Freeway Flyer?

Do these figures include the flat bed time? As Lane says, your mileage may vary

Carl, while GPS could be off a bit, it seems pretty darn close to me on a straight stretch  of road. When your car was on the flatbed it was a steady 62 mph for much of the time. I would say you got EXCELLENT gas mileage for the last 100 miles to Carlisle. 

With a 24.5" (rolling diameter - I believe it's a 185/70) tire the gear charts I have indicate that with a 4.37 r&p and .89 4th gear, 3,000rpm happens at about 57mph and with a 4.125 r&p it's almost 60mph . A 185/65 is slightly shorter, and my charts are on graph paper so I can't adjust for tire height without recalculating and doing another chart. Measure the height from the ground to the center of the wheel on the rear and then double it; that will give a true figure for the rolling diameter of the tires you have. What's the rpm drop like from 3rd (shifting at 4,000rpm) to 4th? With the stock VW 1.31-.89, 4th gear at the same speed should be 23-2400rpm. If you have a bigger drop (2200rpm) then you have a .82 4th gear. Hope this helps. Al

Al (Gallo)...not only did I get extrodinary mileage on that last 100 mile sprint to the Marriott parking lot, but the engine was phenomenally docile too.

and, Al (ALB)...

My rolling diameter for those Yokohama Avid Tourings is 23" (measured from the ground to center x2) which is about 6% less distance covered than 24.5". That would account for some of the disappointing mpg reading and also the slower than expected velocity for a Freeway Flyer at 3000rpm.

I was under the impression that Freeway Flyers had a specific r/p and a specific 4th? I appreciate your posted information but it's a bit confusing, and I still don't know if I have a Flyer or not.

The term "freeway flier" was coined by a VW trans shop (now defunct, iIrc) and originally was a 3.88 r&p with a .82 bus 4th gear. It works, but it makes (especially with a smaller motor) the 3rd-4th gap very big. A smaller motor also can't pull that gear ratio effectively in an 1800-2000lb car, and causes overheating on the highway (again, this is with a smaller motor). There's a reason VW used the gear spacing it did. With the 3.88 the factory used a .93 4th in a beetle, but the slippier shape of the Karmann Ghia they were able to use the 3.88x.89 combo.

 Anyway, these days "freeway flier" means different things to different people, as a number of transaxle rebuilders throw the term around. I think you probably have the 4.125x.89 combo because, when adjusted for the 6% shorter tire diameter it most closely matches your 3000rpm at 56mph figure. A 3.88 r&p with a .82 4th (and your size tire) would give you 65-66 mph, which is too far out (assuming that your speedo is correct). Al

"not only did I get extrordinary mileage on that last 100 mile sprint to the Marriott parking lot, but the engine was phenomenally docile too"

I'll bet it purred like a kitten...

You should be able to figure this out the next time you change plugs.

Put it in 4th, jack up one rear wheel, and see how much you have to turn it to spin the engine one turn.

If your gauges are correct, closest guess is you have a 4.375/0.89 or 4.125/0.92. The first is just a stock ratio, and the second would be non-stock but also a shorter 4th than stock so not a freeway flyer.

But here's a way to check the final ratio: Take out your spark plugs to let you turn the engine over easier. Put the car in 4th gear. Jack up one rear wheel off the ground. Leave the other wheel on the ground. Leave the parking brake off. Put a mark on the tire that's in the air so you can keep track of the number of its rotations. Turn the engine over with a wrench 10 full revolutions. Take the number of engine revolutions divided by the number of tire revolutions and multiply by 2. So if you get 5.45 tire revolutions, (10/5.45) * 2 = 3.671 final drive ratio. Compare that to these combos:

4.375/.92 = 4.025

4.375/.89 = 3.893

4.375/.82 = 3.587

4.125/.92 = 3.795

4.125/.89 = 3.671

4.125/.82 = 3.383

3.88/.92 = 3.570

3.88/.89 = 3.453

3.88/.82 = 3.182

3.44/.92 = 3.165

3.44/.89 = 3.062

You can also do that check in another gear to try to and verify the R&P ratio because 1st-3rd are less likely to be changed from stock. You'd need the first two letters of the transmission code off the right side of the trans to look up the expected stock ratios. But for example 3rd gear is 1.26 on most transmissions, so combined with a 4.125 R&P, that gives a 5.198 final drive ratio, or 3.85 tire rotations.

