^ I agree that incorporating the radiator into the ATF cooler circuit is a good thing. If there were a compatible, 36mm radiator when I swapped mine I would have gone that route. Where I think we differ is how & when the radiator tie-in is actually beneficial.

My understanding of the 5AT radiator/ATF heat exchanger is that it helps get temps up quicker on cold start up and it helps moderate ATF temps on the high end. The built-in ATF cooler doesn't provide much benefit in the mid-range, however, which is why its good to have an aftermarket cooler.

Similar to the way it works with the oil cooler circuit, the built-in ATF heat exchanger is small, but, on the high end, it is efficient enough to keep temps from getting out of control because its moderated by coolant temps. In heavy traffic, you get no flow to your coolers, be they the stock ATF, or aftermarket oil and ATF cooler(s). The tie-in with coolant system is beneficial in this situation because your fans will kick on and lower coolant temps. Since the coolant temp should never get over 212F (unless you've got a bubble or problems keeping temps down), it caps how high the ATF and oil temps can go.

so, IMO, your friend is right about the radiator not providing much cooling, but he's wrong about its ability to cap temps on the high end. i think the goal is to keep temps low within the normal operating range (180-210ish), and an aftermarket ATF coolers is the best way to do it since it should be more efficient when it has flow. when you don't have flow, the tie-in with the radiator/coolant system steps in to keep temps from getting out of control.

and, yep, i have a fan installed on my ATF cooler now (no shroud though ). Pix are in post #12

 

Thanks for the info... Will Red Line High temp transmission fluid work on 350z ? As I have heard to use nissa S-matic is advisable.

 

Sorry to bring an old post back, but has anyone considered adding a electric oil pump into the mix? I mean how much oil is actually getting moved through the system with stock setup? What is pushing the oil through? I can't imagine simply adding an additional radiator and fan would help much if the flow of oil is slow.

My last track day I was able to attend I would hit limp mode about 5 minutes into my run, outside temp was in the 90's. I just don't see adding a small radiator is going to help much.

BTW where does the radiator go, before going to the stock heat exchanger in the stock rad or after?

 

stock pressure is decently high. watch the ATF fluid change DIY video or disconnect your ATF cooler line with the car running and you'll see how much.

the order should be:
transmission --> stock transmission fluid cooler (bottom of stock radiator) --> aftermarket transmission fluid cooler --> back to transmission.

you can bypass the stock transmission fluid cooler, but be aware that 1) it will take longer to get your AT fluid up to temperature, and 2) you will lose the cooling benefit of the stock transmission cooler when you're stuck in traffic (main fans will keep temps from getting too high).

 

I had a large tranny cooler installed about a year ago to help keep the temps down. I just ordered the GTM Stage 1 Supercharger today, which is a good thing. The issue that I have now is should I keep my existing tranny cooler when I install the supercharger. The tranny cooler would be behind the intercooler if I keep everything how it is. Would enough cold air get to the tranny cooler if the intercooler was blocking it, and I really don't want to spend another $500 if I can save a little more $$ for other things. Thanks!

 

do you have enough slack in your lines to relocate the cooler?

 

I have a cooler on my 2005 5AT with TransGo shift kit. The temps depend on the ambient but say on a 80 degree day running 65 on the highway, I'd say in the 175ish range. On the track on a hot day I can hit 200. On the dyno when my tranny got up to about 200, the tuner said my trans was slipping to the point where he could not get accurate torque numbers. This was a super hot (95 degree) day. I use Valvoline trans fluid and not the Nissan stuff.

 

You might want to try Amsoil synthetic auto trans fluid.It has
expreme temp, for cold or hot.
It could be as simple as changing to one of the best fluids for your trans.Zheiland