Sweating the Allison Temps in the Mountains

[Jerry Emert]

Can't claim newbie anymore but...  Finally retirement is here.  Last day of work is Friday.  We will be leaving Orlando FL for the Grand Canyon on the 1st of May, taking 4 or 5 months to get back to Orlando.

I have asked a few times about my Allison temps.  When I first bought the PT in 2014 I noticed the temps went up to as high as 225-226 after driving awhile, no check engine light.  No driving problems noted.  Last year I got the radiator and CAC cleaned before a trip to DC.  On the trip the highest temp was around 215 ish even up and down mountains on I 81 and I 77.  I was researching surge tank replacements here earlier and noticed all the posts on temps again.  Y'all seem to get concerned when your temps even get to 200.  I'm reading all temps on the Aladdin.  You all are my resident experts so now with the trip out West looming ahead, I am again concerned.  Engine temp usually runs at 188 - 190.   My questions:
1.  Since it appears that the coolant is flowing, or I would probably have more issues, what can be causing these higher temps?
2.  Can it be that wax valve I see on posts, how do I test it?
3.  Can it be the fan not going to high speed?  How can I tell?  Am I back to the wax valve again?
An Allison Rep told me that the transmission will not even begin to be bothered until temps North of 250 are reached.
Finally, thanks in advance for your help!  Hope to see y'all on the road.

[Joel Weiss]

Jerry:

I don't have any solid answers for you with respect to the cause of your higher temps, but I can confirm that my Allison rarely gets to 194 and I don't think I've ever seen it get to 200.  Its temps increase when it is actively shifting; straight highway driving reduces temps compared to even rolling countryside where it repeatedly shifts between 4,5 & 6th.  Increased engine rpm reduces the temp under most conditions; when you are in the mountains do you gear down to 4th instead of letting it hunt?  When I'm climbing steep hills I like to force mine into 4th which keeps everything running cool and puts me near the HP peak rpm throughout.

I doubt that anything you are doing is the real reason for the higher temps, but changing some of your driving styles might help you keep it on the lower end of the scale.

[Edward Buker]

Jerry,

If the engine temp is holding temperature in the proper ranges which it seems to, then one has to assume that the wax valve, engine cooling pumps, thermostats, fans and radiator are all working properly. Every coach is a bit different in temperature variation and I assume that you have a standard coolant pass through cooler for the transmission. This means that the transmission cooling heat exchanger is running at engine temp to begin with and the heat exchange temperature differential, the more temperature offset there is, the more effective the cooler. As the engine temperature rises so will the transmission temperature, this is all normal. I think the limit for the transmission to start derating is 262F, you are far from that value. One of the more sensitive values regarding fan speed and cooling is the intake manifold temperature, once the fan initially kicks on that temp will drop significantly and stay reasonably steady at some much lower value. You can check that value and see if it is responding normally and showing that you have good airflow being maintained at driving speed.

So what you can do at your end is go into neutral while stopped at lights (or longer), this helps keep the temps down, lower your gear while climbing to keep the engine rpm up, I would be sure to be using Transynd fluid, have the filters serviced at the proper interval, and have the fluid analyzed. While they are looking things over have them check for any flexible transmission cooler hose that is collapsed, or crimped at a bend. If the fluid is good, hoses are good, and the operating range of temperature for your engine and transmission do not change over time, temps stay consistent with the past history, then don't worry about it and enjoy your retirement. The issue with transmission fluid is temperature over time. That is, if 215 is normal for you and you get to 225 for some duration and when you stop climbing or it is cooler out and the fluid temp is back to 215 then this is all OK. You could spend a lot of money looking into what might be, without ever really gaining anything.

Later Ed

[Mike Groves]

I am noticing for the first time, and also my first trip from Portland to Bend Oregon via 26 that while descending into Madras from the west and while using both exhaust brakes, toggling, between low, high, normal, low, high to keep my speed in check (rather than braking) that my transmission temp got to 200 for the first time I've seen it do that since I purchased the coach in September, 2013.  Sounds like I have nothing to worry about, but with the posts saying keep your rpms up and this will reduce the temperature, well, mine goes into 4 gear and the RPMs on these slopes got to 1900 and 2000 at least.  I don't think I ever got close to 2300 (which I think is max).  Has anyone noticed this sort of temperature rise?

