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Discussion in 'Transmission & Driveline Topics' started by ratpatrol71z28, May 11, 2013.
Ive had 4.10's on just about every car I've ever built. If I wanted an economy car I'd buy a Honda.
There is a lot of good advice here, and my experience has been a 74 Z with factory 3:90s. I've ran 4:56s, but forget highway speeds for any distance. With the 3:90s i traveled back and forth from LA to OK several times and even put a bumper hitch on it from u-haul an traveled from oklahoma, to AZ to tow a 77 Z back home. It had 3:73s, but now 4:30s for stop light to stop light fun.
Oh. That was my 74 back in 1983. It had the 3:90s, the 77 had the 3:73s.
I am running 373 on my 1970 SS with P225/70R14 (26.4") at 60MPH it is around 2900RPM or so.
The 373 are nice gears since get the take off but not the high RPM's of the 410+
It does depend in tire size. I run 4.10's with a 29 inch tire . Probably roughly equivalent to your 3.73's. Mine is sized that way so I can run 135 MPH through the lights at 10 flat.
For an automatic car the converter is going to have more to do with gas mileage than the gears will. I get 5 MPG all day long.
Sounds like my 4:56s. I did however get to make a lot of friends at the local gas stations
My car came with 70R14 (14X7 rims w/ .34 offset) so I wanted to keep as stock as possible with tire size 25.5" BUT.....
Finding 14" tires is getting harder and I got a deal on the P225/70/R14 26.4".
I ordered the P195/75R14 that are the direct size replacement, but when I got tho the tire store to have mine installed another store came over and took my tires since they had a guy come in and ask for them (They where suppose to be held for me since I custom ordered from Firestone, not a normal stocked tire).
So the tire shop sold me the 225/70's for same price (the cost was like $5 more per tire otherwise) and they threw in road hazard for free
I special ordered my 70&1/2 Z28 with the M22 close ratio rock crusher and 4.10 posi 12 bolt. It was, for me, the ultimate combination. I ran it at the track 2-3 times a week, street raced the daylights out of it, and drove across the state of Florida numerous times to most of the tracks. With the stock F60-15 25.9” diameter tires at 32 psi I got a 50:1 ratio of Speed:RPM. So, in 4th gear....
30 mph = 1500 rpm
40 mph = 2000 rpm
55 mph = 2750 rpm
60 mph = 3000 rpm
65 mph = 3250 rpm
70 mph = 3500 rpm
75 mph = 3750 rpm
80 mph = 4000 rpm
100 mph = 5000 rpm
115 mph = 5750 rpm (my trap speed)
120 mph = 6000 rpm
140 mph = 7000 rpm (yes, it would do it)
It would smoke the tires, in any gear, at any speed. Yes, I like 4.10s with that size tire. My current project has 3.73s, so I’ll have to get a smaller diameter tire to get me to an equivalent of a 4.10. If you’re going with a much taller tire than 25.9” I would recommend the 4.10 gear.
We run 3.73's in all our SBC V8 S10's. 19 MPG on the highway.