Burning smell @ high RPMs

[silverado747]

I have a 2008 Silverado Crew Cab LTZ 6.0L engine, just broke 63k miles. Recently when I "floor" it and am in high rpms above 4800 there is a burning smell & actual rattling coming from either the engine or transmission. I cant quite put my finger on it, trying to get an idea of what it could be before going to a mechanic. At about 35000 miles they had to rebuild my trans because some of the gears got tore up & lost their bites, I use to drive it very hard and fast, but since then I do not.

[WorthFlorida]

Is the A/C off? Under a heavy load the compressor clutch is disengage for more power to the transmission but it doesn't last for ever. When the compressor clutch is engaged it might be worn and the rattle you hear is the clutch tearing itself apart. The burning part could be a belt or two slipping, especially when the A/C clutch engages. Since you used to drive it hard these parts are probably at EOL (end of life). Burning belts have a distinct smell and you should be able to tell if it is rubber burning.

 

Another possibility is a idler pulley or the belt tensioner pulley is shot and one or the other can no longer handle the heavy load at those RPMs. And do not overlook all of the other moving pulleys tie to the belt(s).

 

A common cause, and it happens allot in Florida since the AC is on most of the time, is the air conditioner compressor is starting to seize up. I've had a few compressors fail and usually the tell tail sign is the belt starts to squeal like skinned cat and you can smell the belt burning. I've had at least three compressors fail this way in 23 years living in Fl, but all had more than 100K on the clock.