Rear end change

[451Mopar]

I like the 3.54/3.55:1 ratio, but with taller tires. With the short 25" tire, 3.23:1 might be better.
My '69 Coronet has the Dana 3.54:1 ratio, but with a LGT SS-700 5-speed trans (0.69:1 OD), 50 MPH @ 1,500 RPM.

 

[Bladecutter]

I had an 88 LX 5.0 HO Mustang with Tremec 5 spd(5th OD). At 80mph indicated, it was turning 1950rpm, & still accelerated well without downshifting. Fun car but a disposable. Point,,, with a V8, one can do tall gearing & still "jack rabbit" off the line, have usable as opposed to hairball, power in the turns, turn in acceptable gas mileage numbers.
My chop bug I have a Lexus 4.0, 4 cammer V8 for & the 911 transaxle is 3:55 final. I would really like to go as far down as 2:54, but even if a ring & pinion 2:54 set is available, it's gonna be "beddy buddy 'spensive". Those T-axles are bringing between 10K-15K now. Smart money would sell the Porsche' gearbox, build/beef a VW t-axle, & use the remainder of dough towards project completion. But the Porsche box is what My Late Bro built the car with in seventies & I'm more like a long term custodian than owner. Its status is Family Heirloom & will eventually go to my Great Nephew.
Last pic is 1987. I'm going fenderless, open wheel, street rod stance.

 

[lewtot184]

both my cars have 3.23's. I think they're geared to low for the interstate. a 3.55 with the Passon over drive kit might make a nice compromise between town and freeway driving.

 

[Miccara]

both my cars have 3.23's. I think they're geared to low for the interstate. a 3.55 with the Passon over drive kit might make a nice compromise between town and freeway driving.

Really? I would thought 3.23's would be an okay highway gear for reasonable cruising at 55-60 mph.

 

[joe smith]

both my cars have 3.23's. I think they're geared to low for the interstate. a 3.55 with the Passon over drive kit might make a nice compromise between town and freeway driving.

Really? I would thought 3.23's would be an okay highway gear for reasonable cruising at 55-60 mph.

What freeway is 55-60?

 

[Bladecutter]

What freeway is 55-60?

Freeway Minimum speed limit is generally 45 miles an hour. In Ca. Towing max limits are 55 mph, & restricted to the right two lanes...wouldn't do to ticket car traffic for impeding, with towing traffic being restricted to 55 maximum. The rule is stated clearly & simply, though many drivers don't align & engage with it.
"Faster traffic overtakes on left,,,,,slower traffic yields to the right"

 

[BDF6]

I had 25.5" tires with 3.55 and it was rough keeping up with traffic on the highways for extended periods.
Put on 27" tires and that helped some, but I think I will go back to 3.23 (10% drop in ratio) because I like long cruises.
This may help you:
https://www.ringpinion.com/calculators/Calc_RPM.aspx

 

[Miccara]

I had 25.5" tires with 3.55 and it was rough keeping up with traffic on the highways for extended periods.
Put on 27" tires and that helped some, but I think I will go back to 3.23 (10% drop in ratio) because I like long cruises.
This may help you:
https://www.ringpinion.com/calculators/Calc_RPM.aspx

Thanks! That was a big help.

 

[bobtile]

I went from a 3.55 to a 4.10 in my GTX.
Really not that big of a difference in cruising.
If you "need" to launch, 3.23 won't get it done.
I didn't however do a lot of highway driving.

 

[SimDog]

I went from a 3.55 to a 4.10 in my GTX.
Really not that big of a difference in cruising.
If you "need" to launch, 3.23 won't get it done.
I didn't however do a lot of highway driving.

That's just the point. Who really "needs" to launch? People who do more racing than driving that's who. The majority of us just want to get in our cars and drive