My transmission does that. I think it's on the way out. It sometimes slams into gear with a loud thump, particularly when starting out in first, or when going quickly off and back on the throttle. But, heck, maybe I have a busted motor mount too. I thought it was the trans.

Wow! 255's are like 10" wide, aren't they? Do they rub at all?

Thanks a lot for the replies. I was actually looking at Elbrus I05's for the LeSabre (which I intend to put GXP brakes on). Maybe I will just play it safe and go for the 18's. How much difference in performance can there actually be?

OK... let's start with factory 17's. I know that the wheel ID can vary depending on who makes them. Will factory 17's fit over GXP brakes?

Does anybody know if aftermarket 17" wheels will fit over GXP brakes?

From what I've read there needs to be some programming done to make it work with your ECM. I'm not sure if that's true... just what I read on the internet when mine failed. Seems to be a common problem.

I fixed this exact same problem in my 03 LeSabre. I removed the electronic part of the EBCM through the driver's side inner fender (6 torx screws), popped it open, and resoldered everything that looked suspicious. There was a noticeably bad solder joint on the relay pins where it solders into the ...

Thanks for the welcome.
I could post pics, but right now it's just your average beaten-up grandma car. Hopefully I'll have something more to show sooner than later. Suspension mods should be happening soon.

Hello... new to the forum, but I've been browsing for a while looking for information. I'm in the process of rebuilding my 2003 LeSabre into something that handles a little better and has more power. Since there is so much in common with the Bonneville, I'm learning a lot from all of you... thanks ...

It sounds like the brake control module. I had the same problem on my LeSabre, and was able to fix it for free. I have a scanner that will do ABS codes, and I was getting a C1214 "open relay" fault. Here's how I did it on my LeSabre... might be similar for you.
I pulled the left front fender well ...