Odometer was over 200,000 on the original transmission on my 03 Bonneville. Drove it for over a year with hard shifts at times but never gave out. Finally broke down and went to the dealer and got the GM transmission and had the Community College install it for $25 plus fluids. They found the front mount bad and replaced it too. Got the car back on a Friday and noticed fluid leaking from the front mount. Car drove silky smooth until Sunday when it had some hard shifts after exiting the freeway. The first 1-2 shift was hard and then the SES light came on. Took it back to the College, scanned and found code P1811. Reset and car drove silky smooth until the next Sunday when I took the freeway again. Did not have hard shifts at first but after some in town driving the hard 1-2 shift came back and SES light came on. Now to the Dealer, scanned and found P0420 and P1811. Tech says the P0420 is responsible for the SES light and not the P1811. Tech says to drive the car and see if the tranny will smooth out because he is sure he won't find anything if opened up. It has a 3 year 100,00 mile warranty so I guess I'll be driving it for the next 2 years 364 days and then drop it off to have another tranny put in. Or it will smooth out like he says. For the P0420 code a new GM CAT is over $600 because it is the entire exhaust from Cat to tail pipe!!! The CAT was replaced with an aftermarket on July 2008 so do they go bad that quick? As far as the leaky front mount I wanted to let people know that it is from the GM dealer and I feel they might have a flaw in their workmanship. They gave me a new mount and as soon as I stop writing I will be changing the brand new leaky mount for another brand new mount that has some fluid residue on the top of it. They had another brand new mount but it actually dripped fluid when I pulled it out of the box. (The parts guys are great at my local GM and they actually make going to the dealer a great experience.) I'll keep you posted.
Mike

i dont know that much about transmissions but about the general quality of gm parts its not like it used to be where those were the parts you want for you car. they are now just what ever they can buy cheap and sell expensive just because people still have the mindset. they are no where near the quality of aftermarket parts you can get for half the price. i havent had to replace the original cat on any of the three cars 99 yukon 155k, 98 bonny 150k, or my 03 monte with 165k. but if one does go i certainly wont be getting one from the stealer.

The new, new front mount is not leaking. Tranny still has some hard shifts but not all the time. Took over a week for the SES light to come back on.
Mike

Steve has mentioned to me that because GM gives no spec on tolerances in the clutch packs etc, it'* common with a normal rebuild (say one done by them) for the packs to have a lot of excess slop and toss the 1811 from the start.

A neat thing about GM rebuild warranty is they will pay the labor to have it replaced.

It'* bad...have it replaced.