Another Transmission Temp Question

[Jerry Emert]

I am still concerned about my transmission temps.  We are slowly working our way West from Florida.  Not a new problem for me but today we were on I-40 in TN.  Rolling hills for a hundred miles or so.  Temp got as high as 230.  Engine temp never went over 190.  No power issues, no shifting issues.  She was running like a top at 62.  It took about 2 hours to get that high, rising slowly.  Cools quickly when stopping for fuel or at a rest stop.  No check engine or high temp lights lit.  Gauge on dash and Aladdin temps agree.   I checked the temp with an IR thermometer on several places on the transmission immediately after stopping.  Temp was 221 on the thermometer.  Radiator and CAC cleaned about a year ago and temps stayed high after that was done.  We have been checking the hub temps as (I think) Ed suggested for a brake hanging up.  All hubs about the same, give or take. 
I talked to an Allison Rep. who said he wouldn't even begin to be concerned until higher than 250.  My concern is that everyone of you have quoted temps in the 160-190 or so range even going up and down mountains.  We are going to be in those Western mountains in a couple of weeks.  If they are 230 now, what are they going to be in real mountains?  So I guess bottom line is, do any of you have any ideas what is causing this?  Could it be normal?  Any of you routinely see T-temps like mine?  Sorry to be a pain in the Butt with this question again.  I appreciate y'alls expertise and help.
Jerry

[David T. Richelderfer]

I suspect our 2004 Marquis had a transmission temperature issue in the past by its prior owners because there has been an auxiliary transmission cooler installed.  Since we have owned the Marquis the transmission temperature runs 40 to 50 degrees above outside ambient temperature.  On a hot day, say about 100F outside, the transmission temperature will get to about 140F.  And that is the highest temperature I have seen in almost four years.

From all the stories here on the Forum relating concern about transmission temperatures I would submit that high transmission temperatures for our Beaver coaches is the rule, not the exception.

[Keith Moffett]

Seems to me I recall reading in a manual that an Allison doesnt reach operation temp until about 185 deg. But the driver should shift to a higher gear to get the RPMs up if temps go over 220 deg.

[George H. Wall]

Keith, I think you mean a LOWER gear to get RPMs up??  Henry

[Gerald Farris]

Jerry,
What type of transmission cooler does your coach have? If your coach has a cooler in the radiator tank, you are in the ball park with your temperatures. If your coach uses one in the lower radiator hose, your temps are a little high, but not excessively so. In fact, Monaco for some reason built a few coaches without a transmission cooler, and if yours is one of those, you are running cool.

Transmission temperature under normal driving conditions for most coaches will run about the same as the engine temperature, give or take 20 degrees. The reason for this is that in most cases, the transmission is cooled by the engine coolant. The engine coolant heats up faster than the transmission fluid, so it also warms the transmission up to operating temperature as the engine warms up. You can run a 4000 series Allison too cold (I would not like to have a transmission operating at 100 to 120 degrees) as well as too hot, so overcooling is not advised either. I prefer a temperature between 180 and 200 for my transmission, but anything under 250 is acceptable depending on what type of transmission cooler you have.

Gerald     

[Keith Moffett]

Jerry, you certianly have valid questions here. 
Part of the problem (and it is the same for everyone)  is the forum itself.  Temp numbers by themselves arw not too helpful because as Gerald mentions there are so many variables.  The C-9 vs your C-12 or for that matter a 3126 like we had.  Then the transmissions 3000 family or 4000 family each depends on dextron or Transynd and the type of cooler.  Our C-12 has the heat exchanger type as opposed to the in radiator or in hose types.
Seems to me that each combination above will result in different numbers on the forum.
I was just at our radiator shop having this talk with our guy.  The canister / heat exchanger type like ours is tough to service but is basicaly a maritime industry product.  The transmission fluid runs through a bunch of 1/4 inch copper tubes seperated by even finer fins which transfer heat to the engine coolant.  Those fins are so tight that any clogging of the engine coolant (IMHO) could cause a restriction and so less cooling for the transmission.
Seems to me that a real good service on just this cooler would help in many coaches in the mountains.

[Jerry Emert]

Thank you Keith and Gerald!  Next question, how do I tell what type of cooler mine has?  Today was a little less hilly and temps never exceeded 221.  It cools rapidly when I stop or when I get below about 55.  I stopped for literally 2 minutes to close the fuel cover that we left open.  Temp went down 6 degrees and took about 30 minutes to get back.  So I don't see a real emergency here but the mountain!  The mountains!  Thanks again for your help. 
Jerry

[Jerald Cate]

Jerry,
My coach is similar to yours and I see transmission temperatures like yours.  If I'm running in the hills or around 65 mph on warm days 220 - 230 degrees is pretty common.  I understand Transynd is more tolerant to higher temperatures.

Bruce Cate

[Joel Weiss]

I'm not sure what kind of cooler I have, but today I ran for >350 miles of nearly flat Kansas and Oklahoma terrain at a constant 65 mph (in 6th gear) with an ambient temp of 80-85 degrees.  Over the course of the trip, the transmission temp (on the Silverleaf) rose to a maximum of 201 although the majority of the time it ran ~198.  Any reduction in speed resulted in an almost immediate drop to ~194-196.   

My Transynd and filters were replaced a month ago during annual service.I had ~55,000 miles on the fluid, but sampling indicated increases in a few trace elements and I decided it would be better to replace the fluid rather than try to go another year.

[Jerry Emert]

Jerry,
My coach is similar to yours and I see transmission temperatures like yours.  If I'm running in the hills or around 65 mph on warm days 220 - 230 degrees is pretty common.  I understand Transynd is more tolerant to higher temperatures.

Bruce Cate

Bruce, you don't know how much better that makes me feel!  How does it do in real mountains so I know when to start worrying again?  LOL
Thanks
Jerry

[Keith Moffett]

I will leave it to Gerald and others to talk about the in hose or in radiator coolers.  I know our 98 Pat with 3126 had that type.

I would be surprised to find that on a C-12.  If you will look under the coach behind the radiator assembly and behind the fan and then upward toward the frame you should see a cylinder mounted horizontaly with two radiator hoses and two hydraulic lines attached.  This is your transmission cooler.

FYI, we went to Transynd in the 98 Pat.  The shifting became very hard and the temps dropped a fair ammount.  I would think long and hard about using it again.  The viscosity of Transynd and the age of the transmission cooler, I would not want to blow a solder joint and lose a tranny.

There is six cents of my two cents worth.

[Jerald Cate]

Jerry,
I haven't been out west yet, hopefully later this year, so I can't say what it will do in the high passes.  I don't expect to see anything different, like others say just keep the rpm's up and you should be fine.

Bruce Cate

[Joel Weiss]

  I understand Transynd is more tolerant to higher temperatures.

Actually, I think it is sort of the reverse.  Use of Transynd (or other TES295 fluid) results in significantly reduced operating temperatures.

I have to admit I'm a bit puzzled by this post.  Haven't most of you changed to Transynd by now?  The advantages in fluid lifetime and operating temperature alone make it worthwhile IMO.  It's my understanding that for quite a few years Transynd has been the only fluid recommended by Allison for its transmissions.

[Gerald Farris]

Joel Weiss,
You are correct on all three points in the previous post.

Gerald

[Keith Moffett]

So Gerald
Given the weakness of the solder joints in the transmission cooler and their relative age, you have no concern about switching to Transynd?
also.
You may recall that we bought this coach a couple years ago.  It had no maintenance log.  How might I tell if it has Transynd.  We changed the Patriot over and I noted that Transynd is thicker than the original when cold.  Any suggestions?