Transmission question

I'm pretty new to this forum, just got my first Chevy. I've seen a lot of post and referals that say that the transmission will break down before the engine will. What exactly happens to the tranny's, are they really that bad ? My truck has 105,000 miles on it.
http://tinypic.com/4tk4u0
Bert

Well just based on mine, I feel pretty sure my 4L60E could give out at any day. One day it works great, shifts nice and hook the truck up well. Then the next day i have as SES light and extremely hard shifts and it will drop a gear and slip at any time. Basically the 4L60E sucks balls. Im getting a build kit mine, hopefully i dont take it out and find its beyond repair and need a new one.

But in general all sorts of things go bad, you can lose gears, even disinegrate the planetary gear or destroy the valve body. Its all in how it gets used. A babied transmission will last forever, but under normal drving i would guess they hold together for 150K-200K miles.

Two things you can do to prolong trans life--change the fluid regularly and add an external cooler. If the truck has the tow package, it should already have a small auxiliary cooler in front of the a/c condenser. If it doesn't, add one.

From your post, it sounds like you bought the truck used. If you don't know the maintenance history, it would be a good idea to change the fluid and filter. Depending on the year, the trans pan might have a drain plug. (Be very careful removing this plug--they are tight from the factory, and lots of people strip the corners.) Draining the pan will only get out about 4 quarts, so I would recommend draining once and driving for a week. Then drain again and drive another week. Then drop the pan and change the filter. By then, you should have about 2/3 new fluid. Do a search to find more detail about doing a pan drop and filter change.

And as Silverado Brethern said above, trans life also depends on how you drive. If you do a lot of 1/4 mile runs or hard off-roading, the trans will not last as long.