Series 2 Roamerdrive don't know - Transfer Box Drain Plug Thread Size (Imperial)

[109SeriesIIA]

I'm in the process of fitting a Roamer Finned Transfer case sump cover. (Britpart DA9016) I have a Roverdrive so it's a useful upgrade.

Anyone know the S2 Imperial thread size for the sump plug? The S3 has a Metric thread, but the RD plate comes fitted the earlier S2 thread. If I'm forced into buying an S2 plug, whilst I'm on, may as well fit a magnetic plug. The S2 plug needs a slot-key anyway - or I bodge a large screwdriver. A standard hex plug with a magnet in it, offers a mild improvement and it's cheaper. I get a magnet, and don't need a key to do it right. So would be better all round

Even Roamerdrive's blurb, which simply tells you to buy an S2 plug, refers to the thread as an inch, which two days lost, messing about has been proven incorrect.

It gets worse, contacted, and I'm still taking this in, Roamerdrive don't know! Nope, they don't know. And maintain it's an inch.

Standard imperial thread drain plugs are 1" BSP or 3/4" BSP, and I can say it's neither of those. I've some 22mm plumbing fitting here and 22mm seems about right, yet, this can't be?

Anyone?

See: https://www.britpart.com/all-parts/da9016

 

[Webley1991]

Do you have a set of vernier calipers? I may be able to help if I know an accurate measurement.

 

[109SeriesIIA]

Yes I do. I get the internal diam as 26.6mm to 26.7mm dependent on which way I go at it. Also -removing the olive - I can nearly force a male 22mm plumbing compression fitting male thread into it, and that has a external diam of 28.6mm. It'll go 1.5 turns,

And one more... the thread in the casting has only been cut half-way down, hence we're with a clean hole, and that measures 27mm dead. I think we can assume the threaded section started at 27mm.

So, if an imperial thread the nearest drill is 1 1/16 in or 1.0625in. which is 26.9875mm. Which aligns nicely to me seeing 27mm.

Does that lot give you enough of a clue?

 

[Blackburn]

This is the part they recommend was also fitted to early series 3 I always thought it was BSPP.
https://www.ebay.co.uk/itm/Transfer...m4157486b93:g:YQMAAOSwy-5bxGMj&frcectupt=true

 

[Webley1991]

Those sizes don't match closely with any of the standard threads I know.

The number of threads per inch would also help if you have access to a set of thread gauges.

 

[109SeriesIIA]

I am starting to think it's NPT. Only because the unthreaded section of the hole is 27mm. But NPT on a Landover? Can't see it? It's not BSP. I will borrow a thread gauge

 

[rob1miles]

It could be UNF or Whit, the gearboxes are Whit.

 

[109SeriesIIA]

I'm determined to crack this, but not having much luck. Actual LR Drain plug Thread is gauging-up as 16, but I've so little thread I can't be sure if it's 55 or 60. My money is on 55 degs. LR Drain plug Male thread major diam is 28.5mm.

I'm starting to htink this is some proprietry 'weird and wonderful' version, 'cos gauging-up as 16 and 28.5mm doesn't bring anything close to it. I can't be that hard can it? Anyone?

 

[divie]

Got a good chance of being NPT as I believe the Roverdrive/Roamerdrive where originally made in America or Canada. All the info for NPT or BSP (imperial) is just a Google away. Simply multiply the imperial size by 25.4 to get the size in metric.

 

[109SeriesIIA]

I'm making hard work of this. I have googled. Nothing aligns to 16 guage and this diam.

Yet, it's as LR wanted - stock LR drain plug fits Roamerdrive part as indeed RD intend. So hte Roamerdrive element to this is irrelevant. RD thread is as the stock plate.

The question remains, what thread did LR put on the transfer box drain. At 28.5 MD and 16, it's not looking like Whitworth. Multiplying by 25.4 is a red-herring I think, none of the tables seem to want to align.

The male-thread on the LR drain-plug is 28.5mm major diam. and gauging 16. Seems odd, I shan't admit defeat... yet

 

[109SeriesIIA]

Well, and without prompting Roamerdrive came back and gave me this. Thread is 1-1/8" x 16 Parallel . Good for them.

With another half hour of digging, this is a recognised, but non-standard pitch. Full described as 1-1/8" x 16UN Parallel

Major Diam 1-1/8"
Major Diam 1.1250 inch
Major Diam 28.575 mm
Tapping Drill 27.1mm
TPI 16
Pitch 0.0625 Inch
Pitch 1.588 mm

It's a 60 Degree Thread.

I was starting to wonder, this explains my measurements and why my Metric M28 x 1.5 plumbing fittings, near as it gets, force-fits. Trouble is, those drain plugs that are avaible at 1-1/8" are 1-1/8" x 12, and not 1-1/8" x 16.


If it was me, not Roamerdrive making these plates, I'd have gone with a standard pitch thread in there, and be selling a magnetic drain plug whilst I was on. Cheaper than the LR item, and you might argue a small improvement. Along with the extra cooling, the leak-free improvement, it'd be the third decent reason to buy a Roverdrive/ Roamerdrive finned plate. I don't think even the S2 club would object. We live, we learn.

What I'm set to do now is make an adaptor with Male 1-1/8" x 16. to M18 or M22, common drain plug sizes.

Best of all, done 250 miles and not a peep of a leak. Runs quieter too, but to be fair, now it's got full capacity, and is able to stay like it, and fresh oil - so it should be.