City driving with 3.42 gears
Thread Starter
Registered User
Joined: Sep 2009
Posts: 1,450
From: Hamilton, ON
City driving with 3.42 gears
Just curious what RPM's would be like in the city (say 25-40mph) with a 3.42 posi in a 350 4bbl and TH350 with specs similar to a 1970 350 (hopefully near W31 specs)?
I rarely go on the highway, but still would like to. Wondering if 3.73 or 3.90's would be overkill, but on the other hand do not want to be bogging in the city. I also do not want to add an overdrive trans. Want to keep that as stock as possible (other than perhaps beefier internal trans mods).
I rarely go on the highway, but still would like to. Wondering if 3.73 or 3.90's would be overkill, but on the other hand do not want to be bogging in the city. I also do not want to add an overdrive trans. Want to keep that as stock as possible (other than perhaps beefier internal trans mods).
Old(s) Fart
Joined: Mar 2007
Posts: 50,768
From: Northern VA
Just curious what RPM's would be like in the city (say 25-40mph) with a 3.42 posi in a 350 4bbl and TH350 with specs similar to a 1970 350 (hopefully near W31 specs)?
I rarely go on the highway, but still would like to. Wondering if 3.73 or 3.90's would be overkill, but on the other hand do not want to be bogging in the city. I also do not want to add an overdrive trans. Want to keep that as stock as possible (other than perhaps beefier internal trans mods).
I rarely go on the highway, but still would like to. Wondering if 3.73 or 3.90's would be overkill, but on the other hand do not want to be bogging in the city. I also do not want to add an overdrive trans. Want to keep that as stock as possible (other than perhaps beefier internal trans mods).
Registered User
Joined: Mar 2008
Posts: 4,024
You could use 4.88s in the city, you would just be in a higher gear than with 3.42. It would be better to determine how much and what speed highway driving will be in the mix. You can also have different diameter rear tires to moodulate the effect of the gear ratio.
Ben
Joined: Mar 2009
Posts: 1,851
From: Snohomish, WA
Ben
Joined: Mar 2009
Posts: 1,851
From: Snohomish, WA
3.42s are a real nice all around street & freeway gear.
What gears do you have in it now? 2.73 ? Anything would be a huge improvement.
Use the calculator i posted above to find out exact #'s.
3.73+ is fine on the street as well- My 68 elcamino/454 powered had 4.10 gears in it- and i drove it primarily ont he street & occasionally on the freeway- but you just have to realize that freeway speeds for any extended ammount of time need to be slower than you're used to. I think i would crusie at about 55mph on the freeway going to the track in the elcamino. Kind of a PITA- but it was sure fun to kick it down & wind it up to pass someone!
With 3.31's or 3.42's you'd still be able to cruise 70-75mph without turning excessive RPMS.
What gears do you have in it now? 2.73 ? Anything would be a huge improvement.
Use the calculator i posted above to find out exact #'s.
3.73+ is fine on the street as well- My 68 elcamino/454 powered had 4.10 gears in it- and i drove it primarily ont he street & occasionally on the freeway- but you just have to realize that freeway speeds for any extended ammount of time need to be slower than you're used to. I think i would crusie at about 55mph on the freeway going to the track in the elcamino. Kind of a PITA- but it was sure fun to kick it down & wind it up to pass someone!
With 3.31's or 3.42's you'd still be able to cruise 70-75mph without turning excessive RPMS.
Thread Starter
Registered User
Joined: Sep 2009
Posts: 1,450
From: Hamilton, ON
I have 2.73's now. I just don't want to be bogging around the city and have to gear down to S or L to give her a bit at times is all.
Tires will be 15", prob 235/60/15 all around, whatever fits just right in that range. I doubt I will do the bigger back tire with skinnier fronts this time around.
I only go on the highway when needed. For one, I just don't like the highway, and two... I can't stand cleaning plastered bugs off a nice clean front.
Tires will be 15", prob 235/60/15 all around, whatever fits just right in that range. I doubt I will do the bigger back tire with skinnier fronts this time around.
I only go on the highway when needed. For one, I just don't like the highway, and two... I can't stand cleaning plastered bugs off a nice clean front.
Registered User
Joined: May 2009
Posts: 2,212
From: USA
Yep.
My 78 z28 came with that and a peg leg from the factory.
For around town driving AND highway you'll be fine.
I just put 3.73's in my Olds with an EATON posi, and it feels much
better then the 2.78 grandpa gears. Higher RPM's on the Hwy but
I'm going to be putting my 6 speed with a .5 final gear in it soon.
3.73's is a perfect match for it.
My 78 z28 came with that and a peg leg from the factory.
For around town driving AND highway you'll be fine.
I just put 3.73's in my Olds with an EATON posi, and it feels much
better then the 2.78 grandpa gears. Higher RPM's on the Hwy but
I'm going to be putting my 6 speed with a .5 final gear in it soon.
3.73's is a perfect match for it.
Registered User
Joined: Oct 2009
Posts: 3,814
From: Erie,PA
I run 3:73's with a 28" tall tire. At 60mph,it's spinning about 2800rpm.I drive it all over.My trip to work is a half-hour drive,which consists of open road,then city traffic.It gets a little bit of everything along the way.I do this with a stroked bigblock,so your 350 will not have a problem with this.Either way,the 3:42 or 3:73 is where you want to be with that.
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