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Discussion Starter #1
I wrote earlier that in my opinion and with my personal driving style, I find the 3.73 rear produces a too low first gear, and a little too low 6th. Upon reading the factory shop manual, I thought perhaps the CTS 3.42 ring and pinion might fit. For those who are interested, I think there are also a 3.91 and a 3.23 sets made for CTS. I don't launch/drag my CTS-V, so I was not so concerned with case strength.
I bought a CTS-V case on eBay, and then popped for a 3.42 ring and pinion. I did the change over at TPIS's, where I have a long friendship. Both 3.42 and 3.73 have 42 tooth ring gears. Pinion on the 3.73 has 12 teeth and the 3.42 has 11 teeth. Pitch is different of course. It is a drop-in fit - a complete match up with only a slight change to the end of the pinion shaft (cut off an extension). But, if you do this be sure to read the directions first as there are some preliminary steps that must be taken - to wit heating the case to remove the pinion gear.
We painted the gears with white lead to get a matching pattern. It was about perfect needing no shims. My sense is that the case is CNC machined by the factory and that production tolereances are close enough for the factory to drop in without shim measurements.
Next step will be installation, leak check and then there is the problem of speedometer adjustment.
Respecting speedo adjustment, I will appreciate any comments and suggestions, as I haven't figured out how to do this.
 

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2005 CTS-V
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I changed the gear ratio on my Chevy Suburban from 3.73 to 4.56. I was able to correct the speedometer using a Hypertech tuner by selecting a hypothetical tire diameter that equated to end result I needed.
 

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I feel like the only advantage we have against cars like the gto's are our gears. I feel like on the street, thats the only reason we keep up with them. I feel like with 3.42, your going to find yourself further back when racing a car such as the gto.......like my buddy has a gto, its faster than my car, however bc of our gearing, my car feels faster when you drive it, but when we race, he beats me. My gears keep it close, if we had 3.42's he would dstroy me
 

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07 Bermuda Blue EXT - 06 Stealth Gray CTS-V
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I've though about doing the same swap on the rear. I traded a 2001 vette for the V. Gas mileage went from 30 on the highway in the vette to 20 for the V. I know the weight makes a difference, but the vette was just above an idle while cruising at 60 mph, 1300 rpm. The V cruises at about 1700 rpm.

I like more information on the pinion shaft mod. Pics would be great.
 

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2005 CTS-V
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I've though about doing the same swap on the rear. I traded a 2001 vette for the V. Gas mileage went from 30 on the highway in the vette to 20 for the V. I know the weight makes a difference, but the vette was just above an idle while cruising at 60 mph, 1300 rpm. The V cruises at about 1700 rpm.

I like more information on the pinion shaft mod. Pics would be great.
I consistently get 24 mpg on highway in my V. I tend to cruise a lot at almost 2,000 rpm.
 

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24-26 here - HOWEVER - I can see benefits for the gearing change. I've done this with many street/dirt bikes and after getting used to it, like it. Personally, I'd like to see 60 mph in 1st gear <4 seconds...but this is the wrong car for that :D

WW
 

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2005 CTS-V
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24-26 here - HOWEVER - I can see benefits for the gearing change. I've done this with many street/dirt bikes and after getting used to it, like it. Personally, I'd like to see 60 mph in 1st gear <4 seconds...but this is the wrong car for that :D

WW
Your objective may not be that far out of reach. A modified motor could use 2nd gear starts (a stock motor already does smooth 2nd gear starts) which would take you past 60 with no shift.
 

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Discussion Starter #12
The CTS pinion shaft modification is quite simple, and will be readily apparent when one compares the CTS-V pinion shaft. The CTS-V pinon shaft ends with threads for a large nut that holds the coupling for the drive shaft. The CTS/3.42 pinion allows for a different type of drive shaft (I think), and has a tapered extension of the shaft past the threaded section. We simply cut off this extension with a cut-off grinding wheel. Note, a band saw or hack saw will have a difficult time. What this means is that a CTS owner probably cannot use the 3.73 ring and pinion unless the driveshaft is also changed.
 

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2005 Stealth Gray CTS-V, 2009 Black CTS-V
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I've though about doing the same swap on the rear. I traded a 2001 vette for the V. Gas mileage went from 30 on the highway in the vette to 20 for the V. I know the weight makes a difference, but the vette was just above an idle while cruising at 60 mph, 1300 rpm. The V cruises at about 1700 rpm.

I like more information on the pinion shaft mod. Pics would be great.
It's because the Vette is lighter that they can go with the taller gearing; weight pretty much is the reason.

And who would consider the CTS-V for gas mileage purposes? :suspect:
 
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