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vwracerdave
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PostPosted: Sun May 16, 2021 11:27 am    Post subject: K vs G Reply with quote

I have a K831 (Klinkenberg) 3.88 R&P gear out of a '71 Ghia. I have always heard the G831 (Gleason) is stronger but everybody always says the K4.12 is stronger then the G4.12. Why would this be?

Does anybody have any actual experience with the K831 is drag racing?

I know Weddle produces only the K style for all their aftermarket R&P gears.
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PostPosted: Sun May 16, 2021 12:31 pm    Post subject: Re: K vs G Reply with quote

For maximum abuse, Klingenberg is the way to go. It has the edge.
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PostPosted: Sun May 16, 2021 12:49 pm    Post subject: Re: K vs G Reply with quote

While the Klingelnberg gear shape lends itself to the greatest strength, material plays a big part as well. From my experience, and many others with more than me, the OEM VW Gleason 3.88 is stronger than the Klingelnberg 3.88 because of the material, not the tooth shape. The OEM VW Klingelnberg 4.12 is stronger than the Gleason 4.12 because of the tooth shape. The OEM VW Oerlikon 4.12 is stronger than the Klingelnberg 4.12 because of the tooth shape. I would assume an OEM 3.88 would be made from better material than a sportsman r&p from Weddle, but a 3.44 sportsman is stronger because of the tooth shape/size.
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PostPosted: Sun May 16, 2021 1:41 pm    Post subject: Re: K vs G Reply with quote

I was talking 4,125. but apart from that
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Casting Timmy
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PostPosted: Tue May 18, 2021 6:54 pm    Post subject: Re: K vs G Reply with quote

I'd double check the tooth cut on that K831, I had one marked as K but the cut was a G. They did make K's in that gear ratio, but also mislabeled some as well.

One interesting thing I read on the shop talk forums about the K cut was for the earlier 4.12 and someone talked about the transaxle builder tempering it some more and warning the guy to keep the backlash in check. He mentioned it did well until he stopped adjusting the backlash.

I'd be more for the limiting factor with beetles being in the quality of the part produced more than what the ideal strength of the tooth cut would be. Personally I think it's kind of amazing how Weddle and others up the quality of the steel and process and the design can handle a whole lot more power.

Ohio Tom would be the one to ask, but I think you'll find the G version better in the 3.88. My guess would be like G mentioned, something about the quality of the part as opposed to the design itself.
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PostPosted: Tue May 18, 2021 7:27 pm    Post subject: Re: K vs G Reply with quote

I find it very hard to believe there is a material difference between any of the VW factory ring & pinion gears. VW was consistent with all their forward gears and also engine parts like crank, rods & flywheels.

How rare are the K831 gears? If you tore apart 1000 3.88 transaxles how many would be K and how many G? I've always read it is cheaper and faster to cut G R&P gears then K gears so that is why the majority of 4.12 and 4.37 are G.

I have never seen or heard of a "O" (Oreliken) 3.88 but I know they made them in 4.12

Bruce ask this same question on STF but didn't get very many answers.
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PostPosted: Tue May 18, 2021 8:06 pm    Post subject: Re: K vs G Reply with quote

Yes, I also find it hard to believe the material would be different. I’ve seen the K 3.88’s crack/chip easier than the G ones.

Any of the K 3.88’s I’ve found have been like yours, out of the AN Ghia transaxles. Maybe they were assembled somewhere different with the .89 4th, and the supply chain to that location were K gear sets, like the Thing’s got the O 4.12’s.

And yeah, the only O gears I know of are the 4.12’s.
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PostPosted: Wed May 19, 2021 12:07 pm    Post subject: Re: K vs G Reply with quote

3.88K is a turd. Not sure how 4.12K would compare with 4.12O

Strongest of each ratio that I've seen are 4.37K, 4.12O, 3.88G

Many years ago, I had surprisingly good luck with a Brazilian 3.88G ground down for Hewland, but I would never use one in a drag car. Same with the Brazilian 4.12O .. likely too brittle.
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PostPosted: Wed May 19, 2021 7:42 pm    Post subject: Re: K vs G Reply with quote

In my latest Trans build, I had the choice of using a 4.12G or 4.12K, Scott advised to go with the 4.12K cause it would be stronger. He mentioned the 4.12 "O" also, but it was not something that was common or easy to get. I know it has no bearing on the 3.88 choice, but just a example that fits for information in this thread on a subject that is rarely talked about.
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Bruce
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PostPosted: Mon Jun 07, 2021 3:26 am    Post subject: Re: K vs G Reply with quote

vwracerdave wrote:
How rare are the K831 gears? If you tore apart 1000 3.88 transaxles how many would be K and how many G?

I've only ever found 2. A friend who also rebuilds gearboxes locally is a drag racer. For about 20 years he ran a Type 1 gearbox, replacing the G 3.88 every 30-35 passes. I asked him how strong he thought the K was. In all his years, he's never had one!

vwracerdave wrote:
I've always read it is cheaper and faster to cut G R&P gears then K gears so that is why the majority of 4.12 and 4.37 are G.

There are videos on YT that show the different gear cutting machines and how they machine differently. For example, on one cut, the pinion is spinning while the cutter cuts all the teeth at once, slowly cutting down to the root. In another, the pinion is stationary while the cutter cuts down to the root between only two teeth. Then when it's done, the pinion advances one tooth. Obviously, this second method is much slower.

vwracerdave wrote:
I have never seen or heard of a "O" (Oreliken) 3.88 but I know they made them in 4.12.
I've got an "O" 4.37. I've not seen a 3.88.
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Ohio Tom
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PostPosted: Mon Jun 07, 2021 7:48 am    Post subject: Re: K vs G Reply with quote

I can speak from experience on this.

Weakest to strongest based on personal and customer experiences:

G 4.12
G 3.88
K 4.12
O 4.12.


No doubt the O (thought it was Oettinger?) is the strongest stock R/P I have ever run. They come from Thing transaxles.

I can shatter a G 3.88 in 20-30 maybe 50 passes. The O 4.12 I have yet to see a broken one.
They are rugged for sure.

I got 100+ passes on one. Now it lives in my street buggy. No cracks after years of drag racing abuse. I was amazed that it looks like the day I installed it. No evidence of cracks or wear.

I put them in drag boxes for choice customers. (when available).
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