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901 to 911 Transaxle Upgrade: Replace or Upgrade
When I rebuild my car for track use, I am planning on replacing my 901 transmission with a 911 transmission because there is a lot wider range of clutch options available. I'm aware that in order to make the change I will need to update my clutch cable and some related stuff. My question regards the transaxle itself, or more specifically the bell housing. The question that I have is:
A) Should I just replace my 901 with 911 transaxle? or B) Can I update my 901 bell housing to use the 911 style clutch? Either way I'm planning on doing a complete transaxle rebuild including replacing the intermediate plate, mainshaft, ratios, as well diff and all the related service items like synchros, gaskets, etc. I'm just wondering if it will be cheaper/easier to start with the box that I have or do I need to get a newer version?
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John '69 911E "It's a poor craftsman who blames their tools" -- Unknown "Any suspension -- no matter how poorly designed -- can be made to work reasonably well if you just stop it from moving." -- Colin Chapman |
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11-11-2002, 07:17 AM
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The belhousing is not a separate piece, but you can replace just the bellhousing/case from a 911 with all the parts from your 901. The intermediate plate, gear stacks, etc. are the same.
If you can find just a case then you are set. If ou have to buy a whole trans, it might be worthwhile to select one with the ratios you desire (such as an original E or S box for example) and use those gears. An advantage of getting a complete trans is that you can place less worn components (such as 4-5 slider) into more worn positions (2-3) and save on new parts cost. |
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11-11-2002, 08:40 AM
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John - try pm'ing Sherwood Lee - he changed his own car to a 915.
Mine has been changed but I didn't do it. Issues included: - clutch mechanism - 915 shift tower gives better shifting - trans tunnel needs "massaging" Stuff that didn't matter for me but probably will for you: - CVs etc (I got axles with the box and upgraded to '74 alloy arms) - 69 has really tight fit between engine, heat exchanger, transmission, '74 trailing arms and shocks. The shocks needed the dust covers to be removed - clutch, as you say (I also got a 3.0 engine) Unfortunately I don't really have the details - I paid for someone to do it. Cam
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1975 911S (in bits) 1969 911T (goes, but need fettling) 1973 BMW 2002tii (in bits, now with turbo) |
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11-11-2002, 12:25 PM
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A type 911 trans is not the same thing as a 915 trans.
The 911 is the same gearbox as the 901, but uses a pull clutch (like the 915) instead of the earlier push clutch. |
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11-11-2002, 12:32 PM
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Ooops, shows what I know
 Me = dunce Disregard previous post.
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1975 911S (in bits) 1969 911T (goes, but need fettling) 1973 BMW 2002tii (in bits, now with turbo) |
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11-11-2002, 12:53 PM
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Navin Johnson
Join Date: Mar 2002
Location: Wantagh, NY
Posts: 8,786
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John,
Im going throught this exact conversion now. You need a type 911 case, the 911 is very similar to the 901 case except that the 911 case has an boss cast in that the clutch cable passes through. You will also need a guide for the cable. This conversion allows a whole new world of clutch options. Kennedy Engineering makes some lightweight 915 pressure plates that can be used with the 911 gearbox, the Sachs all aluminum RSR plate is unobtanium now. I happen to have some desireable gears for the 901/911 box also
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Don't feed the trolls. Don't quote the trolls  http://www.southshoreperformanceny.com '69 911 GT-5 '75 914 GT-3 and others |
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11-11-2002, 01:20 PM
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use a 70-71 case. it's the only 901 that uses the later "pull" clutch. just swap the parts from the 69 trans into it. the dimensions are the same, so the R+P won't have to be reset. the 70-71 release fork and T/O bearing need to be used with it.
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https://www.instagram.com/johnwalker8704 8009 103rd pl ne Marysville Wa 98270 206 637 4071 |
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11-11-2002, 01:45 PM
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Navin Johnson
Join Date: Mar 2002
Location: Wantagh, NY
Posts: 8,786
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I knew I had some pics of the case handy.
  Upon closer inspection it is the side cover that has the extra boss cast in it, maybe you could just replace that and pick up a guide, then be on your way, you also need a different shift fork. Im not sure if Pelican sells them I,m sure PH11 could help as well as Gary Fairbanks.
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Don't feed the trolls. Don't quote the trolls http://www.southshoreperformanceny.com '69 911 GT-5 '75 914 GT-3 and others Last edited by TimT; 11-11-2002 at 01:48 PM.. |
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11-11-2002, 01:46 PM
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the bellhousing also has an extra tit, that the end of the clutch cable clips into with a slotted sleeve. you can see it in the picture just below the hole where the engine stud goes thru.
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https://www.instagram.com/johnwalker8704 8009 103rd pl ne Marysville Wa 98270 206 637 4071 |
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11-11-2002, 01:50 PM
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Navin Johnson
Join Date: Mar 2002
Location: Wantagh, NY
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Yea, failed to notice that, thats where you terminate the clutch cable.
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Don't feed the trolls. Don't quote the trolls http://www.southshoreperformanceny.com '69 911 GT-5 '75 914 GT-3 and others |
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11-11-2002, 01:52 PM
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Thanks guys -- you answered my question.
Cam; while upgrading to a 915 is certainly an option, the rules for the class which I'll be preparing my car for add 50 pounds to the minimum weight for the car if I use an "alternate syncro transmission". - John
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John '69 911E "It's a poor craftsman who blames their tools" -- Unknown "Any suspension -- no matter how poorly designed -- can be made to work reasonably well if you just stop it from moving." -- Colin Chapman |
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11-12-2002, 04:44 AM
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I believe that you might have to use a 904 main shaft to be able to utilize the interchangeable gearsets that are available for the 901/911 transmission. You might check with J. Walker about this.
Good luck, David Duffield Last edited by Oldporsche; 11-12-2002 at 06:56 AM.. |
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11-12-2002, 06:54 AM
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Good point - the 904 mainshaft allows 2nd gear to be interchanged - all other gears are interchangeable in any 901/911 box.
Production mainshafts have 2nd gear made as part of the shaft - to change the gear you need a complete mainshaft. |
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11-12-2002, 07:02 AM
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1969 Porsche 911E 2.0 E
1975, 1969 Porsche 911S, 911T 2.7S CIS, 2.0T ca
