Yer and they use a wrench size 17mm. The originals use 14mm. That will cause the socket to bind on the bellhousing giving you incorrect torque readings.

I used genuine nissan. They were 3x 60mm and 1 was 65mm. The 65mm bolt goes nest to the exhaust. That thread is sunken 5mm in the block which makes the 60mm too short.

Edited June 17, 20159 yr by EuroDat

Torque wrench?

Transmission bolt torque value= tight!

Torque wrench?

Transmission bolt torque value= tight!

You're right Steve. I should have said spanner or socket rachet. He can try the 17mm head. He will know soon enough when he has to fight it to get the spanner or socket off the bolt head. 17mm is a big increase compared to the original 14mm.

What I was thinking is he could get them started with not problems because the bolt thread tolerance would allow enough movement for the socket to clear the bell housing. When it starts to torque up the bolt will centre itself and jam the socket against the bell housing.

Yes, I've been there.....

I was actually trying to be funny about worrying about using a torque wrench on the trans in a pinch.. Tight will get you there. Not saying you shouldn't use one if you can.

Sorry to burst your bubble(s) but those 10.9 grade bolts with a 17mm head have more than enough space to get a standard socket on them without any issues. I did a dry run on 4 and 5 spds (a/b versions) along with a BW 5spd

Given that the tranny will be mated to the engine before it goes in I'm not sure what problem I was supposedly going to have.

He was just pointing out a potential problem.  Probably depends on if you use a thick wall or thin wall socket.  Fairly easy concept to understand though, the socket won't fit in the bolt head well if it's too big.  Apparently your isn't.

Standard sized socket works fine. Glad it was mentioned so I could verify everything before assembly this weekend. Will post some pics next week.

I recall something about different specs for metric bolts.  I usually purchase ss bolts from a local marine shop and the head is usually 1mm or 2mm bigger than on typical datsun bolts with the same diameter and thread. i.e. I would have to use a 13mm socket instead of a 12mm socket.

 

Beware the Fat Heads!!! 

My notes indicate for the proper head size the bolts should be 'JIS for proper head size', the DIN spec has larger head size. 

 

I also have run into this problem when finding bolts for the hold down hooks on the rear of my Z, larger than the originals, same thread size & pitch, just a bigger head, hard to get a wrench in there.

 

Bonzi Lon

My notes indicate for the proper head size the bolts should be 'JIS for proper head size', the DIN spec has larger head size. 

 

I also have run into this problem when finding bolts for the hold down hooks on the rear of my Z, larger than the originals, same thread size & pitch, just a bigger head, hard to get a wrench in there.

 

Bonzi Lon

So you kept the hold down hooks on your's too?  I have removed mine after I read their original purpose was for shipping, not towing.  But since learning that I see a lot of restored cars still have them.  Originality I suppose, but I read the dealerships just didn't take them off.  I guess that's why the dealer prep fee was only $75.   

The difference in bolt head size is due to the two standards used.

DIN931:

M8x1.25mm = 13mm (min: 12.73mm)

M10x1.5mm = 17mm (min: 16.67mm)

M12 = 19mm

M14 = 22mm

M16 = 24mm

JIS B-1189:

M8x1.25mm = 12mm (min: 11.75mm)

M10x1.5mm = 14mm (min: 13.75mm)

M12 = 17mm

M14 = 19mm

M16 = 22mm

Originality I suppose, but I read the dealerships just didn't take them off.  I guess that's why the dealer prep fee was only $75.

Let me think about this a little. If you paid them more dealer prep charges they would take parts of your car. Just doesn't sound right.