7/16ths head gearbox bolts
Turbo Mini Forums

Ive had a quick search, and im not near the car or haynes manual for a few days, so can anyone help..

What are the threads of the 7/16th head bolts that go into the alumium gearbox casing?

Im needing to get a helicoil kit

Thanking you greatly

Over and Out

1/4 UNF is the standard block to box thread - but standard A+ bolts are a 3/8 head are they not?

Go into the casing from where Nic? To hold what?
The block to box bolts thread into the block so I guess you mean some other bolts?

The ones that tend to strip are the 5/16 UNC bolts into the gearbox casing.

I think that this is what Nic is talking about.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I feel that Dave is spot on...I both sense and feel it.

If you mean bolts into the alumium box (rather than connecting bolts to the block) the later A+ used weird sized bolt heads, all of which were 1/16" down on what they should have been. So the 7/16" AF head on these weird bolts were for a 5/16" UNC threaded bolt. On a proper box, the 5/16" UNC bolts would have had a 1/2" AF head, and would have been studs/nuts, not bolts, in some places.
In fact I'm not even sure if the heads on these weird ones is 7/16" AF as I always find a 10mm socket seems to fit better !!!
Which ones are they? Diff output shaft flanges at a guess ???

Rod.

Schrödinger's cat - so which one am I ???

do we win anything for a right answer?

speedo drive?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

do we win anything for a right answer?

speedo drive?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

the diff side plates and speedo drive housing bolts. (the ones that actually bolt into the gearbox casing)

You may win a prize, but you dont win anything for a double post!!!nana na na naaa

You need that many helicoils ????

That's 18 bolts if you include the 3 long ones through the speedo drive housing (which would have been studs/nuts on an earlier box).

I think the ones from the transfer housing into the end of the gearbox were also these strange bolts on later boxes, rather than studs/nuts.

Schrödinger's cat - so which one am I ???

I claim first prize.

They are 5/16 UNC.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

That's a lot of helicoils! You're going to be busy :)

Cheers Paul

Ill be buggered if i do them all, ive just got a few that are a bit 'loose'

I'll claim second then !!!

Seriously, one thing I noticed on the two boxes I took apart with these strange small headed bolts, was the ones through the diff side plates were all the same length.
On the earlier boxes with standard 5/16" UNC bolts (1/2" AF head) the ones that went through the exhaust support bracket were about 3-4mm longer (to account for the thickness of the bracket) which is why I guessed it might be those you needed to helicoil.
I've always replaced thes strange small headed ones with standard ones.

Schrödinger's cat - so which one am I ???

Yep, its those 2 and one of the ones that the gearbox steady goes in to

I was thinking as I took it all apart last night and something occured to me:

Does the F in UNF stand for Fine, and the C mean Course thread pitch

yes.

and S stands for special,

and EF , extra fine

Ahhhhh, well you learn something new everyday

If i knew that it would have saved me having to ask a question

What about JNC and the like?

JNC??

Just Nearly Coarse!

i might be confused, isnt that the american stuff?

JIC?

Yes, durr

Or ANC (along with ANF) - American National Coarse/Fine.

Was their sort of equivilant of our BSW (Whitworth) and BSF (British Standard Fine) but when the two countries (and others) got together many years ago to come up with the UNIFIED series (UNC, UNF, UNS) then the Americans dropped their own AN series a bit quicker than we dropped the BS series.

And of course it's all metric (ISO) nowadays apart from America who are only half way there.

Schrödinger's cat - so which one am I ???

Ah ha, this thread has developed into something quite useful

I now have an understanding of these threads that i never used to understand, and now realise that theyre not that complicated at all