Driveshafts

[alfadave]

Just about to fit the driveshafts to my sud,reminded me that years ago,I had a left driveshaft come undone at the inner end.....luckily at low speed.

Some cars have the left side hubs/driveshafts with a left hand thread,so the rotation tends to keep them tight.
But Alfa didn't do this....my Haynes manual mentions locktite being used instead.

I wondered if anyone...maybe racers... has used longer cap screws on the inner end,with locknuts behind to stop this happening?

Thanks
Dave

[rsfruitbat]

I dont think there is enough space behind to fit a nut.

rsfruitbat

[alfadave]

Forgot to say.....i have coverted mine to outboard type brakes.

[adsblacksud]

I had this happen to me on a track day Dave, luckily on the entry to the pit-lane.
Since then I thoroughly clean/degrease the bolts and the threads in the gearbox flange and use stud lock on the bolts.
It's a bit of a challenge to get the bolts out again but it's worth grubbing around on the garage floor for the sake of security when you are out on the road.

I also thought of putting self locking k-nuts behind the flange as you suggest as they are compact compared to ordinary nuts I can't remember if it worked or not but I have some spares so can have a look this weekend - I also use k-nuts on my exhaust manifold by the way as they use a 10mm rather than 13mm socket so give useful extra clearance in that fiddly area.
Thanks

Adam

[Fluffyduff]

I had a new set of bolts made up with small holes drilled in the head to allow me to wirelock them into place. I lost a sud driveshaft at speed destroying a gearbox and brake calliper in the process as the disc made a break for freedom.

[alfadave]

The existing bolts are M8x 50 x 1mm pitch thread when I had them checked at my local engineers supplier.
I cant see k nuts this size on line after a quick check......but nylocs are available.

The only bolts I could get were 65mm long with hex heads....the hex heads do seem to fit ok..and the 13mm/half inch drive socket will just fit.

Dave

[dave.armstrong]

They must be high tensile or something like.

When I broke one of mine it looked like it was case hardened

[adsblacksud]

K- nuts are available in m8 x 1.0 e.g.
http://k-nuts.com/index.php/products/me ... hexagonal/
but I haven't checked if there is clearance yet.
The driveshaft bolts are 12.9 grade, which a higher tensile grade than most of the other bolts used in the drivetrain which are 8.8 grade - the grade is normally stamped into the head of the fastener.
http://www.engineeringtoolbox.com/steel ... _1428.html

Thanks,

Adam

[adsblacksud]

Well I've just checked and there is less than 3mm clearance so neither a k- nut or plain half nut will fit on the driveshaft bolt end without fouling between the inside face of the output flange and the bolt heads on the gearbox casing.
This is on a gearbox with outboard brakes. It's probably why I ended up using stud lock, I wish my memory was a little better..

Thanks

Adam

[rsfruitbat]

with 3 mm of clearance is that just enough to have longer bolts, 1mm hole at the end and wirelock them?

Would be a fiddle but if you are really concerned....


For me with the rally car i use the 12:9 bolts and it is just a stanadard check item every event. I made up a T bar so if you have got some "holy" alloys you dont nee to jack the car up or anything. Put the T bar through the wheel, check the top 3, role the car forward and check the 3 that were on the bottom which are now on the top. Job done

rsfruitbat

[PETROLHEAD]

If the threads are all clean, then loctite and appropriate tightening should be sufficient.

A tensile strength of 12.9 is plenty up to the job. If anything most folks poor exerience of them is them coming lose rather than snapping, and that can be down ti the fact that they are cap head allen bolts. I never understood why alfa chose such a small headed allen bolt in an awkward and critical area that needs proper tightening, its asking for a rounding issue.

In my opinion the best method of safety if still using the allen bolts is to drill the heads for lockwiring to each other aswell as loctite, alternatively if you can find a suitable hex head bolt at least you can get some proper torque on it, but clear access becomes more difficult.


Never be tempted to use a high finish material such as stainless. Not wanting to teach granny to suck eggs but for those that don't know stainless steels are mostly far far from the tensile strength required that is required unless spending a small fortune on specialised recipe stainless.

So many folk have rebuilt split rim wheels with good looking studs that whilst look pretty, come in at about a 3rd of the strength they need to be!

[alfadave]

K nuts are certainly pricey at a fiver each.
My final solution is cap screws 8x60x 1.0mm 12.9 grade, with nyloc nuts on the back.
Plenty of clearance on mine.
Not perfect engineering,but some guarantee of the driveshaft staying on for less than a tenner all in.
Dave