Piston Slap: If You Must Tow With a Minivan…

Sajeev Mehta
by Sajeev Mehta
piston slap if you must tow with a minivan
TTAC Commentator 70Cougar writes:Dear Sajeev:

My wife has a 2005 Odyssey with 50,000 miles. To date, we’ve had no problems with the transmission, but I keep reading about how the transmission on the Odyssey isn’t cut out for a vehicle that heavy. I’ve been contemplating getting a utility trailer for it (although, shockingly, my wife isn’t too hip on having a utility trailer in the driveway) and, in the course of my research, I’ve found that a transmission cooler is recommended if you’re going to haul a trailer. Is it worthwhile to install a transmission cooler even if I don’t get a trailer? Is there any downside to transmission coolers (e.g., the trans runs cold for too long)?

My wife has a 5 mile commute (10 miles round trip) and we hope to keep the van at least another 5 years.

Sajeev answers:

Before we start, it’s time to change your transmission fluid. The reason is twofold: transmission fluid has a finite lifespan, and it will die at the mere sight of a utility trailer attached to its minivan home. I love minivans for their efficient use of space and command seating position, but their transaxles are never good enough.

I think every minivan needs the largest external transmission cooler possible behind the front bumper. That is almost as important as regular fluid changes. If you plan on towing anything, carrying enough people/cargo to make the rear springs sag, and/or live in a climate that’s brutal on transmission fluid temperatures, both are mandatory. I’d consider annual transmission fluid changes on any minivan that tows on a regular basis, at highway speeds.

A downside to transmission coolers? Not that I can think of. Because transmission fluid gets far hotter than engine coolant (hence why many tranny coolers are just a heat exchanger inside the engine radiator) the odds of being too cold aren’t a big concern. But if you aren’t a Houstonian like yours truly, maybe you will need a radiator block-off pad for your front bumper…in the Yukon Territory.

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry.
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6 of 37 comments
  • Krhodes1 Krhodes1 on Apr 09, 2012

    Towing a little lightweight utility trailer short distances is a non-issue. It is no different from having 5-6 people in the car, even with 1000lbs on the trailer. You won't notice it, and neither will the car. Change the fluid using the severe service schedule and call it good. The transmission may grenade at 123K instead of 125K, who cares? From the previous responces, you would think the OP is planning to tow a 10Klb boat across the Rockies. Sheesh. And backing up a small trailer is hardly rocket science - add corner flags. I've had a little 4X8 utility trailer for a decade, just the ticket for hauling crap to the dump or home from Lowes. No insurance, no inspection, and registration is $14 every other year. I've towed it with a variety of cars, from an '02 Golf TDI to sundry Saabs and Volvos.

    • See 2 previous
    • Moparman426W Moparman426W on Apr 10, 2012

      @Moparman426W I see what you are saying, but in this gentleman's case it looks like he may not have much space for the trailer in his driveway, that was why I made those suggestions. I meant that he could trade the minivan for a smaller engined pickup, saving space in his driveway. Dunno the mpg of an oddysey, but a smaller engined truck should be close in mileage.

  • 70Cougar 70Cougar on Apr 13, 2012

    Original poster here. Busy week and missed the entry. Thanks for all the input. Update--my dad bought a 5x8 utlility trailer to haul ATVs for hunting. He keeps it at my house and my wife is cool with it. We have a third parking spot next to our two car carport, one of life's simple luxuries. He has a Passport with a transmission cooler (I wonder if the Passport trans is any tougher than the Odyssey's). You guys have put the fear in me about destroying my transmission. If I do any towing it would local and light duty. I'm off to change my fluid and put in a cooler. I'll have to think about the risk/reward of towing with the van. By the way, I ruled out a pickup because of the cost purchase, maintenance, insurance, and annual registration.

    • 70Cougar 70Cougar on Apr 19, 2012

      Actually, he has a Pilot, not a Passport--I get those two confused.

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