[MeToo]

Undo the KS bypass. The SC engine needs it to keep from grenading itself, and it requires Premium fuel. Lower octane has a greater chance of pinging sooner, which is what the KS is supposed to act on by reducing the boost and/or retarding the ignition. No KS is a risk. No KS while towing is too much risk, if you ask me.

I agree with not bypassing the radiator, and with adding an extra trans cooler. Only the 2005-2009 suffered with the SMOD issue, so unless your rad is bad, use it. It's also twice the capacity of the non-SC rad!

I also agree with keeping a check on your speed. For whatever you load into the trailer, but the heavy stuff at the front, not the back. Too much weight behind the trailer's axle can/will cause loss of control as it tris to steer your Xterra from the rear, eventually resulting in a death whip. Lots of pics on the internet of poorly-loaded trailers being pulled at speeds that were too high! Slow down and get there, even if it's a little later. Better than not getting there for sure!

If you rent a trailer, see if you can get one with automatic brakes. I'm not sure if they're still available, but I've used them in the past and they are great!

 

[MeToo]

The core inside the rad is considered to be for cooling the transmission since most of the time that the trans is being used, it generates heat. Only in very cold climates will it serve to warm the trans fluid, and that will take some time since the engine has to first come to operating temp to warm the coolant in the rad before it can warm the trans fluid.

Unless there's some kind of extreme case, such as operating in the Arctic, I've never had an automatic fail to shift or work properly, even at temps below zero.

That said, if warming the fluid helps the trans, then it helps. Nobody told the "cooler" that it was not allowed to heat the fluid as well. Looking at it objectively, it is a device to transfer heat from something that's hotter to something that's colder. Whether heat leaves or enters the trans fluid is up to the temperature differential, not the name given to the device.

It's interesting that you linked that DeRale fluid control valve. That is the exact model that I installed on my rig last year. I added a temperature switch to turn the 7" fan on/off as well.

 

[MeToo]

Good information, as always.

 

[MeToo]

There are 2 lines going to the bottom of the radiator for the trans fluid. One goes IN, one goes OUT. The recommendation from trans cooler companies is to have the fluid go to the radiator first, then to the new external cooler(s), then to the transmission.

So, find the line that pumps fluid to the IN port and reattach it. Take the fluid from the OUT port and go to the new cooler, then run a hose from from the new cooler to the stock trans fluid line.

Make sure that you protect the hoses from chafing, and make sure the new cooler is in the airflow, either by mounting it in front of the radiator or by providing it its own fan, which is what I did.

It is not necessary to use the thermostatically-controlled valve that @JianTao linked, but it won't hurt. Pay attention to the little arrows molded into the housing. I'm using one on my rig.

 

[MeToo]

So that thermostat allows atf to access the transcooler once it has warmed up enough to lock in the torque converter?

Pretty neat little setup!

It allows 10% to pass through at all times, and gradually increases that as the temp rises. I can get the TC to lock immediately while it is still cold. The freeway is only 1 mile from my place, with only 3 traffic lights and 2 stop signs in between, so I don't think it warms up enough to consider it as being at normal operating temp in the trans. And for sure the engine doesn't warm up fast!

Thanks for the info! So to clarify, when you say to “reattach the IN port” you mean just don’t detach it from the radiator? Would you put the thermo-valve before the radiator?

You have a 50-50 chance of removing 1 line and it being the OUT port. If you remove both to see 1 pumping out and the other trying to suck fluid in, then the one pumping goes to the IN port (they're not actually labeled, but I'm referring to them to keep the lines identified). If you didn't take it off, then yes, it stays put.

Then you take the fluid from the OUT port to the other cooler, and then to the remaining trans fluid line that used to be on the OUT port.

Stock:
From trans IN --- Rad --- OUT to trans

Extra cooler:
From trans IN --- Rad --- OUT to extra cooler --- to trans

Extra cooler with thermo valve:
From trans IN --- Rad --- OUT to thermo valve --- to extra cooler --- to thermo valve --- to trans

The thermo valve unit has 4 ports. It comes in one port and the thermo valve allows 10% to go to the new cooler, while 90% makes a u-turn back to the transmission. The other 2 ports go to the extra cooler and are controlled by the thermo valve. When the temp rises, less makes the u-turn to the trans and goes to the new cooler.

I would not recommend placing it before the radiator, since the system is designed with it going to and from the rad with no re-routing. However, I also don't see it as hurting anything, but I'll let others weigh in on that.

 

[MeToo]

My take on doing a radiator flush before a trip: Don't do it!

I had 2 bad experiences when doing that, several years apart. Both times I was quite a few hours from home. Both times, the water pump failed. Both times, the pump was older but not leaking. Both times, the schmutz that had gathered around the bearing seal was flushed away, and not long afterward the bearing failed.

If you just gotta flush your coolant, my recommendation (for any vehicle, not just the Xterra) is to replace the water pump, all hoses, and t-stat.

Either top off the system, or replace all parts with pliable components, such as hoses, seals, etc.

 

[MeToo]

What he said.

Adding a cooler or even just stretching the lines will cause some of the fluid in the trans to fill those, so checking the level would be good. Just use the normal dipstick and fill to the same level.

 

[MeToo]

Changes the shift points (higher rpms) before it shifts to the next gear. Makes better use of the power and torque of the engine. With OD on, the ECU is programmed for peak efficiency (economy). With OD off, the programming is focused on max power and torque. Granted, the first gen X is neither economical nor powerful in the first place.

The other issue is transmission heat. Across the board for all manufacturers, the guidelines in owners manuals if the vehicle has OD on/off or tow/haul mode is to turn OD off or engage tow mode when towing. Failure to do so could overheat the trans. Excess heat is the greatest danger to an auto trans.

I wish I had been a little more aware of this particular "feature". 🤣