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The Datsun 1200 used a leaf-spring live axle with an H145 differential. This is a Hitachi design with 145mm ring gear (5.71 inch). It is a lightweight unit suitable to handle the torque from an A12 engine. Light weight is good, remember that heavy parts take more horsepower to accelerate. The complete assembly (housing, differential, etc) is know as the Rear Axle Assembly. Some Australian-assembled B110s used a Borg Warner Model 60 rear axle. All Datsun 1200 utes (trucks) used the stronger H165 rear axle assembly.
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Differential
The Differential is the part in the center of the rear axle assembly. Also known as the "Gear carrier assembly", "pumpkin", "center" or "diff head". It has two purposes: 1) reduce the speed ("rear gearing") and 2) equalize power distribution to left and right wheels even when turning corners (differential).
The gear reduction is accomplished by the Ring & Pinion gearset a.k.a. (Crown Ring and Pinion (CRP). The differential action is enabled by the spider gears.
See main articles: H145 and H165
Specifications
Also see: Rear Suspension Specifications
- 3.90:1 ratio - sedans and coupes
- 4.11:1 ratio - VB110 wagons with aluminum gear case
- 4.11:1 ratio - B120 Truck H165
- Ring gear diameter: 145mm (5.71 inch)
- Torque Rating: about 100 lb. ft.
- Axle assembly width: 1305 mm drum-to-drum
Weight
Maintenance
The stock Datsun 1200 differential is a reliable, long lasting part behind an A12 or A13 engine.
- As long as it doesn't run dry on gear lube it will usually last forever. So check it every few months for signs of leaking.
- The only common maintenance is to pack the rear wheel bearings every two years or so. This will also keep the bearings quiet and reduce gear lube leakage into the brake area.
Differential Lubricant
Since the differential is a typical hypoid-gear unit, you can use any lubricant designed for such:
- the traditional "90 weight" gear oil
- the newer 75W-140 or 85W-140 multi-weight gear oil
For maximum fuel economy, use a modern multi-weight gear oil. Otherwise use this chart to select a single-weight oil:
1972 Nissan Specification * API GL-4 * MIL-L-2105
Such as: * Chevron Multiservice Gear Lub. 75,80,90,140 * Esso Gear Oil GP 80,90,140 * Mobil Mobilube EP or GX 80-90,90,140 * Shell Spirax 75EP,80EP,90EP,140EP * Sunoco Multipurpose Gear Lub. GL-4 80,90,140 * Texaco Universal Gear Lub. EP 80,90,140
1972 USA Owners manual (Page 23)
Recommended Lubricants
GL-4 vs GL-5
The differential can use a GL-4 oil, same as the transmission lube.
GL-5 is now recommmended for the differential, but should not be used in the gearbox unless it is marked both GL-4 AND GL-5.
Nissan 1981 Specification * API GL-5
Borg Warner Model 60
Australian-assembled B110s used a Borg Warner Model 60 rear axle, starting in Late 1971.
See main article: Borg Warner Differential
Leaf Spring Mounting
Sedan, Coupe, Wagon and Ute (Truck) all have different mounting points. See Leaf Springs
Swapping
Datsun 1200 Coupe, sedan, van, and ute housing are all just slightly different.
discussion in main forum
Sedan axle housing has no welded-on leaf perches. The others do. Plus other small differences.
Best Ratio
1200 sedans and coupe come with 3.90 ratio. This is the best all-around ratio for the stock-diameter tires, balancing enough torque for take-off with highway speeds. Top speed is 90 mph with the 3.90 ratio.
The Datsun 1200 truck comes with a 4.11 ratio for extra torque taking off and pulling loads up hills. This is excellent for acceleration, but some feel it is too low for highway driving. Rest assured, the A12 engine can run at 110 kph all day long even with the 4.11 gears.
Or you can change the gears. Read this discussion: starting at Post 11.
The Ute uses the H165 gears. See H165 for more information about ratios and donor cars.
Differential Repair
Replacing diff bearings or spider gears? Or ring & pinion? The procedure for re-assembly the differential gear carrier is very complicated. Be sure to get the factory service manual.
We recommend: Just swap the whole center section "pumpkin" from a 1971-1973 B110 or 1974 B210 in there. It will be cheaper and certainly easier, someone has one for free. The center section rarely goes bad unless the diff runs low on oil, so your chances of getting a good used one are high.
Yes, B110 and 1974 B210 center section is identical. You could also swap a 1975-1978 pumpkin they say you need a 2mm spacer between the pumpkin and the housing.
Bumpers
Coupe & Van rear suspension bumper (above the Leaf Spring) 55240-H1400 ASSY-BUMPER REAR AXLE 08911-64010 NUT-HEX M10X1.25 08915-14010 WASHER-SPRING LOCK
Sedan rear suspension bumper (on the Shocks) 55240-H1001 BOUND BUMPER A 56124-H1001 BOUND-BUMPER B
Pinion Snubber
The pinion snubber is a rubber bumper that prevents the differential from rotating too much under torque input.
Axles
Datsun 1200 -- both car H145 and truck H165 -- uses 23-spline axles. The truck axles are a larger diameter and so they do not interchange.
See main article: Axle Shaft
Part Numbers
See the various related articles such as:
- Axle Shaft
- Differential
- Leaf Springs
- Rear Suspension
- Rear Axle And Rear Suspension
Limited Slip
Datsun 1200 was not offered with a limited-slip differential, however Datsun Competition sold an LSD for the H145. This part is NLA, however it may be found occasionally in specialty shops or on eBay.
See main article: Limited Slip