Yet another freeway flyer Vs taller tires question...

[Pruneman99]

So for a more accurate "feel" ( I know that's an oxymoron ) I used my GPS to track my speed on the interstate. At 70mph, stock gearing and 4.37 with 26" tall tires, then engine felt comfortable (approx 3600rpm) at cruise. I still had more pedal. At 75, my shift light in my head was going off. 65 felt very nice and easy.

I know, nothing scientific, but a better description on feel.

[modok]

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[thomas.]

[pbenn]

You're going up a long hill in 4th and losing power... do you want a wide ratio drop to 3rd or the stock ratio drop?

To my mind, that's why I would prefer a 3:88 R&P with stock ratios to a Freeway Flyer. '70s Mexican swingaxles were 3:88.

[VW_Jimbo]

[modok]

[Mos6502]

I always laugh when people want a beetle that'll cruise at 80mph.

Buy a new car.

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[modok]

The heads.
"happy place" is a function of port velocity and displacement.
Camshaft.,....a good simplification is, with cam shaft duration you can adjust the much is above VS how much is below the happy place.

but, i didn't even look at the cam, but the combo IMo isn't ideal for highway cruising and maybe THAT needs adjustment? We are really headed off topic then, maybe I best crawl back into the high performance section and leave you guys be.

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This is a tangent to the thread, but is a reminder that there are cause, and effect situations when things start deviating from stock. Sorry to have gotten things off track. I’ve taken apart way too many engines with burnt pistons, and dropped seats from melted heads. Some were careless things like missing engine seals, or tin, but most were customers that had good/fresh engines that simply didn’t pay attention to the limitations of them.

You have to really determine what you are going to use the vehicle for 80% of the time, and base any gearing change on that. Then you will have to live with what the choice for the other 20%, whether it turns out good/bad/o.k., gives you while driving during the 80%. Building the engine to accommodate a specific change optimizes both. The op hasen’t replied in a week, so they have moved on, but at least this may be another reference point for someone else’s search.

[63 roach coach]

Thanks to all of you that have chimed in and provided valuable information. I appreciate it.

[63 roach coach]

[AZOffTheWall]

Stock VW transaxle from 67-72 was 3.80/2.06/1.26/.88 or .89 with a 4.12 ring and pinion, they work perfectly with a slightly modified dual port and larger tire. I think the biggest tire you'll be able to fit with a short axle and lowered is a 205/70/15.
I have 205's and a 3.88 with 3.80/2.06/1.26 but a .93 fourth so the final drive is about the same but 1st thru 3rd are taller. Car is at about 2800 rpm at 60mph, 3200 @ 70mph, i also have a bigger motor making more power to pull the taller gear.
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[glutamodo]

FWIW - I've run my 4.375:1 final drive Baja with 215/75R15 tires for over 20 years now. It's just a 1600DP, nothing special beyond a Baja QP extractor. But I like how it runs. It's comparable to the Mid-70s era Beetles. Just from a statistical point of view, I saved ratio-tire size-speed calculator eons ago and have used to create a few charts here and there.

This is my Baja compared to how a stock 1973 lines out with modern 165/80R15 radials (original bias plies were often a bit taller than their radial equivalents)


-damn, I thought in the past I've been able to get these two images to display side by side but the site is stacking them instead.-

edit: and old photo of my speedometer vs tachometer (which reads high by like 200RPM) in this Baja:

Making that 200RPM correction, that's 4100 at 86, which is actually right in line with the the chart above, which says to expect 4000RPM at 84.66.
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Andy T.


IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.

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[63 roach coach]

[glutamodo]

I guess now, it's to the point where the 4.375 swingaxle is like totally unwanted these days. I think it's fine with the 1200 engine... I've always had that in my 62, and that's always been a 1385 big bore 40HP. However, at one point when working on the 1600DP engine in my aforementioned Baja bug, I temporarily put in an extra engine I had lying around, another big bore 40HP. With the taller ratios provided by the 215 rear tires, the Baja was a hell of a lot less enjoyable to drive than I was used to. I mean, it still drove OK, but it felt like it needed to "grow a pair" if you know what I mean.

Now, in my 62, ever since I started to lose 4th gear several years ago, I had planned to replace that tranny with one set up 4.125, which I think will work OK with my big bore 40HP and will be even better if I ever finish putting together the low-key economy/performance 1500SP with dual ICTs that is a work in progress ( I should have all the parts to finish it, some assembly required, short block is ready though) And the plans to change the tranny came to a head recently when I totally lost 4th gear. So I bought a replacement rebuilt 412. Unfortunately, I think I'll have to eat the core charge - they specified "only 12V transaxles" as acceptable cores. Really, why not just SAY "We don't want no more stinking 4.375s" but I will have to check the core I have in shipping box stored away, for all I know the case might be from the 12V era, even though I know it's a 4.375 diff)

Still, despite 4.375 final drive in my 62, in preparation to remove that tranny from my car, I though I'd heat the drivetrain up a bit prior to draining the oil out of it. So last week, I did a 40 mile round trip out of town on a state highway that doesn't see much traffic. Even limited to 3rd gear, I was still hitting 60MPH much of time and sometimes 65MPH down hills - you might say I'm pushing that 1385 too hard, maybe, but I remember taking a lot of precise care in balancing the pistons and rods when I built it, it's the smoothest running 40HP-series engine I've ever built. And it was time to change the oil on it as well, so just heat the thing up!
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Andy T.


IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.

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There are some parts more desireable in the early swing axle trans than the later ones, so they aren’t totally worthless. The 4.37 r&p is simply not used as often. I’m coming across more and more people with original 36/40hp engines actually wanting a 4.37 trans for more pep cruising around town. The Pre-60 split cased trans 4.43 r&p with an .80/.82 is actually a closer to the 4.12/.89. Installing a 4.37 61-66 trans in a Pre-60 car with a 36hp wakes up the engine a little with the lower gearing.

[glutamodo]

Good points there. Still, I got a distinct impression when talking on the phone when ordering up that 4.125 tranny that the 4.375s were like totally out of vogue.
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Andy T.


IMAGE NOTE: It has been noted that Chrome based browsers may have issues in displaying my vast image library, which use non-secure links and are on an FTP server. Images should still be viewable if the link is clicked though.
I do not know how to fix this. All I can say is it all works fine for me with what I use, Firefox.