Transmission Cooler Bypass Question

[Scott & Heather]

So I've fully deleted my water/oil cooler for my Allison 748. Talked to Allison and Hayden and both specd out a huge air cooler for me that can be used standalone. I've installed it but just need to connect trans lines to it. Before I do, I want to buy a reliable thermal bypass valve that bypasses the cooler until proper trans fluid temps are reached. I'm finding a ton of these in smaller sizes but of course I need something in the 1" or larger sizes. Anyone have a source for this? I found this but can't figure out what my crack pressure needs to be?

https://ph.parker.com/us/en/valves-thermal-bypass-up-to-250-psi-th-series/th-1000-16fo-65

[6805eagleguy]

Scott, exact problem we had less then a week ago, we ordered one of these valves: http://www.thermaltransfer.com/include/uploads/1/Literature/Product_Documents/Oil%20Cooling/M/M%20Accessories.pdf

Bought is from airengineering.com, Call them and see how fast they could ship it.

[chessie4905]

Another way to do this is to put solenoid valve in the cooler bypass loop and control it with a relay and a temp sensor into bypass loop. I would want valve normally open, and then close when oil is cold. That way a failed valve, relay, or temp sensor wouldn't cause overheated trans fluid. Personally, I would try the setup out without bothering till you see whether it "overcools". Maybe a temp switch for cooling fan would be enough or  blocking off part  of surface area in very cold weather.

[TomC]

Radiator powered shell transmission cooler does two things-one it warms up the transmission faster and keeps it warm in cold weather. Then of course cools it in warm weather. I have an air to oil cooler with thermostatically controlled electric fan that the hot fluid goes through first then to the normal shell cooler. Takes much of the heat transfer from the radiator, yet keeps the transmission at a more constant temperature. Good Luck, TomC

[chessie4905]

Still adds heat to radiator when you don't need it. Climbing mountain in 90 plus degrees. Overcooling transmission is way overblown, except in sub 30 temps. Never saw an automatic trans not work ok, even at Zero temps even not warmed up yet.