IRS 5spd Occmans Razor

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Vic Skirmants
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Re: IRS 5spd Occmans Razor

#16 Post by Vic Skirmants »

"So what else is required to install a 901 into a 356"
Mark; a whole bunch of fabricating and welding is required. It's not a bolt-in proposition.

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Jacques Lefriant
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Re: IRS 5spd Occmans Razor

#17 Post by Jacques Lefriant »

Vic
but what if it were?
j
 

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Larry Coreth
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Re: IRS 5spd Occmans Razor

#18 Post by Larry Coreth »

As an engineer I am intrigued by the potential upgrade of a 901 gearbox in a 356 ! I've even seen an example at the Registry ECHH a few years back in South Boston, VA., really neat installation. No doubt it did wonders for the handling and a 5th gear would really be nice. However several things I believe will prevent a serious, wide spread, interest in this conversion project except by possibly the most enthusiastic 356 cognoscenti.
First cost, this is no minor bit of surgery or simple parts swap. Secondly if you were to develop a "kit" to make it do-able by the average home mechanic, what would the selling price need to be to make cost effective for you, $8-10K ? Now there are most likely some "outlaw" 356's enthusiasts who just salivate at the thought of this concept but how many such owners are there really, a dozen maybe ? Then what percentage are well healed enough to spend this kind of money on “neat to have” extra?
Even back in the day when 356’s and early 911 parts were cheap and plentiful, this would have been a major project. But as a thought experiment as Einstein was so famous for, a great theoretical exercise and food for discussion for all of us technically minded 356 enthusiasts.
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Jacques Lefriant
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Re: IRS 5spd Occmans Razor

#19 Post by Jacques Lefriant »

Hi Larry
It's been 25 years since i did one of these conversions so maybe it was easier then. As many have pointed out the present transmission is inadequate. Even if you "rebuild" with a new R+P diff 4th gear etc you may spend the 8-10K and you haven't addressed the deficiency. So cost is not that much a problem given the asking price of the cars now. the engineering needed is to make the conversion totally reversible and robust i think it is doable so break out the drawing board and the slide rules oh i meant the CAD program and the FEA program.
j
 

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Larry Coreth
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Re: IRS 5spd Occmans Razor

#20 Post by Larry Coreth »

Well Jacques,
I think you are tilting windmills, and just like Don Quixote for the most noble of reasons. If I were living close by I would be glad to help with the development, even enthusiastic but not hopeful for an economic success.
Oh I have a box full of early 901 gears and other parts that I would let go without much arm twisting, for the Cause !
Larry Coreth
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Jacques Lefriant
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Re: IRS 5spd Occmans Razor

#21 Post by Jacques Lefriant »

Larry
thanks for the parts offer but i am good. My title as an engineer was a system engineer. so i am a big picture guy. This project is very minor and the economics don't bother me since i am in it for the long haul. Phase 1 of this project is to do the IRS conversion. It is a no brainier for me to convert 356 tunnel case transmission to IRS so if we accomplish this we have the IRS conversion and then the 901 is practically a bolt in. I need some encouragement to continue. i have no personal need since one of my Carrera2s already has a 901 in it and i am up to my eyeballs in 4-Cam parts production besides all the pushrod engine/transmission parts i have had done.
j
 

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C J Murray
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Re: IRS 5spd Occmans Razor

#22 Post by C J Murray »

Hi Jacques,
You should get serious and make a six speed cluster that slips into the 741 case. Screw the 911 axles and suspension; who wants to have the same handling as the crappy SWB 900 cars? Six speeds with zero visual clues is the way to go.
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Jacques Lefriant
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Re: IRS 5spd Occmans Razor

#23 Post by Jacques Lefriant »

Some people want suspension travel and good tire wear if you want to go fast just drive a shifter Kart.
j
BTW The 6 spd sequential paddle shift box was supposed to be a secret.
 

Edwin Ek
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Re: IRS 5spd Occmans Razor

#24 Post by Edwin Ek »

How about just a fiver in the 741?
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Martin Benade
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Re: IRS 5spd Occmans Razor

#25 Post by Martin Benade »

Perhaps a more elegant solution would be 3-speed non-synchro internals for the 741 box. A lot less moving parts, better weight distribution.
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Jacques Lefriant
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Re: IRS 5spd Occmans Razor

#26 Post by Jacques Lefriant »

Martin i hope that was an attempt at humor. a more elegant solution would be a CVT.
OK guys seriously should i abandon the project? Judging from the response the majority don't even have a clue of what i am proposing. and even the technically minded have not come to a full understanding of what it is all about. This project may be the "final frontier"
AMDG
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Larry Coreth
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Re: IRS 5spd Occmans Razor

#27 Post by Larry Coreth »

Jacques,

I applaud your enthusiasm for this project concept, be it a complete conversion to 901 trans with suspension changes or some variation thereof. Having owned and worked on lots of early 911’s (up to ’73) the technical advantages are obvious. The Speedster I saw at the ECH (sorry don’t recall the owner’s name) converted to complete 901 read running gear was beautifully done although pretty much irreversible. If I were to take on such a project that is the way I would do it
My discussion in previous posts has been to, in my opinion, express my doubts as to the economic viability of the project. So Jacques, if your heart is set on doing this project, go for it ! I would assist in any way I can but you know this will be a labor of love and personal satisfaction, I just don’t see any monetary return here.
Larry Coreth
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Jacques Lefriant
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Re: IRS 5spd Occmans Razor

#28 Post by Jacques Lefriant »

Hi Larry and thanks
I don't think most of you get this. To do the 901 transmission conversion it requires having IRS. On a one off it is easier to use 901 trailing arms or 944 turbo so everyone cuts up the car to make it into a 901 suspension vehicle. Most SWB 901 arms are bent and hard to come by. You have to change the spring plate and the shocks unless you graft in the 901 upper shock mounts you are stuck with 901 disc brakes. My approach would be to focus on the IRS conversion and incorporate the existing spring plates and use the original brakes cables etc. That done the 901 conversion should utilize the original hoop (with mod for the cable) and a mount that uses the forward mounts. besides the the 901 conversion customers these MODS may interest customers who would like IRS and keep their original transmission. The Cadrobbi conversion for the big swing axle diff is also available as an IRS diff.
j
 

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Jacques Lefriant
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Re: IRS 5spd Occmans Razor

#29 Post by Jacques Lefriant »

Hi All
Just a tease
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Re: IRS 5spd Occmans Razor

#30 Post by Craig Richter »

So far, so good...
 

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