I have a 99 Chev 3/4 ton 4WD Silverado pickup with a 4L80E transmission that I purchased a few months ago. Seemed okay, a bit rough which I attributed to age. On the way home a heater hose failed, which I easily replaced, but left me with doubts. Then the fuel pump failed, which I had replaced with a grimmace. Everything was fine then for a couple months, but then the transmission started to whine and slip. I dropped the pan, to find darkish fluid and dust on the magnet. I replaced filter and fluid, and also added Lucas transmission treatment. Also, the shift lever had stopped going into Low2 and Low1, and was kinda floppy. I also replaced the shift module on the column thinking this might have been the issue.
So, it then worked beautifully in Drive, and 3 for about 300 miles. (but still would not shift to L2 or L1) Then it started to whine again, and not work. I had it towed in, and was simply told I needed a new transmission. $4K. I don't think so......
At issue is that it worked beautifully for that 300 miles, but now the fluid again is dark, and smells burnt. I limped it home from the shop. I noticed that it will work for about a quarter mile before the transmission slips again. I can reset this if I put it in park, turn off the engine, start the engine again, and it will kinda work for another quarter to half mile.
But, new fluid is burnt, and it is back to behaving just as it did before I "fixed" it. Could it be that a pump is failed that pumps the transmission fluid through the cooler? Could it be that the torque convertor is failing and is destroying the fluid? (although I would anticipate it would not have worked as well for the 300 miles....) If anyone knows this transmission, please let me know any ideas. The transmission is supposed to have a very good reputation, so.....hmm
Thanks!
Mark