Extra transmission oil cooler

[rayshound]

I Have a HTB 748 ATEC on an Series 60. I have the oil to coolant heat exchanger and will hook in the proper water pipe on the water pump. My question is I also found a air to oil cooler that is off of an airport shuttle bus auto trans & hyd fan cooler. Can I hook them (the oil side) in series to increase cooling? I can have an electric fan on the air to oil cooler that can be switched on during increased temps. If not in series how about one in the normal trans cooling circuit & the other one in the exterinal oil filter line curcuit? Just concerned about the heat generated by the retarder. Thanks Ray

[buswarrior]

Hello rayshound,

Popularly, folks seem to be plumbing an extra oil to air tranny cooler in series, ahead of the stock oil to coolant cooler.

That way, the excess heat from the tranny is dumped overboard without putting it into the engine coolant, and running it through the stock cooler ensures everything stays close to the right temperatures, regardless of where or how you try to operate.

You are right to be concerned about the retarder making a lot of heat.

happy coaching!
buswarrior

[Clarke Echols]

First of all, treat the retarder like brakes.  Use gearing whenever possible coming down grades to minimize
speed and load on the retarder.  The retarder heats up the transmission VERY FAST.

If you plumb the oil-to-air cooler ahead of the oil-to-coolant cooler, you have more heat transfer because
the oil is hotter at that point.

Normal order of coolant flow:  Radiator to transmission cooler to water pump to engine to radiator.

I don't know what kind of driving you're doing, but if you are using the retarder correctly (don't try to
use it all the way down a 6% grade; run the bus so you only have to use the retarder intermittently
and quickly), you should have no need for an oil-to-air cooler.

Some bus drivers don't seem to understand that.  They think they should be able to take a bus down
a grade and control the speed by keeping the retarder on lightly to moderately all the way down the
hill.  That is NOT how it works.

Clarke

[rayshound]

Thanks guys that is how I will plumb it. I will put an electric fan on the air to oil cooler and let ddec turn it on. Ray