Topic: Help picking a transmission cooler.

[dexetr30]

I'm looking at trans coolers and and I'm a bit confused.  GVW of the TJ 4 banger is 4360 lbs. I know I'm supposed to use that number to choose the correct trans cooler but everything I'm looking at is for vehicles around  10,000 lbs. gvw. With such a difference in numbers how am I supposed to pick the correct cooler? Am I missing something in the equation? I'm looking at completely bypassing the stock cooler so I know I have to double the size when I make the purchase.

Can someone help out with picking the right size?

[oldjeep]

Go with the biggest one that will fit.  GVW is irrelevant in an offroad vehicle, and an automatic tranny never got hurt from running too cool.

[dexetr30]

An automatic tranny never got hurt from running too cool.

That was one of the things I was wondering about, especially up here in the north east. I'm ordering this one.
http://www.jegs.com/webapp/wcs/stores/servlet/ProductDisplayPopup?storeId=10001&catalogId=10002&productId=1032939&itemId=990330&langId=-1&showValue=1

Thanks.

[Bounty Hunter]

That one will work.  I run one about half that size on my power steering, no slush box here.

[Castr8r]

OK, we got a bit of mis-information here.  You can run an automatic tranny too cold.  Most of the new vehicles with autos will tell you in the owners manual to take it easy when the temp is cold; at least until the engine is putting some heat into it via the "cooler" in the radiator.  In fact, my Dakota will not shift- electrically controlled- until it does get warm enough.  I've been told by a very good transmission rebuilder that it's a good idea to run a cooler if you're going to stress the unit, but to run the return line thru the "cooler" in the radiator to assure that it will maintain the proper temp.  Not doing so can result in disasterous cosequences in the colder months of the year as well as when it's hot.  If you have a good transmission specialist in your area, I'd talk to him and see what he says for a second opinion.

Do it Dirty!

[oldjeep]

OK, we got a bit of mis-information here.  You can run an automatic tranny too cold.  Most of the new vehicles with autos will tell you in the owners manual to take it easy when the temp is cold; at least until the engine is putting some heat into it via the "cooler" in the radiator.  In fact, my Dakota will not shift- electrically controlled- until it does get warm enough.  I've been told by a very good transmission rebuilder that it's a good idea to run a cooler if you're going to stress the unit, but to run the return line thru the "cooler" in the radiator to assure that it will maintain the proper temp.  Not doing so can result in disasterous cosequences in the colder months of the year as well as when it's hot.  If you have a good transmission specialist in your area, I'd talk to him and see what he says for a second opinion.

Do it Dirty!

Never heard of over cooling a transmission to death.  My jeeps have both run oversized trans coolers, and I live and wheel in a place where it gets to be -20F.  Both jeeps are running through the radiator as well as the aux cooler.

[aw12345]

Well there is some truth to it. OBD2 equiped vehicles with an automatic trans will not shift into overdrive untill the trans fluid warm up. Some run a temp sensor in the engine cooling system other have a temp sensor in the trans, all this happiness is to get the engine warmed up faster so it will emit less emisions. So on obd2 stuff you might want to go easy on the cooler or trick the temp sensor and call it good. Trick the ecm into thinking the trans fluid is warm and it will shift the way it ought too

[dexetr30]

Well there is some truth to it. OBD2 equipped vehicles with an automatic trans will not shift into overdrive untill the trans fluid warm up. Some run a temp sensor in the engine cooling system other have a temp sensor in the trans, all this happiness is to get the engine warmed up faster so it will emit less emissions. So on obd2 stuff you might want to go easy on the cooler or trick the temp sensor and call it good. Trick the e.c.m. into thinking the trans fluid is warm and it will shift the way it ought too

The 30rh and 32rh transmissions do not have overdrive. They are 3 speeds with a locking converter. Also, they are not electronically controlled transmissions with the exception being the converter. I usually warm the Jeep up on cold morning with the trans in neutral (so the pump is running) for about 10 minutes before leaving the house.  I may still run the the aux cooler with the o.e. radiator cooler just for warm up purposes. I won't know exactly how I want to do it until I start this project over the weekend. Still, since it's not electronically controlled and I have no overdrive, I may not reconnect the o.e. cooler in the radiator.