Transmission overheating

[Edward Buker]

Tim,

This seems so strange that it coincided with a transmission oil service timing wise. Did you also see a loss of coolant or contaminated antifreeze? If not maybe there is a chance they added the wrong fluid to the transmission at time of service.

later Ed

[Keith Duner]

Tim:  Sorry to hear about the outcome.  Not what anyone had hoped for.  If you decide pursue a used transmission, I'd suggest requesting a dated dyno report from the seller indicating it's health (or pay to have the unit run on a transmission dyno yourself).  As you know, the removal/replacement labor is going to be significant, so you don't want to have to go through it twice.  Regards,

[Keith Duner]

Tim:  Another thought.  As you search for replacement options please keep in mind that there are subtle differences in the 4000 Series transmissions based on year of manufacture (and of course, the Assembly Number found on the transmission data tag).  You will want to avoid any unintended issues such as harness connector changes or calibration compatibility problems that could add to the complexity of the job.  I would suggest working with an experienced service outlet to help you with the selection process (my vote will always be to stick with an Authorized Allison distributor or dealer).   Regards

[John Hennessey]

Has this diagnosis been determined by an authorized Allision tech center?  The reason I ask is that the manual says to test the fluid and if found contaminated to change the seals gasket etc.  It implies damages not a need for an entire new transmission.  I would call Allision before doing anything.  This just doesn't seem right.  You wouldn't be the first RVer to be told something that just doesn't need to be done.

[Joel Weiss]

Here's an Allison "service tip" dealing with glycol coolant in the transmission fluid.  To echo John Hennessey's point, nowhere in this note is a transmission replacement indicated.

http://www.allisontransmission.com/servlet/DownloadOnDemand?ApplicationID=155&DownloadID=6

The key recommendation is:

Any trace of Glycol or greater than 0.2% water contamination requires a complete disassembly and cleanup of the
transmission and replacement of seals, gaskets, clutch plates, and bearings.

[Gerald Farris]

The point here is that both John and Joel are saying that the transmission will need to be overhauled. That is the term that is commonly used for replacing the clutches, seals and bearings. It is normally cheaper to replace the transmission with a rebuilt transmission than it is to rebuild your transmission because of the labor difference between a factory worker sitting at a bench assembling transmission parts at $20 an hour and the labor rates that you have for and experienced transmission technician at a repair shop. Therefore you just replace the transmission with a rebuilt transmission if it is contaminated with coolant.

Gerald    

[Tim Bentley Co-Admin]

We are working with Vally Power Systems the Allison dealer in San Diego.  We will get a factory rebuilt transmission and new cooler.  

[Tim Bentley Co-Admin]

Need help with another problem.  Apparently the leak was in the heat exchanger part of the transmission.  This is the cylinder that has the hoses from the transmission running into it.  We cannot find what this is called or where we can get one.  Beaver coach sales says they don't have the slightest idea what we are talking about.  

Does anyone know what this unit is called and where we can get one.

We currently have a call into Monaco.

[Jerry Carr]

Tim can you get a photo of the unit; we don't have anything like you describe.

[Edward Buker]

Tim,

The unit is a liquid to liquid heat exchanger. It should be listed somewhere in their parts list as a transmission cooler or a transmission oil cooler assembly one would think. This is a link to a rectangular liquid to liquid version on the web. This is just an example, not implying this unit is appropriately sized, but it may be able to get you going on the right track with the parts folks as to what you are talking about with this photo. Hope this helps.

http://www.makcotransmissionparts.com/TDI-13680.html

Later Ed

[Edward Buker]

Tim,

I gave a call to Steve Harris the service manager at Pacific Power Products, an Allison Dealer in Kent Washington. Phone 253-854-0505. They are well familiar with these type fails. They are in the process of proactively changing out 10 of these units on fire trucks in Seattle before they fail. He indicated that the heating and cooling cycles over time will cause a crack to form which allows the fluids to mix. In the reliability field that is called a thermal cycle fail which I have some experience with in semiconductors.

He said to look closely at the unit for any PN or build identifier if you cannot get help from Navistar as a part source. Steve at Pacific Power is having high quality units built by Seakamp Engineering for his retrofits. Basically you would need to take photographs of the existing unit with dimensions, end to end, and of the ports location and sizes. They can take that info and build what you need. Basically these are a vessel with many copper tubes that the transmission fluid travels through surrounded by the antifreeze. The construction is much like a heat exchanger in a boat. Seakamps phone number is 800-753-4436. Steve indicated that the ones he had built were $750 but it will vary a bit by size and configuration. If you cannot find the current PN, or Navistar is of no help, or if the source is out of business this may be a good path to follow. Steve at Pacific Power would be happy to field your call to discuss this if needed. Hope this helps.

Later Ed

[Tim Bentley Co-Admin]

This is what the cooler looks like.  We have found one but will take a week to build and we would like to get the Coach out this week.  

[Steve Jewell]

Tim
     That looks like a Rocore shell and tube cooler. If there are no numbers on it they can figure out by dimensions. Go to ( rocore.com ) they have a catalog there.

Steve

[Tim Bentley Co-Admin]

Steve

Thank you, you are right it is a  Rocore shell and tube cooler.  Thanks to you we have one on the way.  Don't know why BCS and Monaco were unable to give us any information.  

The forum and all our fellow members have done it again.  

Don't really know if I am happy putting in the same product that failed and ruined our transmission.  Maybe we should replace it every 5 years just in case.  This would be cheaper than replacing the transmission the next time the cooler fails.  Seems that there is no way to tell if you have a problem until its to late.

[Jeremy Parrett]

Ed,    
       does the Marquis 2000 C12/Alison transmission have a liquid to liquid heat exchanger??
        I found this one that is an Allison product.  http://www.makcotransmissionparts.com/TDI-13680.html
       Should we be changing the core  or replacing the whole unit  at a certain mileage or age??  
     Could we remove the existing unit if it is the liquid/liquid type and replace it with a fan cooled radiator type??
            Jeremy