Topic: Has anyone swapped the 3.91 into a GXP/Redline?

[epbrown]

I did a search and didn't find anything. I'm curious if anyone has swapped a 3.91 final drive into a 2.0L. I swapped the 3.62 in my Z4 M Coupe for a 3.91 and I like the bump in gitalong, and wonder what it would be like in the torquier (now that it's been chipped) GXP if I replaced the 3.73. Can the 3.91 even handle the additional power?

[Critterman]

I'm running 245 rwhp in my 06

[DeepBlueGXP]

I don't know if anyone has changed the gears in the rear diff.   I like the current one for the gas mileage.

[NormSky]

Once the mods start you'll need taller gears, not shorter.

Norm

[snaponbob]

Norm is correct. With the silly gear set we have, 1st and 2nd are already way too short. I'd love a 3.5x rear.

[epbrown]

Norm is correct. With the silly gear set we have, 1st and 2nd are already way too short. I'd love a 3.5x rear.

The grass is always greener, I guess:

Solstice GXP Gears:
1st - 3.75
2nd - 2.26
3rd - 1.37
4th - 1.00
5th -  .73

BMW Z4 M Coupe:
1st - 4.35
2nd - 2.50
3rd - 1.66
4th - 1.23
5th - 1.00
6th -  .85

The M can afford the taller gears with the 8000rpm redline, but I figure I wouldn't rev the GXP as much with all that torque anyway. This would be the only performance mod I'd do to the car, btw. Only other thing I want is nicer wheels with stickier tires.

[kennysabarese]

The M can afford the taller gears with the 8000rpm redline, but I figure I wouldn't rev the GXP as much with all that torque anyway. This would be the only performance mod I'd do to the car, btw. Only other thing I want is nicer wheels with stickier tires.

Revving higher with the stock turbo is pretty much useless, it's better to short shift which is why I think changing the gearing or the rear could be helpful.

Does anyone have the specs handy on the rear ends for other cars that will pop into our cars easily? If any are a good match would swapping rears be easier/cheaper than swapping gears in our rear?

[Treeman]

Norm is correct. With the silly gear set we have, 1st and 2nd are already way too short. I'd love a 3.5x rear.

   ....but not enough to make the change.

[LatinVenom]

I do not think there is anything more than the 3:91 as a complete swap.

[SolNut]

Cadillac CTS has 3.23, 3.42 and 4.15 Ratios available in different power combos. 

Should swap right in. 

Steve
 

[G8TR]

Okay, so who's first to do this mod?

[kennysabarese]

Drifting solstices have diferrent rears but I don't recall the ratio

[Graywolf]

Since I race my car in high speed driving events, Road racing tracks, I always thought 3rd gear should be 1.5, 4th gear1.25 and 5th 1.0.  Switching to the cts 4.15 may give me better . Will the CTS 4.15 gear fit in our diff?  

[shabby]

Shorter gears make sense on a miata/s2k, but with the torque that our engines put out you'd want taller gears, don't understand why you'd want less traction.