Differential drain plug size

Differential drain plug size

Author
Discussion

Adambul

Original Poster:

99 posts

85 months

Tuesday 2nd March
quotequote all
Hi all,

Just changing my diff oil and the drain plug appears to be very tight and an unusual size. Any idea what size so I dont end up rounding it off. Its smaller than 13mm but bigger than 12mm and a standard 1/2" socket still feels too big. Any ideas so I can get the exact size socket to avoid damageing what appears to be avery tight nut!?


TwinKam

1,762 posts

59 months

Tuesday 2nd March
quotequote all
On my late '98 with a BTR diff, the drain plug has a 17mm hex... the thread is metric, M12
That doesn't help you, but it really doesn't matter what size it's meant to be, just use a six sided socket that's the best fit. I suspect yours is 13mm.

Fast by Fred

4,731 posts

194 months

Tuesday 2nd March
quotequote all
Here's My Diff Story
(2001 4.5 HW)
HTH
thumbup

Adambul

Original Poster:

99 posts

85 months

Tuesday 2nd March
quotequote all
Fast by Fred said:
Here's My Diff Story
(2001 4.5 HW)
HTH
thumbup
Wow, no wonder im having trouble. The fill nut came off very easy for me the drain plug however is a different matter. I don’t have access to a welder so will have to get creative. Mine is smaller than 13mm but larger than 12mm so very odd size!

WIL35

481 posts

174 months

Wednesday 3rd March
quotequote all
Adambul said:
Mine is smaller than 13mm but larger than 12mm so very odd size!
1/2 an inch is 12.7mm. Have you tried an imperial socket/spanner?

Rufus Roughcut

512 posts

139 months

Wednesday 3rd March
quotequote all
I had no luck in removing mine with socket or spanner and even a touch of heat, it was too far gone.

2 mins with the Stilsons and it was out, replaced with a new screw, from memory the thread is common, can't remember if it was metric or imperial though.

TwinKam

1,762 posts

59 months

Wednesday 3rd March
quotequote all
Mine is M12 (std 1.75 pitch) x 25mm. As previously stated, with a 17mm flanged hex head.
Which is odd as the 8 rear cover bolts are 5/16" UNC! ...no guarantee that all are the same, possibility it's been rethreaded/helicoiled.

Edit: ...been thinking, this drain plug thread should surely have been 7/16" UNC originally, anyone else care to check theirs? All the other threads on the diff are imperial...
The pitches are too close to call ; 7/16" UNC is 14tpi which equates to 1.81 mm, M12 (coarse) is 1.75 mm.
Dia. of M12 bolt is 11.8 mm whereas dia. of 7/16" bolt is 11.1 mm.
My plug's thread measures 11.7 mm. and a new M12 bolt is a lovely fit, so I am 100% sure mine is M12.
I don't have a 7/16" UNC bolt to try, but I would expect it to be very loose.

Edited by TwinKam on Wednesday 3rd March 16:39

Adambul

Original Poster:

99 posts

85 months

Wednesday 3rd March
quotequote all
I think mine is 1/2" as suggested above but it is so tight and with a star socket is in danger of being rounded off with my efforts! I've just ordered another flat faced socket and if that doesn't work it will be exhaust off and stilsons out!

Fast by Fred

4,731 posts

194 months

Thursday 4th March
quotequote all
TwinKam said:
Mine is M12 (std 1.75 pitch) x 25mm. As previously stated, with a 17mm flanged hex head.
Which is odd as the 8 rear cover bolts are 5/16" UNC! ...no guarantee that all are the same, possibility it's been rethreaded/helicoiled.

Edit: ...been thinking, this drain plug thread should surely have been 7/16" UNC originally, anyone else care to check theirs? All the other threads on the diff are imperial...
The pitches are too close to call ; 7/16" UNC is 14tpi which equates to 1.81 mm, M12 (coarse) is 1.75 mm.
Dia. of M12 bolt is 11.8 mm whereas dia. of 7/16" bolt is 11.1 mm.
My plug's thread measures 11.7 mm. and a new M12 bolt is a lovely fit, so I am 100% sure mine is M12.
I don't have a 7/16" UNC bolt to try, but I would expect it to be very loose.

