Lost 3rd Allison in 20k

[Cat568]

It does have the 2nd cooler.

[Mutt]

John, I just spoke with a fellow camper who had a 98 Model Diplomat with the 5.9 ISB setup. I know this is going back two years beyond your unit, but his kept running hot. He said that Monaco/Cummins replaced his Radiator and Engine cooling fan and pulleys. He said the fan had more blades on it than the OEM Fan in the Coach when he originally purchased it. If/is there is a possibility that yours somehow has a smaller Fan or smaller Radiator that might contribute to an equipment failure. You may have already covered this in an earlier post. Hopefully, you will find a "Smoking Gun" out there somewhere. FWIW.

[RobRoy]

Let me say this from the get-go I know nothing about Allisons Transmissions.

That said and reading some of the thoughtful ideas on what to look for? as to the cooler being the issue? Let me say this my 2001 F350 diesel uses a trans cooler bypass so that when the coolant is cold it by-passes the transmission cooler until the fluid reaches a specific temperature then opens and allows the fluid to pass thu the trans oil cooler to then do its job.


In the light-duty vehicle world, they use these transmission oil cooler bypass valves in many applications and manufactures... and they have been known to fail and when doing so they can be very hard to diagnose ..especially if it is sticking intermittently because the trans isn't running hot at al times

As to flushing your trans oil cooler?

If the cooler type is a continuous serpentine loop meaning one continuous line in the cooler and is the same continual line coming out .....flushing the cooler is is fine if done properly. If your cooler is what I refer to as a manifold type meaning the trans fluid goes in one side or end of the trans cooler tank and the fluid can randomly go thu any of the cooling tubes and out the other end? and you have had a catastrophic trans failure you will never get it clean unless disassembled or replace it.

Seen here is a pic of one example of a transmission oil cooler by-pass from a Ford transmission and like I said many manufacturers use some sort of ny-pass to get the fluid up optimum operating temperature quickly.

I to believe that from what you report here that the trans failure is due to something else such as a high fluid temp issue or electrical issue.

IMO you need a schematic of your transmission that covers from from A to Z and examine it very closely.

I also think that if it was severely overheated trans that a seasoned trans tech would have reported that to you or the service advisor ...these folks do this day in and day out and most failures they are failed components and not severely overheated and when seeing a severely overheat trans that would normally send their diagnostics antenna's thu the roof and start question things.

I feel your pain with your tranny issue and wish you well with both your coach and your health.

Happy Trails.

[Cat568]

It does have the 2nd cooler

[Cat568]

Rob Roy. Thank you so much. I watch the temp more than speedo (cruise). Eng and trans. I too think electronic problem. The only common factor is the trans controller under driver, the one Monaco always sprayed over. Or wiring. Still don't know how intermittant wiring problems could cause clutch failures every time. And why no codes come up.

[RobRoy]

Originally Posted by jacwjames

I would also check the cooler lines to make sure there is not an obstruction causing restriction (or no) flow.

The cooler being cleaned open is one thing ....what about the cooler lines? are they open and flowing fluid?

That said the OP says never see's excessive fluid temps

[Cat568]

Fluid sample kit arrived today. 1st thing in a.m. I'll get sample and overnight it to a fellow. He'll let me know soon, most likely. The cooler and radiator are seperate. Pretty sure its the updated cooler. I posted earlier it had a second cooler, I was wrong. But...the plastic inside the trans should melt before it hurt the transynd or clutches. Kind of. They can take a lot of heat. Old ATF didnt last long, and life was cut in half by every 10° raising operating temp. Kind of. Approximately. From what I've read.

[Cat568]

And forgot to mention... the install includes flush lines and cooler..I hope they did, or do. Reciepts claim it's done.

[bigjim8499]

John you need to call Inland Truck in Fort Worth Tx 800 700 2557. They are Allison specialist. Work on a lot of truck with Allison. They work on MH also For chassis work. They have the best prices for filters in the country. Maybe theh have some ideas.
Jim E
06 exec

[Cat568]

Dropping veh Mon a.m. Soon as I get a minute w/o a new disaster, i will call them. Thank You, Jim. Should have fluid analysis report Mon p.m. (I hope) I anticipate a VERY thorough analysis.

[Cat568]

A conclusion. The TCM, ECU transmission control module was burning them up.

[Radacravitz]

Originally Posted by Cat568

A conclusion. The TCM, ECU transmission control module was burning them up.

nice to get it id’d, cost to repair / replace?

[CountryB]

Originally Posted by Cat568

A conclusion. The TCM, ECU transmission control module was burning them up.

Has that been verified - or is that "conclusion" just the last idea the mechanic has to explain this conundrum?

[Cat568]

I don't know. We all hope. I don't know if they've tested the old one. The name for the condition is "clutch tie up". They haven't been very forthcoming with information.