Installing a 915 trans from a 73 in an 82 SC

What is involved in replacing the transmission in my 82 SC with one from a 73 911T (with the 7:31 r & p)? Is it a direct replacement? Or will I have to add/subtract components? I was looking at getting my trans rebuilt with the 7:31, but I found a guy that will sell me the trans (rebuilt 20K ago)from his 73 at a great price. Which way should I go? Thanks in advance.

There are only two issues, really, speedometer and CV-joints/axles, and the CV-joints may not be a problem!

The '73 915 used a mechanical speedometer cable drive on rhe nosecone, and can't readily be changed over to the electronic sensor. That means changing out your speedometer, and running a new cable down through your tunnel ... not that big a deal, compared to the advantage of the shorter gearing and the fun it means with that 7:31 r & p, in my opinion! If the guy with the trans can sell you his speedometer, that is an easy solution. Otherwise, it's eBay, or one of the recyclers, unless you want to buy a new mechanical speedometer!

You probably want to get the CV-joints and axles with that '73 915, if they are available, too. I'm not sure whether the CV-joint bolt pattern changed with the coarse-spline output flanges in '76 or not, but it wouldn't hurt to have a spare set to play with. It might be as simple as putting inner CV's from the '73 on your SC axles, or there may not be a problem at all. But, the output flanges ARE different, and, for example, a Quaife limited slip cant' use the '73 flanges!

You might want to confer with Andial, CarQuip, or PowerHaus II about the CV-joint issue.

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Warren Hall
1973 911S Targa

Thanks Warren. I was going to replace the CV joints anyway, so no problem! I will be sure to keep you posted as to my progress. Thanks again for the valuable information.

uuugggghhhh!

if only i had known about this 7:31 stuff 6 months ago, when i had my transmission redone!!! i was lucky (sarcasm emphasized) enough to have had to replace my ring and pinion at that time. i didn't know about the 7:31 stuff having such an influence on acceleration. otherwise, i'm assuming i could have had the different size installed, instead and now be enjoying even more whiplash.

oh well. this is why warren needs to write his book! so i don't have to learn hard lessons late. :-)

by the way, i think my new ring/pinion cost me around $1200, which was at the shop's cost. tranny parts are not cheap on these cars. all the more reason i am completely bewildered when i hear some on this bbs estimating overhaul costs of around $1200-1500 for a 915 tranny. my parts costs alone for my rebuild (once again at shop cost) i seem to remember were almost twice this figure... maybe the mechanic took even more precaution than was absolutely necessary when ordering replacement parts.

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Adam Nitti www.adamnitti.com
'85 Carrera

[This message has been edited by adamnitti (edited 09-01-2000).]