WORK IN PROGRESS
First, identify what type of transmission you have originally in the car.
(insert modified pic of metal firewall tag)
S12 'C'--------------------------------------------------------------------------------------------------S12 'B'
Nissan "B" manual transmissions (full code: FS5W71B) were used in S12s thru mid 1986. Following the Mark 2 body and mechanical revision of mid '86, all manual S12's used Nissan "C" transmissions (full code: FS5W71C). If the tag isn't there, look at the transmission itself, you'll see that "C" transmissions have internal linkage (note the large plate) while the smaller "B" transmission has external linkage.
The S13 and S14 cars w/ manual transmissions all used the FS5W71C, although the front section (called the bellhousing
) has the bolt pattern for the KA (or SR), and the rear half is longer by approx. 6 inches to better fit the S13/S14 chassis. This is why the S13/S14 manual transmission is not a direct fit into an S12.
Depending on your original transmission, there are a variety of options.1.
In an originally manual transmission S12, if you are putting a KA bellhousing
on an S12 transmission
, then you retain the original driveshaft and trans mount/crossmember
. If you have an S12 "C" trans (and possibly "B" trans), you can hybrid the transmission and use your original s12 hardware http://club-s12.org/v3/index.php?topic=24095
. On some "B" transmissions, the swap works the same, other times machining is necessary for a larger front bearing (does anyone have the info as to what year "B" trans are OK and which need machining?) In an originally automatic transmission S12, you can still hybrid a manual transmission for OEM fitment, but you'll need to source an S12 "C" transmission, the front half of an S12 Mark 2 manual transmission driveshaft, and build a custom trans mount/crossmember.2.
If you are going to run the full S13/S14 transmission, you will need to modify the transmission crossmember and use the front half of a KA driveshaft (see below). Basically,, the S13/S14 manual transmission is longer than the S12 "C" or "B" trans, which will locate the shifter further back (floorpan modification) and require mix/matching driveshaft portions. Some drivers find this advantageous, as it locates the shifter in a more comfortable position; some have criticized the S12 manual transmissions as a bit too far forward, making shifts into 5th gear uncomfortable for taller (longer legged) drivers.
(insert pic of mix&matched driveshaft next to OE style assembly)
(insert pic of all 3 transmissions together)Depending on what your car was originally, this is how you will need to modify the trans crossmember to work with the S13/S14 trans...
...IF you have a Mark 1 automatic transmission
[/u] car, you will need to take your original transmission crossmember and modify it according to Waylon's guide http://club-s12.org/v3/index.php?topic=18215
...IF you have a Mark 1 manual transmission
car, you can take the original crossmember and modify it as follows:http://www.club-s12.org/forums/index.php?s...66&hl=ashes
post #3 for more pics/how-to.
Some slotting of the holes is still necessary to allow for proper clearance and slight chassis/setup variations.
...IF you have a Mark 2 auto trans car, a custom crossmember is needed. There are several ways to do this, it isn't uncommon for swappers to use the S13 trans' exhaust hanger location, which is nearly dead on to the S12 chassis mount location,
Or a custom dogbone-style mount could be made, in this pic you can see the exhaust hanger location that is used in the above pic,
...IF you have a Mark 2 manual trans car, (idk? is this a bolt in? who has done this? i dont remember)
If you have a midyear '86 model (MK1.5) the metal chassis itself is either Mark 1 or Mark 2. Using the above pics and this thread http://club-s12.org/v3/index.php?topic=22446
it should be obvious.
Once again, if you choose to use the S13/S14 manual transmission, you'll need to use the front half of a KA manual trans driveshaft with the S12 rear half and cut the transmission tunnel back to accommodate the shifter's further aft position. Updated 10/23/10