Lotus Elan

Diff plug torque

PostPost by: mariodschy » Thu Mar 26, 2015 12:32 pm

I've rebuildt the diff, only have to fill it with oil but can't find the right indicate tourque for:

- Level Plug
- Drain Plug
- Breather/Ventilation Plug

Searched the lotus manuall and brian buckland book, nothing to find for these 3 plugs.
- 1972 Lotus Elan Sprint LHD/DHC
- 1962 Austin Healey Sprite MK II - Sold 09.05.2016

Sorry for my bad survival English ;-)
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PostPost by: billwill » Thu Mar 26, 2015 1:49 pm

That's because basically you do them up until you think they are tight enough :D


Seriously, if they have fibre washer just do them up until you feel the fibre compress a bit then add a quarter to half a turn.


That's all I do anyway and I've not had one come out of its own accord.
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PostPost by: elanner » Fri Mar 27, 2015 1:30 am

The biggest risk with the plugs is that various dopes over the years don't have the correct BSP/Whitworth spanners so make do with poorly fitting Metric/SAE/adjustable spanners. Eventually the corners wear off so that you either can't tighten them enough, or can't get them out. :x

Been there.

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PostPost by: billwill » Fri Mar 27, 2015 11:49 am

I'm pretty sure that the actual plugs are standard plumbing parts and can be bought for a few quid at a local plumbers shop such as B&Q.
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PostPost by: elanner » Fri Mar 27, 2015 1:35 pm

Bill,

Thanks. That's good to know. I'll get fill/drain plugs the next time I'm in Blighty. They ain't so easy over here (although I recently got one from Ray)....

Or kinda pricey:
http://magneticdrainplugs.co/purchasebythreadsize.php

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PostPost by: prezoom » Fri Mar 27, 2015 4:20 pm

Have always hated those knuckle bashing square headed plugs that are not exactly square. Now, the first time they are removed, I chuck up the plug in the lathe and turn the squared portion to round. Then I TIG weld an appropriate sized nut to the plug. Then the corresponding sized socket or wrench can be used. No more left handed adjustable wrenches needed. If the next owner is offended, he can replace them with a new original style plug and a new box of bandages for his knuckles.
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PostPost by: mariodschy » Wed Apr 01, 2015 11:47 am

billwill wrote:That's because basically you do them up until you think they are tight enough :D


Seriously, if they have fibre washer just do them up until you feel the fibre compress a bit then add a quarter to half a turn.


That's all I do anyway and I've not had one come out of its own accord.



Thanks for your advice, i've done it by "feeling"
- 1972 Lotus Elan Sprint LHD/DHC
- 1962 Austin Healey Sprite MK II - Sold 09.05.2016

Sorry for my bad survival English ;-)
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PostPost by: Tahoe » Thu Apr 02, 2015 2:42 am

I didn't think they were Witworth, are they? I had no issues witha spanner. I didn't have a drain so last year I pulled the difference took it apart and added a drain plug. I used a fiber washer but it was too hard. I had some leakage so drained the fluid to check for any issues after a year and replaced it with a soft copper washer and have no leaks.
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PostPost by: elanner » Sat Apr 04, 2015 3:42 pm

Hmm, strange, I'm pretty sure they're 1/4" W - but only as a result of personal observation. I don't have any documentation.

I have two diffs on the go right now. A 3.77 in the car with an original plug that seems best suited to a 1/4 W. And a rebuilt 3.54 waiting to go in this Spring (I hope) that has a replacement plug. I have the original, nicely rounded plug for it and it appears to have been a 1/4" W. I guess brass is soft enough that using the wrong size is both easy and damaging.

The replacement is the correct thread but has a metric head (14mm). Presumably that's the most useful thing to produce these days because Whitworth wrenches are so uncommon.

The larger diff plugs, of course, are less prone to damage. Sticking with my Whitworth premise: ;-)
- Breather - 7/16" W
- Filler - 3/8" W

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