255 Degree NV5600 ... Cause for Concern?

[JeffBob]

I just picked up a used 2005 3500 w/ 60k on it and towed from Atlanta to Mid-Ohio with it pulling a 12,500 lb trailer at 65 mph. Part of the route is through TN mountains (hills if you're from out west ). Before leaving out, I installed Hawk Superduty brake pads, Bilstein shocks, a pair of Fast Coolers, Amzoil in the trans and diff, and a set of gauges, one a temp on the six speed manual trans. Since this is a 12 hour tow I watched (in horror) as the manual trans temp gauge continued to march northward -- past 180, past 200, past 220 ... At 250 #@$%! I stopped by the side of the highway on an off ramp and shot the PTO covers with my infra-red heat gun -- it showed 225, so 250 in the oil seemed (unfortunately) to be plausibly accurate. I was hoping for a bad sender on the temp gauge. :{



It would go on to peak at 255 ... twice. Cooler ambient temps and rain cooled it down for a bit, but slowing & 5th gear didn't seem to help much. Temp sure goes up faster than it comes down unless you shut down, then it cools to 180 in 30 minutes or so if you shut down.



My truck has 2:75 rear gears and I filled the trans to the fill hole, I did not over fill it. So with the pair of Fast Coolers it took about 1 quarter more to the fill hole than without. There were no oil leaks, the Fast Coolers sealed fine.



Please tell me this is perfectly normal and sustainable for the transmission.



But just in case, anybody try installing one of these?



NV4500 NV5600 Dodge Transmission Cooler ATS 310-910-2164



I didn't expect more than 220 through the mountains.



I've dropped trannys before, and this one shifts fine and has no gear wine. Other than the temp gauge, there would have been no indication of the heat in the unit.



I bought the truck to pull this trailer, so it would seem I should eat the $1200 and install a real oil cooler, or perhaps something is amiss inside the unit?



I'll pull an oil sample and send it to the lab tomorrow and see if the 1,200 miles shows any oil breakdown or metal / bearing material in the oil.

 

[HBarlow]

JeffBob,

You posted this in the Cab and Chassis forum so it won't get much attention if any from NV-5600 owners.

With a sustained period of operation the transmission is not likely to run any cooler than the engine block. I don't know if 255* is common or uncommon. I had a NV-5600 in an '01 Ram dually and pulled heavy with it on occasion. I don't know what transmission fluid temp was, didn't have a gauge on it. That might be completely normal. Mine failed at a little over 300k miles due to inadequate lubrication and lots of miles, but not heat.

Try calling Standard Transmission in Fort Worth, TX. Standard is a top notch rebuilder and TDR advertiser. They should be able to answer your question.

How could your truck have 2. 75:1 differential gears? Standard gears in your truck should be 3. 73 or 4. 10.

 

[seafish]

Sure is NICE to have gauges, isn't it ?? Oo.

Did you add the extra quart of oil with the Fastcoolers ?
Some people find that the extra fluid might actually make the NV5600 run hotter instead of cooler, based on the info in this thread--


Check out the info in this thread here on TDR,,,


https://www.turbodieselregister.com...mal-operating-temperature-nv5600-6-speed.html

 

[AH64ID]

The fast coolers should require 2 extra quarts to get to the OE fill level. I put 7 qts in mine to get it slightly overfilled as recommended by many.

I beleive that the Amsoil MTF is good to 300 or 325° before there is any cause for fluid concern.

I don't monitor trans temps, but I have recently wrapped my downpipe with exhaust wrap and the trans seems cooler to the touch.

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[Diesel Thunder]

Welcome to TDR,



I really wouldn't worry about it. I have the fast coolers with guage and put in around 7-7. 5 qts and I can hit 220F while cruising at 80mph in 100F Texas heat---unloaded. So 255F pulling 12K over (most likely) Monteagle Mountain, North of Chattanooga, TN; does not sound too bad to me.



I would just watch for leaks and go ahead and fill it up with additional fluid (to the top of the fill plug on the fast cooler--not the transmission fill plug) and change at regular intervals. My interval is 25K with the OEM Mopar fluid. And, as you mentioned... ALWAYS drop to 5th when pulling grades, even though the Cummins will laugh at that load and do it in 6th, your transmission will appreciate you. From past posts, I believe 6th gear is on a countershaft while 5th is on the mainshaft---so when loading up with torque, 5th is more robust. (OTHERS CHIME IN IF I'M WRONG PLEASE).



One other piece of advice, check to make sure the vent hose on the transmission is free of crud on the vent (mine comes up into the engine bay near the exhaust elbow behind the turbo). If blocked, the expansion of the fluid can be hard on seals when hot.





Congrats on the truck... . I love my '05.



Cheers.

 

[Kirwin]

It's normal

I have had gauges on both of my 5600s. Normal, not towing, they run 220-235. Towing in 95 F ambient, temperature can exceed 255 F which is the top of the range on my Cyberdyne gauge. Normally I see around 240-250 towing my 12K trailer. I takes several hours for the transmission to reach that temperature. My combined weight is around 22K. I do have a Fast cooler on one side and a manual transmission filter from Genos on the other. I run the stock oil from Dodge. Ken Irwin

 

[ENafziger]

As mentioned above, unless you heavily wrap your exhaust, I think the cooler on the passenger side may not be helping to cool the transmission. Just curious, where do you have the temp sender installed?

