Hi guys, I have 3.45 in my VLT manual and love it and now need something for the daily. It is a 2003 WK Caprice 5.7 Auto with mafless tune, DUS OTR and Sureflo 3.5 inch cat-back and 220rwkw. I want to know if 3.9s is gonna be too radical for a daily driver. I do half my driving in the city and half on highway. I am edging towards 3.7 as a compromise but everyone is pushing me to 3.9s due to the weight of the Caprice and the 4 speed auto. I am open to all input as this decision is a big one due to the $2K price of doing the swap properly. Cheers.

A mate of mine had a cammed VT HSV he was using as a daily, and he was in the same position you're in. He ended up going the 3.9's and says he would never go back. From what he was saying, fuel economy wasnt all that different(this is talking from a cammed LS mind you), but it did completely change the drive when you put the boot into it.

Thats what I have heard too but have not had a chance to go in an auto with 3.9s. Apparently the city driving economy is improved as you get up to 60ks better and the hwy economy is worse but I am not sure by how much. I dont want stupid wheelspin though or for it to be dangerous in the wet etc. Even with the 3.07's it will squirm off the line and chirp pretty hard into 2nd gear. ---------- Post added 19-04-13 at 10:16 ---------- I will also be getting a very mild cam next year, low 220's.

yeah I have heard the city driving is improved, not as much load from driveline etc. how much highway driving are you looking at doing? I had a VT exec 6 speed with a comp 222/224 which I was going to go either 3.9 or 4.11 just before I sold it on. Awesome little street setup, and really wasnt all that bad on fuel. If I was in ur position with an auto looking at a cam later I think I'd go 3.9's mate.

Quote: Originally Posted by Big Lee [View Post] Hi guys, I have 3.45 in my VLT manual and love it and now need something for the daily. It is a 2003 WK Caprice 5.7 Auto with mafless tune, DUS OTR and Sureflo 3.5 inch cat-back and 220rwkw. I want to know if 3.9s is gonna be too radical for a daily driver. I do half my driving in the city and half on highway. I am edging towards 3.7 as a compromise but everyone is pushing me to 3.9s due to the weight of the Caprice and the 4 speed auto. I am open to all input as this decision is a big one due to the $2K price of doing the swap properly. Cheers. What size rims you running?

My WK has 3.9, 5.7, Auto, stage 2 shift kit, 3 or 3500 stall can't remember, cammed, hi flow extractors twin 2.5" exhaust, roller rockers, OTR intake, and a bunch of other things, all dyno tuned. And I would never change a thing. You mentioned you do a bit of highway driving which I don't but mine is setup to be driven in third gear and when your doing more then 130+ I just shift it to 4th and its fine. Mine drinks fuel hard no matter what so I can't really see a difference.

Quote: Originally Posted by pro747 [View Post] What size rims you running? I am running the factory Caprice 17s with 235/45/17s ---------- Post added 19-04-13 at 14:24 ---------- Mine is really good on fuel now though, 8.3l/100 at 90ks on the freeway and sits on 7.3/100 cruise control at 60ks/hour. I dont wanna smash it too badly. ) Some original photos have not been recovered yet.

Quote: Originally Posted by Big Lee [View Post] I am running the factory Caprice 17s with 235/45/17s ---------- Post added 19-04-13 at 14:24 ---------- Mine is really good on fuel now though, 8.3l/100 at 90ks on the freeway and sits on 7.3/100 cruise control at 60ks/hour. I dont wanna smash it too badly. ) If your gonna stay with those rims id go 3.7 mate Some original photos have not been recovered yet.