Mike

[Dwight Wilson]

We just returned to Canada from San Diego and had been pulling the Toad up/down during some 80 degree days when the hydraulic line to the side draft fan started blowing ATF as the fan pressure increased so I was keeping very close attention to the temps on my Aladdin. The engine seldom went above the thermostat temp of 194 and the trans maintains a temp of 175 or below pretty consistently. At 194 the fan pressure was low enough to drive without a cloud of embarrassment until I had the hose replaced a few miles up the road in Las Vegas. Caught it fairly early as I only dumped about 1 gallon of Dextron.  Please check those lines to the fan motor as they were assembled at the factory in such a way that they rub against each other so over time can fail.
My normal engine temp is about 194, trans about 175F,
Dwight

[Dave Atherton]

Mr. Wilson, sounds like the new hydraulic hose may be the problem. All hydraulic hoses may
Have different size for fluid to flow under pressure. it sounds you may have a restricted opening
Creating back pressure flow and creating heat expanding your fluid. The restriction may be in the size of the insert fitting into the hose or wrong size hose. Dave Atherton Retired Cat Mechanic

[Jerry Emert]

Jerry,

If the engine temp is holding temperature in the proper ranges which it seems to, then one has to assume that the wax valve, engine cooling pumps, thermostats, fans and radiator are all working properly. Every coach is a bit different in temperature variation and I assume that you have a standard coolant pass through cooler for the transmission. This means that the transmission cooling heat exchanger is running at engine temp to begin with and the heat exchange temperature differential, the more temperature offset there is, the more effective the cooler. As the engine temperature rises so will the transmission temperature, this is all normal. I think the limit for the transmission to start derating is 262F, you are far from that value. One of the more sensitive values regarding fan speed and cooling is the intake manifold temperature, once the fan initially kicks on that temp will drop significantly and stay reasonably steady at some much lower value. You can check that value and see if it is responding normally and showing that you have good airflow being maintained at driving speed.

So what you can do at your end is go into neutral while stopped at lights (or longer), this helps keep the temps down, lower your gear while climbing to keep the engine rpm up, I would be sure to be using Transynd fluid, have the filters serviced at the proper interval, and have the fluid analyzed. While they are looking things over have them check for any flexible transmission cooler hose that is collapsed, or crimped at a bend. If the fluid is good, hoses are good, and the operating range of temperature for your engine and transmission do not change over time, temps stay consistent with the past history, then don't worry about it and enjoy your retirement. The issue with transmission fluid is temperature over time. That is, if 215 is normal for you and you get to 225 for some duration and when you stop climbing or it is cooler out and the fluid temp is back to 215 then this is all OK. You could spend a lot of money looking into what might be, without ever really gaining anything.

Later Ed

Thanks all, I guess I forgot to add that the transmission temp seems to go down significantly my speed decreases.  Everytime I stop at a light when I get into town, without shifting to neutral, the temp goes way down.  It seems that it is just highway driving at 60 or so that the temp creeps up over time.  I guess I'll just keep an eye on it and hope we don't end up on the side of the road on the first "real" mountain.
Retirement party tomorrow night.  50 of my fellow Law Enf. Officers and "friends" in attendance so I'm sure it will be a "roast" of epic proportions.  Wish me luck!!
Jerry

[Edward Buker]

Jerry,

One other thought, also take a infrared gun and check your rotor temps after driving some distance maybe a mile or so without using your brakes to any extent. Try and pretty much coast to a stop and try and get a temp reading on your rotors and/or drums. See if they are similar. Check rotor temps vs other rotors and drums vs drums. If you had a brake partially dragging it could add some issues with heat being generated in the drive train. Usually there are other signs if you had a brake dragging, like an overheated brake smell. The other way is to jack the coach up and verify that the effort used to move the wheels is normal. This seems unlikely but I thought I would mention it given your concern.

Later Ed

[Jerry Emert]

Thanks Ed, I'll check.

[Jerry Emert]

Thanks Ed, I'll check.

Ed, I checked all the hubs several times.  Temps were all in the same ballpark 130ish.  On the trip from Tusayan to Cortez the other day the trans temp got up to 240 which made me a little concerned.  Hills don't seem to affect the temps much.  If I was doing my normal 62mph the temps just keep rising.  As soon as I slow they drop.  Doing around 57 they stayed in the 232 range which I am OK with, surprisingly.  Outside temp was around 95. 
Do you, or anyone, know of some manual, a book I can buy or something that will explain the workings of the transmission cooling and engine accessories.  There has got to be something.  I will try to check the hoses as well as I can for kinks and such.  I know very little about how these beasts work and I need to know more.  I read all these posts and others religiously every day.  They have helped immensely but I need to get deeper. 

