Friday, March 6, 2015

Gearbox Stripdown - Part 4 - Mainshaft Strip

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

In the previous post, I got the gearbox completely stripped of parts, however the fun doesn't stop there. I want to get the main shaft stripped down to check everything is in tip top condition.

1st Gear
Working from the left, which is where the large 1.5" nut sits, the first gear and its roller bearing is the first thing to be lifted off.

1st Gear off.

Leaving this.

The next thing to get off is the 1st speed gear journal, it's a tight interference fit on the shaft. I managed to remove it by dropping the shaft on it's end (on a carpeted floor) a number of times and it eventually moved down the shaft and off.

1st Speed Gear Journal...

,,, is off.

1st/2nd Syncro Hub
Next to come off is the 1st/2nd synchronising hub which just lifts off, along with its baulk rings. The hub itself breaks down further as there's an inner and an outer part. The inner separates by sliding it out from the outer, however as I found out, there are 3 spring loaded ball bearing detents that catapult out when separated. After this happened to me the first time, I now separate them in a food bag which captures the ball bearings then they ping.

2nd Gear
So far, so good, but that was the easy part. Next to come off is the 2nd gear, but that is held in place behind a locking washer which is a bit of a sod to get off. At least I think so anyway.

On this particular gear, there are 2 detents about 180 degrees from each other, locking the washer in place on the splines. Both detents need to be pressed in to enable the locking washer to rotate to the unlocked position. It sounds simple, but I found it very tricky. After about half an hour of faffing, I found a tool and method that made the job a little less tricky.

Using a small screwdriver, I was able to press one of the detents in, while pressed in, the locking ring will rotate just a little to hold the detent in place.

Press the detent in and rotate the locking ring.

One detent down, one to go.

Now the even trickier part, pressing the other detent in with the screwdriver and rotating the locking ring round a bit more. On more that one occasion I rotated the ring round too far, releasing both detents, forcing you to start again. After the 5th or 6th time of doing this it gets just a bit annoying, but with deep breaths and patience, it was possible to get both detents pressed in and the locking washer in the right place.

After about an hour of trying, I finally got the locking washer to the point where it could be slid down the splines and off.

2nd gear off! Finally!

3rd Gear
Now I need to work on the other end of the shaft. where there's another locking washer that holds the 3rd gear in place. Thankfully there is only the one detent to deal with here.


Using the same method as before, I was able to press the detent in and get the locking washer to the position I wanted much quicker that before.


And with that, the 3rd and final gear can be removed from the shaft. Obviously I need to lay everything out logically to satisfy my need for order.

To complete the picture, I separated the syncro hubs into their individual parts, taking care not to lose the detents as they come poinging out.

Actually it's not a totally complete picture as the 4th gear is mising. The 4th gear resides on the 1st motion shaft and as it didn't need any work to dismantle, I didn't show it here.

Parts Assessment
With the parts from this and the other gearbox I stripped earlier in the year, I have a good selection of spare parts to choose from mixing and matching the best parts to use, however the journals, bearings and gear teeth looked pretty good on both sets.

The baulk rings I took out of this gearbox were quite worn down and I wouldn't want to use them again, however the baulk rings in the other gearbox looked to be okay. Looking around a few websites a set of new original Rover baulk rings are nearly £100 (I know!!!) so I will have to have to decide if they are worth it.

Both gearboxes had a damaged main centre bearing, so that will need to be replaced which is a bit disappointing as a decent quality new item is a whopping £50. Ouch! That's a bit painful along with the baulk rings!

So shopping around a little more and getting advice from others, I stumbled upon a company called Guessworks that sells quality second hand bearings for £12. This is more like it. Had my original bearings been okay, I would have used them. So I have no problem in using a good quality second hand set so I went ahead and bought it through the website here.

Then the next day after pondering on the baulk rings a little more, I decided to buy a set of non-genuine items as they were considerably cheaper, so I rang Guessworks to see if I could add them to the order to save on delivery and thankfully I wasn't too late. Speaking to a guy called John, I could tell he was passionate about what he did and was very knowledgeable and helpful and willing to give advice about all things gearbox related.

When I get around to rebuilding the other gearboxes I have to sell on, I will definitely be going back to Guessworks for the parts I need. Cheers John.

Baulk Ring Wear
So how do you tell if the baulk rings are worn too much? This was something I wasn't quite sure about, but I knew it was to do with the gap between the baulk ring and the gear.

This gap.

What I didn't know was how big or small that gap should be. It's pretty obvious that if there is no gap between the baulk ring and the gear then it's too far gone and will almost definitely lead to gear crunch. Something I currently endure when going from 3rd to 2nd, and it's annoying so I want to avoid that.

Zero Gap = Crunchy Gears

One tip I picked up from speaking with John from Guessworks was that if the gap is below 40 thou (about 1.02 mm), then it's probably time to replace them. Using this rule of thumb, I have one set the are definitely below this spec, so they will be discarded and one set that is just above, so I may use them at some point in the future, who knows!!

Below 0.040" = Scrap
Being over 0.040", I might use these again.

I must admit, at first I was daunted by the task of stripping down the gearbox and was just tempted to use it as is. But thankfully I took the plunge and I'm glad I did as that crunched bearing would mote certainly have been a major problem in a year or so. Also the wear on the baulk rings would have meant that the gears would probably be crunching by then also.

Stripping it down also gave me the opportunity to learn so much I never know about how the gearbox works and what can go wrong. This has been a very satisfying little project and one I will be glad to do again and again.

Next Time
Well I suppose that the stripdown was the easy part, putting it all back together might be the real challenge. Who knows, me soon hopefully. But after watching this gearbox build video from Mini Mania about a 100 times (slight exaggeration), I'm hopeful that it too will be an equally rewarding if not more so experience.

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