Can anyone confirm that the hose with the two clamps is the return to the transmission?



This line goes to the lower portion of the radiator. The routing from factory is correct per the shop manual.

The reason I ask is because I just installed a 12,500 btu trans cooler and its getting me weird data.
I know it aint big but its 12,500 btu as opposed to the suggested tube and fin one at 3,500 btu.
I didn't have much room and I didn't want to rip my front end off.


I attached thermocouples to the hard lines, seen in the photo.
Aftermarket cooler in series with radiator.
The data is not very consistent, but here is the confusing part

Ambient temp 97°
OEM SETUP - While cruising, trans fluid over 180°- the radiator is putting heat back into the coolant about 5 degrees.
Sitting in the driveway, trans fluid is above 200° - the radiator is cooling about 5 degrees.

After Market Trans Cooler - Cruising, coolant going back to transmission goes as high as 15°
Sitting in driveway the coolant going back is about 5° cooler.

This behavior makes me think my thermocouples are swapped, but I have double and triple checked.

I TC'd the cooler and it looks like the lines are not correct. I appears the cooler is prior to the radiator.
I thought the lower radiator line is the return.

Any input will be appreciated.

Vertical Nissan heat exchangers are almost always oriented pressure-bottom return-top in order to let buoyancy assist in chasing bubbles out. However, they rarely air-bind even if they're routed backward. Most Nissan exchangers have very tiny passages, on the order of half a millimeter, so it is very possible your exchanger is clogged. If the exchanger and external cooler are arranged in series, that will stop both devices from working.

Thanks. It should only take me a few minutes to swap lines. I am too lazy to swap the hoses, hook up the TC and go for a drive.
I was hoping someone could confirm soon. Car is still on the rack and skid plates removed.

I know the aftermarket one flows. Blew it out with shop air and also pressure tested it for leaks.
Doesn't flow as well as I would think.

Swapped lines. Temps look consistent.

This little booger doesn't do much, but it works.

Ambient 104°
Coolant temp 196° - Cruising 55 mph - Trans Fluid in 185° out 172° for a Δ13°

Ambient 88°
Coolant temp 188° Cruising 75 mph - Trans Fluid in 168° out 144° for a Δ24°

Coming to stop the trans fluid actually starts to get hotter, but if you let the engine idle at 800rpm, eventually it will cool about 6°.
If the rpms go to 1000 temps will go up. AC has no effect during this. Somehow its rpm related.

That still sounds like maybe low flow through the factory exchanger in the radiator, I think I'd back-flush it. Has to be a back flush, the passages are very tiny and debris won't blow through it forward. If you're not sure then just blow both ways, but start top-to-bottom, that's opposite the flow on typical Nissan side tanks. The temp increase at idle after cruising is just thermal mass, no different than why the engine fans kick on after stopping from a cruise. Flow is reduced but residual heat still exists and needs to be dumped. There's nothing much you can do about that.