Sunday, April 26, 2015

Gearbox Idler Bearing Extraction

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

A few weeks ago I was trying unsuccessfully to get the idler bearing out of the transfer case, but I'm not defeated yet! Anyway while I'm pondering that little problem, I also need to get the corresponding idler bearing out of the gearbox housing as it's holding up the work a little. Again, I'm just too stingy to invest in the correct tool, so like a proper hooligan, it's time to have a go and see what happens.

Gearbox idler bearing.


Firstly it's worth mentioning that I spent over a month stripping and rebuilding the gearbox so I really don't want to mess this up and end up having to rebuild another gearbox. So for that reason, I tried out a few methods on a spare empty gearbox I had lying about in order to work out the most effective and least risky method.

Hammer Time!
I'm sorry if you are now singing 'Hammer Time' in your head, but it just seemed a bit strange putting 'Mallet Time' as the heading. Anyway, moving on from that, the simplest idea that sprung to my mind was to use a socket that was about the same size as the back of the idler bearing and try to tap the bearing out with a mallet. Tipping the gearbox on end and propping it up in some wood, I gave the end of the socket a few taps with a wooden mallet.



At first there was very little in the way of movement, so I bashed a little harder, then harder still. It took quite a considerable whack to get the bearing moving. Once it was on it's way though it did get easier and easier.



Success! Kind of anyway. Although this method did get the bearing out, there are two slight issues that would cause me a problem were I to try this on the actual gearbox I am intending to use.

One is that there is nothing inside this gearbox, meaning there is ample room to place the socket and swing the mallet. If I were to try this on a fully assembled gearbox, I would probably hit the oil pickup pipe as many times as I hit the socket.

The other big problem is that as it took me nearly 6 weeks to refurbish the 'good' gearbox, there is just no way I am hitting it with a mallet. Knowing my luck, rather than the bearing coming out, I would probably fracture the outer case. It's just not worth the risk as there are not enough swear words in this or any other languages to cope with the breakage.

Tapping the bearing back into place, I move on to method two, which took me a week to dream up.


Cone Compression Tool Time!
One tool I do have is my trusty suspension cone compressor tool. I have used it a number of times for a number of different jobs. It proved very effective at driving the bearings into the front suspension arm, so if it can drive bearings in, surely it can drive them out again.


As this tool wasn't designed for this job, a little adaptation would be needed to make it work. You can see from the picture that the compression tool consists of an inner shaft and an outer part. Threading the inner shaft through the bearing as seen below...

In there...

to this position.

... the outer part could be slid over the inner part. This in principle should work, the only slight snag is though, the bottom of the outer part is butted up against the idler bearing, stopping it from coming out.


After a little head scratching and looking around for bits, I found that four old baulk rings stacked up solved this problem. It created a cavity for the bearing to be pulled into as it's extracted.



I also used an old piece of pipe I had kicking about as a spacer, this basically moves the outer part of the tool further up so that there will be fewer turns needed when putting the the top nut in place.



 Once the top nut was in place, we are left with this little setup...



All that is needed now, is to hold the allen key and turn the spanner. As the thread is very fine, there are many turns required, but I could feel it doing the job as it gently pulled the bearing out. Eventually the bearing successfully came free. The only snag was that the nut had been driven into the bearings, damaging them. Not a massive issue as I will be replacing them anyway, but this could be solved with an appropriately sized washer.




It seems I have found my method of getting the bearing out, so now onto the real thing...


Make or Break Time!
Gulp, it's actually time now to move onto my precious refurbished gearbox! For this I made some minor changes to the method. The first was to use a washer behind the bearing to avoid the nut being driven into the bearing.




The second was to tape the baulk rings together and tape them to the pipe, this just made them easier to work with.




Apart from that, the equipment was set up in the same way...



Feeling a tad apprehensive, I began to put the bearing under tension and... eventually out it popped.



Just like this...





Conclusion Time
Phew, it was a massive relief to get the bearing out without any damage to the gearbox housing. The problem now of course is get the new one back in. But that problem is for another day as I need to turn my attention to the other more problematic idler bearing in the transfer case. Once that's out, I can start to move on with the project a little more.

Also what do you thing about the addition of video. I'm hoping that it will be a useful addition when it comes to showing how I have done things. Let me know either in the comments here on the blog or on the facebook page.




For updates, stick a 'Like' on Wayne's Mini Progress facebook page.

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