Although not wide spread, I've seen a few posts recently that involve NV5600 failures. Those who have had failures, what fluid were you running in the transmission. I know the options are basiclly OEM, Penzoil Synchromesh, Quaker State Synchromesh, Redline and maybe an amsoil product. My understanding is the First three are the same, just diffrent labels and prices. That leaves 3 choices. I know the latter 2 do not meet DC spec for the transmission, but some people like them.

I wonder if everyone who had failures were using the OEM lube. If so, why would one care if they were using one of the lubes that dont meet the spec. Chances are the failure is not going to occur before 70,000 miles anyway. I'm all for keeping the warranty in tact, but not at the cost of using an inferior lube.

I switched to Redline MTL at 15,000 miles, and just put Penzoil Synchromesh in today at 23000. I did not notice any change in shift habits between the OEM, Redline and now Penzoil. I basically got scared, and want to leave this in until I get good proof that the Redline is not going to damage the tranny. I'd be interested in hearing from some high mileage guys with the 6-speed and hear what they use.

 

One of the critical things on the NV5600 is the oil level. If going on fill plug level alone, the truck should be level or even slightly high at the rear to ensure oil level at front of trans is always good.

Rear of truck could be lower than spec by an inch or 2 which automatically lowers the actual front level when using the fill plug to check level. This learning goes back to the 2nd gen NV4500 through to the 3rd gen NV5600.

Penz Manual Sycromesh is what comes in it from the factory. Used to be Texaco until they were bought out.

 

Mine is perfect at 160,000 miles. It has the Texico lube from Chevy in it (same as Dodge but half the price.) It has about one quart over and has never been changed. The miles are all heavy towing and in Alabama temperatures.

 

I maybe a little **** about the fluid level in the tranny but I jacked up the rear of the truck to get 4.5 qts in. Running Pennzoil Synchromesh at the moment.

MikeyB

 

I have had the same oem fluid in mine since the 5 to 6 speed swap was done @ 120,000 miles. There is 2 extra oem qts plus 1 bottle of lucas in there, all put in from the shifter cover. I barely unscrew the plug to see if fluid will leak out the threads to check for level. The miles are not all towing but it is more than half.