Dan R Posted September 16, 2022 Share Posted September 16, 2022 Does anyone know the size/thread/spec for the Sierra diff fill plug? (Currently have a second diff with no plug at all)I want to get a magnetic one but have no idea what size it would be. I can see the 'Gold' magnetic plugs have codes so any help would be appreciated! Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted September 17, 2022 Member Share Posted September 17, 2022 "M20 x 1.5"Jonathan Link to comment Share on other sites More sharing options...
Area Representative Geoff Brown Posted September 17, 2022 Area Representative Share Posted September 17, 2022 M20x1.5 is indeed the size for the BMW diff but I would hazard that it would not be for the Sierra diff on a R500. Knowing the assortment of AF & Metric threads on cars of the R500 era the Sierra diff plug is likely not to be be metric. Link to comment Share on other sites More sharing options...
Dan R Posted September 17, 2022 Author Share Posted September 17, 2022 Thank you Jonathan! Link to comment Share on other sites More sharing options...
Dan R Posted September 17, 2022 Author Share Posted September 17, 2022 Thanks Geoff, .... how did i know this wasn't going to be straightforward!! Surely the standard Sierra diff casings all have the same fill plug? or am i being extremely naive ?? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted September 17, 2022 Member Share Posted September 17, 2022 If you're searching outside the Caterham world beware... there are several different Sierra diffs.That was the only reference that I could find in the archives. That surprised me as I thought that various threads had mentioned various threads.Please let us know what fits.Jonathan Link to comment Share on other sites More sharing options...
Wrightpayne Posted September 17, 2022 Share Posted September 17, 2022 My money is on it being metric!!The original OEM plug has a magnet in/on it. Seem to be available on line albeit £20ish :-0I'm fairly certain the K series Caterham dry sump pan uses the same plug.https://www.bearingkits.co.uk/FORD-SIERRA-DIFF-MAGNETIC-FILLER-PLUG/123.htm Link to comment Share on other sites More sharing options...
Englishmaninwales Posted September 17, 2022 Share Posted September 17, 2022 Correct, same as the later K series DS sump. Link to comment Share on other sites More sharing options...
Wrightpayne Posted September 17, 2022 Share Posted September 17, 2022 This thread (no pun intended) has some part numbers...looks like it was also used on the K series apollo tank!!https://www.caterhamlotus7.club/forum/techtalk/bits-n-pieces-apollo-tank-fitment Link to comment Share on other sites More sharing options...
Area Representative Geoff Brown Posted September 17, 2022 Area Representative Share Posted September 17, 2022 I do not mind being proved wrong but as an example my late 2012 Six Speed has a three eighth inch allen key recess in both fill & drain plugs. BUT the BMW diff has a metric fill plug both in thread & hex insert.All in a metric chassis......well 95% of it any way !! Link to comment Share on other sites More sharing options...
Dan R Posted September 17, 2022 Author Share Posted September 17, 2022 Having looked at the various links, it does seem like M20x1.5 is the favourite. Either a branded one or the Ford original Link to comment Share on other sites More sharing options...
ScottR400D Posted September 18, 2022 Share Posted September 18, 2022 #10 That's interesting Geoff. My 2015 6 speed has 1 x M10 and 1 x 3/8" hex plug! My BMW diff doesn't have a drain plug. Link to comment Share on other sites More sharing options...
Area Representative Geoff Brown Posted September 18, 2022 Area Representative Share Posted September 18, 2022 Three years makes all the difference between a 95% & 100% metric chassis ? Sorry Diff fill plug. (ammended) Link to comment Share on other sites More sharing options...
ScottR400D Posted September 18, 2022 Share Posted September 18, 2022 My chassis was hardly metric, Geoff, I'm not sure that exists. . It's hard to understand why they changed just one of the two plugs in the 6 speed too! Link to comment Share on other sites More sharing options...
rj Posted September 18, 2022 Share Posted September 18, 2022 It certainly is metric - just a bit unsure if it's M18 and not M20. Link to comment Share on other sites More sharing options...
7 wonders of the world Posted September 18, 2022 Share Posted September 18, 2022 Sierra final drives have all metric fastenters, CC merely machine off the re portion of the OE coverM20x1.5I use this one, much much easier access with a ring spanner https://www.ebay.co.uk/itm/312779345179 Link to comment Share on other sites More sharing options...
Dan R Posted October 10, 2022 Author Share Posted October 10, 2022 To resolve the topic, i can confirm the size of the plug was indeed M20x1.5Thanks for everyones input and information Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted October 10, 2022 Member Share Posted October 10, 2022 Thanks for adding the answer.Jonathan Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 10, 2023 Member Share Posted July 10, 2023 Size and source of a magnetic plug for the BMW diff.Jonathan Link to comment Share on other sites More sharing options...
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