79 Datsun 280 z 5 spd torque rating

[cr83]

Does anyone know what these transmissions are rated for? Don't want to push it too far

[datsunaholic]

Nissan trusted the 71B 5-speed in a 280ZX, but not a 280ZX turbo.  So the answer is probably in between as far as torque.   While that's probably conservative, the gearboxes are all well over 30 years old now and some almost 40.

[datzenmike]

Does anyone know what these transmissions are rated for? Don't want to push it too far

 

The '79 280zx was rated at about 145 ft lbs of torque.

 

The '80 FS5W71B transmissions received many changes and up-grades. Presumably they may have been strengthened also?

 

Half way through the '81 model year production (December '80 and on build dates) a turbo was offered but Nissan feared the 71B might not be reliable enough so it only came with an automatic. The turbo option produced about 200 ft lbs of torque. One year later half way through the '82 model year (Jan. '82) a Borg WarnerT-5 was offered through to the end of the zx in '83. The 71B was retired for Z car use but continued in the Maxima, S12 and the 720 through '86.5.

 

Nissan first used the new and much improved FS5W71C for the '84 300zx non turbo rated at about 175 ft lbs. It's successfully been used to replace the BW T-5 in turbo cars rated at 227 ft lbs torque and more... when they blow up. It's been used in KA24ET engines of over 400 HP. The 71B is extremely strong with improved bearings and wider gears for strength.

 

 

So somewhere between 150 and 175 ft lbs for a 71B should be safe I would think. What kills these beautiful transmissions is lack of maintenance. Oil should be changed every 30K miles but is ignored or only topped up. Fix the tailshaft seal when it starts to drip. They are only $4. Abuse is next, by driving with a dragging clutch or air in the clutch hydraulic system. Fifth gear is an over drive intended for dropping light throttle cruise speed RPMs on the highway. It's not for climbing hills or passing at full throttle. For that down shift. The 71B was the same transmission used in the 620 truck, the 810 and the 280z so if it can handle a six cylinder it will handle a 4.