I have the G56, which obviously is an aluminum cased transmission, but I've never seen over 225° F towing at over 20k for a couple thousand miles at a time in summer.

--Eric

 

[steved]

Keep in mind, gauges aren't always accurate...



I have personally never seen over 230*F before FastCoolers, and never seen over 205*F with FastCoolers; and that was verified with a infrared thermometer. And that includes towing upwards of 10k. I run about 100*F above ambient.



There are probably many variables... fluid choices, load, build tolerances, external heat sources, fluid level, gauge accuracy, sending unit placement, etc... .

 

[JeffBob]

Thanks for all the replies, experience and perspective. I'm feeling better about this as it does not sound uncommon to hit 250+ on long tows pulling 12k lbs.

I have a theory that the Fast Coolers may be heating the oil in the exhaust side od the tray, since they are close to the exhaust, so I like the advice of adding a heat wrap or barrier to the "hot" side of the transmission.

Had a typo in my gears, meant 3:75.

Here's what I've done in the interim:

I pulled an oil sample and sent it to the lab to determine whether the Amzoil is breaking down from the heat or whether something in the transmission is coming apart and shedding metal into the oil. Awaiting results. As for max oil temp, the Amzoil is good to 300 degrees, but if the bath is 255 on average, then what's the temp of the oil coming off the gear face? And the hotter the bath temp, the hotter the oil on the gear face perhaps? By 255 I suspect the oil could be over it's max temp.

So, I cobbled together another oil cooler system to remove the excess heat on long tows - Derale stacked plate cooler with a powered fan, 8AN steel braided hose and fittings, Tilton gear oil pump, sandwich plate and oil filter and I'm going to plumb it into my Fast Coolers.

For about $700 in bits, I figure a cooler trans has to live longer than a very hot one.

 

[HOBrian]

I eould love to see pics of the install!!!

 

[JeffBob]

I will try to shoot some and post them, so far, it's just a box of incomplete parts; hoping to tackle the project this weekend. I'm going to have to remove both Fast Coolers and re-install them (I installed one upside down, with the fill plug "down" thinking "drain" rather than "up" for fill. This also left my temp sender mounted in the air, above the oil, so I suspect an inaccurate reading as I'm not sure it's immersed in oil, so we'll see what happens when I flip it. I don't plan to overfill the transmission above the fill hole level as I believe that will actually impair its ability to circulate (throw) it's oil properly throughout the case.

But the first challenge will be where to put the oil cooler -- I purchased 20 feet of steel-braided line thinking I'd mount the oil cooler under the front grill, but now I don't want to mount it to the front of the truck as it will heat all the other units behind it -- a/c condenser, inter-cooler, radiator. I put an engine oil cooler on my E350 class C and the radiator temp has been forever higher.

 

[macdaddy]

Remove the cooler from the passenger side and see what happens??



Mac

 

[JeffBob]

Yes, that would be an interesting test, wouldn't it? I suspect the exhaust pipe IS heating the oil on that side.

Also, the Fast Coolers really aren't in any air stream, and certainly not a cool one, as all the air from the engine compartment -- past the a/c condenser, the intercooler and the engine radiator has all been "pre-heated" by the time it arrives in the transmission tunnel.

I did notice big drops in transmission temp with ambient temps and rain -- cold water hitting the underside really helped cool it down.

I still haven't decided which side to pull the hot oil and which side to return the cool oil ... I'm assuming the big main center gear rotates and spins such that oil is splashed at the top of the gear from the driver's side toward the passenger side of the transmission. So if I return cool oil on the driver's side, it will be distributed toward the passenger side, heated by the gears (and the exhaust), so thinking I should pull hot oil out on the passenger side.

Anyone have any thoughts on this? If so, I welcome any and all ideas.

The oil temp sender is on the driver's side, or cool side, plumbed to the Fast Cooler, but upside down. This might inflate the temp sender read. But my infra-red heat gun registered 225 on the PTO plate when the gauge read 250. So the oil bath may be hotter near the trans center, than out at the end of the PTO plate. Which would indicate the Fast Cooler is doing something. And that the temp at the gear faces could be > 300 degrees F, which is my concern and will be interesting to see oil sample test results. If the Amzoil broke down in the 1800 miles I towed with it, then we know the gear face temp exceeds 300 degrees.

Place your bets! Should know in a couple more days the oil sample test results.

 

[NavyDood]

Thanks for all the replies, experience and perspective. I'm feeling better about this as it does not sound uncommon to hit 250+ on long tows pulling 12k lbs.

I have a theory that the Fast Coolers may be heating the oil in the exhaust side od the tray, since they are close to the exhaust, so I like the advice of adding a heat wrap or barrier to the "hot" side of the transmission.

Had a typo in my gears, meant 3:75.

