3.91 Gears for weekend toy opinions?

popinsmoke · Apr 30, 2012

Gentlemen,

So I have done a few upgrades to my 67 Coronet 440.

Car was a 318 2bbl,auto,no power options, plain Jane go to church car.

Just got done installing 2.25 dual exhaust, Edelbrock performer rpm air gap intake, Carter AFB 750cfm(Big I know but it was free), MP electronic ignition conversion, Comp 268H,Lifters,Timing set,Springs,Pushrods,etc

Couple of things jump out to me after install.

1.) The drum brakes are scary! I see disc brakes in my future.

2.) The car needs gears gears which brings me to my question anyone here run 3.91 gears on a weekend toy does your car rev itself apart?

I run 4.10 rear gears on my DD but a have a 6 speed double overdrive transmission kind of worried about steep gears on a 3 speed auto.

Any thoughts, opinions, rants and raves? Thank you in advance for any and all information.

john.thompson068 · Apr 30, 2012

1. Install front disk brakes. I think you can install them from a 76 Dodge Aspen like I did on my 66.

2. 3.91 gear is actually the optimum gear for cruising around town considering average speed is 50 mph. The only problem is when you want to drive on the freeway. I want to retain my 3.91 gear and install a 700 R4 with a .69 overdrive, or whatever is the latest and greatest.

65 Plymouth Satellite 426 · Apr 30, 2012

If You Plan On Driving Distances With Your Car You May Want To Drop A 3:55 Ring & Pinion In Instead Of Those 3:91's. They'll Kill Your Gas Mileage On Long Trips.

Propwash · Apr 30, 2012

No one mentioned tire height.......obviously affects your RPM.

Try out this calculator...Find a gear you're comfortable with.

http://www.richmondgear.com/101032.html

racedodge · Apr 30, 2012

i have 3.91's on my RR.. love the exhaust note at 65

had them on my 72 charger too... ditto on the exhaust note.. got about 9-10mpg

Meep-Meep · Apr 30, 2012

I'm running around with 4.30's in my 66 440 powered Belvedere and it could care less. And on the freeway I make no effort to go 60! Around here it's keep up with traffic at 70+ or get run over, so needless to say my tach is well into the 4K RPM range. I don't drive it much and not on long trips, but a half hour ride is no big deal. For a car that you want to spend some time in I'd recommend no lower than 3.23 for the long trips. I'm setting my 69 RR up with a 3.70 Dana, and with the Passon OD gear set, I will end up with something like 2.96 final. If you spend nearly half your time at the track then 3.55 or lower depending on your engine power band.

Rippin · Mar 2, 2013

Have 3:91s in my 383 Dart...built it more for racing, but now is driven regularly on the street. Not bad for just cruising, but highway use is less than optimal. I also upgraded to 15" rims which helped a bit. All depends on what your intentions are. Definetly will help wake up your car...will likely feel like you just gained 50hp.

YY1 · Mar 2, 2013

The 3.55s in my 70 Bee weren't too bad on the highway, but my buddy's 340 challenger with 3.91s were a bit much.

I've always thought a 3.7x would be a nice compromise.

caveman85635 · Mar 2, 2013

I'm running 4.56 Dana 60, 70 RR 425hp 383, 4-speed. Keep in mind it's the "toy". I cruise 2500-2800 at 40-43 mph. Short trips and some racing on nearby country roads. No freeway driving, that's for sure. And don't even consider figuring out the mileage. But it's a load of fun on the street.

RustyRatRod · Mar 2, 2013

Drive the DD around in 4th for a day. That's about what the 3.91s will feel like.

Jeff_383 · Mar 6, 2013

Come on pansies. 3.91's with a 28-29" tire is fine for highway driving. I've gone 180-220 miles with 3.91's and 25" tall tires. Now if you've got gobs of torque a 3:55 is great too. With 3:55's and 28" tire I do 70 with ease. With the 3.91's and 28" tire I keep it around 60-63. My MPG's really stay the same with either gear, if it matters, at 7-8 "city" and 10 highway. My buddy has a Dart with a 416 stroker, crossram with 2 750's, and 4:30's, and gets 15.5 MPG on the highway. It's just tuned razor sharp with an LM-1 and lots of time.

