Community Forums

CountryB · 10-04-2019, 01:41 PM

On a 2003 Beaver Patriot Thunder with CAT C12 (505hp) with an Allison 4000 MH, the transmission oil temp is running much hotter than the engine coolant temperature. Usually the transmission and engine are within 10 degrees of each other (on other coaches).
On this coach, the engine temps run 190 all day but the transmission will hit 250 degrees under normal to heavy load in 6th gear. Dropping to 5th gear and getting engine rpm up will reduce the trans temps.

The transmission oil cooler is built into the radiator.

Is there any way to test the trans oil cooler (to determine if its clogged or if there is a flow issue)?

Any other ideas to what could be causing oil temps to run so high?

steve52 · 10-04-2019, 05:03 PM

A trans shop can flush it. That's all I got.

CountryB · 10-04-2019, 05:45 PM

Thanks for replying.
I figured a trans shop (or truck radiator shop) could do something - just wondering if there is anything that can be checked or done at home. I'm not even sure if that is the cause of the high temps.

Chargerman · 10-04-2019, 05:47 PM

When was you fluid and filters last changed?

Bob_C · 10-04-2019, 05:53 PM

Add an external one....more capacity....

CountryB · 10-05-2019, 06:33 AM

Thanks for the help and suggestions.

It not my coach so I cant tell you when the filters and oil was last changed.
It's a friends coach (very similar to mine but two years older). I know he takes good care of it.

We talked about adding a second cooler. That would not be an easy job considering the space and size of hoses, etc. But that is an option.

before that, I would like to rule out the factory trans cooler. It may be clogged (maybe it was undersized from the factory).

I also asked him to verify that the engine (hyd) fan is working properly. He knows it does not spin when the engine is cold but has not really noticed if it spins when the engine is hot. However the engine coolant temperatures are in the normal range (no overheating).

Chargerman · 10-05-2019, 08:08 AM

I would try to verify last filter and fluid change. The factory cooler should be sufficient since it was previously. I would remove the cooler lines and flush the cooler out as see what comes out. Be sure not to flush through the trans or you can create a much bigger problem. I changed my fluid at 60k and it looked discolored and kind of burnt in color. I did not do a fluid sample but it is also a good idea. There’s an Allison post on here and it might be good to post there as there was a a former Allison Engineer there and he is VERY knowledgeable

CountryB · 10-05-2019, 01:22 PM

Quote:

Originally Posted by Chargerman

The factory cooler should be sufficient since it was previously.

He said it has always run hot since he has owned the coach (about 4 years now I think). Sounds like it was this way when he bought it. Maybe it was this way from factory (defective cooler) or perhaps it clogged up years ago, or maybe something else going on.

This higher than normal transmission temperature has always bothered him. But he watches the temp and downshifts when it hit 250 degrees and gets temps down to under 220 before continuing.

He shouldn't have to do that.
My trans temps run about the same as my water temps. He has the C12 (40 footer with tag) mines a C13 (42 footer with tag).

Any idea what the proper/best way to flush is? I know tranny shops have a machines for flushing. Can this be done at home with simple tools?

dbarton291 · 10-08-2019, 06:16 AM

A couple of suggestions:
1. Make sure the trans fluid and the engine coolant cross flow. If the trans cooler is a bottom tank, make sure the trans flow to the cooler is on the opposite side of the top radiator hose which should be hot coolant from the engine. If the trans cooler is a side tank, make sure the trans oil to the cooler goes in the bottom and out the top.

2. One simple way to get some flushing action is to back flush. Reverse the to and from cooler lines from the transmission. Leave the hose that is coming out of the cooler into a bucket and start the engine. As the engine is running, make sure the trans stays at a proper oil level. Look at what comes out of the cooler to see if it contains any debris.