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NV5600 Broke...again!

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So I had my NV5600 completely rebuilt a year ago Friday, and now it I am waiting for the rollback to show up to have it worked over again. I was driving home last night on a half ice/half pavement road, so to keep the boost/torque from slamming the drive train when it went from ice to pavement, I kept it in 6th and anywhere from 45-60 MPH to keep the RPM's down. Well about 5 miles into my trip it starts making all kinds of noise, switch to 5th, sounds fine. Back to 6th, noise comes back again. Not sure what is going on this time around, but it was rebuilt before because 5th or 6th (can't remember which one) busted a tooth and rolled around and damaged the main and counter pretty badly. Here is the gear set from the first go around:
NV5600 Carnage pictures by natehas - Photobucket
They are going to warranty it at the shop where it was re-done as long as it is something in the tranny messed up, which I am sure it is, so at least I shouldn't have to fork over $2700 again for it to be re-built. Anyone know what would cause the described symptoms or had this happen to them before?
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· vvv SOME PEOPLE'S KIDS vvv
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Ouch!!! IDK what could cause it but who ever did the work should stand behind it, I hope...
 

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the NV5600 is rated MAX at 650 lbs ft of torque, what's your truck make max?

800 lbs ft will walk right through 6th gear and set it up for failure

do you tow heavy?

what tranny lube and how much?

any PTO cover coolers on the tranny?

stock NV5600s run too hot towing heavy
 

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where did you get it rebuilt, ouch, I just had mine rebuilt for $1300 and had it back in less then a week? 6th gear was out just like yours, and all the synros were toast
 

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Discussion Starter · #5 ·
Steelhead01, I haven't towed anything with it in months but when I do most of the time it is just out 23' boat which is maybe 2 tons trailer and all. The tranny was supposed to be re-built using upgraded components the last time around. I was using Royal Purple Synchromax when it went out the first time, now it has the Mopar stuff in it since the re-build, that was what they put in it. I'm not sure what mine makes max in torque, but I usually have my TST on 3-3 standard power which is rated 50 HP and 120 torque. Those setting seems to be the best compromise of power/fuel economy for me. I don't have the PTO cover coolers but I was not aware they were available until recently. Seems a little ridiculous to me that it is already crapped after just 10 months of driving (I was called up to active duty for 2 months). I have a ZOOM stage 2 ceramic clutch and it works good, hold the power just fine, but I want to try a Valair double disk instead. If it happens again I will be going to the NV4500 with the upgraded input shaft and all, that is what my buddy uses in his pulling truck that is making over 1000HP and it works great for him.

Twhetten, I had it done at a local shop here in MO, M&M transmission. I am really starting to wonder whether they know much if anything about the NV5600 transmissions. I looked online and found all the parts (yesterday) a whole lot cheaper than what they did, the labor was $792, the rest was parts. If they don't want to fix it under warranty I will probably just take it to another shop, or maybe even my local dealer, at least they have experience working on them.
 

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the NV5600 is rated MAX at 650 lbs ft of torque, what's your truck make max?

800 lbs ft will walk right through 6th gear and set it up for failure

do you tow heavy?

what tranny lube and how much?

any PTO cover coolers on the tranny?

stock NV5600s run too hot towing heavy
Are you serious? I have over 900 ft lbs on mine..
 

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i have over 1100 ft/lbs on my nv5600
 
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Discussion Starter · #9 · (Edited)
Either way guys I am getting really F'n pissed about this, 3rd complete rebuild in a year now! I am seriously thinking about swapping to a NV4500, hell of a lot cheaper! My buddy who pull said the gears are weak in the 5600's so that is why he uses a modified 4500, he was busting input shafts until Valair got him one of their made in the USA billet ones, now he hasn't had any problems. I don't tow that much with mine so I don't really need the extra gear spread to be honest. Any thoughts guys? I agree with the 550 TQ thing, sure, but that is probably on stock EVERYTHING. I think once you up the clutch they are much much more capable from what I have seen and read. My truck is no where near a heavy modded truck so I can't see why it keeps crapping out on me!

Anyone on here think this shop I used just really doesn't know how to work on the 6 speeds? It seems that way to me because other than clutches i never had a problem in 4 years, now i'm going for round 3 in less than a year!
 

