Tranny cooler needed?

90tbirdsc

Registered User
Hey everybody, ive been considering putting a tranny cooler on my car for awile now but im not sure if I really need it. I have a AOD with some brand of aftermarket valve body(maybe lentech) ill be running a late model blower spun at 15% od with a MP plenum and coated rotors and larger tb, maf and intake,ported maniflolds and exhaust and fmic and other mods. basicly Im hoping for 250ish hp to the wheels and Im not sure if a tranny cooler is needed? is it worth the work to put it in? ( I know its not too hard) but do they really extend tranny life? I might make it to the track 1 time a year. its a weekend street car.
 
Hey everybody, ive been considering putting a tranny cooler on my car for awile now but im not sure if I really need it. I have a AOD with some brand of aftermarket valve body(maybe lentech) ill be running a late model blower spun at 15% od with a MP plenum and coated rotors and larger tb, maf and intake,ported maniflolds and exhaust and fmic and other mods. basicly Im hoping for 250ish hp to the wheels and Im not sure if a tranny cooler is needed? is it worth the work to put it in? ( I know its not too hard) but do they really extend tranny life? I might make it to the track 1 time a year. its a weekend street car.

The answer is yes. Transmission coolers are a must have on our cars. In fact I recommend using a transmission cooler only and bypassing the cooler built into the radiator. The reason being is that over time the cooler that is integrated as part of the radiator gets restricted and reduces the flow rate. They also suck at cooling. It is never a good idea to try and cool a transmission down with 200 degree water.
 
The answer is yes. Transmission coolers are a must have on our cars. In fact I recommend using a transmission cooler only and bypassing the cooler built into the radiator. The reason being is that over time the cooler that is integrated as part of the radiator gets restricted and reduces the flow rate. They also suck at cooling. It is never a good idea to try and cool a transmission down with 200 degree water.

The main purpose of the heat exchanger in the radiator is to bring the trans fluid up to temp quickly, not to cool the trans fluid. It's a good idea to keep it in the circuit if the car will be driven in cold weather often.

OP, a trans fluid cooler is a good idea even if you're staying completely stock.
 
Many transmission cooler kits come with flexible hoses. The problem with hoses is that they can wear and break. If the hose breaks your car stops moving. It happened to me once with a high performance transmission. This is why I prefer to run all my transmission cooler lines with steel tubing. :)
 
The main purpose of the heat exchanger in the radiator is to bring the trans fluid up to temp quickly, not to cool the trans fluid. It's a good idea to keep it in the circuit if the car will be driven in cold weather often.

OP, a trans fluid cooler is a good idea even if you're staying completely stock.

Initially you are correct. The heat exchanger helps to warm the fluid. However since the transmission is operating longer at higher temperatures the heat exchanger spends more time keeping the transmission fluid cool than it does heating it up, unless of course you are only driving 15 minutes each time you drive your car. I would bet this is not the case most of the time. Think about it. Would you operate your car without a trans cooler and heat exchanger by simply looping the lines? Of course not because you would cook your transmission. Having worked on transmissions for a very long time I can say from experience that the single greatest failure with the heat exchangers is restricted flow. Heat kills transmissions and the more you can do to keep it cool the better. We always bypassed the heat exchanger as it hurt flow and the transmission cooler could easily keep the transmission fluid within acceptable operating temperatures by itself.


BTW - Every good transmission shop will check for flow through the heat exchanger first if there has been a transmission failure of any kind. Why do you think that is?????

Why do you think torque converters balloon up? It's heat every time.

Besides I have never seen a trans failure in my life because the transmission was running too cool. Albeit that may hurt fuel economy but I don't believe there are many on these boards worried about that.


So what I am saying is that the benefits of increased flow are outweighed by the benefit of the heat exchanger during warm up.
 
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Many transmission cooler kits come with flexible hoses. The problem with hoses is that they can wear and break. If the hose breaks your car stops moving. It happened to me once with a high performance transmission. This is why I prefer to run all my transmission cooler lines with steel tubing. :)

You could always run steel braided rubber lines too.
 
Hey everybody, ive been considering putting a tranny cooler on my car for awile now but im not sure if I really need it. I have a AOD with some brand of aftermarket valve body(maybe lentech) ill be running a late model blower spun at 15% od with a MP plenum and coated rotors and larger tb, maf and intake,ported maniflolds and exhaust and fmic and other mods. basicly Im hoping for 250ish hp to the wheels and Im not sure if a tranny cooler is needed? is it worth the work to put it in? ( I know its not too hard) but do they really extend tranny life? I might make it to the track 1 time a year. its a weekend street car.

Adding a cooler certainly won't hurt anything, but unless you switched to a non locking converter (direct drive delete) with stall rating above 2500 rpms, I don't think it's really necessary.

