Hey guys,

I'm not FI yet, but starting out with the FastInt exh and UTEC and decided to go with a tranny flush (at dealer) and tranny cooler.

This is the cooler I picked up: click here.

It has the viscosity valve so it really only starts flowing through the plates when the fluid warms up (when cold it returns through a bypass).

This thing is rated at 14,400 BTU.

MAIN QUESTION: do I have to keep the stock tranny cooler? Or can I just pop this one in it's place? The stock one looks so wimpy but I don't know it's specs so I'm hesitant to replace it... If no one has a good answer, I'll add the B&M unit in series (or should it be in parallel? [that's main Q#2]) to the stock one. That raises another question though...

Also I have seen only posts by Roneski (thanks man!) about where to place it so as not to interfere with the intercoolers in the future (JWT twin intercoolers for the G35) - anyone else found clever locations?

Here are some related posts about location and here's Roneski's.

Here is a post by SLFG35 with a good breakdown of different coolers available and a cross post at my350z though not sure if the AT cooling is the same on the Z.

 

Thats the same one I have. U dont replace anything, just add the new cooler and u are done.

 

So did you just put it right next to the existing one (to left or right) in front of the radiator and re-route the piping from the existing cooler?

Did you add it in series (simplest, no additional fittings necessary) or in parallel to the existing cooler?

 

Understand that 14,400 BTU is a very low number. Each horsepower generates 2545 BTU/hr...............so the cooler can handle 5 HP worth of heating from friction losses.

The torque convertor generates 88% of the losses [gears 3% tranny internal pump and others consume the rest 9%] So 3% slip loss would need a 10 HP cooler depending on ambient and how long power was applied.

Think bigger than 14,000 BTU.

To extend life of AT the maximum temperature of ATF should stay at or below 176F............whereas an engine can function fine with 220F coolant

Once the coolant is hotter than the ATF, the in radiator heat exchanger sends HEAT from coolant to ATF [BAD except during vehicle warm up].

 

A tranny cooler is a good thing to add.The one you picked out looks like a good one.The stock tranny cooler you do not see,It is the bottom portion of the radiator.The cooler you are probably thinking of is the power steering cooler.I have had one on my G for over 2 years.I also installed one for another member a couple of weeks ago.

 

I have the service manual for my year (2004 coupe) and cannot find the reference to the existing piping. Anyone have pics or a link to a DIY guide.

I don't get it. I can see the coolant hoses in the service manual coming off the AT - they don't show where they go. But those hoses are filled with ATF, right? Not coolant.

Y'all are saying that the bottom portion of the radiator is used as the tranny fluid cooler?

I'm definitely confused now. The coolant is in separate pipes in the radiator but exchanges heat with the ATF that also circulates (but through different pipiing)?

Maybe I just need to get under the car and follow the piping...

Q45: If hot coolant is actually heating the tranny, perhaps a thermostat controlled valve is in order? I will log tranny and oil temps with CIPHER if I can for a before/after comparison.

And the unit I picked out is the largest transmission-specific cooler that B&M makes. I could've gotten a larger one, but those do not have the viscosity-dependent flow valves.

Finally Q45, I think your worries about the thermal dissipation properties of the cooler are not practical. Even if the engine outputs 300 hp and the tranny friction loss is 3% = 10 hp figure you quoted, the cooler is capable of dissipating the heat from 14,400/2500 = 5+ hp in friction losses per HOUR. That is 1 horsepower generates 2500 BTU to dissipate every hour.

I don't know, but I think it's impossible for the car to put out 300 HP continuously for an hour. That would overwhelm the tranny cooler, but that would be the least of the problems the car would be coping with...

So that still begs the question of whether the existing cooling lines for the ATF should be maintained or re-routed to the new tranny cooler... Perhaps hook them up in parallel with a thermostat controlled valve set to 170 on the stock radiator hook up (so flow decreases to it relative to the new tranny cooler when the coolant is hot).

 

rcdash good luck with your setup, i might go with the same route as you soon, but i have an idea dunno if it will work, why don`t you use the stock tranny cooler to cool the power steering ? dunno if it will work but i guess it will cool it down a bit vs the stock power steering cooler.

This is where the Stock Tranny Cooler is

 

Run the tranny fluid through the aftermarket cooler last (before returning to the tranny) and you will get the lowest possible fluid temperature.

 

If that's the case, then during a long enough drive, the engine temp will cause the tranny to run over the optimal 176F temp. That doesn't sound like something the engineers would miss.

 

Thanks guys, I think I'm set now.

I found another pic in the service manual which actually shows the AT cooler.

I can't imagine it is very effective as a cooler (maybe it is just a warm-up device as Q45 states more than a cooler) - the stock power steering cooler looks much better.

It also looks like the sealing rubber insulates the tranny cooler from the radiator, but I could be wrong.

 

Sounds good - that way even if the temp is 220 before entering, hopefully it'll be closer to optimal on the way out.

 

Measure the temperature going into the cooler [from the torque convertor] that is the temperature you want to limit to avoid degrading the ATF and the TC lockup clutches.

Worse case condition is not a single quarter mile run [15 seconds], it is going up an incline in 5 th gear with the TC slipping in Summer for minutes or stuck in traffic in gear with almost continuous starts and stops for 30 minutes.

Remember the tranny is bolted to engine block where heat is transfered back and forth and at road speed the air flowing by tranny cools the case and pan plus the drive shaft gets some heat transfer.

Anyway the weakest hottest link is the TC lockup clutch, so measure the heat at its ouput [TC] not after the cooler.

ATF contains temperature sensitive dyes which desaturate [color intensity fades] on overheats .............a drop of old vs a drop of new on a white paper towel tells its condition.

In coldish climates you need the heat from radiator heat exchanger to warm up ATF install any add on cooler [in series] AFTER oem exchanger.

When you locate between condenser and rad remember air flow after condenser with AC on is 30F warmer than road ambient so 40F warmer than radio report.....still 140-150F air is colder than 190-200F coolant.

 

In series, after the OEM, in front of the radiator and not behind the condenser - just what i needed to know...

Thanks!

(I wasn't planning on adding a temp gauge, just using the CIPHER tool as there are apparently two temp sensors there... hope it's an ECM and not TCM parameter though as CIPHER doesn't "do" TCM yet).

 

Q45, so what is the solution? If an aftermarket cooler simply heats up the tranny fluid how do we cool it further than stock?

 

Under normal low load conditions the coolant is 184F going into radiator and after the radiator drops it by 10-15F [so the ATF is dropped to 174-180F leaving the AT heat exchanger].

TC slip or quarter mile heats ATF up but it cools down eventually.

Depends on whether you want your tranny to last 100k or 150k or 200k?