GXP differential in a GT...

[G8 GT V8]

I would hope that they can get your trans squared away fairly easily, but you might want to run it by then...

[I12XLR8]

Awesome feedback guys! I'm still working through this decision in my head but skinsfangreg's suggestion to check out what Greg has to offer has given me a lot to think about. He's got new Camaro 3.45 differentials for $1100 shipped!!!

Thanks to everyone for all of the advice - I've said it before and I'm sure I'll say it again...I love this forum!!!

[Bonnetts02Vette]

Greg is a good guy.

If you decide to go the 3.70 rear route then you can't beat my gxp 3.70 diff with only 3k miles for $1000 shipped. It's sitting hee in the original wooden crate ready to be shipped out.

[familycaronROIDS!]

I see more folks regretting the 3.45 in favor of the 3.27.
The change in HWY mileage and RPM is the main reason. With the A6 the 2.92 yields around 1800 rpm at 80 mph. with a 3.27 = about 2100 rpm (my estimate, but close enough for this exercise). with a 3.45 - about 2350 rpm (too much for my taste), and I have not done the numbers for the 3.70. gotta be in the neighborhood of 2600 rpm. I could not live with that on the HWY. My original thoughts were to go 3.45 with a taller tire to get back to the 3.27 range, and at the track, use the DRs to get my gear back. If I come across another 3.45 cheap - that's where I'm going.

I have a cammed car with a 3200 stall and 3.45's at hwy speeds normal driving my car is at 2200 and somewhat quiet. I do not regret getting the 3.45's. To be honest from 2.92-3.45's is a slight difference. The car feels lighter but it is not alot quicker at the track.

[todds87ss]

I have a cammed car with a 3200 stall and 3.45's at hwy speeds normal driving my car is at 2200 and somewhat quiet. I do not regret getting the 3.45's. To be honest from 2.92-3.45's is a slight difference. The car feels lighter but it is not alot quicker at the track.

what size tire are you using on the street and at the track? A larger street tire will tame it down, and a slightly smaller tire than stock will light it up a the track.

[I12XLR8]

If I'm running the stock set up (Camaro 20's, OEM 18's and 19's with suggested tires all have the same outside diameter) then I am to understand that my 80MPH RPM will be close to 2600?

I don't think I could/would want to deal with that. I will set up the car for city driving, mainly. But when I am on the highway I don't want the engine screaming at me. On the bright side I guess there wouldn't be any drone...

Steve at Vector also just got back to me and says that now they have tuned a large number of G8's with different gearing they can usually get it right on the first try. Than you to everyone that went before me!!!

[SpeedRacerX]

If I'm running the stock set up (Camaro 20's, OEM 18's and 19's with suggested tires all have the same outside diameter) then I am to understand that my 80MPH RPM will be close to 2600?

I don't think I could/would want to deal with that. I will set up the car for city driving, mainly. But when I am on the highway I don't want the engine screaming at me. On the bright side I guess there wouldn't be any drone...

Steve at Vector also just got back to me and says that now they have tuned a large number of G8's with different gearing they can usually get it right on the first try. Than you to everyone that went before me!!!

G8 GT Auto.

Stock 2.92 rear, 80 mph, 6th gear, 2040 RPMs. Personally, I spend a lot of time on the highway. Right at about 80 mph, my exhaust gets quiet in this RPM range.
if.......3.45 rear, 80 mph, 6th gear, 2410 RPMs.
if.......3.70 rear, 80 mph, 6th gear, 2585 RPMs.

Put your car in 5th in manual mode on the highway and that'll be very darn close to where 3.70 gears will be. See if you can deal with it. Driving around in 4th gear in manual mode will simulate approx 4.10 gears. That I can't deal with.

PM me your email address and I'll send you the PDF for G8 speed, RPMs, and gear options, courtesy of another member who put it together.

[I12XLR8]

Great info SpeedracerX! Now I'll have something I can do to simulate the gearing in the car. Thanks.

PM sent with my email address (soon).

[SpeedRacerX]

^ Emailed. Let me know if you received it.

If anyone else wants the PDF, PM me your email address and I'll forward it.

[I12XLR8]

OK. I got the file but now I have a problem...the 3.45 and 3.70 gearing is so close that I am considering the GXP unit again. I drove around for just less than an hour today, mainly between 70 and 80MPH and kept it in 5th gear. To be honest I was hard-pressed to tell the difference in engine noise between 5th (GXP simulated 6th gear RPM) and 6th (must be that acoustic windshield!).

So...now that I'm not concerned about noise on the highway I have some other questions:

1. Will the DOD still work at that RPM?
2. It has been said that the Camaro differential is sturdier than the GXP...is that a concern for a VERY mildly modded GT? I have never lost a differential before and I'm sure there are some 500RWHP GXP's out there with the stock diff in them.

Thoughts?