in there. There are many methods to accomplish this.
Passageways for lube are enlarged. I will try to get more info on what specifically is modified. This requires a full teardown. Any time you are going through the effort of fully rebuilding you should do this. At ~$275 its money well spent. The shifting is a lot faster and smoother with this mod performed and it really helps 6th live longer by keeping the smaller gear cool. I have driven non powerlubed trans and powerlubed trans within hrs of each other. The difference is very tangible at all RPM's. This gets even more pronounced at 3,000+. The non treated trans I had would NEVER shift above 3500 rpm's. Even above 3,000 it would really take some muscling. Modded, its no problem ripping a gear at 4,000 rpm with normal'ish effort.
On page 16 the following is discussed. "He(Fabian) installed a spray bar and jets to provide additional oiling to the gears. The case has a -8AN for the suction and 2 -6AN feed that is routed to a cooler up front. Basically like an automatic trans cooler system."
Weighted shift knob
I have the Unita Diesel SS weighted shift knob. At 1.5 lbs it has a nice heft to it and makes a significant impact on the shifting. I have gone back to a stock knob a few times and hate it. The weighted knob makes missed shifts extremely rare for me. Shifting is buttery with it on. I have modified mine a bit so its more comfortable. The lower edge was in a very odd spot for me so I lathed it of. Thinking about knocking off the upper lip also but not sure yet. Disclaimer: Later in the thread a builder discusses that weighted shift knobs decrease the life of the synchro. Use at your own risk. I like the improvement too much to skip it.
Try them if you must but my recommendation is to skip them. My experience with the BD STS was terrible. I hated the clunkiness. Tried it for 2 months. Went back to the stocker and haven't looked back. Hurst makes a full replacement shift tower but I hear similar things about notchy/clunkiness. You need all the leverage you can get when shifting quickly and shortening the shift time is not helping any of the internals either. Grinding was very common for me on the BD. All this coming from a guy who has had short shifters in every other vehicle I've owned.
Enterprise Engine mainshaft
(AKA output shaft). 300m material. Only aftermarket strength improvement shaft available. Jury still out on this.
Liberty Gears input shaft
300m material. Stronger than OEM. Only aftermarket strength improvement shaft available. This shaft makes clutch rattle ever so slightly louder than the OEM shaft. You will notice it has a different look than the OEM shaft. Edit: Later I switch back to factory shaft at Cody's recommendation and cause he wants to try it. It actually necks down a little thinner than factory. I appreciate going back to the quieter shaft.
Shot peen and micro polish
This is the last step before giving up the handshakers in favor of the automagic slush boxes. This will not make the trans stand up to limitless abuse. It will just increase the abuse it will tolerate and for how long. The topic of metalurgical treatments is vast with limitless reading material. I suggest you read up to see if these options are right for your application. These treatments are offered by Liberty Gears. They charge by the pound. I will update rough costs when I get the bill. These treatments increase the fatigue resistance more than increase the actual strength of the material. Shot peening targets the fatigue strength whereas micropolishing aims at reducing heat production in gear contact. On my built trans I only had 3rd, 4th, 5th and 6th treated. No need for the other gears because the tires will spin long before something in the trans lets go. The only visible change from this process was the deburred edges of the gears.
Even with all these things done, 6th is the weak link. The small gear of the pair is just really tiny and doesn't have enough teeth to distribute the load well. Big tires and high power in 6th are not your friend. Suggestions for 6th are to be gentle as possible. Roll into the throttle if on the street. If drag racing slip the clutch more than other gears as you let out in 6th if WOT. Keep the revs high when going WOT in 6th. When racing, I don't hit 6th until ~95mph. I try to ring out 5th to 3400+ and then slip into 6th. For towing heavy stay in 5th. Lugging in 6th will greatly reduce its lifespan. Even the owners manual recommends towing in 5th.
There are some inferior "AT" brand gears out there and I had one in my built unit. Anyway, it crapped out and Superstick got me all fixed up with a good brand 6th gear. Cody tells me upgraded 6th gears are not needed. They just need to be good brand.
There is some interest in upgraded 6th gears. If you are truly interested please post as such and I will add everyone to this list. Expected cost is variable.
1. Broaner - 2
2. Gecoveyc - 2
3. Jeremy - 1 https://www.cumminsforum.com/forum/2...7-post262.html
4th in 4lo is your best bet for 500-700+hp. Wheel speed is up in the 30's at redline in 4th 4lo. This is perfect wheel speed for moderate power trucks. 5th 4lo is manageable depending on power, gearing, tire size, sled weight and track conditions. In 5th you need a lot more power to keep from bogging out at end of pull. I would not personally try it with less than 800hp.