Running the tranny cooler
Running the tranny cooler I heard it is better to bypass the tranny oil running through the radiator if you have a tranny cooler. The guy told me it would be better if I just ran the oil through the cooler and then back to the tranny. Yes or No?
TECH Resident
Joined: Feb 2002
Posts: 992
Likes: 0
From: Schererville, IN
I previously used a 19k B&M that was routed through the radiator. The trans would run pretty hot in stop and got driving, sometimes over 200 
.
I now have a B&M race cooler, it is rated at 29k BTU. I don't know how the BTU rating compares w/the GVW rating but it is twice the size and thickness of my old cooler.
I bypassed the radiator this time and it hasn't gone over 160 on the street. It hit 180 at the track after 3 back to back passes and cooled down quickly after.
It does take a while to heat up on the street, about a half hour of driving to reach 150. Can the trans run too cool?
.I now have a B&M race cooler, it is rated at 29k BTU. I don't know how the BTU rating compares w/the GVW rating but it is twice the size and thickness of my old cooler.
I bypassed the radiator this time and it hasn't gone over 160 on the street. It hit 180 at the track after 3 back to back passes and cooled down quickly after.
It does take a while to heat up on the street, about a half hour of driving to reach 150. Can the trans run too cool?
So this means bypassing the radiator is better? The explanation I got for it being better was that the radiator tries to cool down the tranny fluid with the water that is in it, and most of the time this water is very hot.
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TECH Enthusiast
Joined: Jan 2004
Posts: 742
Likes: 0
From: Cincinnati, OH
Think about it this way: If you try to cool off the trans. fluid with 160-210deg. engine coolant, what happens? If you cool it off with 75-95deg. ambient air, then what happens? Correct on both counts. I say ditch the radiator and go straight to air-cooling.
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12 Second Club
Joined: Aug 2002
Posts: 115
Likes: 0
From: Tampa, Fl
fyi, I think the idea is, you want your transmission fluid to be in normal operating range sooner, so running it through the factory cooler will actually bring it to that temperature faster, but having the 2nd cooler right after the output of the factory one will cool it back down to reasonable levels. Depends on where you live I suppose, but in most cases, I'd think you'd still want it to run through both.
Staging Lane
Joined: Jul 2004
Posts: 72
Likes: 0
From: Alexandria, VA
This hasn't been mentioned in the above posts.
The B&M series coolers have a vicosity (thermal) bypass value. As the oil warms, the value opens and oil passes through this supplemental cooler. The warmer the oil, the more oil that goes through the cooler.
The higher the GVW rating on the tranny cooler, the larger the cooler is so that it'll accommodate more oil and generate more cooling. This cooled oil is then recirculated to the transmission.
I'm not sure whether the factory installed (stock) tranny cooler works under this principle (thermal bypass) or not but I do know that B&M does.
Hope this helps.
The B&M series coolers have a vicosity (thermal) bypass value. As the oil warms, the value opens and oil passes through this supplemental cooler. The warmer the oil, the more oil that goes through the cooler.
The higher the GVW rating on the tranny cooler, the larger the cooler is so that it'll accommodate more oil and generate more cooling. This cooled oil is then recirculated to the transmission.
I'm not sure whether the factory installed (stock) tranny cooler works under this principle (thermal bypass) or not but I do know that B&M does.
Hope this helps.
Teching In
Joined: Aug 2004
Posts: 7
Likes: 0
From: Mead, CO
The truth of the matter is that a stock system (thru the radiator) is a heat exchanger type of system. works well with stock components and NORMAL driving habits. We all know none of us are doing this so the largest external coolers are far more superior than any stock system. Temperature is the worst enemy to your transmission. Using high stall converters, hard acceleration, stop and go driving are all considered severe driving conditions and an external cooler is a must as well as trans servicing every 12,000 to 15,000 mile intervals. the other situation that is avoided by bypassing the factory cooler is that you eliminate any poss. of coolant contamination into the trans that can completely destroy your transmission.
