NV5600 and quart overfill = hotter trans?

[steved]

Very interesting info Kirwin, 260 would concern me and if I towed heavier, I would have a temp gage for sure.

Before FastCoolers, I could reach 235*F unloaded on flat ground...

 

[Kirwin]

Transmission temperatures

I can't really say that the fast coolers lowered temperature but I "think" that the combination of the coolers and the additional fluid capacity did. I have only seen it above 260 F that one time in west Texas. We were pulling toward Albuquerque NM. We started out in Amarillo and headed west. It wasn't too hot first thing in the morning with us cruising along at 68 MPH, temperatures slowly rose up to 255 F and as the day got warmer they slowly creped over 260 F. I'm used to seeing up to about 225 F pulling at 65 MPH. The transmission wasn't the only thing that was running warm. My coolant temperature normally runs about 205-208 F pulling, with the A/C cranking. This day we were seeing up to about 220 F at which point the fan would lock up and temperature would slowly fall back to 208 F or so and the fan would slowly disengage and temperature would slowly climb back up. We finally passed through a cold front near the NM border and ambient dropped nearly 30 F. After lunch temperature never got over 245 F the rest of the day. The odd thing is the only reason I know how high the temperature got is that I installed a sending unit in the transmission. Other people pull much heavier than I do and they don't seem to have any more failures than average. The NV5600 seems to me to be a very stout transmission. I service it regularly, and I read the failures that I see on the TDR, and for what some ask of the NV5600, any LD truck transmission couldn't take the strain forever. Any one (like Doug Leno in the current TDR issue) that builds up boost pressure and dumps the clutch in third gear with over 1300 lb-ft of torque on tap proves that the transmission is very strong. Note all temperatures are by my Cyberdyne gauge set up.

 

[amsoilman]

My 03' with the NV-5600 now has 100K on it(sold to my Grandson this past fall) and the tyranny never shifted hard, even in colder weather. It was filled with the specified amount, using the Amsoil MTF fluid. The fluid was installed around 40K... ... . still there! I do not have any temp gauge installed, but have on occasion crawled under to feel it. It was never so hot I couldn't touch it... ... . Wouldn't want to leave my hand on it very long however.

 

[Prairie Dog]

Mine has never been hard to shift, just been a bear at times to get into 1st or 2nd after sitting at a light or stopped and idling in neutral for any length of time.

 

[JMetzger]

I wrote to John Holmes who use to work at Carson Dodge and asked him about the overfilling of the NV 5600 and this was his answer. "Yes, the early transmissions had the fill plug too low in the case. As I recall there was a TSB on those, but later models had the location moved upward. Have them check for TSB against your VIN at Carson Dodge. If you are really concerned, jack up the truck and tilt it upward on the side of the plug and the fill it. " I checked it out at Carson Dodge and my NV 5600 is a newer one so I just fill it as factory say's and with a 100,000 miles and 95% of it trailer towing it still works great (knock on wood).

 

[AH64ID]

Hmm, my truck was built 3 months before they quit making the NV-5600, think I have the newer version?!



I'll stick with 7 qts, thats about 1/4 quart overfull with my Fast Coolers.

 

[rbattelle]

Its not foaming in my case, I already checked for that several times... the oil contains no air bubbles when checked within 30 seconds of driving for several hours. I run either Reldine MTL (straight) or a blend of Redline MTL and MT-90 (1 quart of MT-90 and remainder MTL).

I just rolled 242k. Only part of those miles was run significantly overfilled. I overfill by a quart now, but I also run FastCoolers which make the added volume less than adding a quart to a stock trans.

I also have fastcoolers. My findings at the last fluid change:

-Factory capacity is 4. 75 quarts
-Fastcoolers allow 5. 0 quart at the fill plug level
-I added 5. 5 quarts total to the system at the last change, bringing the level within 1/2" of the top of the fastcoolers.
-Assuming there was 1/2 quart of residue left behind in the transmission when I started refilling, my total overfill could be as high as 1. 25 quarts.

So I'm somewhere between 0. 75 and 1. 25 quarts overfull.

What's interesting is that I have the clear lexan cover on one of my fastcoolers (no longer offered as an option). At both the factory capacity and the overfill that I have, I can see entrained air in the oil when the engine is running. Immediately after shutdown there is a layer of bubbles sitting on top of the oil, and the oil has a more "milky" appearance, indicating entrained air in tiny pockets (bubbles).

I'm not sure I'd call this "foaming", but there is definitely air being entrained in the fluid whether or not you overfill.

I've not tried pulling a sample 30 seconds after shutdown to see what it looks like.

Given the air space above the oil and the fact that during one revolution of the gearset some of the gears will exit the oil pool and then re-enter, it seems inevitable that you're going to entrain some air.

-Ryan

 

[AH64ID]

-Factory capacity is 4. 75 quarts

-Fastcoolers allow 5. 0 quart at the fill plug level

-I added 5. 5 quarts total to the system at the last change, bringing the level within 1/2" of the top of the fastcoolers.

-Assuming there was 1/2 quart of residue left behind in the transmission when I started refilling, my total overfill could be as high as 1. 25 quarts.



So I'm somewhere between 0. 75 and 1. 25 quarts overfull.

