Problems with Datsun 240z Locks

The biggest problem with these locks is wear and tear. You can not rekey the locks and ignition tumblers with the same pin numbers. The tumbler housing for the pins is made out of pot metal, over a period of decades they wear differently. The door and ignition are used daily, but the glove box and rear hatch are rarely used. The pins and keys also have wear. Measuring the key cut depth is an approximate. When you rekey the locks, you must test them all. Start with the existing pins or measure the key cut depths, replace with new pins and springs, dont forget to use lube, then test the key and lock. You can eyeball the pins in the tumblers, they should be as flush to the tumbler as possible, but not extending past the tumbler housing. As you insert the key into the tumbler, you will see the pins rise and fall. It takes a little effort to match the pins with the worn tumbler. If you have a new key, key everything to it. The old key may be difficult to use because it may be too worn down. Starting with a new cut key is highly recommended, print the key depth chart and take it to your locksmith.

The rear hatch locks require inspection before rekeying. The problem lies in the materials used for the tumblers again, cheap pot metal. I have seen tumblers shattered into pieces by the slamming of the rear hatch over time. NEVER SLAM YOUR REAR HATCH SHUT! Let it down gently, push hatch down it should lock. If not raise hatch up about 4-6 inches and let it drop. New seals may keep the hatch from being flush, silicone them to reduce friction. I really try not to open these locks to rekey them, its very disappointing to open it and the tumbler crumble on you, making your lock worthless! Before you do this, insert the key into the lock. Does it go in smooth or do you have to jiggle it to go in? Rough..add some lube to key and lock and try again. If it works smoothly great, if not your tumbler is probably into pieces. This is not full proof, the tumbler is in the housing so its really tough to tell. If the thing cracked decades ago and the key has been inserted quite a bit the tumbler will probably be destroyed! If the lock is rarely used, the tumbler may be cracked but not worn slap out and destroyed by forcing the key in the lock. My advice is don’t take this lock apart! If the lock works with a good key, then rekey everything to this key. If you do take it apart and it is cracked you may be able to glue it back, use minimal glue. To much glue will interfere with clearances for the key, pins, tumbler and tumbler housing. If the pieces where the pins go in is crushed good luck! Send it to me and I will see if I can fix it.

What is the difference between a “Master Key” and a “Submaster Key” for Datsun 240z 260z 280z

The master key fits everything, door locks, ignition, glove box lock, and rear hatch lock.
Master keys have the code series (# on Key) M6001-7000 and M7001-8000.

The submaster key fits the Doors and the Ignition, not the glove box or rear hatch. This is also known as a “valet” key. Submaster keys have the code series (# on Key) M4001-5000 and M5001-6000.

For more information go to Datsun 240z 260z 280z Key and Lock Reference Materials