Edited by TwinKam on Wednesday 3rd March 16:39
Holy Dingbats Rik, You should write a book on your thread knowledge and experiences thumbuplaugh

TwinKam

1,762 posts

59 months

Thursday 4th March
quotequote all
No need Paul, it's all there in the Holy Bible already wink






PS What's with the new moniker?

Rufus Roughcut

512 posts

139 months

Friday 5th March
quotequote all
I've found the screw I removed 12 years ago, jeez I keep some junk. 12mm x1.75 19mm nut.

Rufus Roughcut

512 posts

139 months

Friday 5th March
quotequote all
Forgot to add, I have no idea what the original size of the nut is, from the photo you can see it's all chewed up.

sixor8

3,851 posts

232 months

Friday 5th March
quotequote all
3/4" AF is 19.05mm. It's one of the few sizes that an imperial or metric socket will fit. smile

Another one is 1 1/16" = 26.99mm.

I've doing a bit of this conversion recently to get a socket to fit the pinion nut on my Triumph Toledo. I have had to order a 1 1/8" AF socket. I have slightly too small and slightly too big in my toolbox, of course I have ....... frown

Rufus Roughcut

512 posts

139 months

Friday 5th March
quotequote all
sixor8 said:
3/4" AF is 19.05mm. It's one of the few sizes that an imperial or metric socket will fit. smile

Another one is 1 1/16" = 26.99mm.

I've doing a bit of this conversion recently to get a socket to fit the pinion nut on my Triumph Toledo. I have had to order a 1 1/8" AF socket. I have slightly too small and slightly too big in my toolbox, of course I have ....... frown
Good info thumbup

The 19mm nut is just for info (Proof it is a metric thread) thumbup

Rufus Roughcut

512 posts

139 months

Friday 5th March
quotequote all



14 teeth in old money and 1.75 in new.

Fast by Fred

4,731 posts

194 months

Friday 5th March
quotequote all
TwinKam said:
No need Paul, it's all there in the Holy Bible already wink






PS What's with the new moniker?
Thanks to your earlier advice, I have equiped myself with one.
Just need to acquire an electron microscope to read the damn thing laugh

Name changed due to the relentless grief I was getting about
"What an arrogant asshole you are for thinking you are Mr. Cerbera"

'Fast by Fred' was a company that I wanted to start with My Old Man frown

sixor8

3,851 posts

232 months

Friday 5th March
quotequote all
Fast by Fred said:
TwinKam said:
No need Paul, it's all there in the Holy Bible already wink






PS What's with the new moniker?
Thanks to your earlier advice, I have equiped myself with one.
Just need to acquire an electron microscope to read the damn thing laugh

Name changed due to the relentless grief I was getting about
"What an arrogant asshole you are for thinking you are Mr. Cerbera"

'Fast by Fred' was a company that I wanted to start with My Old Man frown
Blimey that's a flashback. We had a copy each of Zeus in our top overall pocket during my apprenticeship in 1983! Now, you download it as a pdf and print off your own..... frown


TwinKam

1,762 posts

59 months

Friday 5th March
quotequote all
Download? pdf? Wash your mouth out!
Can't beat the little book IMHO... it's laminated for starters... smokin

TwinKam

1,762 posts

59 months

Friday 5th March
quotequote all
@RR
Thanks, same as mine then.
But what a mix-up, when the other threads at that end are UNC, and at the front they're M12

TwinKam

1,762 posts

59 months

Friday 5th March
quotequote all
TwinKam said:
What's with the new moniker?
Fast by Fred said:
Name changed due to the relentless grief I was getting about
"What an arrogant asshole you are for thinking you are Mr. Cerbera"

'Fast by Fred' was a company that I wanted to start with My Old Man frown
What arrogant asshole told you that? Tcensoredt!
You'll always be Mr. Cerbera to me, Paul biglaugh