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Discussion Starter · #10 ·
Any thoughts on the 5 speed conversion?
 

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Either way guys I am getting really F'n pissed about this, 3rd complete rebuild in a year now! I am seriously thinking about swapping to a NV4500, hell of a lot cheaper! My buddy who pull said the gears are weak in the 5600's so that is why he uses a modified 4500, he was busting input shafts until Valair got him one of their made in the USA billet ones, now he hasn't had any problems. I don't tow that much with mine so I don't really need the extra gear spread to be honest. Any thoughts guys? I agree with the 550 TQ thing, sure, but that is probably on stock EVERYTHING. I think once you up the clutch they are much much more capable from what I have seen and read. My truck is no where near a heavy modded truck so I can't see why it keeps crapping out on me!

Anyone on here think this shop I used just really doesn't know how to work on the 6 speeds? It seems that way to me because other than clutches i never had a problem in 4 years, now i'm going for round 3 in less than a year!
I have never heard of 5600 breaking that much, sorry to hear that man
 

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6th gear is at the top of the box, gets very little lube oil since it is lubed by oil fling only, the NV5600 does not run a pump like many of the big rig trannys.
gear cooling is by the lube flow only
gear gets hot beyond metallurgy specs. looses strength and surface hardening. tooth fails. gear fails.

put at least 6 qts in the next tranny with 2 coolers on it to get lots of cool lube oil to 6th gear.
i run 7 qts of Redline, 5 of MTL and 2 of MT90 mix

a Dodge shop will require their special lube for a rebuild warranty.
 

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5 speed is cheaper to fix, but with alot of hp will tend to break more often
 

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Be careful running RedlineMTL It ate the top boot of my NV5600 causing oil to leak out on a roadtrip, burning mine up. I had it rebuilt for 1100 bucks. Replaced all the boots and run syncromesh now. They were all gooie, and sticky, the only thing different from the time I had it from new was the redline. It will never go in any of my vehicles. As far a NV5600 they are very strong, lots of pullers use them, just hard to find parts for. Mine has over 1400ftlbs on it daily now, and no trouble
 

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Stay away from the NV4500's. They have an issue with 5th gear, the nut backs off and will tear the tranny up. I'd have it built up again, I tried researching beefed up internals and came up with nothing. Seems like the guy building it is not doin something right.
 

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That 5th gear nut backing off is usually a one time fix and then you dont have that issue anymore, but i think stock to stock the 5600 will for sure hold more power and also already has upgraded input shaft
 

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5 speed is cheaper to fix, but with alot of hp will tend to break more often
I disagree... with the fully splined main shaft and a new 5th gear, the 4500 is more reliable than the 5600 IMO.

and people seem to actually build them and get them to last.

I think lugging the truck along for so long in 6th is what killed it. sad to say, but the 5600 doesn't like to haul heavy in 6th. Buddy of mine lost 5 of them in the span of 2yrs hot shotting.

I would swap a 4500 in it and never look back. I've had 3 4500 trucks and two 5600 trucks, I'll take the 4500 every time
 

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I disagree... with the fully splined main shaft and a new 5th gear, the 4500 is more reliable than the 5600 IMO.

and people seem to actually build them and get them to last.

I think lugging the truck along for so long in 6th is what killed it. sad to say, but the 5600 doesn't like to haul heavy in 6th. Buddy of mine lost 5 of them in the span of 2yrs hot shotting.

I would swap a 4500 in it and never look back. I've had 3 4500 trucks and two 5600 trucks, I'll take the 4500 every time
Notice i said stock to stock, of course a fully splined main shaft and (new) 5th gear its going to be great and yes if guys build them they will last, but i have seen alot more nv4500's go then 5600's. I have a 4500,5600, and a G56 and have had less issues with the 5600 then any of them, i cant keep the g56 together and the 4500 is always having problem, the 5600 is in the 4wd and has been hauling 40ft PJ trailers loaded with 20 round bales for a while and seen a few sled pulls and see alot of low 13 second runs adn still no issues, just my experience
 

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my friend (displaced okie) cant keep a 4500 behind his 370hp 12v
 
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