Diff bolt thread size

Technical advice Q&A

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Simonjrwinter
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Joined: Tue Nov 26, 2019 5:42 pm
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#1 Diff bolt thread size

Post by Simonjrwinter » Sun Dec 01, 2019 5:37 pm

Could someone tell me the thread size of the four bolt that go into the top of the diff please? I want to order a tap to clean out the threads of a diff that’s been standing for a while.
Thanks

Simon

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Robbiee
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#2 Re: Diff bolt thread size

Post by Robbiee » Mon Dec 02, 2019 2:08 pm

Hi
They’re large and coarse!
Not sure of the thread/type
I didn’t tap mine but used a small wire brush on a drill which got any muck/rust out
Robbie
Robbie 1962 3.8 Coupe OSG 1962 OTS ODG

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mgcjag
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#3 Re: Diff bolt thread size

Post by mgcjag » Mon Dec 02, 2019 3:14 pm

Get yourself a thread guage...quite cheap and will come in really handy....Steve
Steve
1969 S2 2+2 & Building a C type replica

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neal herridge
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#4 Re: Diff bolt thread size

Post by neal herridge » Mon Dec 02, 2019 5:49 pm

They are UNC will check tomorrow but they are ether 1/2" or 7/16" UNC.
Neal.

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PeterCrespin
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#5 Re: Diff bolt thread size

Post by PeterCrespin » Mon Dec 02, 2019 11:02 pm

A new, bolt would be cheaper than a 1/2" 13 tpi tap, IMO. Cut some slightly helical slots in an old bolt (try to mimic the flutes and cutting edges of a tap) and use the slotted bolt as a thread chaser. Not only cheaper but kinder, with little/no chance of removing material beyond the original threads - unlike a brand new sharp tap.

Sometimes, less is more.
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas

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Series1 Stu
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#6 Re: Diff bolt thread size

Post by Series1 Stu » Mon Dec 02, 2019 11:19 pm

:yeahthat:

Add a little grease to pick up the debris and the job's done!

Works well in spark plug holes too.

Regards
Stuart

If you can't make it work, make it complicated!

'62 FHC - Work In (slow) Progress
'69 Daimler 420 Sovereign
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