383man · Mar 6, 2013

I use 4.30's and run a 30" tall tire. It runs about 3300 at 60 mph. I drive the freeway all the time with it. I drove the 90 mile trip to Carlisle with it and it was all freeway driving. I keep it between 55 to 60 and just run the slow lane. Ron

YY1 · Mar 7, 2013

Meep-Meep said:
I'm running around with 4.30's in my 66 440 powered Belvedere and it could care less. And on the freeway I make no effort to go 60! Around here it's keep up with traffic at 70+ or get run over, so needless to say my tach is well into the 4K RPM range. I don't drive it much and not on long trips, but a half hour ride is no big deal. For a car that you want to spend some time in I'd recommend no lower than 3.23 for the long trips. I'm setting my 69 RR up with a 3.70 Dana, and with the Passon OD gear set, I will end up with something like 2.96 final. If you spend nearly half your time at the track then 3.55 or lower depending on your engine power band.

I like that answer.

I don't want to be in the slow lane doing 60 in a car that looks like it should be doing 100.

(but I don't want v6 mustangs beating me off the line, either)

I think the 3.7x with o/d 2.9x final is probably the ultmate compromise.

Is that Passon 5 speed on the market, yet?

Stumper · Mar 7, 2013

383man said:
I keep it between 55 to 60 and just run the slow lane. Ron

You mean the left lane??

That seems to be the slow lane (cellphone lane) these days..
I run 4:56 gears in my hot rod with 29" tires. I'm about 3100rpm at 55 mph. Driving around locally it's fine since I rarely go over 45mph and I will drive it to cruise ins and car shows within a 25 miles radius. When I do I usually hold it to 55 or so. Mileage????
I would like to drop to a taller set of gears but even a drop to 4:10s I also need to replace my carrier or so I am told (Dana 60). Also the next step from 4:10s in a dana is all the way to 3:73 and if i went that far I'd probably need to change my converter and maybe even my intake. So I stay with the 4:56s for now. They are fun for playing around when you don't go over 55mph much.

1970GTX · Mar 7, 2013

YY1 said:
The 3.55s in my 70 Bee weren't too bad on the highway, but my buddy's 340 challenger with 3.91s were a bit much.

I've always thought a 3.7x would be a nice compromise.

there is a 3.73 available. Try Randy's ring and Pinion.

67Satty · Mar 7, 2013

I run 3.91s with a 27" tall tire in my '67 Satellite with a 440. It doesn't seem too steep to me at all. In fact I'm thinking of switching to 4.30s since I like to do TNTs and the local track is 1/8 mile.

tallhair · Mar 7, 2013

RustyRatRod said:
Drive the DD around in 4th for a day. That's about what the 3.91s will feel like.

yep rusty i just had the Durango out for a jaunt and tested that out. turned off the OD and took it up to ~65 and was at ~2950 RPM

also check this out: http://vexer.com/automotive-tools/speed-rpm-calculator

also posted for future ref here: http://www.forbbodiesonly.com/mopar...688-You-will-love-this-and-play-with-it-often

383man · Mar 8, 2013

I love the 4.30's at the track and for a quick pop off at the stop sign but I honestly think if I drop to 4.10's or even 3.91's it will not slow down and might even like it better. The torque of my 493 just seems so strong that I think it will still run just as fast. One weekend I want to borrow a 3.91 jackpot and pop it in my 8-3/4 to try it. Ron

3.91 Gears for weekend toy opinions?

popinsmoke

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john.thompson068

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65 Plymouth Satellite 426

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Propwash

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racedodge

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Meep-Meep

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Rippin

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YY1

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383man

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