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Old 04-25-2006, 08:15 PM   #1
Join Date: Nov 2005
Posts: 213
Allison trans cooler

What trans cooler do I need to use for a Allison 545 trans, I was looking at mine and it looks like the trans lines are about 1/2" not 5/16 like a TH400 or other transmissions I have seen.

Thanks in advance
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Old 04-25-2006, 11:21 PM   #2
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Location: Twin Falls, Idaho
Posts: 808
Allison transmission coolers.

Comparing a Allison trans to a Turbohydramatic trans is like comparing a shovel to an excavator. Both can move dirt but the comparison ends there.
The HD Allison trans are very tough and reliable. Quick reference, Allison trans are rated for application by the usual 3 digit numbers. The first number, 5 is the torque rating of the trans,in hundred of foot pounds of torque, the next number is the number of forward gears and the last number is reference to number of factory modifications to the series trans. There are usually 3 seperate classes of Allisons and several designs. There are 543, 643, and 743. The 743 is nearly indestructable with proper care and feeding. Allisons have large, typically 1/2 inch cooler lines but many Allisons use 3/4 and 7/8 inch lines to the cooler,for the required volume of fluid. Most Allisons are cooled via a cooler that shares engine coolant. These units can fail and destroy a complete trans in a very short period of time. I am partial to having a dedicated cooler just for the trans fluid. The absolute best trans fluid is synthetic fluid costing about $5 per quart. Standard red ATF can be scalded is 20 minutes and lead to trans failure. There are many types of coolers made for liquid to air. The most effective cooler is the stacked plate design with a common inlet and discharge manifolds. When this type cooler is used with an enclosure and a large cooling fan, thermostatically controlled, the trans in nearly bulletproof. The cheaper in cost are the tube and fin design that are marginal at best. Any vehicle with an auto trans should have a trans temp guage. Have I answered the question? Frank
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Old 04-26-2006, 06:17 AM   #3
Join Date: Nov 2005
Posts: 213
You gave some great info but didnt answer the question, where do I get a cooler (have links?) I am not sure what I am looking for I have installed coolers on other trans before but nothing this big.

FYI 99.9% of my driving will be on the interstate traffic driving for this bus is all done. Pulling a trailer in the future that weighs about 2500 lbs could happen I would like to be ready for it. The bus is a 87 chevy C60 366 engine 66 passenger 35' long bumper to bumper.

Thanks again.
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