Major Errors Fixes

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Jacques Lefriant
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Joined: Mon Dec 06, 2010 1:50 pm
Location: Washoe county NV

Major Errors Fixes

#1 Post by Jacques Lefriant »

Hi All
the previous topic did not yield much information but basically it shows the need for the "old timers" and the new guys to share important information as to what we now would treat as recalls. i will give an example.
1. Differential ring gear bolts. There may even be a bulletin about replacing them.
j
 

Brendan Head
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Joined: Sun Mar 14, 2021 12:51 am

Re: Major Errors Fixes

#2 Post by Brendan Head »

Hi Jacques,
Thanks for posting up the thread and starting a great conversation.
As I’m one of the very new guys hoping to absorb what I can could you please explain in greater detail of both the problem and the solution.
Likewise I have seen you mention the Cadrobi conversion but am still unsure exactly what it is? Many thanks from down under Australia.

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Jacques Lefriant
356 Fan
Posts: 4744
Joined: Mon Dec 06, 2010 1:50 pm
Location: Washoe county NV

Re: Major Errors Fixes

#3 Post by Jacques Lefriant »

Hi Brendan
The inherent problem was the flange that the ring gear was bolted to was 2 pieces. for a while Porsche used lock taps under the head of the bolts but they would deform, then they drilled the heads for lock wire which helped but the bolt would fail and next bolts went from 10 to12.9 and were grooved for lock tabs then finally they went to 12 rather than 6 bolts to secure the ring gear. Another nuanced fix was instead of reducing the diff housing OD which promoted cracking for clearance to the input shaft they grooved the input shaft.
The Caddrobi conversion has been discussed already . however the big takeaway is that it is based on the opportunity to benefit from upgrades that VW made when they could "improve" from the original 1950 vintage beginnings. Porsche sometimes rather than completely revamp parts they stuck with improving earlier versions. It took VW till 1960 to get rid of the split case transmission case that was the basis of the 519 Porsche box. in 1956 Porshe went to a tunnel case that was much stronger but unlike VW they kept the 2 piece differential even thought they used a beefier diff bearing wise on the Spyder(718) configuration. dimensionally VW incorporated in 1960 a swing axle open diff to accommodate the more robust 40hp engine. It was a no-brainer to use in the Porsche trans case a similar diff is what is now used in the Caddrobi Conversio and the Weevo. i venture most of the errors or miscues were staying with marginal for the task easily obtained VW based parts and not having the resources to incorporate better parts in production that had been proven in racing for economic reasons.
j
 

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