2002 GMC Sierra transmission slips after driving 100 miles

2002 GMC SIERRA
48,000 MILES • V8 • 4WD • AUTOMATIC
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2002 GMC Sierra 1500 4x4 mileage: 48,000. When driving long trips (one hundred plus miles) the transmission begins slipping, and gradually gets worst. When I checked the fluid it appeared foamy, I added transmission fluid and the problem went away for about a week. The transmission only slips when the engine is hot. I took the truck to the dealer, it wasn’t slipping, they replaced the fluid and filters. Is this indicative of a coolant leak? Thanks for your help!

Jan 10, 2011 at 6:58 PM
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The problem with your transmission fluid foaming may have been caused by a low fluid level. When the fluid is low, air gets into the system which causes the foam. In your question you stated that the dealer replaced the filter and fluid and we assume it was okay after that. What you have described does not sound like coolant leaking into the transmission fluid. If it were, the foam would look like a strawberry milkshake. Check the transmission fluid once a week for several months to monitor the fluid level.
Jan 10, 2011 at 7:06 PM