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Does anyone know the dimensions of the selector shaft O ring ..... or the diameter of the shaft itself ?

Got a leak unfortunately, only slight but it needs attention....

Darryl Walker ( TWOA ? ) did a mod to fit a new lip seal, hope these pictures have enough detail.

Have you tried Robsport or Rimmers for a new one? Rimmers are showing them as 'in stock'':
https://rimmerbros.com/Item--i-UKC7

Ok, thanks for the replies.

I couldn't get my caliper in to measure the the size of the selector shaft at first but a 5/8" spanner is almost a snug fit so it looks like 5/8" is the size, which ties in with the size of the lipped oil seal above, and yep, both Robsport and Rimmers do them but at nearly 5 quid inc postage from Robsport and a whopping £6.55 inc post from Rimmers for a teeny rubber ring the size of my thumbnail.... I think I'll pass.

Seals'R'us on Ebay do 5/8 imperial nitrile O rings at just £1.80 for 5.... with free postage. I'll give them a whirl....

This modification was covered in my blog some years ago ...
https://tr7beans.blogspot.com/2012/04/dhcs-gearbox-rebuild-part-2.html
https://tr7beans.blogspot.com/2012/05/dhcs-gearbox-rebuild-part-3.html

tr7dan wrote: the selector shaft ... looks like 5/8" is the size

The LT77 'box is metric

[quote="Beans"][/quote]
The LT77 'box is metric

I wonder did they mix metric and imperial because the above pictured oil seal looks to be imperial 1" x 5/8" x 1/4" (1 x 0.625 x 0.25) ?

Maybe it’s meant to be 25mm x 16mm x 6mm

According to a vernier gauge on my spare gearbox, it measured the shaft at 15.97mm diameter…

Interesting to see the lip seal as a successful option. I’m not an engineer and always thought these were designed for sealing rotary motion items not reciprocating.

(The spare gearbox was an eBay purchase when the noises from the existing one sounded terminal. Removing the new aftermarket rubber gearbox mount for a Volvo part solved it)

tr7dan wrote: I wonder did they mix metric and imperial because the above pictured oil seal looks to be imperial 1" x 5/8" x 1/4" (1 x 0.625 x 0.25) ?

Well it's an after market US conversion, and they were never good at metric dimensions

busheytrader wrote: ... Interesting to see the lip seal as a successful option ...

Bear in mind it is an extra seal, supplementing the original O-ring seal.
And in my case I also fitted a sealed rear main shaft bearing.

Beans wrote:

busheytrader wrote: ... Interesting to see the lip seal as a successful option ...

Bear in mind it is an extra seal, supplementing the original O-ring seal.
And in my case I also fitted a sealed rear main shaft bearing.

A “belt and braces” solution as we would say in the UK.

So, after a bit of head scratching I decided to see if I could fit an external seal to the selector shaft to save the hassle having to delve into the alloy gearbox end case to get at that O ring.... but it was very tight for space!

There was only about 4-5mm of space between the knuckle of the selector mechanism and the alloy case with the gearchange in the fully forward position and also there was only about 2mm of smooth shaft protruding on which to get a nitrile seal to sit.

After looking at all the various seal options I decided the only one that would fit was a M16 bonded seal washer (Dowty washer). I used Adiseal sealant / adhesive to glue it in place and, as the metal part of the washer isn't very wide I fitted a larger dished washer over it to give it more support.

I know this is not how they are normally fitted but it was a perfect fit on the shaft and up to now it has worked. I measured the gap between the selector mechanism and the seal, once I had reassembled it, and there is about 2mm of clearance.

Will it be a long term solution ? I don't know but it's worth a try and as it's easily removed and completely non-destuctive, what's the worst that could happen ?....

This thread got me thinking, never had the problem yet but thinking it might be a worthwhile mod on the spare gearbox before it is actually needed.

Well, 150 test miles in and the ad hoc selector shaft seal is still drizabone, not exhaustive testing I know, but promising....

I've now painted the sills in satin black and fitted the original steel wheels and plastic trims - I think there's just the door mirror to paint black now and that's it - back to how it was in 1982 when I bought it.... well.....apart from the fact that it came originally with just a drivers door mirror, I mean, why would they do that ?