Time to change out the fluid before our heavy fall towing season. This trans was rebuild 3 years ago, and had the oil fill plug moved up on the case for overfilling capability. Dodge dealer installed the trans for me (they didn't rebuild it, just r and r'd it). I assumed they used the correct fluid at the time. This trans still has the 1.25 input shaft, so probably has the composite syncro rings, not the brass. Does the composite rings demand Chryslers spec oil? I've read a bazillion posts with many recipes for various blends of engine oil, synthetic trans fluid, ATF, and straight syncro fluids. Not looking for saving a few bucks... just the best oil for this trans! (especially one that would not jack-up my synchronizer rings) I've visited with a guy on CF about his fleet of nv's, and he runs delo 50 wt synthetic mixed half with 15/40 synthetic. ( delo doesn't make that... he uses royal purple, amsoil, or whatever is available at the time) If the Chrysler is the best, so be it. I'll drive 100 miles to pick some up

I have been using the Penzoil Synchromesh for the past many years with no ill effects. The only problem I ever had was caused by lack of fluid and not the fluid it self. Strictly my fault. I have seen alot of different things people use, but as long as the Penzoil keeps working I am going to stick with it.

Penzoil here also.

No problems with my composite syncros, running Pennz?

here is a picture of the label. It says compatible with brass, bronze and copper but does not mention composite. It does list the part # and spec # it can be used for. I dont personally know about them.

Here is another option: http://www.amsoil.com/shop/by-product/transmission-fluid/manual/manual-transmission-and-transaxle-gear-lube-75w-90/?code=MTGQT-EA

For an NV5600 the oil must meet Chrysler's MS9224 specification. If you are going to use Amsoil, I would recommend this: http://www.amsoil.com/shop/by-product/transmission-fluid/manual/manual-synchromesh-transmission-fluid-5w-30/?code=MTFQT-EA Pennzoil Syncromesh is always a good choice. I have it in both of our truck transmissions.

From what I learned from a write up on another site. You can run just about anything for fluid in the trans but there is a catch. The Dodge Factory fluid is a GL-4 fluid and its rated for 100k miles between changes. But if you using any GL-5 fluids it does attack the syncro's over time so as the writeup suggested was to change GL-5 fluids at 30k miles and Dodge factory fluids every 100k miles. Being I'm at 224k miles and rolling with the Cummins and never had a 5th gear nut problem with all the heavy hauling, towing, etc. I say stick to the factory fluid. We know its design for it...

Amsoil MTF here.

From what I learned from a write up on another site. You can run just about anything for fluid in the trans but there is a catch. The Dodge Factory fluid is a GL-4 fluid and its rated for 100k miles between changes. But if you using any GL-5 fluids it does attack the syncro's over time so as the writeup suggested was to change GL-5 fluids at 30k miles and Dodge factory fluids every 100k miles. Being I'm at 224k miles and rolling with the Cummins and never had a 5th gear nut problem with all the heavy hauling, towing, etc. I say stick to the factory fluid. We know its design for it...

The NV4500 and NV5600 use different spec fluids, the GL-4 is not rated for NV5600. I use Amsoil MTF and like the way it shifts.

I have done a fair amount of looking but cant seem to find what the syncromesh is, GL4 or 5 or what. My 96 5 speed to auto tranny fluid as I remember.

I have done a fair amount of looking but cant seem to find what the syncromesh is, GL4 or 5 or what. My 96 5 speed to auto tranny fluid as I remember.

It is neither, synchromesh is its own fluid specification. GL-4 and GL-5 are normally 75w-90, or there acouts; whereas syncromesh is called a 5w-30.

It is neither, synchromesh is its own fluid specification. GL-4 and GL-5 are normally 75w-90, or there acouts; whereas syncromesh is called a 5w-30.

Have you ever seen any fluid change intervals? I cant seem to find that either? I have been changing mine around 70k+ and the fluid does not appear contaminated. Darker in color is about all that is apparent.

Red line MTF is what I use for the last 21/2 yr 55k. I have 223k on truck now and will change next summer.

I change mine every 50K miles. But it's not "required"Lubricant Selection for NV-5600 (6-Speed ManualTransmission) — If EquippedThis transmission does not require periodic changing. Ifit becomes necessary to add fluid or change the fluid, besure to use the same lubricant or equivalent. Refer toRecommended Fluids, Lubricants and Genuine Parts forthe correct lubricant type.

im running amsoil

Amsoil here, shifts nicer now.

I just changed my fluid while installing the fast coolers I bought 3 years ago. Had about 70k on the fluid and it was just a bit darker than the new fluid, Penzoil Synchromesh. I have read many threads about different fluids making the shifting better. I guess what I dont get is I never had any trouble shifting mine. I can shift pretty much as fast as I want to.