I've got a 1998 XLT ext. cab 3.0L V6 with the 4R55E automatic transmission. It has the add on tranny fluid cooler which I found beneficial here in Phoenix. 99% of my driving for the last 12 years has been highway (driving at least 30 to 40 miles nonstop) with essentially zero stop and go or sitting in stopped traffic.

Its had its fluid changes at every 30,000 miles and no repairs. I'm experiencing no problems and when you pull the stick its still very clean fluid. If I floor the gas the engine revs off the chart and you don't really move very fast....so its pretty worn out for heavy/explosive acceleration. But under normal and light acceleration it feels really strong...still grabs like new in that situation.

I just turned 174,000 miles and have this impending doom feeling even though everything is running fine. What has been everyone's experience with the lifespan until failure/major repair? I can't decide whether to sell it before something goes bad or wait. I think a new transmission would equal the value of the truck. The truck body and interior is in near perfect conditon as I've always been **** about hand washing/hand waxing and keeping it clean. The only defect the truck has currently is a failed heater core, otherwise everything is fine.

Thanks.