You can do this test backwards as well but it takes more muscle. Rotate the tire 2 revolutions, count the number of rotations of the engine. That is your final drive ratio.

There is no standard for "freeway flyers". Generally, it just means that your 4th gear is taller than stock, but there are multiple combinations of R&P and gears (one or all) that will do that.

I agree with Al.  You probably have a 0.89 4th and a 4.12 R&P.

Using this gear ratio calculator

http://www.et-studios.com/moto...rts/gears/gears.html 

you would be turning 56 mph at 3000 rpm.

By the way, a 185/65-15 tire has a diameter of 24.5"

Ron- Check the rolling diameter- it's different. Al

Al, is there an online calculator that will do that?

Yes, the rolling diameter is less than the static diameter. Your estimate of ground-to-axle x 2 seems high too me. That's about 6% less. I'd say 3% less diameter is a closer estimate. Some tire manufacturers (bf goodrich for example) will list in their specs a revs/mile stat that we really should be using in estimates like this if we can get it.

My sincere thanks to everyone...I'm taking copious notes.

You people are doing a great job of flattening my steep learning curve.

Ron and ALB: It's only flat on the bottom!

Yeah, I saw those original figures and thought, "Geez....that thing has stock gearing!"

Why did I think that?  Because in original Volkswagens you were always safe by looking at the tach reading and almost doubling it for miles per hour.  Depending on the R&P ratio, you would be pretty close to actual MPH - stock gearing would bring you in a little low in MPH, a typical 3:88 rear would get you slightly high in mph and a 3:44 would get you about 17% higher.  Looks like the rule of thumb from the 1960's is still pretty close.

OUCH!!

Gordon, yours is a discouraging, unwelcomed analysis.

Sometimes ignorance is bliss... 'cause in this instance information that flattens some of my steep learning curve is depressing. 

Does anybody have a 3:44 that's just collecting dust in a drawer?

3.44:1 R/P are pretty unusual, Carl. Spendy too. New ones are about $350 from Rancho.

http://www.thesamba.com/vw/cla...detail.php?id=819410

Here's a complete IRS transaxle in the Niagara Falls area for $1400 complete. Believe it or not, that's not too bad:

http://www.thesamba.com/vw/cla...etail.php?id=1493475

Stan, thanks for the 'sticker shock' heads up.

Maybe...just maybe...I can simply fake being satisfied with what I've got! 

Carl, I may be selling my IRS tranny with a newly installed 3.44 r&p.  You may remember that I'm having a 901 gearbox installed in my IM. 

I'm not sure when I'll put it up for sale, but I can tell you it won't be close to $1400.

you cany go by the tire manufactures sizes, there usualy off a good bit. why I dont have a clue execpt for they make it and then figure out what size it is close to and then add the size to the mold.you would think it would be a sciance but aparently not. I just replaced my

205 75 15 with 235 75 15  and what a diferance it makes driving, 3rd is almost where 4th was.the mpg sucked with the short tires, much better with the taller ones. I used to get about 34~37mpg with the 19.5 wide x32 tall mickey thomopson prostreet tires.the tires were about 70lbs each, a lot of tire to haul around, I doont know what the mpg was with the 205 75's but it sucked gass, probably about 26mpg. it should be up around 31 now. trans has 412 gear now, had 388 with the 32" tall tires. dia times pie will get you close,but it's easy to just run over a peice of string & rap around the tire and them mark it &mesure.devide by pie and you know how tall they realy are, and air pressure does affect it a lot. so when your done go have a diet coke and some pie.