Hot Rodders, advice on choosing a gear for my SS

[TOTS]

Gents, Im stuck with analysis paralysis. Thoughts on choosing a rear gear for my SS. Car will be a 100% street car; back-road blaster and never see a track. Pretty much narrowed it down to 3.50 or 3.70.

Details: 70 Nova SS. Built 6.0L LS with all the Texas Speed stuff - custom cam (228/231, .612/.617, 108 centerline, 110 lsa), their valve-train and 243 heads, and 1 7/8 long tubes. Trans set up will be Tremec TKX with 2.87 1st and .68 final drive, C6 Z06 clutch and flywheel. Rear will be a ride-tech 4-link, built 9 inch with an Eaton Tru-Trac; BFG 295/50/15 tires at 26.5 in tall. Weight will end up being about 3500 max wet.

Im looking for a mid-range torque monster that kills on the country back roads but can still be driven the 30 hwy miles (60-65 mph) to work when I want to. I've done the math, and the 3.50 gear set will give me 63 mph at 1800 rpm which is perfect. Wondering if ill miss the difference in acceleration the 3.70s will give me. Im not one to "fear the gear" - daily drove a built 99 mustang with a Vortech T-trim and 4.10s through a 5 speed, but I was really happy with the feel of my 03 Z06 with LS6 and 3.42s through the M12 6 speed as well. So, I figure 3.50-3.70s will be the sweet spot for this project; now to finally choose!

I just want to do some smoky burnouts/ hard launches with the kids, and then take them to get ice cream at the beach!

[rd62]

Not a Nova but once upon a time I put 3.55 gears in my 92 LX 5.0 Mustang and was very pleased. Good mid-range torque, good top end, much better off the line than factory.

[OlongJohnson]

I have a whole bunch of spreadsheets to work out gearing for turbo four cylinder projects.

I don't have enough any experience with LS stuff to recommend RPM ranges.

@JRB

[Suvorov]

I feel your quandary. This summer I finally changed the ratio on my 98 Cobra after 23 years of thinking about it. Most of the internet hot rodders favor the taller 4.10 and even 4.30 gears as the 4.6 DOHC is a high reving engine, those who are more track oriented or interested in driving longer distances go with the 3.73. In then end I went with the 3.73s and am really happy as I gained noticeable strength of pull. Even with a more modest gear, the shifts come a lot quicker - especially 1st to 2nd. I really wonder how jerky the 4.30s would have been. I don’t know how high or LS revs and I’m guessing you aren’t adding any traction control so here are my thoughts.
- Torque to the wheels is wasted once they break traction. It may make smoking them easier, but just about any muscle car and do a burn out. On my car I feel there is a limit to how useful taller gear really are.
- Where do you want your shift points? With my 3.73s I only need to make one shift to get up to 70 mph, the downside is that on the strip the 3 to 4 shift happens right around the 1/4 mile mark.
With those things in mind I guess I would favor the lower ratio, but I readily acknowledge I am in the minority and know less than most have forgotten.

[0ddl0t]

Not a huge difference, but I'd probably find 3.50 more enjoyable on the highway.

[Bucky]

I’d go 3.70. My 1979 Z28 came with 3.73 and it felt like a good balance of street / drag. It revved a bit more than I’d like on a highway, but that was with a 1 to 1 top gear. You should do a bit better.

[CSW]

If you're not looking for a quarter miler, or dragger, don't step over the line of 4.0 and higher.
The 3.50 is a good all around gear, mostly not too revvy at highway speed, and if you are not worried about gas consumption, a good choice with the mods you listed, especially the cam!
A 3.70 and above will get you off the line quicker, but limit [or start to limit] your top end.

For what you have described, I'd probably go 3.70.

When I was in high school, I had a 428 cobrajet in a '69 mach one, that I put 4:11's in for a while. From stoplight to stoplight she was a killer.
Pretty fast to the Texaco station as well.

[octagon]

I would go with the 3.70s without a doubt. I had almost the same motor and trans gearing in my C5 Zo6 and unless you plan on doing 1/2 mile or mile racing you won't ever feel the too short of gearing with 3.70s but every launch and regular street start the 3.70 helps. No worries about fuel economy or high revs on the highway since you have the .68 and double overdrive.

BTW mine made 470 WHP and 499 WTQ. LS6 intake, 243 TEA stage 2 ported heads, same headers(with catted X pipe) on 6.0 liter shortblock with similar cam. I don't have the specs anymore but it was also a Texas Speed cam but back from 2010 or so.

[TOTS]

I feel your quandary. …
- Torque to the wheels is wasted once they break traction. It may make smoking them easier, but just about any muscle car and do a burn out. On my car I feel there is a limit to how useful taller gear really are.
- Where do you want your shift points? With my 3.73s I only need to make one shift to get up to 70 mph, the downside is that on the strip the 3 to 4 shift happens right around the 1/4 mile mark.
With those things in mind I guess I would favor the lower ratio, but I readily acknowledge I am in the minority and know less than most have forgotten.

Great points. To answer, I’m with you on the traction. I have a 27 in tall MT drag radial for when I want traction. Or, if the BFG will hold decently, I’ll stick with them; yet to see.

For the second, I’m still building the car so the dyno will answer the shift point question. TX Speed has a graphic for their 228R cam on a stock LS that I am using to base the shape of my curve off of (my extra displacement will lower the peaks locations but cam timing and lightweight springs etc will raise it back up). So I’m planning on a Tq peak around 5100 and a shift point around 1200 or so rpm above that.

ETA: I’m usually running 55-65 on all the roads I use to get anywhere. I’m not in town so not all stoplight-to-light.

[Doc_Glock]

Not a Nova but once upon a time I put 3.55 gears in my 92 LX 5.0 Mustang and was very pleased. Good mid-range torque, good top end, much better off the line than factory.

Same. Loved the 3.55 rear.