Thanks as always.
Jerry

[Edward Buker]

Jerry,

Do you know if you have Transynd synthetic fluid in your transmission? You may have said at one time but I do not recall. There should be a round unit with the name Racor on it between the transmission and the radiator. There are several hoses from the transmission that the fluid runs through and a larger one at each end that the coolant runs through. That is the transmission cooler if you have the same configuration as mine.

Sometime when it is at temps that seem high to you, see if you can IR gun the outside metal tube of the Racor Cooler unit and the bottom pan of the transmission. See what temps you get with a few readings on each vs what the transmission temp monitor readout is at the same time. You would do this stopped at idle in a rest area or truck stop. Be safe when you check these if you decide to do this. You can usually get a reading at some distance. You can check out the access to get these readings and the locations when the coach is cool in a campground. One possibility is that the temp sensor is defective or is improperly calibrated. While this is not to likely, it is possible and would be an easy solution.

Beyond that you should consider having the transmission fluid analyzed by an Allison shop. If the fluid is fine and they inspect the hoses and they are fine and the engine temps are well managed then the cooling system is doing what it was intended to do.

I know these higher temps bother you but the question is will the transmission tolerate these temps well and function properly. You might get a shorter fluid life but that is manageable. This is not a clear cut case where there is some root cause that has declared itself and you know a solution or if it is enough of an issue to spend a lot of money on. I think a visual inspection of the transmission fluid piping to the Racor,  engine coolant lines going to the Racor cooler, and the cooler itself would be prudent to see if anything obvious is seen by a knowledgeable shop. I also think that having Transynd in the transmission and analysis done is prudent. At some point it may be prudent to pull and inspect the transmission cooler if it is suspect. If you did that I would consider putting a new one in given they have a life and have been known to fail. In your discussion with the Allison shop or truck shop you choose there may be some other action but pulling things apart and starting replacing things without a known cause is a path you do not want to be going down in my opinion.

In my work life we were always trying to determine what is a blemish vs what is a defect. Some time things look bad but will function perfectly well and last. Sometimes the opposite was true. This is one of those cases where it is not clear cut and take your time sorting it out with a good shop.

Later Ed

[Jerry Emert]

Thank you Ed.  I did check the temps at the pan and they were the same as the Aladdin and temp gauge.  I will try to find a trustworthy shop in an area I'm at to inspect the hoses and pipes.  Thanks to everyone that has tried to guide me in this.
Jerry

[Gerald Farris]

Jerry,
It sounds like your coach is not equipped with the liquid to liquid transmission cooler in the lower radiator hose the Ed is referring to. Monaco used an internal radiator tank cooler (less efficient) on some coaches and no cooler at all on other ones. So to give you an informed opinion about your transmission temperature we need to know which transmission cooler you have. If you have no transmission cooler, you might consider installing one, but don't over do it because it is not good for the 4000 Allison to run too cold either.

The bottom line is that the safe operating range for TranSynd in A 4000 series Allison is up to 250 degrees, and since you are not hitting that temperature, there is no need for alarm. However a transmission fluid analysis my be a good idea at your next chassis service.

Gerald

[Jerry Emert]

Thanks Gerald.  We are on our way to Moab now.  Temps started creeping up so I dropped into 5th gear.  Even running at the same speed as I was temps dropped about 9 degrees.  62 was about 1700 rpm =- in 5th, 1595 in 6th.  So fuel milage suffered but I got temps down a little.  I wish I knew how to tell if it had a temp cooler or what kind.  I checked all temps in the engine area.  Temps on engine were about 190.  What looked like it should have been the intake on left of engine was about140ish.  All hubs less than 140.Transmission pan after sitting for about 5 minutes was about 209.  When I pulled in to rest stop the Aladdin was reading 223 which isn't bad.
Another note is that I still have the Amsoil ATF in the transmission that the mechanic put in last year.  I'm about recovered from that almost 2k LOF to have it changed soon.  The Amsoil does say that it is 295 compliant.  The transmission guy on the other forum declined to say that it would not work in the transmission and just recommended a analysis from his company!  Thanks again I will update if I get any new info.
Jerry

[Lee Welbanks]

It is pretty easy to tell of you have some kind of cooler on your trans, the cooling lines (2 hoses) come out of the back of the trans and will go to whatever you have for a cooler, mine go into the bottom of the radiator and come out the other end back to the trans, I would say your trans temps are way too high, I suppose that if you do have a cooler it could be plugged up in some way, I've seen some really weird things in all my days with trucks so most anything is possible.