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Hello.

If you have a 2007 NA. Is it worthwhile upgrading the differential - what kind of improvement in performance?

What should I look for?

What is better (ignoring the money - focus on the parts) auction 1 or 2?

Auction #2 has me concerned that auction #1 - or that part purchased on a gm parts site - would leave me missing some parts.


1. REAR DIFFERENTIAL 2007 SKY WITH 37K! MILES 3.91 RATIO LIMITED SLIP COMPLETE | eBay

This - I gather - is somewhat rare having a 3.91 instead of 3.7 ratio.

The auction appears to be for a single part.

2. Alternative... This auction has a whole slew of parts:


3. Not that I can afford it. I'm not serious. But should the axles be upgraded at the same time?

 

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Have you experienced a single wheel spinning when you were trying to accelerate, or have you noticed the car pulling to one side when accelerating even though you know the alignment is good? No? You don't need limited slip.
 

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Have you experienced a single wheel spinning when you were trying to accelerate in a straight line, or have you noticed the car pulling to one side when accelerating even though you know the alignment is good? No? You don't need limited slip.
IMO, limited slip has more to do with being able to effectively power out of corners.
 

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There is a difference between automatic and stick. The stick has driveline support.
This is splitting hairs but I mention it in the name of clarity.

What sahein is talking about is the differential case or housing...the part that has the differential inside it. Most refer to the whole assembly as the "differential". In reality though, the differential is inside that case.

While the cases were different on the outside based on whether or not the car had the driveline bracing (and I never thought about the autos not having it at all...) the diff inside the case remained the same throughout the build with the base models having the LSD as an option and the Redline/GXPs having the LSD standard. The two diffs are also interchangeable meaning you an take a LSD diff and put it in a car that had the open diff and visa versa.

You may need to re-shim the diff if putting a different diff into your case. If you go to a GM dealership and ask for a diff shim for a Saturn Sky, they may tell you that they don't sell them separately and you have to buy an entire assembly. If they do, have them look up the part for a 2005 Cadillac CTS (not the V...just the regular CTS). Its the exact same diff (the diff assembly part numbers...meaning the diff and case already put together...was the same part number). If they do that, the parts listing for THAT car has all the diff shim sizes and part numbers.

I'm not sure if you have to change the pinion gear in the diff case if you change the ring gear on the diff (I think you do) but the ring gear on the diff is removeable and will bolt to either diff. I replaced my OEM LSD diff with a Quiafe LSD diff and that diff came without the ring gear. It was designed to reuse whatever was on the OEM stock diff.
 

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There is a difference between automatic and stick. The stick has driveline support.
Do you have any documentation about this?
I think that both transmissions were fitted with the support.

The '08 service manual instructions for removing the support have different notes for the auto and manual as well as for the 2.0 and 2.4, so it seems to me that it was offered in all configurations at some point.

My understanding is that all 2.0 (RL and GXP) were fitted with the brace from the beginning, and that the 2.4s were fitted with it either after mid-'08 MY or the beginning of the '09 MY. The front differential carrier bracket (used when there is not a brace) is described in the '08 manual, and I do not have an '09 manual to see if it is there also.
 
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