When using a Lentech stock stall (1800-1900 rpm) non locking converter, I added a B&M stack plate style cooler #70264 that was plumbed in series with the stock cooler (after the radiator cooler plumbed into the return line) and mounted in front of the AC condenser coil with no fan. It worked fine and trans pan temps seldom went over 180 degrees.

David
 
Adding a cooler certainly won't hurt anything, but unless you switched to a non locking converter (direct drive delete) with stall rating above 2500 rpms, I don't think it's really necessary.

When using a Lentech stock stall (1800-1900 rpm) non locking converter, I added a B&M stack plate style cooler #70264 that was plumbed in series with the stock cooler (after the radiator cooler plumbed into the return line) and mounted in front of the AC condenser coil with no fan. It worked fine and trans pan temps seldom went over 180 degrees.

David

What was stock temps? Or what would be your guess?
 
We always bypassed the heat exchanger as it hurt flow and the transmission cooler could easily keep the transmission fluid within acceptable operating temperatures by itself.

From my experience with a 3500 stall TC, 28K B&M cooler, and -8AN lines to/from the 4R70W, I have to block off most of the cooler to get temps to even register on the gauge (>100* F) if ambient temps are below ~50* F. That's a small cooler compared to what most guys here are running. If the car was a daily driver, that would be a pain.


BTW - Every good transmission shop will check for flow through the heat exchanger first if there has been a transmission failure of any kind. Why do you think that is?????

If the customer absolutely refuses to replace the heat exchanger, then at the very least it should be flushed. Reasoning? The same reason said shop checks for flow.


Why do you think torque converters balloon up? It's heat every time.

Every time? Certainly converters aren't ballooned due to rpm. :rolleyes:


Besides I have never seen a trans failure in my life because the transmission was running too cool. Albeit that may hurt fuel economy but I don't believe there are many on these boards worried about that.

So what I am saying is that the benefits of increased flow are outweighed by the benefit of the heat exchanger during warm up.

There are issues with running fluid temps "too cool" beyond fuel economy. Hence why it's common practice around here to recommend keeping the stock heat exchanger in the loop when installing a trans cooler on a vehicle that will be driven in cold climates.


You could always run steel braided rubber lines too.

Agreed.
 
If the trans isn't getting up to temperature then your cooler is too large. That's an entirely different conversation.


The stock heat exchanger can only be replaced if you replace with a new radiator and I agree with flushing but you still check for flow.

Converters inherently create heat by design. Certainly with high rpm they will create lots more heat. It's the excess heat that balloons the converter caused by the rpm. Of course when you load the converter more heavily it creates more heat.
 
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I prefer to run from the transmission to the cooler built in the radiator to an external transmission cooler. I modified two small aluminum punchout strut channels by bolting it in front of the radiator with some rubber anti-vibration backing pads. It has done an excellent job for over 14 years on MY 4R70W.

Isolating the cooler in front of the radiator prevents heat transfer from the radiator. Attached are old picture from the 90's before the hose leaked and I ran steel tube.

If there has been a transmission failure I would replace or refurbish my torque converter when the transmission is rebuilt. Metal chips or fins can be left in the system that will ruin your investment. Hoses, radiators and coolers are prime areas to collect these fines.
 

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I know ford uses inline transmission filters on the expeditions with 4r75w and some other vehicles. How do folks feel about them? I know others who use magnefine filters. Does anyone on here use them? It sounds like a pretty cool idea. It would certainly help capture some of the debris that can get caught in the fluid.

http://www.emergingent.com/subpage1Magnefine.htm
 
It is never a good idea to try and cool a transmission down with 200 degree water.

The heat exchanger in the radiator is on the chilled side which needs to be less than about 125F or you'll have overheating problems. Temperature drop of the coolant across the radiator should be in the 80-100F range.
 
Converters inherently create heat by design. Certainly with high rpm they will create lots more heat. It's the excess heat that balloons the converter caused by the rpm.

I agree that excessive heat can cause ballooning. I don't agree that it is the only cause of ballooning.
 
Yeah, I thought excessive torque caused more converter ballooning than excessive heat.

David

I dunno Dave. Ford had a bad issue with converter ballooning in the 80's and 90's and most I saw were in Lincoln's and crown Vic's. I don't consider those power plants very tourqy.
 
As 90sc35thann pointed out pinching or blocking the transmission cooler lines can generate excess pump pressure. This can make the converter to act like a hydraulic ram, continuously jamming the crank forward against the thrust bearings. The thrust bearings absorb the forward thrust loads from the transmission. Over time worn crankshaft thrust bearings can cause torque converter ballooning.

Some other causes are:
  • Incorrect flexplate bolts.
  • Improper converter selection.
  • Excess converter play from loose converter tolerances or bad installation.
  • Transmission pump gears installed wrong.
  • Incorrect transmission alignment to engine block.
 
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