Does the stock ZF 6 Speed come with a transmission cooler? If not, has anyone installed an aftermarket one to keep the temp nice and cool?

 

It uses the radiator to cool, cost saving device.

 

Most cars do this, obviously doesn't work as well as an external dedicated cooler. You can get a good transmission cooler for $100, well worth it.

 

I agree, the only downside is when it is cold outside it will take the fluid longer to warm up.

 

Any such aftermarket systems that can be disengaged/bypassed for those freezing mornings?

 

Yes! It's a problem too, so if you do this get a thermostat as well.

 

I've added a B&M stacked plate style tranny cooler to both my Jeep and Rover (they both tow a good bit and get off-roaded frequently) and I'm very happy with the results. Prefer the stacked plate design over the tube and fin style. I buy the kit that goes for about $65 from Jegs or Summit. Not very hard to plumb on the trucks. On the S-Type, I'm thinking right behind the grille might be a good spot.

I plumb them in circuit with the OEM in-radiator coolers. This helps get the temps up early on. Then the B&M helps stabilize the temps. Fluid path i use: tranny to OEM in-rad cooler to B&M back to tranny.

Not sure if adding one to an S-Type is really all that necessary though. Would need to install a guage first and gather some data.