Posts Tagged ‘Mini Cooper Transmission’

Part One
Building a new gearbox for the Mini is exciting not because of the amount of work and thought that has to go into it but rather the thoughts of the sheer pleasure in looking forward to driving it. The “Dog Engagement system” as found in the latest sets of gears from Quaiff and often thought of as being special because of this ‘dog type synchro system’. But in reality the benefit is most significant when you are on the race track and need to use all 4 gears, they are a stunning close ratio that means you always can find the right gear for the right turn on almost any track.
Getting started in our case it was first required that we decide if we were going to go with the older remote set-up or the later ‘rod-change’ version. In either case it was going to require starting with process of cleaning, inspecting and modifying the case to accept the gears and Limited Slip. We took into consideration that for the drop gears in our somewhat economy minded project we would go with standard helical version. But again, as we were starting from scratch we had a choice of using the early size idler gear or the later ‘big shaft’ version. As the Big shaft was the very obvious first choice, it simplified the case selection as only the later model rod change housing used the big shaft type idlers.
As all of my choices for a starting point were absolutely filthy, the first step was to take a high pressure water hose to them in an attempt to at least blast off some of years of baked on gunk! But the solvent tank and had brushes were needed steps before even a good inspection could be done.
With the gearbox gutted and cleaned the next step was to drill out the holes where it bolts to the engine block. Mini Cooper Trans to Engine boltsOur experience tells us that even with the thick flange late blocks we can still benefit from using these larger bolts. We use a special bolts with small drive to allow for much easier fixing, 5/16”X24 bolts, 7 are 1” long and 5 of them are 1.5”.
Next in our process was the installation of the new shift forks required for this gear set, a pretty straight forward job after you mange to find a punch of the correct size to drift our the roll pin holding in place the 3rd/4th gear fork. All’s well that ends well!
The real change for the task thus far was the modifications needed to install a modern limited slip into any Mini Gearbox. IMini Cooper Stock Diff Housingt has been my experience that no LSD will fit into any housing without the need to grind some additional clearance in both the differential housing and the tranny case itself. The process is very much a grind a little and try it one that has to be repeated a numbLSD modifiled Diff Housinger of time until you are sure it will fit. And for sure you don’t want to install the gears in the housing before you know the diff will clear everything.
On the diff rear case you can see in the pictures with the stock ribs on the inside, these have to be ground off as shown in the after picture. The next step is to take the diff and see how it all fits.
Mini Cooper Rod Change BushingPS, whilMini Cooper Diff Bushinge we were working on the Diff housing, we also took the time to install a new bushing for the rod change linkage. Although we used a actual press, it can just as easily be done on the workbench.

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