Gearbox mainshaft nut left hand thread

[PeterH]

Can any one tell me when the left hand thread on the mainshaft nut was introduced?

 

Pete

[C.A.R.]

All 71C boxs run the LH mainshaft thread.

But I'd have to check with the Guru if any late 71B's were LH threaded.

[PeterH]

Thanks Lurch..... I thought you'd be the best person to answer that..my situation is this .... the car I bought is an auto... the seller supplied a manual box reported  to be out of a 2+2 260Z ( I had no reason to doubt that ) .... I also have another box I believe to be out of an early 280ZX

I dismantled the 260 box today and did a tooth count.....2.906 1st gear etc and a blue speedo drive pinion. the other box ( counting the input and out put rotations ) appears to have a 3.21 1st , 2.077 2nd etc and wondering if it might have the left hand nut.

the 260 box has been apart....red silicon and the mainshft nut restaked in a  different place.

Is the left hand nut a big issue on a road use car if the nut is tightened and staked correctly.....

for what it matters the baulk rings are not brass

 

the car by the way is under restoration.....and not registered

 

Thanks for the reply Pete

[dat2kman]

Yes, seen plenty of 71B type, with LH thread, and some short ext housing ( "Stumpy") ones.

Some ealy boxes used a single plain nut with a thickish tab ring, that you hammered over onto a flat, others used two thin nuts that were tightened ( these come undone too easily)

Worst of all is the ham-fisted repairer, who just welds the nut onto the mainshaft,,,,,,,,,,

[PeterH]

Ive only ever seen the " tack weld " tab washer a few times...... but it makes a lot of work for the next person,...UGH!!!!!

[C.A.R.]

Neither type of mainshaft is an issue if it's been staked correctly - I'd add a dab of thread locker just to make sure.

 

If your are not intending to use the 260Z box Peter, do you want to sell it?

 

[PeterH]

Thanks Lurch ...that's the box I'll be using......now that I've had alook inside and the gard parts look good... the ratios will suit better than the later box....my first 240z was an early 1973 bought new....do you knowif it would be the same ratios as the 260Z box?

[PeterH]

should have spell checked......"had a look inside and the hard parts look good"

and I'm only sixty five and a half....

[C.A.R.]

As far as I know Peter, yes the ratios will be the same as the 260Z box - maybe Jason can confirm?

 

P.S. The 'Modify' button is your friend

[dat2kman]

Always an dea to pull bellhousing ff and do a toothcount, as, due to time, and various mechanical work, bellhousings can and do get swapped!

Yes, go with the 2.9 first gear gearset, much sweeter!

[PeterH]

Thanks for your help all.... it looks like the mainshaft nut is no longer available...is that correct??

[dat2kman]

Stew Wilkins or Lou Mondello have plenty of new ones.

If enquiring at a Nissan dealer, only quote the part number, never what its from, as most dealer spares will automatically tell you, "sorry, tyat is an old car, nothing available,,,"

[PeterH]

Thanks....I rang the local dealer with the part number this morning and Nissan's system was down...they didn't get back to me yet ,  although they have been very good in the past.....it wouldn't take much to machine a couple up.

[ScottyB]

Sorry to bring up an old thread.

My 240 apparently has an early 280ZX 5 speed in it. Fifth gear pops out regularly and I have to hold reverse inmanually.

 

Strong chance that is just the nut has come a little loose?

[C.A.R.]

No. Late 71B (280ZX & Bluebird) run a LH thread main-shaft nut - they don't come loose.

The jumping out of 5th/Rev indicates that the coupling sleeve or the dog ring is badly worn.

Time for a rebuild

[ScottyB]

Thanks Lurch.