Hello!

[MgoBlue78]

I wanted to introduce myself. I'm Ryan and I live in northern Indiana. I've been looking for a good forum to join and I'm liking what I'm reading! I recently bought my first Bonneville GXP. Its a 2005, Black and has 106,000 miles. I love my car and can't wait to get working on her! My first question is, do these cars have the Caddy's drive-train or is it just the engine? The dealer I bought it from thought it was a Caddy's tranny with different gears. My mechanic isn't a fan of the gm cars with V8's... IDIOT!! He said gm put big V8's with tranny's that are meant for V6's and they have all kinds of problems. So needless to say, I'm searching for a new mechanic. In my research I couldn't find where these cars had many issues with the drive-train.

[PaulyGXP]

It is a Northstar engine, mated to a 4T80 transmission. The 4T80 was specifically designed for the Cadillac Northstar engine in 1993, and continued to be used until 2011 on virtually all Northstar front wheel drive vehicles. The transmission is not the problem with these cars. It has been proven one of GM's strongest and most reliable FWD transmissions. If anything the Northstar itself is the problem. Do some searches and you'll find all kinds of stuff on the forum about the Northstar. I would say almost every common problem is on here. I myself have 111,000 on my 04 Bonneville GXP and it has been a great car for the almost 40,000 miles I have accrued so far. That's not to say I haven't ran into issues, but all in all its been solid.

FYI to your mechanic, the Grand Prix GXP, Monte Carlo SS, and Impala SS with the 5.3 liter LS4 is paired to a 4T65E-HD transmission. While the transmission is also fairly good and you will see a lot of them lasting many many miles, when paired to the LS4 they do suffer from shorter lifespans. There are ways to help them last, but that's a whole different topic! Welcome aboard!

[MgoBlue78]

Thanks so much for the insight!

[CMNTMXR57]

By the time it was put in a Bonneville, it's all the same GM Powertrain behind a Northstar.

I would even add to Pauly's post that the Northstar isn't a bad or unreliable engine by any standards. It has it's nuances just like any other engine. The issue is, between it and the 4T80E, it's a size 10 powertrain in a size 5 dress, which is where the difficulty ensues.

Your mechanic needs his head examined.

[Bad GXP]

Welcome to Pontiac Bonneville Club Ryan!

I would tend agree that the N* is pretty reliable in most regards. I think you should get good service from your tranny too with regular maintenance.


Good luck and enjoy the ride!

[ZimGXP]

X2 on the mechanic.