Wednesday, March 18, 2015

Gearbox Rebuild - Part 4 - Finishing Off

<This post is part of the 'Winter Project 2014/15 - (Gearbox Refurb)' project>

In the previous post, I got to the point of putting the mainshaft in and getting it all bolted up. Now I just have a few bits to finish off, the speedo housing and the oil pickup pipe to be specific. This should be very straight forward, but it does leave me questioning what is the best way to gasket them up.

Speedo Housing
After leaving the speedo housing and all it's little bits and bobs submerged in red diesel for a few days and then spending quite some time cleaning them up, they were in a presentable state to be used.

Speedo Housing
The speedo housing needs to be bolted to the side of the gearbox with a gasket between to create an oil tight seal. As there are a vast selection of different gasket compounds and adhesives to choose from, the question is which to use, if any at all. Seeking other peoples opinions on the matter yields a number of different answers as each person has their favoured product.

One recommended method that stood out to me as a good idea was to use a thin smear of RTV silicone on either side of the gasket just prior to bolting it up. As I still had some RTV in the shed from a previous job, it seemed like I had found my favoured method.

Room Temperature Vulcanising silicone.
I always wondered what RTV stood for!!

After cleaning both gasket surfaces on both the speedo housing and the gearbox, I used my fingers (with nitrile gloves) to lay down a thin layer around the back of the gasket.

Then carefully setting in place on the speedo housing, making sure the holes lined up. Once on, I smeared another even layer of RTV on the other side of the gasket

Offering up the speedo housing to the dowels on the gearbox, it was pushed into place. Then the speedo drive spindle was inserted and the housing plate was put in place using the same gasketing technique.

Next thing is to bolt the speedo housing down. As the bolts that hold the adaptor block in place also go through the speedo housing, it needs to be bolted on also.

The last thing to do is pop the speedo drive in and bolt it in place with it's housing. Again the RTV gasket smear technique was used. I should have checked the gasket size and trimmed it for neatness as it was a bit too big, but not to worry.

Oil Pickup Pipe
The last thing to finish off on the gearbox is to connect up the oil pickup pipe and the blanking plate. The blanking plate sits on the back of the box and is bolted into place with a RTV'd gasket, as is the inner part of the pipe also.

Well, this has been an excellent adventure into what I suppose is a fairly complex area of the Mini. As it turned out, just like many other things I have looked at, it's not as difficult as you first think. I have learnt a great deal about not only the anatomy of the gearbox, but also why baulk ring wear is important and also to check the bearings, no matter how good you 'think' they are, until you see them, you just don't know.

I am incredibly grateful that the step by step videos were there on YouTube as they made the whole process a lot easier. If they had not been there to follow, the job would not have been impossible, just more difficult. I dare say that if you took enough photos and were very methodical, it would be just as doable.

So what now? Well there is still the 'small' task of reassembling the differential unit and bolting it to the gearbox. Oh, the fun never ends, well I hope it doesn't anyway!!!

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