I thought I'd post this up here as I've had a few people ask about the conversion & I've gotten sick of directing people to the FAQ thread on Ozdat...
Please note: the S13/R31 gearbox is only a evolution of the Zed box.
Meaning it's only marginally stronger than a 240/260Z box. But it does provide a cheap & readily available conversion.
BIG thanks to Dave & Richard for writing the article!
SR gearbox onto L tutorial. Parts Required:
L6 gearbox
SR/CA gearbox
New L6 gearbox countershaft bearing (optional) Part Numbers: 63/22C3, TMB3/22C3, or 22BC0655X. Call CBC (
www.conbear.com).
Specific Tools Required:
16mm drill bit
Dremel with a small grinding disc.
Optionals: 16mm H7 reamer bit, 41/64ths drill bit.
Step 1:
Remove L6 bell housing from gearbox. To do this unbolt the bolts halfway on the gearbox that go from the extension housing through the sandwich plate to the bell. Also unbolt the cover on the inside of the bell that the clutch arm sits on.
You will then need to remove the circlip on the front of the input shaft bearing. Use circlip pliers and a screw driver.
Put everything aside as you will be using some of it again.
Remove SR/CA bell housing from gearbox following the same procedure.
Step 2:
Remove the SR/CA countershaft front bearing using two chisel point screw drivers to get it started, then lever it off against the bearing (as opposed to the gear) so you don't ruin the gear.
Step 3:
Reinstall the 240Z countershaft bearing. Either reusing the one from the L6 box, or a new one. Gently knock it down with a rubber mallet.
Step 4:
Drill out the 1st/2nd selector shaft hole in the L6 bell housing using a 15 or 16mm drill bit then a 16mm H7 reaming bit. Or you could try a 41/64ths bit if you happen to have one lying around (thats what I ended up using).
Step 5:
Get a dremel/rotary tool and grind away 1mm or so from the countershaft casting on the inside side of the gearbox bell housing. This is necessary as the casting has been modified between the 71B and the 71C to accommodate the wider gears assumedly.
You also need to put a chamfer on the edge which is square standard. I made this chamfer between 1 and 2mm big.
Step 6:
Trial fit this bell onto the SR/CA gearbox being careful of the oil supply cup on the upper passenger side just above the 1st mainshaft gear. Rotate the input shaft by hand. If it is very difficult to turn you need to die grind some more off the countershaft casting in the bell.
Step 7:
When you can bolt the gearbox up and rotate the input shaft easily you are just about ready to bolt the box together.
You could possibly have trouble with the 1st/2nd input shaft not wanting to go into the bell housing because this metal doesn't have any oil sitting on it, I suggest you squirt a dab in there. If the selector doesn't go in it can slide backwards (engaging 1st gear).
If this happens and the gearbox shifter is not in the 1st position you won't be able to select any gears (except 5th/Rev) from then on. If putting some oil in the 1st/2nd selector shaft hole doesn't solve the problem, you can put the gearbox in the 1st position before you bolt it up and it will be fine. Worked for me atleast.
Step 8:
Reassemble the gearbox as you took it apart and you're ready to go. Don't forget the circlip on the mainshaft bearing. Use the L6 front gearbox cover, clutch arm and throw out bearing carrier.
Additional issues:
The SR/CA gearbox has the bolts for the gearbox x-member around 35mm further back than the 71B box. Depends on your car what you do to fix this. Here is what I did, tad dogey, but it works.
This gearbox is also 50mm longer at the end of the tailshaft. I took a tailshaft that was used on a 71B box and had it shortened by 50mm and it fits just fine (after you remove the cover for the front spline as it doesn't fit into the gearbox).
Big thanks to Mad1600 for helping me and motivation.
Dave (Thehelix).