Here's what I've done in the interim:

I pulled an oil sample and sent it to the lab to determine whether the Amzoil is breaking down from the heat or whether something in the transmission is coming apart and shedding metal into the oil. Awaiting results. As for max oil temp, the Amzoil is good to 300 degrees, but if the bath is 255 on average, then what's the temp of the oil coming off the gear face? And the hotter the bath temp, the hotter the oil on the gear face perhaps? By 255 I suspect the oil could be over it's max temp.

So, I cobbled together another oil cooler system to remove the excess heat on long tows - Derale stacked plate cooler with a powered fan, 8AN steel braided hose and fittings, Tilton gear oil pump, sandwich plate and oil filter and I'm going to plumb it into my Fast Coolers.

For about $700 in bits, I figure a cooler trans has to live longer than a very hot one.

Not to sound like a smartarse, but you did use the Amsoil Manual Synchromesh Transmission Fluid (MTF), right?

 

[JeffBob]

Yes, that's the oil that the Amsoil website recommended. Ironically, I've used Redline in all my drivetrains for, wow, I guess > 25 years now but gave this stuff a whirl. If the Syncromesh is "burned" or compromised by the oil analysis I'll take that opportunity to switch to the Redline MTL when I install the oil cooler and filter system.

 

[S.Morris]

"

. As for max oil temp, the Amzoil is good to 300 degrees, but if the bath is 255 on average, then what's the temp of the oil coming off the gear face? And the hotter the bath temp, the hotter the oil on the gear face perhaps? By 255 I suspect the oil could be over it's max temp. "







The gear contact temp underload runs approx 50% higher than the oil bath temp. I once saw a Fuller RR 15 spd come into shop that had been driven over 500 miles(after he dropped his trailer) that was locked in 8th gear(4th on the front box). (Made for interesting takeoffs from a stop).

Anyhow..... when we pulled transmission there was not much more than a cup of oil in it instead of 20Liters. Most of the gears were blue, except the4th gear it was running in and the bearings were not blued. The oil was synthetic(what there was of it). The whole cause was from a leaking cooler line. Cost the guy a lot of $ as the whole thing pretty much junk . I could not believe the transmission had come that far with next to no oil in it without seizing . This was more than 15yrs ago in British Columbia.

 

[SRadke]

FWIW, most of the trans coolers on older class 8 trucks are mounted under the truck somewhere. Some not even where they'll get much airflow but they still do what is required.

 

[JeffBob]

I've seen a lot of concern expressed about the risks of oil coolers and lines that could leak and cause catastrophic transmission damage.

Perhaps because I have a 911 track car that's significantly oil cooled, I'm more comfortable with steel-braided oil lines (my Porsche runs 12-AN lines from the rear oil tank to a front sandwich plate oil cooler and back). Clearly these must be inspected and kept maintained. The biggest risk is a puncture to the front oil cooler. While I have an oil pressure gauge in my 911, that doesn't mean I'm looking at it (I should tie a large alarm to oil pressure drop). The first indication of an oil leak is (unfortunately) usually oil on the tires and total sudden loss of traction. This happened to my father in an M3 when he suffered a puncture to his car's engine oil cooler. Fortunately, the resulting on-track wreck was very minor despite the high speed.

I believe that periodic visual inspection of the oil lines is sufficient protection AND the fact that this NV5600 seems very sensitive to falling oil levels (the synchros in 3rd are not happy since I removed 1/2 a pint of oil for the oil sample. ) Or, I'm thinking I should just make the switch to the Redline MTL when I install the oil coolers and just toss the $60 in Amsoil that's in there. In my experience, the Redline is much better formulated for accurate synchromesh performance. My 911 and BMW's shift like butter with it. These synchros require very slow shifts, esp since I took the oil sample! (Or fried the oil from the last trip at such high temps. )

 

[JeffBob]

As for the 50% higher oil temp over bath -- that would confirm my worst fears -- So at 255 degrees, 50% higher is another 127 degrees, which is a whopping 382 degrees! That's 82 degrees over the Amsoil's 300 degree limit.

Based on that 50% relationship, 200 degrees is the max average bath temp that should be permitted using a synthetic. I don't even know when the dino oils would give up the ghost.

Wow, that's scary.

No wonder these transmissions are dying, they're just too hot!

I saw this with RV engine's too -- blowing at 40k and 60k miles -- and it's not like you see RV's burning up the highway at 80 mph!

Had a Class C, so I put a gauge on the engine oil pan -- 250! On a cool night, pulling an empty trailer! So what? 285 degrees plus on a hot day, pulling a full load up a hill with a headwind? (Which seems to be the norm wherever you're going in an RV, even in FL where there's no hills. ).

So I put a $70 oil cooler on it and never saw more than 230 degrees.

I think the NV5600 suffers from the same plight.

Look, let's face it, they want us to buy new vehicles, the best way to do that is plant bombs somewhere in the vehicles we already have.

And what better way then high oil temps? Who's bothering to put gauges on everything? It's expensive! Only nut job enthusiasts!

My 911 couldn't cool itself either without me adding the front oil cooler. Tried to put one on my BMW, but you can't! It's like $4k in parts?! I can get a used motor for that! Coincidence or conspiracy?

 

[AH64ID]

I don't read or hear about enough NV5600 failures to buy into that.