'05 GTO acting like it has an open diff

3degOfrdm · 09-28-2008, 10:12 PM

I recently purchased a 2005 GTO with 29k on it.

It is behaving a lot like it has an open diff. I took it out autoxing and all it wanted to do was spin the inside tire, and it will not easily do a doughnut. I have owned a '03 z06 and have an Rx7 with a limited slip. I am used to how those differentials behave.

Is there something wrong with my diff? Am I expecting too much out of it (i.e. should it behave similar to my z06)? Have others had this problem?

Thanks in advance!

Rukee · 09-29-2008, 08:19 AM

Welcome to the forums.
First thing I would do is maybe change the fluid back there and make sure you use the right fluid going back in.

gm4life · 09-29-2008, 09:00 PM

Have you tried doing a burnout in a stright line? That is very common for our diffs to do that from what I hear. I'm not sure why its like that but it might be because our diffs are a cone type rather than the clutch type limited slip.

6QTS11OZ · 09-29-2008, 09:42 PM

The 2 cars you mentioned also have overall better balance than the GTO. Also the GTO wasn't designed for auto cross. It's a touring coupe with a softer suspension designed for comfort not canyon carving. With that said, you may have a handling issue more than a rear end problem. The first thing I would do is a suspension upgrade until you can find the sweet spot you're looking for. Maybe start off with adjustable shocks, stiffer lowering springs, thicker sway bars, strut brace, better tires, etc. Then from there you can add polyurethane bushings and a camber kit. Pedder's sell complete kits so you may want to look into their stuff. I do suggest you change you're rear end fluid anyway. I've had great success with Torco products but I'm sure others will work fine too. Good luck!

Rob@WretchedMS · 10-01-2008, 12:21 AM

Change the rear end fluid, and when you replace it be sure to use the correct friction modifier.

If you go with Torco fluid (I did) you will need the Type F modifier, NOT the Type G like every other GM in the world.

3degOfrdm · 11-15-2008, 12:57 AM

Thank you all for your input...

So I changed the fluid as recommended. It did not look right... there were some metal shavings in it! I tried driving it a while with the new fluid. The behavior got worse.

In the rain, both tires would not hook up. And then i started to get a serious clunking when turning tight!

I have the Certified Used GM warranty that lasts 3000 miles. I took it back to the dealer and they took a look. Turns out they replaced the entire thing! Parts came out to $2800 ... but the cost to me was $0.

I just got the car back today... the result: hooks up just like any other limited slip diff I've owned.... so i'm happy... see

What I think happened: I had the shop print up a repair history for the car and the diff gasket had been replaced. I'm thinking that the gear oil had probably drained out and was driven a ways low/without and that did some damage. Instead of fixing things then, they just put on a new gasket and added some fluid.

Thanks again everyone for the input!!!

GTO JUDGE · 11-15-2008, 06:59 AM

Looks like you got your GMPP money back almost twice. Good thing you had it!
I had my rear changed out too. Not that I want anything to happen but I have the GMPP too. For this type car, its wise to have one.

Rukee · 11-15-2008, 08:23 AM

Glad it's all sorted!