Piston Slap: Lifespan of the Suburban Tranny?

Duncan writes: Hi Sajeev, I have a question about a 4L60-E transmission in a 2001 Chevy Suburban K1500. The truck has 159k miles. The previous owner purchased the truck 7 years ago with 90k miles and hasn't changed any fluids in that time other than oil – I don't know anything about the truck's early history. The transmission feels fine, but the fluid is dark and doesn't smell great. The pan looks like a deep (vs shallow) pan and has a drain plug – my internet research leads me to believe these trucks came without a drain plug, but it's a recommended upgrade – does this mean the transmission has been serviced at least once in its lifetime and the pan swapped with an aftermarket one, or did Chevy deliver some trucks with and some trucks without plugs? Onto the meat of the question – I'd like the transmission to last forever – what can I do to ensure that? Can I change the transmission filter and replace the Dexron III that I drain out of the pan with Dexron VI? Should I do another drain and fill soon after to increase the ratio of fresh fluid to old fluid? Will I do damage by drain, filter, Dexron VI? Are $50 electronic shift kits that program the transmission to be a little more aggressive worth anything for longevity/fuel economy on a transmission that already has so many miles? I won't be driving the vehicle much, so I don't want to go overboard on maintenance/upgrades, but it's really a nice truck and I don't want its life to be cut short by neglect. Thanks for the advice, Duncan Sajeev answers: Not being an expert in Mr. Goodwrench related products, I poked around Rockauto.com to see what tranny pans are available for this rig.  Sure enough, the cheapo part has no drain plug, but there are several alternatives that are deeper with a drain plug.  Gotta love the aftermarket. YOU LOVE IT RIGHT NOW!!! (shakes fist) I say this as I put on my flame suit: this 'burb either has a factory towing package that mandates a better oil pan (possible) or its been serviced once before. And serviced quite well, considering it takes forethought to feel the need for an upgraded pan. Your question: what can you do to make a transmission last forever?  Answer: Nothing. It will normally be the weakest link in a powertrain. I suspect more older vehicles wind up in the junkyard from a bad tranny (i.e. a $2000 repair on a $1000 car) than any other automotive malady. So what's my advice to improve the life of the tranny?  If you can electronically speed up the shifts for $50, do it.  Slow shifting is the worst enemy to a transmission's lifespan, and its never too late to fix that. Now about the fluid: go to Dextron VI if you believe GM's recommendation. I believe in a fully synthetic fluid from any big name manufacturer that's reverse compatable with Dextron III. Read the bottle's label thoroughly and buy the brand you want… And finally, the $64,000 Question: change the fluid at this mileage or not?  Who knows if the fluid's been changed on a regular basis, but from your assessment, I suspect its been changed at least once.  If so, another fluid service will extend the life of the tranny, not shorten it. Should you trust my suspicions?  That's a very expensive question that only YOU can answer. Good luck with that. Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you're in a hurry.   from The Truth About Cars http://www.thetruthaboutcars.com

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