Replace your Radiator as a Preventative Maintenance..

Normally, I'm not the type that's too anal on PM unless it's something that can cause catostraphic damage or leave you stranded.

In this case, the radiator in the MDX should be a PM IMO as there are both transmission fluid and coolant running through the same unit. For warmer climate peeps, you can elect to go the external tranny cooler mod that has been outlined by Skirmich. For peeps living in snow states, it's gonna be a personal toss up on whether you want to maintain the factory setup. I'd rather not get into a debate about that in this thread though.

I would say if you're after the 8-9 yr period, you are pushing it depending on where you live.

If you wait til after the fact, you'll have to flush out both systems(tranny and coolant) which will cause you more headaches in labor and material costs down the line. You can do it as a PM which will set you back ~$300 for OEM Radiator or ~$160 for a Denso unit which also makes OEM radiators for various cars. I'm not sure about the other popular alternative which is Spectra as they seem to have a few different lines for the same car. I'd rather just stick to a Japanese OEM manufacturer personally.

It could cost you potentially more in towing fees if you get stranded from this or if you decide to keep driving it to the nearest shop, you're at their mercy. If you drive it home and it's far, you could be looking at a transmission repair or replacement cost.

So bottom line is if you're driving or don't notice the intermix and continue driving it, you could potentially damage your transmission.

I'd say this is a pretty good case to PM the radiator IMO.

In my case, I lucked out as it slowly started leaking(from passenger front corner) in my driveway. When I went to move it and let it run, the internal line must've ruptured and whole bunch of fluid spilled over out of the coolant reservoir tank.

It's pretty easy to diagnose this vs. say blown head gasket, cracked cylinder head by the color which should be strawberry milkshake like since tranny fluid is normally a reddish color.