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Bolts for a diff guard - the definitive answer?


darthdicky

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I've got a QT diff guard which I'd like to fit again, but have lost the bolt that fits underneath the diff nose. It seems these are a strange thread which changed partway through production and as such, I've got no idea what I need.

I've ended up with 2 lots of bolts that all seem the same, the latest ones with part number SH406062. These don't fit my diff which I think is quite an early one, they're too big.

Can anyone confirm what the part number or size and thread I need for an early diff, and where I can get them at reasonable cost?

Thanks,

Richard

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I helicoiled mine to M10, seems easier than messing about with obscure threads

There's a reason the designers used a fine thread. Fine bolts have higher tension and shear strength and are less likely to loosen. I find it bizzare advice to weaken the design rather than just find the right bolt.

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This must be a hangover from the Series days.

Engines were UNC & UNF threads, while axles and transmissions were BSF & Whitworth IIRC,

BSF is pretty obscure nowadays over here, although I daresay the good ol' US of A may still be using them.

I was quite surprised to see them in Paul's link above.

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There must be plenty Discovery 1 steering damper brackets still on diffs languishing on salvage yard floors / spares bits boxes.

For the job in question, helicoil or correct bolt wont make a scrap of difference really

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This must be a hangover from the Series days.

Engines were UNC & UNF threads, while axles and transmissions were BSF & Whitworth IIRC,

BSF is pretty obscure nowadays over here, although I daresay the good ol' US of A may still be using them.

I was quite surprised to see them in Paul's link above.

Series one's had Whitwoth threads IIRC.certainly the prop bolts were Whit because the heads of the bolts were held in place by the shoulder of the diff flange. I don't remember when they went to BSF, remember the BSF bolts had the smaller heads.

As for the US of A. They were using SAE threads on the lend lease stuff of WW2. That's one of the reasons I had to buy AF spanners.

The 1930's Morris cars had Morris made Hotchiss engines fitted which had metric threads BUT with Whitworth size nuts and bolt heads.

I still have some BSF brake unions

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And early Morris Minor's (the Issigonis version) had BSF/BSW on the chassis/body, and due to buying a load of french machinery, a mixture of UNC,UNF and yes, even metric on the engine, but not every one of them :hysterical:

And you lot think Land Rover is bad?

BTW, I seem to remember that the Defender/RRC/Disco propshaft bolts remained Whitworth, this is why a 14mm spanner is a really tight fit on them(should be 9/16").

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  • 4 weeks later...

Cheers for the thoughts all, as I've got a collection of what should be the right bolts I'm starting to wonder whether the rear axle on there is an mid-80's Range Rover one, if they were any different?

One thing I haven't tried is swapping a bolt from the front guard to the back, I might give that a go this weekend as that'll show whether it's different to a Defender/Disco one. I'm sure the right sized bolts will be cheaper than a Helicoil, I just need to figure out what the right sized bolt is!

Richard

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I picked up front and rear diff guards second hand on Tuesday, the front will replace the NVH damper and use those bolts but I will check them in the back when they are out.

This thread clears the water by muddying it up further lol

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