NV5600 and quart overfill = hotter trans?

[steved]

Anyone else notice this? Overfill by the "recommended" quart and the trans runs hotter. Not the first time I've noticed this either...



I would see temps typically less than 40* over ambient outside temps. Running with the quart overfill, I'm seeing around 100*F over outside temps.



Thoughts?

 

[abranz]

When I bought my reman nv4500 from standard trans I asked about overfilling and they said not to do so due to excessive foaming and consequently higher temps.

Tony

 

[moonranch]

When I run my truck on the highway I typically see trans temps of 160-180deg once it finally warms up.

 

[steved]

When I bought my reman nv4500 from standard trans I asked about overfilling and they said not to do so due to excessive foaming and consequently higher temps.

Tony

Different trans, and different fluids (75w90 gear oil versus 70w80 synchromesh fluid). Not saying that couldn't happen...



I did suspect foaming at one point, immediately pulled into my driveway after a 300 mile run, and pulled the fill plug... no foaming was indicated, the fluid that ran out was clear.

 

[steved]

When I run my truck on the highway I typically see trans temps of 160-180deg once it finally warms up.

If I would drain the excess fluid out right now, my temps would not even make the guage move off the cold mark of 125*F. With it overfilled, it runs 100*F over ambient (if its 40*F outside, it runs 140*F).



I have been back and forth over this several times... so I have seen the trend.

 

[Gary - K7GLD]

If I would drain the excess fluid out right now, my temps would not even make the guage move off the cold mark of 125*F. With it overfilled, it runs 100*F over ambient (if its 40*F outside, it runs 140*F).



I have been back and forth over this several times... so I have seen the trend.

As has been suggested previously, I sorta wonder if any increased transmission temps seen with significantly increased lube levels is more related to better heat transfer off upper transmission shafts, gears and bearings - possibly a GOOD thing, if the choice is between keeping that heat localized in those components vs dispersing them with the lube?



A possible analogy might be engine lube level that falls below the oil pump pickup - in which case, the engine starves for lube, and eventually fails - but the lube temp is quite cool...



I did some trial runs a while back with "normal" lube levels, and saw typical fluid temps rise about 50 degrees nominal above ambient, both towing and empty - I have since added a couple quarts additional, and when weather improves, will try another bunch of runs to see what differences surface...

 

[steved]

From what I have gathered, there are two typical thoughts (assuming no fluid foaming)...



The first is that some part in the trans typically runs hot and is being cooled by the increased oil level. Imagine, if you will, that cruising 60mph has all the oil (at a normal fill level) whipped up into the recesses of the trans (the oil whipped upwards exceeds that which runs back to the sump) and the big gears hanging down into the bottom of the case are simply scavenging oil that runs back to the sump... potentially something isn't getting all the needed oil for cooling.



The second is that we've flooded the sump and the oil can no longer get whipped/slung around the case. In this theory, some part is not getting the lube it needs and is running hotter than it normally would at a normal fill level.



In either case, we see an elevated temperature... something is getting cooled that was running hot, or something is running hotter since its not getting lube.

 

[steved]

I've got right around 100k on this trans with the quart overfill... some of that is with coolers. The main thing I've noticed its the temperature, but that also typically translates in shorter fluid service life in my trans... when it runs hot (during summer months I reach around 200*F), the fluid will start to degrade shifting qualities... drain and refilling brings everything back to normal for another go around.

I've probably ran 55 gallons of lube through this thing to date... the longest I've gotten is around 20k before the shifting starts getting bad again. Most times, one 500 mile run of 200*F+ will cause the fluid to require changing.

 

[Gary - K7GLD]

I've probably ran 55 gallons of lube through this thing to date... the longest I've gotten is around 20k before the shifting starts getting bad again. Most times, one 500 mile run of 200*F+ will cause the fluid to require changing.

Makes me wonder if there might be a significantly wide variation between transmissions and internal tolerances - enough in your case to cause the lube temp variations relative to levels, as well as shifting quality?



My own 5600 has always displayed the typical 5600 tightness in shifting, combined with a very SLIGHT tendency to "catch" a tooth on 2-3 and 3-4 shifts - mostly limited to the first half mile of driving in cooler ambient temps. Otherwise, my specific transmission has been fine, far less complaints as to shifting quality than some here have with theirs.



It will be interesting to see if I come up with the same higher lube temps as you have, now that I too am running a couple of quarts overfilled.

 

[steved]

And as far as shifting goes... by degraded, I mean it takes longer and longer to catch the next gear.



When my fluid is bad, it will literally take several seconds to shift between gears (without catching "teeth", which I think I was told are actually the synchronizers)... if I force it, it catches teeth.



New fluid is almost (and I said almost) like driving a car... but one good run of 200*F will severely degrade the shifting.

 

[AH64ID]

New fluid is almost (and I said almost) like driving a car... but one good run of 200*F will severely degrade the shifting.

That there tells me the extra heat isn't good...

 

[steved]

That there tells me the extra heat isn't good...

But that happens regardless of fill... before the coolers, the temps would approach 235*F with normal fill and temps approaching 110*F. The temps affect the fluid, but the heat can be there there regardless of fill.



Even overfilled the temps with coolers don't approach those without coolers and normal fill...

 

[JHorst]

steved

I agree with your experience to date. My 5600 operates the same. I have a set of fast coolers and run about 7 qts. The temps as you say are about 100* over ambient (in 6 gear). If I drop down to 5th, (towing 14,000 lbs) it will cool down to about 80* or about 170* in the summer. I also watch the temp and down shift to keep the temp not over 195* or as you say the shifting quality goes out the window and need to change fluid $$$. I installed a extra heat sink with fan from a old CPU on the driver side pto cover. This helps a little, mostly after stop. I am thinking about bending some metal for a air scoop on the passenger side and wrapping the exhaust pipe. Anything the keep the temps under 195*

 

[Gary - K7GLD]

I installed a extra heat sink with fan from a old CPU on the driver side pto cover.

Sorta like this? :-laf



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[MMeier]

Gary...

... is that sending unit just epoxied to the case? Steve, how are you getting your readings?

 

[steved]

... is that sending unit just epoxied to the case? Steve, how are you getting your readings?

I have an actual oil temp sender installed into one of the PTO covers...

 

[JHorst]

Yep, however I kept the fan attached to the heat sink. The rain does not seem to effect the fan. Wired the fan with a thermo switch.

 

[MMeier]

I have an actual oil temp sender installed into one of the PTO covers...

Whereabouts on the cover? Just trying to get an idea of where some get their readings from. The covers that went on my 5600 do have a port on them... just for the record, not the real deal FAST coolers but a close resemblance. I have the a pillar mount with single gauge hole I'll put the gauge into here in a few months when I first service it. Then on the 4500 in the '93 I'll use the port on the actual FAST coolers I 'll be installing.

 

[JHorst]

I have a sender in both fast coolers (backup) and the temperature runs about the same. Same temperature side to side.

 

[AH64ID]

But that happens regardless of fill... before the coolers, the temps would approach 235*F with normal fill and temps approaching 110*F. The temps affect the fluid, but the heat can be there there regardless of fill.



Even overfilled the temps with coolers don't approach those without coolers and normal fill...

Gotcha. . what fluid are you running? Have you tried amsoil, supposed to be good to 300*F...

I have a sender in both fast coolers (backup) and the temperature runs about the same. Same temperature side to side.

Did you buy 2 sets? My Fast coolers only came with one tapped cooler.