Bypass radiator/tranny cooler combo?

hotpepperkid wrote:

LarryJM wrote:
Bypassing the OTW cooler in the bottom of the radiator is the worst thing you can do for maintaining tranny temps especially when towing. It it always the first cooler that the hot tranny fluid goes thru since it is the one that can extract the most heat due to the temp differential and is not dependent on the speed of the vehicle like the OTA cooler is. You examples of light weight non towing vehicles and any comparison of turbo intercoolers is comparing apples to oranges and IMO your worries about cooler failures is basically not founded on any data or reliable reports I have ever read.

Even the gaggle of engineers at FORD failed to appreciate this in the original design of the SD series when all they initially had was the OTA cooler and started loosing trannys from heat especially for those who were towing. They had to put out a service bulletin to replace or add the OTW cooler in the bottom of the radiator to solve the issue.

My recommendation is not to MUCK around with the engineered design of your OEM cooling system and definitely DO NOT bypass that OTW cooler in the bottom of the radiator if you want to keep your tranny.

Larry

My 2000 F-350 has an OTA only. I have 225,000 mile on the trans. It does just fine as far as temps go. It heats up when going light to light when them air temps are over 100 but it has never been over 225 deg. The up grade a lot have done is put a cooler from the 6.0 on. It is about 3 times the size of the OEM cooler

I would say you have been fortunate and the vast majority of 7.3L owners generally never see temps above 2000. I work the snot out of my PSD towing and have only once seen my temp go to 200 and it's max is generally 190. With only around 200hp and towing at 17.5K GCW I routinely have pre turbo EGTs staying above 1000 and often have to turn off OD to keep EGTs under 1300 which can even happen on a lot of the more significant Interstate hills. The TSB I mentioned is 00-24-4 and only applied to SDs made before 6-6-2000.

You are correct on the 6.0 cooler (not sure if it's actually 3x the size, but is bigger) and my understanding that is now a standard addition that Brian Thompson does for all his built 4R100 trannies now.

Larry