Actually, the NV-5600 is VERY picky on which oil you use! Use any of the heavy gear oils (i.e. 75W-90) and you will lock it up as the oil is too thick to get into the recesses of the bearings and other internals. The ONLY suitable oil you can use in the NV-5600 is Syncromech Manual Transmission Fluid, which is 5W-30! Some people actually use 5W-30 motor oil, though it's obviously not formulated for transmission use.

Of course, Mopar sells their version, but it's like $26.00 a quart! I've found the Penzoil version at the auto stores for around $9.00 a quart. I myself am using Amsoil's version as it's synthetic (imagine that) and ran about $10.00 a quart when I changed it last year.

Whatever brand you choose, for the love of Pete don't use the heavy gear oil in your NV-5600 as they aren't made anymore, are very difficult to find if your roach the one you have and will likely have to shell out close to $4000.00 if/when you find a replacement.

Here's a little trick I learned from the old diesel mechanic at the local Dodge Garage... It takes about 5 quarts to fill the case to the fill hole on the 5600 if you drain it from one of the bottom side-cover bolts. If you live or tow in hilly terrain, an extra quart in these transmissions is very beneficial as the input shaft and center support bearings can go dry and fail while towing uphill. The trick is to get the extra quart in there. You can either park your truck sideways on a steep ramp or in a ditch so the oil in the case migrates away from the fill plug or pull the shifter from the top of the case and pour the extra quart directly down as I did. The extra quart doesn't hurt anything at all and is cheap insurance against damage.

Please check the link below. You'll notice your trans on the list.

Hope this helps and good luck!

AMSOIL - Synthetic Manual Synchromesh Transmission Fluid (MTF)

 

I did that park on a hill trick before so I could get extra fluid in.


Sounds just like the info I gave. Thanks.

 

I know. I just thought I'd go a little more in depth with it as in his last post after yours and before mine he stated he was gonna try 75W-90 synthetic, which is a long ways from 5W-30. I know it's his trans and he can do what he wants with it, but it's an awfully expensive critter to make well if it gets sick on him.

 

No worries - Nobody listens to me...


Thanks for the support bud - it never hurts to have accurate information.

 

Not a proplem Doc. If there's one thing I've learned while driving a diesel rig, there's NOTHING on them that's cheap to fix, and if I can help somebody from having to dig into their wallet I'll at least try to steer them the right direction.

 

Another vote for amsoil MTF here. I float shift mine and it works really well. I'm getting to time for a change of it again. I only put in a pint extra though. Might have to try a quart this time...

 

Thanks for the info. The local auto parts store sells Amsoil so i'm gonna see if I can get 6 qts. of the MTF. Spent 2 days puttin the 6 speed in, dont want to have to pull it out anytime soon. Cant afford any more down time on the truck.

 

I feel your pain, that bugger is heavy. Took me three days and lots of beer to get it back in

 

i used the royal purple synthetic oil in my trans when i changed it it's gl-5 rated and i havent had any issues with grinding or any other trouble. what is the recommended interval to change the oil in my nv5600?

 

Put an extra quart in there! Amsoil or Royal Purple, I put mine in through the shifter!