Very interesting, considering the Fast Coolers claim 1qt additional per cooler, so it should take 6. 75 qts to get to the factory fill plug. I know I put 7 qts in, and it just barely above the fill plug. It took about 6. 5 qts to get to the fill plug.

 

[steved]

If you don't pull the coolers and swab out the fluid trapped in the "sump" of the trans, it takes less than expected to fill... its surprising how much fluid gets trapped in the sump. Empty, I filled at 4. 75Qts; with Coolers, I'm around 7Qts.



As I said, I have literally shut the truck down, hopped out, rolled underneath, and popped the plug and drained MTL into a container... it was never foamy. You will always have some entrained air... it is the nature of the beast, but it should not look like a milk shake (for lack of a better description). Some fluids are better than others at resisting foaming, and anti-foam additives are used for this very reason.

 

[steved]

One thing I will note is that, in my case, trans temps do not mimic engine temps unless you do extended idling.

I run almost exactly 100*F over ambient temps (e. g. if its 50*F outside, my trans runs 150*F). You can also watch the temp rise/fall with load... pull a mountain in the Rockies might cause a 10*F rise, but it will fall off as soon as you level off. Towing doesn't really increase temps all that much... I just did three trips from GA to PA towing between 5000 and 8500 pounds, and temperature increase was minimal (although the increase was more apparent when pulling a hill).

If I overfill by a lot, the temperature runs hotter across the board and there is no variation at all... it simply rises, to around 120*F over ambient IIRC, and then stays right there regardless of load/terrain.

As previously noted, I have only been overfilling by a quart (fill until it runs out the OE fill plug, then add a quart through the FastCoolers) since I started this thread... I sit with 242k and finally feel my trans has only recently broken in (as far as shifting goes). I have not seen any appreciable metal on any of my magnets (rare earth magnets) in that time, so not sure if the overfilling actually poses an issue.

 

[steved]

I wrote to John Holmes who use to work at Carson Dodge and asked him about the overfilling of the NV 5600 and this was his answer. "Yes, the early transmissions had the fill plug too low in the case. As I recall there was a TSB on those, but later models had the location moved upward. Have them check for TSB against your VIN at Carson Dodge. If you are really concerned, jack up the truck and tilt it upward on the side of the plug and the fill it. " I checked it out at Carson Dodge and my NV 5600 is a newer one so I just fill it as factory say's and with a 100,000 miles and 95% of it trailer towing it still works great (knock on wood).

I thought this was later determined to be a G56 thing, and was not because of a misplaced fill plug; but because the bearings had not been prelubed on assembly???



I've read a lot of threads (probably thousands) on the NV5600, and this is the first I've heard of it... can you provide a TSB #??

 

[JMetzger]

I don't have a TSB# but I will see if I can get it from Carson Dodge.

 

[steved]

I'd definitely be interested in reading it!

 

[amsoilman]

Just for information, there is a test that is done for gear lubes called a "Foaming tnedancy" test (ASTM D-893)

This test is ran in three sequences. Sequence I is conducted at 24c, Sequence II is conducted at 93. 5C, and Sequence III after allowing the oil to cool back to 24C.



Air is bubbled through the oil for 5 minutes, and the foam generated is measured in millimeters immediately following the test. At the end of each Sequence the the oil is allowed to settle for 10 minutes and the remaining foam is measured again. Different grades of oils have differing minimum standards. For an example: a 50 grade oil has a 10/50/10 as a minimum.

 

[rbattelle]

If I overfill by a lot, the temperature runs hotter across the board and there is no variation at all... it simply rises, to around 120*F over ambient IIRC, and then stays right there regardless of load/terrain.

I don't see any reason to expect anything but higher temperatures with overfilling.

Too much lube in any closed system tends to generate more heat. More fluid means more pumping losses, which manifest as lower delivered power and higher oil temperature. "In this house we obey the laws of thermodynamics!"

-Ryan

 

[rbattelle]

As I said, I have literally shut the truck down, hopped out, rolled underneath, and popped the plug and drained MTL into a container... it was never foamy.

What plug did you pull, and did you drain out the entire transmission?



-Ryan

 

[steved]

I've done it two different ways... with 244k on the clock now (yep, another 2k last week), and average 20k changes; well, you can do the math. Obviously, the issue doesn't seem to have an immediate affect on transmission durability.

I've simply pulled the fill plug and let the excess drain out, and I've also popped the drain plug and drained the entire fill. I've never seen anything indicating foaming was an issue.

 

[rbattelle]

I've simply pulled the fill plug and let the excess drain out, and I've also popped the drain plug and drained the entire fill. I've never seen anything indicating foaming was an issue.

Very smart. You obviously see where I was going with that question.



Seems to me, then, that my fluid is foaming. Has been for many years now. We'll see if (or when) my transmission goes bad.



-Ryan

 

[AHofner]

The post about there being two different fill levels based on build date is interesting. Suppose someone was to find the difference between the fill hole levels and use that difference to determine the amount of extra fluid that the owners of the older NV5600's were to add in order to bring the capacity in line with newer NV5600. Shouldn't be too hard, they were only offered for 4-5 years.

 

[TMorgan1]

Has anyone considered placing a low flow low pressure pump and a transmission cooler on the NV5600? Looks like this would be a fix for the high temps created in this transmission. I would think a small cooler with fluid flowing through it would make the fluid stay cooler and last longer between changes. I haven't tried it yet but to me it is something to consider... ...