Put a new clutch in my truck so I went ahead and changed the tranny fluid as well. I picked up some Royal Purple 75-140 full synthetic at O'reilys and put in there and the guys said it would be fine. I was wanting your guys opnions because I thought it was supposed to take synchromesh.

 

I don't think that would be good, synchromesh is like a 30 wt synthetic oil with additives. IMO get it out and find some other oil

 

Slap those guys at O'Reilly's.
Should be able to find Pennzoil Synchromesh Fluid pretty easy, or pay more for the Mopar or GM fluid (same fluid used in the NV3500).
Or you can use synthetic like Redline MTL or Amsoil MTF.

MikeyB

 

Ask the guys at O'Reilly's if they even know what a Synchro even is...
You need to use the oil that Dodge recommends or go to a oil like Amsoil Synchromesh or one of the other FULL SYNTHETIC synchromesh oils.
Topper

 

That oil will tear up your trans. The 5600 is pretty particular on the oil you use. I contacted Redline about the MTL and they guarantee it exceeds the synchromesh specs. Thats what I run and it shifts smoother for it. Its a little notchy when its cold out but it warms up pretty quick.

 

You need to get that crap out of your tranny ASAP!!!! The NV5600's have VERY small oil holes in the gears, and the heavier oils like the 75-140 cannot get into the oil holes fast enough to keep the bearings lubed and cool. Replace with a 75-90 synthetic, and try to overfill the tranny with as much oil as possible, the more, the better. Any brand of good quality synthetic oil will do, one brand is not much different from another. Just make sure that the GL-4 or GL-5 requirement is met.

 

I used Amsoil MTF. As per the tech's recomendation I did not overfill mine because it causes seals to blow out. Don't know if theres truth to that or not but I figure the manufacturer knows where to put the fill plug.

 

The fluid needs to be compatible with the yellow metal (synchro's) that are in the trans. As I understand, it's CRITICAL that you use the proper fluids.

If you do a lot of towing in the mountains or hills (uphill/downhill), I understand that over-filling is a good idea. Otherwise, either the front or rear of the trans will not get enough lubrication.

Joe F.(Buffalo)

 

I have RP synchromax in mine and like it better than the oem or mtf. I see some parts stores have RP now like checker and pepboys. Craig

 

Actually that was a flaw for these transmissions failures. Overfilling will increase life, lubrication, and smoothness.

 

Well I'm only reporting what the tech told me personally when I was talking to him about changing the fluid. He also reported that the problem which caused oil to not flow all the way forward and back (on hills) was corrected after a period of time. I don't know which modle years, or claim to know more about the topic than anyone else; I'm just reporting what I heard so everyone can have the same info.

 

Ha.. they screwed you... Amsoil MTF, what I use, is 5w-30....

 

The only way you would blow out a seal is if you had the breather hose pinched off and then the oil would have no other place to go. You would probably have to add 3 extra quarts to blow it out the overflow anyway. I added 1 1/2 quarts extra a year ago and have not blown any out yet.

I also put a extra quart in the transfer case but it blew some of that out. I would recommend only 1/2 quart extra on that one.

 

in 2001 i changed oil in a 5600 i called amsoil and they sent me 70w 140 when it got wintertime it would shift kind of stiff but we have 250,000 miles on the oil pulling heavy i have thought about changing it and mixing 5-30 with 70-140 to put back in , i am afraid to put 5-30 in now that it has ran that long on 70-140 . in these transmissions the gear lube needs to have a mt1 rating do not go by the gl rating

 

That doesn't sounds right... 70w-140 is no where near the grade that the 5600 requires... It would be like putting 70-140 motor oil in your engine.... I susspect that you dont have a 70-140 in there or it wouldn't shift, the 70-140 wont have the properties the syncros want, and wouldn't lube the gears properly... Now the 4500 takes 75w-90, but not the 5600...