Drivetrain - "If something's gotta break..."
Differentials
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The original Datsun 1600 comes supplied with an R160 differential.
That is, the crown wheel of the differential is 160mm in diameter.
Different size differentials can be acquired from other makes and models:
Datsun, Nissan and Subaru are just to name a few. These are a few
facts I've managed to glean from different sources about these diffs:
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The Dazda was originally supplied
with an standard open R160 differential. Due to experiences in other
fields with the breakability of R160s behind L18s we thought it prudent to install an R180. Being strapped for
cash the obvious improvement for traction was a CIG (now
BOC) locker.
This involves welding the spider gears to the carrier, and for additional
support we welded a plate between all four gears.
Due to the R180 selected we had to change to circlip flanges (rather than the original bolt flanges). This meant redrilling the flanges to accept the original half-shaft bolt pattern. As there was no longer any room between the flange and the differential we also had to use some chamfered hex head bolts (in place of the existing bolt/washer/nut arrangement). During the welding process care must be taken to minimise the amount of heat build-up in the carrier assembly. |
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After some success with the locked R180, we started snapping half-shafts.
Now it's not a well known fact (well it wasn't to us at the time!), but you shouldn't run a back left half-shaft in the back right location, and visa versa. This is because the shafts torque up in a particular direction and when you change this they simply shatter/shear from fatigue. This may have been the cause of one of our failures (however we only had one spare with us so it had to go in - regardless of the side). We then decided to install an R200 LSD (ex-Skyline) (that are supposedly quite rare, but we found one anyway) with a 4.375 ratio (we would have gone for a higher ratio but pickers can't be choosers). Installing this diff had the added advantage of acquiring a pair of CVs to replace the half-shafts. The CV shaft diameters are larger than the half-shaft's, so the hope is that we won't be breaking many of these at all. |
The yoke of the R200 is slightly larger than the R180, which necessitates a small amount of grinding of the cross-member; and the moustache bar (rear diff support) requires re-welding. Note that this sucker is made out of spring steel that tempers if you get it too hot. When drilling out the diff stud mounting holes don't heat the holes up too much. Use oil/lube and take your time. Drill slowly. If the holes go hard then you'll have to either file or grind them to size. You have been warned!
Constant Velocity (CV) Joints
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The CV's themselves are the shortest ones we could find. As the rear track of the 1600 is narrower (about 50mm I think) than a Skyline, the selection of short CVs is a must. It also must be noted that the CV splines are different lengths from right to left and are NOT swappable. You can however get the ends popped to make up shorter shafts from other cars. These shafts are a tight fit. There is almost no play left at the minimum extension position (i.e.. wheels parallel to the differential). |
Lastly the pinion gear flange (bolted to the prop shaft) is completely different on the R200 (compared to the R160/180) and cannot be swapped over. This requires a matching flange mounted on the prop shaft that means either you try to match the uni-joint bearing sizes or you fork over some more bucks to get another prop cut and spliced. As props are cheap, and getting them re-welded relatively cheap, we decided to keep the old prop/diff/shaft combination as a backup and acquire a completely new prop.
I've heard that CVs don't loose as much power as half-shafts in cornering situations, but I can't say whether this is true or not. Certainly the CVs have lasted longer than any of the drive-shafts we've had in the car, however we'll have to keep an eye on the dust/grease boots. These things have about a mm clearance between them and the diff. moustache bar mounting points and are in a particularly prone position under the car.
Clutch, Pressure Plate & Flywheel
As the motor is a Mazda 13B bolted to a bog-stock standard RX7 (series 1-3) 5 speed box, the pressure plate is also a Mazda item. It has, however, been rebuilt to accept some 1 tonne fingers which makes it exceptionally hard on the left leg (sort of reminds me of the 1 tonne clutch in my old Monaro). This pressure plate, coupled to a brass-button clutch, makes the whole setup very grabby. This is good, as the last thing you want whilst racing is any clutch slip. BTW, the stock Mazda clutch master and slave cylinders appear to be holding the additional pressure, although the slave cylinder rod is not long enough.
The flywheel is a new steel item thinner (and thus much lighter) than the original cast design. The only thing you've got to be wary of here is the lack of thread to tension the pressure plate bolts up with. As it's just over 10mm thick there's not a lot of lee-way when torquing 'em. We worked around this problem by using longer bolts (same grade of steel) with Nyloc's and Loctite to hold the whole thing together. We check these every time we pop (3 hrs of blood, sweat and tears) out the gearbox and have never had any loose.
Rear Axles & Flanges
There is no difference between the axles on a Skyline and those on a 1600. This is a pity, as we have sheared the odd axle and wanted to replace them with a somewhat bigger item. The bearings and bearing carriers on later model cars are significantly larger than those on a 1600, however using these would require replacement of the rear swing arm assemblies (which actually fit, but don't have the same spring arrangement).
The flanges to pick up the CV's are quite different from the original 1600 half-shaft flanges. They do, however, bolt directly onto the original axles without any modification what-so-ever. You may wish to move the dust seals around on the CV flanges, as they don't align with the 1600 swing arm carriers. It's close, but for some of you, not close enough.
