I know this has been asked and talked about several times but even with searching through the search I still haven't found the answer. I am trying to find out how many quarts of Pennzoil Syncromesh should I put in? I have a 2005 4x4 3500 with 76k miles on it. I bought it in 2013 with 71k miles on it. I literally only use this truck to tow my camper as my wife doesn't care for the ride in any of my 1st gens. So since I don't know the history of the maintenance schedule of the truck before I bought it. I am going through everything now before the Spring. I already added a Mag-Hytec pan on the rear and added new fluid. Now I just ordered a set of Geno's finned one piece trans_coolers for the trans. I believe most with a NV5600 put 6 to 7 quarts in it with the factory pto covers on it. The two finned pto coolers according to the Geno's website add a total of 1 quart for them both. So does that mean I should try and install 8 quarts? I know someone out there has installed the exact coolers on their NV5600 who could shed some light on how many they used. I just don't want to over or under fill the trans that's all. Any help?

 

The factory fill for the 5600 is 4.75 quarts, but its been suggested for as long as I can remember to overfill the 5600 by one quart due to lubrication issues. So that means if you're going to install Fastcoolers then you'll want to put about 8 quarts in there. Which also means you'll have to fill from the shift tower otherwise the fill plug will be too low.

As for running with the Fastcoolers, I installed them on my 4500 and they work great. But I noticed that my transmission was still heating up on long hill pulls until I realized that the 900*+ hot exhaust pipe running next to the Fastcooler was adding more heat than the coolers could dissipate. So I installed a exhaust blanket (not wrap) on the section of exhaust running right along side the transmission. Helped tremendously... Here's a picture for reference.

 

Thanks Katoom. I actually didnt go with the fastcooler I went with the trans_cool finned versions. I asked Genos and they preferred these over the fastcooler due to only needing one gasket to prevent potential leaks and better heat decepation. Now they don't hold as much as the fastcoolers like you have. According to Geno's fast coolers adds 1 qrt apiece while the trans_cool finned version only add a half qrt apiece. So I would be one less qrt than you. I was planning on filling through the top PTO cover bolt. Do you think I can get 7qrts in through the top PTO cover bolt? I might take your advice on the exhaust blanket as I installed a 5" exhaust so I might be close to the cover as well.

 

You can try filling from the PTO bolt. If it works then great. And yes, your exhaust will be very close to the coolers. You'll want to get a blanket or create some sort of shield. I got mine from Jegs. https://www.jegs.com/i/Thermo-Tec/893/11630/10002/-1

 

I like the exhaust wrap so it is not dumping heat into the coolers. I may look into that for my tow rig.
The rest of my rigs which are 1st gens I usually only add the cooler on the drivers side as between the exhaust and the front driveshaft the passenger side is kind of crowded.

Yes you can add fluid in through the top PTO cover hole, that is what I do with my Getrags that I over fill. I fill them through the standard fill hole then top off the extra QT through the top PTO hole.

I have those same coolers on a couple of NV-4500s myself freight train

 

I've had the Trans Cool 1 Piece coolers on my NV5600 for over 12 years.
I don't recommend to install the passenger side cooler as I don't think it helps since the exhaust is so close.
I had to trim several fins off my passenger side cooler to clear my exhaust brake that is mounted right there.
If I ever have to remove my trans, I will remove the passenger side Trans cool and leave it off.

I too agree that over filling the nv5600 trans by 1 quart/litre is a good idea and I have done that forever also.
I do recommend running heavier trans fluid than the really thin Synchromesh, especially for a summer only truck that is hauling/towing heavily.

There are several options for adding an extra quart of trans fluid. Disassembling/reassembling the shift tower is not something I would ever do.
I used to jack up one side of the truck and add the extra quart thru the fill hole on the side of the trans, a total pain.
I don't see how you can add fluid thru the small top PTO bolt hole.

What I ended up doing was removing the drivers side Trans cool. Drilled and tapped the top of it with a large pipe tap. 1/2" or something like that. And put in a pipe plug.
There is lots of room above the driver's side Trans cooler to pour in trans fluid easily.

Remove the side fill plug and top pipe plug on the top of the driver's side trans cooler. Pour in enough fluid thru the top hole in the Trans cooler until it starts to over flow the side fill plug.
Put some thread sealant on the side fill plug, or it will leak. Screw in the side fill plug. Add another quart thru the top of the driver's side trans cooler. Simple.

Synchromesh flud is super thin. 70W-80 if I recall. 75W-90 trans fluid is way better for heavy loads in your NV5600. I actually run 50/50 Red Line 75W-90 / 75W140 trans fluid.
Note you have to run TRANS fluid, NOT differential fluid. Be very careful here.

Hope this info helps.