Sunday 22 February 2015

Gearbox 5.

After a bit of lamenting, we went for 3.44:1 final drive as a balance of cruising and acceleration.



The differential pin is an item that is also prone to wear. For longevity we went for competitions grade replacement.


Diff side covers get distorted quite common.


Some hand filing was necessary to restore the mating surface.


Diff bering preload is set by shims on the mini gearbox.






Gearbox 4.

The old layshaft was worn, which is quite not unlikely as theese shafts take quite some load.


To avoid such premature wear, we went for a hi grade replacement.






Minis have a construction problem around the oil pickup pipe. As the sucking end of the pipe is located on the left side of the case, in a longer left-hend curve, the engine might suffer from oil starvation. To prevent this, it is adviceable to replace the original item with a central oil pickup type.


The oil pump is also an item that usualy has short service life in a mini engine. The reason is also  costruction related. The engine shares the oil with the gearbox. There are always metalic particles in a gearbox it is part of their "normal" operation. Unfortunatly the oil pump is before the oil filter in the circuit, soo it sees unfiltered oil. To lessen this problem. I put this little gadget in the oil line. This is a small filter with a magnet. If this part is looked at from time to time, the oil pressure will stay strong much longer. 



An often overlooked item: the selector oil seal. 



A very slight preload is necessary on the shaft bearings


Gearbox 3.

For the best results, we went for a complete gearbox and differential rebuild kit, which was by no means "complete", but most of the usual wearing parts were there.



Original bearings were metal case, but theese plastic case items are just as good if not better as the originals.





A place hard to check: the inner bearing surface if the primary gear shaft. This time it was in perfect condition.




Gearbox 2.

After preparing the parts, I started building the unit.


First the selectors go in.


The selectors are held in position in gear and neutral by theese items, which end in a ball. They need to move free and need to be held tight by their springs in order to make the gearchange feel all right.


The springs sit behind their securing bolts. Theese bolts are sealed with copper rings. In order to make them seal, I heated them before instaling.


You have to pay attention when fixing the selector forks onto their shafts. They have to be in perfect position, unless You will end up with a pudding stearing like gearchange and sooner or later a destroyed selector shaft.


The reverse gear shaft was checked for straightness and wear.


No problem was found, soo I installed the assembly.



Gearbox 1.

Although we did not have the correct original gearbox in the car, luckily we had an Innocenty Cooper Export unit, which is identical internaly as the original, just in a rod change housing. This gave most of the hard-to-find parts for an original setup. We also needed a remote change 4 syncro gearbox case, and some internals. Luckily I had one in my shed, collecting dust a few years now. This is 90%. The rest 10% was a bit of a problem. The Inno had the late pot type inner driveshaft joint, the 4 syncro came from a plain 1000ccm modell, thus had the rubber cross type, unlike the Cooper S, which had the hardy spicer joint. The parts that are available new, we bought, but still there are 3 parts that are not available of the shelf. Theese we got from a mini racer, whom we are very gratefull for this, and as soon as possible we will give them back :-).

Rebuilding the gearbox on a mini is not a one afternoon job, and although it might look easy, need a bit of attention at some points. Especialy if You would like to do it only once.

First I cleaned everithing. This time I took a chance with the dishwasher. Although it was technicaly a success, I am not sure how many times the Wife will forgive it to me.



I have a couple of dismantled gearboxes, I wanted to pick the best parts with as few wear as possible. Take care: 3 syncro and 4 syncro box parts might look similar, but they are not always interchangeable (dont ask me how I learned this).



Nice clean case just out of the paint cabinet. Case inspected for damage on the sealing surfaces, at the bearings and at some places for cracks. 


With some parts the condition is obvios, but some parts need to be investigated quite close.



All the gears inspected outside...




...and inside for wear.


Old sycro rings were definitely worrn. Look at the gap between the ring and the gear here...


...and here with the new item.


As a final point the gearbox mainshaft was checked for straightness.