Transmission Anomoly

[Randall Brink]

First trip of the new season here in the NW and Caribou Monaco (Dodge 440/727 TF Trans) runs fine. I pulled a long 7 mile grade, which was 6%+ the last mile. Transmission downshifted 4-5 times, no problem, but upon cresting the grade and descending, I reached a level stretch, tried to accelerate, and it was as if the transmission were in neutral. A mile or two coasting, and the trans again engaged and performed fine the rest of the day.

The transmission was serviced last year with new fluid and filters. Fluid is clear. Level was 1-pint low upon inspection at bottom of grade.

Any ideas on what happened here? Any suggestions on what should be done to rectify will be greatly appreciated!

[Russell E Johnson]

OK, I called 3 different mechanics, one in MT, one in St Louis, and a local one who has done a couple of repairs for us.  The one in MT always bypasses the radiator unless the owners wants the radiator left in.  The one in AR always cuts in the extra cooler into the return line from the radiator.  The one in MO has done it both ways and over the years has seen no difference in tranny failures.  So he leaves it up to the customer and if they cannot make a choice goes the easier route of cutting the cooler into the return line from the radiator.  I was a little surprised that the one in MT would cut out the radiator entirely in such cold climate but as he pointed out most trailers are pulled in the summer, and it has minimal effect on the temp of the tranny that the cold weather is not a problem.

I do not have a transmission fluid temp gauge, but it would be interesting to know the before and after effect of bypassing the radiator.

Anyway, there you have it, 3 mechanics and basically 3 different ways of doing the transmission cooler.

[Lakota Wolf]

Have you ever wwondered why they run the tranny lines too the side tank of the radiator? its NOT to cool the radiator,,its to WARM UP the radiator to operating temp. The engine has a thermostat and the tranny does not. The engine water temp brings the trans temp up. Just some info to pass along.That's why trans ccoolers are installed.

[chuck king]

Trans oil temp is a lot hotter then water temp so rad cooler will keep trans oil at water temp with no damage to trans if you are pulling a trailer behind then extra cooler is good idea

[Randall Brink]

Didn't know that. Makes sense. So the transmission-connected radiator grid mounted along with the radiator is not really a transmission cooler at all. I will look into adding a trans cooler. Thanks!

[chuck king]

The factory trans cooler in rad will cool trans oil to water temp but if your pulling heavy load extra cooler is a good plan all factory trans are cooled from rad

[Randall Brink]

Ok, that makes it more clear to me. I'm leaning toward the high-capacity pan withe the flow-through cool-air ports, as an addition.

[Russell E Johnson]

I am sorry Lakota, I do not understand what you are trying to say about the radiator and tranny cooling/warming.

[Lakota Wolf]

My typos are bad. When we were younger our vehicles didn't have fule injection and electronics. You push the gad pedal once and started the engine and ya waited a couple minuttes before taking off. Had to let it warm up a bit. The original reason they put trans *cooling lines was to bring the transmission fluid up to operating temp, fluid moves easier when warm. They were called cooling lines fefering to the cooling system. They did keep the trans fluid cooled to a point. But the original reason was to warm the hydrolic fluid and it kept it equal to engine temps. External coolers were installed vvehicles that pulled more weight then general daily use.motorhomes and tow vehicles need them due to the extra demand on the drive train. Oil.and power steering coolers were later installed to remove heat.

[Russell E Johnson]

Thanks Lakota, that helps my understanding.  Yes I well remember carbs and the need to warm up, if nothing else our 87 MH brought back all those memories. LOL

[Lakota Wolf]

Don't panic. the 727's where know to FLOAT when rpms are to low for one gear and.to high for the next. I experienced that a few times and.trans tech said that's a fluke that the 727's had. And like mentioned. a tans cooler and oil cooler will make a difference .

[Randall Brink]

That may be what happened, as I was beginning the descent on the downhill side of the grade.

[chuck king]

If throttle pressure rod is adjusted at specs this will not happen I have An a727 with 440 and after doing adjustments the prob never happend again