rpm and gearing

[Dino]

That's what I had in mine and highway driving was less than amusing.   

I still have it though, I  may use those for the truetrac conversion with the T56.  My wife's T/A has 3:42 gears with a T56 and slightly shorter tires than mine and it is perfect.

[Ghoste]

I've had 3:91 and 4:10 sets in cars and they didn't bother me much.  I suppose it depends how much highway driving too. 

[c00nhunterjoe]

99% of my driving is 50 mph. I dont like highways. People drive way too crazy. That being said, i settled for 4.88's in mine... 

[moparnation74]

99% of my driving is 50 mph. I dont like highways. People drive way too crazy. That being said, i settled for 4.88's in mine... 

Or do you mean a 1/4 mile after every light, lol

[c00nhunterjoe]

99% of my driving is 50 mph. I dont like highways. People drive way too crazy. That being said, i settled for 4.88's in mine... 

Or do you mean a 1/4 mile after every light, lol

I cruise my car everywhere, and decent distances too. A typical cruising weekend starts 25 miles away from home to get to the "main street" areas. I have no second thoughts driving 100 miles or so 1 way.
   I cant deny that everytime i come to a stop, i have to take off like im racing for pinks...lol

[1974dodgecharger]

U ever stop at a light and rehearse the fast and furious scene dialogue guy next to u?

[A383Wing]

you wanna play with gearing & tires first?

Go here  http://vexer.com/automotive-tools/speed-rpm-calculator

[Ghoste]

I love that you can select a 2nd gen Charger for the dash graphic. 

[firefighter3931]

I love my 4.10's 

With a 29.5in Drag radial I'm at 2800 cruising at 60 mph....right in the meat of the powerband 


Ron

[Ghoste]

They were great in my last car too Ron for the same reason.  This one will likely end up as a 3:54 but I'll make my decision after I make the decision on some of the other variables.  There is a 3:23 in it now which is great for now and the Dana waiting to go in has a 4:10 as it sits but I don't know that I'll want that this time.

[rt green]

I love my 4.10's 

With a 29.5in Drag radial I'm at 2800 cruising at 60 mph....right in the meat of the powerband 


Ron

what cam were you runnin?  was this a drag car?

[firefighter3931]

I love my 4.10's 

With a 29.5in Drag radial I'm at 2800 cruising at 60 mph....right in the meat of the powerband 


Ron

what cam were you runnin?  was this a drag car?

Street/Strip car with 2 different engine combinations ;

(1) pump gas 446 with a big solid flat tappet cam

(2) pump gas 572 stroker with big solid roller cam


The best way to gear the car is to match the engine's powerband. If the engine is laboring at 2000 rpm the car will be inefficient. Keep the engine in the happy zone and it will perform much better. 

One of our members run's a 3.55 geared combo with 275/60 BFG's and on a recent visit he checked the milage and got 15mpg on the hwy on his trip out to visit me. Mild 440 build with a small Crower HDP hyd cam, dual plane intake manifold, HP exhaust manifolds and 750DP carb. He's done a lot of tuning using my wideband O2 meter and optimized the jetting and timing for maximum efficiency. The car cruises nicely at 2500 rpm on the hwy and it has descent fuel economy as well. 


Ron

[BSB67]

The best way to gear the car is to match the engine's powerband. If the engine is laboring at 2000 rpm the car will be inefficient. Keep the engine in the happy zone and it will perform much better. 

One of our members run's a 3.55 geared combo with 275/60 BFG's and on a recent visit he checked the milage and got 15mpg on the hwy on his trip out to visit me. Mild 440 build with a small Crower HDP hyd cam, dual plane intake manifold, HP exhaust manifolds and 750DP carb. He's done a lot of tuning using my wideband O2 meter and optimized the jetting and timing for maximum efficiency. The car cruises nicely at 2500 rpm on the hwy and it has descent fuel economy as well. 

Ron

I can never understand guys getting less than 10mpg.  That would have to be huge overlap cam and very short gear, and/or poorly tuned car.  14 -15 is about what I get with my 508 w/ 3.23s on the freeway.  It never gets less that 12 mpg and that is driving around town beating on it all the time.  That will include track time too.

[RECHRGD]

Years ago, I sold a 3.91 pig to the old DC.COM owner.  He replaced his 3.23's with them.  After driving it on the street, he thought the car would be at least .50 quicker and couldn't wait to hit the track.  It didn't change his times at all.....

[Cooter]

Top Fuel runs like 3second 1/4 mile with 300 gear. Sure, you won't cruise it 50 miles, but enough motor and gearing isn't as much a concern. Hence the reference to guys and 10 mpg. Most just have too big a carb, way too big of cam, doo-doo low comp. Bottom end with $3k worth of cyl. Heads AFTER a .030 piston I is installed cause they write checks instead of checkin behind that "cover his ass" machine shop owner.

VE is key. Many think they got a 10.5:1 440 back from machine shop, when in fact they got a really nicely machined, low comp. Turd.

[redmist]

I have 3.91 gears in my car, on street radial 285/40-R17's

I cross the traps in the 1/4 mile at 6000 RPM exactly...

Best time so far is a 13.2 @ 110 MPH.  Obviously I have a traction problem.

[Ghoste]

Ultimately your rearend gears are a lever and the ratio is just altering the pivot point.  Because the same load isn't being applied toone end of the lever (your engine) and the same results aren't desired at the opposite end (are you racing, are you looking for greatest mileage etc.) you can't put a one ratio is best for all to it.

[Paul G]

My 72 is about a 4100# car with 3.91 gears, 28" tall BFG 275/60-15 tires, and 2400 stahl. It ran 14.9 at 92 with 2.2 60'. It is a small block, less than 300 HP at the crank, dynod 230hp, 330'# at the wheels a few years ago. At the track it was still traction limited a little bit. I could not just nail the gas or the BFG's would spin. 

When this car was put together in 01 for the previous owner I suspect they chose the 3.91 gears because of the lack of power the small block would make. It moves pretty good stop light to stop light. But the steep gearing and low HP means it runs out of steam relatively quickly. It does not pull hard on the top end. I would imagine in this case the tall gearing has helped the low end city driving/street performance.