During the last year and a half since fitting the LSD unit in my Ford axle I haven't been happy with the way the rear end of the car was handling. The initial feeling was good from the axle, but after approximately 4 months the rear end of the car felt less inclined to turn into corner. I have a very stiff front end setup (300lb springs and adjustable anti-roll bar) and this gives a very quick turn-in. The rear of the car didn't match this and it felt like a slightly odd oversteer feeling, the front would dive into the bend but the back felt like it was on tiptoes and didn't want to follow it around. The result was that I lost confidence in the way it went around bends and so set about trying to find the problem.

The first area that I looked at was the corner weighting. Towards the end of the first year with the LSD I visited Steve and we checked over the car. It wasn't very far off from the previous settings so that wasn't the problem.
Next up was the ride heights. I know from previous experience that small changes can make a big difference. I tried lowering the rear of the car by 5mm at a time, the lowering of the rear tending to settle down oversteer. The car felt a little better, but when the platforms were all of the way down to the bottom of their travel the problem was still there. The car was almost level (no rake at all) so I knew something must be wrong somewhere else.

I'm not sure what prompted the thought, possibly a chat with my boss, but however it came about I started to think about the effect the LSD was having, and how it works. The LSD locks to rear wheels together by means of clutch plates. When one wheel starts to slip, the power is transferred to the non-spinning wheel to maximize grip. The way it knows that one wheel is spinning is if it is rotating faster than the other. However, when you corner, the outside wheel will need to rotate quicker that the inside wheel as it has to travel further. The way the LSD overcomes this is to allow a breakaway torque. This is effectively how tightly locked together the two wheels are and how much torque has to be applied in order to break the locking of the two. I called Raceline for some advice as I knew they had built a Ford axle for a friend. Pete was very helpful and talked me through how to check the breakaway torque of my axle, and also what kind of figure it should be set to.

The checking method of the breakaway torque:

1. Jack one side of the car up and remove the wheel, lower the car so it is back to the normal height.
2. Place a chock in front of each front wheel to stop the car from moving (although it is highly unlikely that it will).
3. Make something to allow you to rotate the wheel from the canter, to ensure you don't multiply the torque you apply. I used some 5mm thick steel plate and drilled two holes for the wheel studs to poke through and a third hole in the centre. In the middle hole I fitted an M8 bolt and nut.
4. Fit the above plate to the wheel studs and loosely tighten the wheel nuts to hold the plate in place.
5. Using a torque wrench, start with a low setting, eg. 10 ftlb, and try to rotate the wheel in the normal direction.
6. If the torque wrench clicks then the breakaway torque of the LSD is higher than the setting.
7. Increase the torque of the wrench 5lb and repeat step 6 until the wheel starts to slip and the wrench no longer clicks.
8. Repeat steps 1 - 7 on the other wheel as a double check.

When I tested mine in this manner I got results around the 60 - 65 ftlb area. The recommended values was 25-30 ftlb, so clearly mine was a little on the high side. The more I thought about it the more I thought this was my handling problem, the wheels were locked tighter together than they should have been and the outside wheel less willing to travel faster than the inside in a corner.
When I was next over at Steve's I tested his car in the same way, although only one side, to gauge if the recommended values were in the right area. Steve's car is a De-Dion, so I expected it to be slightly different. I was slightly surprised when his wheel started slipping at around 15 ftlb.

The next task was to track down somewhere that could adjust the LSD settings. This is done by changing or grinding down some packing shims inside the unit. After asking around I found a local company called Old Fords in Bracknell, 15 mins away from me. They were happy to take a look so I arranged to take them the diff/LSD unit.
I decided to take the diff out of the axle to save having to disconnect the brakes lines, handbrake, etc. It would also have been a pain removing the axle without taking the car out of the garage due to the width - it is then fun getting it back in with no rear wheels!
Removing the diff housing meant that I has to remove the half shafts. This was a first for me. I looked around for slide hammer to get them out and thought they were a little expensive. I decided to make my own. I used my plate from the testing above and replaced the middle bolt with a length of M8 studding I had lying around, fixed with a nut either side of the plate. Onto this I passed a couple of weights and large sockets and washers (to stop the weights falling off of the end) and finally a nut. I could then slide the weights along the studding until it hit the socket and washer and nut. The four bolts holding the half shaft in place were removed and the plate fitted to the wheel studs. It only took a couple of light pulls on the weights to get the shaft moving - easy. Both sides were removed from the axle casing and stood up next to the side the came out of. The propshaft was unbolted next and then the A-frame was undone so the axle to hang from the dampers and rotate so the housing was pointing down and easy to remove. Each of the nuts was undone a little at a time, 1/2 a turn in turn to avoid distorting the case or the housing. A bowl was positioned just in time to catch all of the horrible smelly diff oil that started pouring out of the gaps appearing. I left this for a night to drain and them dropped the diff the rest of the way out. It is bloody heavy!
Old Fords had told me they were going to be around on a Saturday morning so I loaded the diff into a box and took it to them. It was snowing - so I nearly laughed when they made appologies that they couldn't do it that week. I decided to go for a half way setting and asked for 20 ftlb. It was two weeks later when I got the diff back and fitted it back into the diff, fitted the half shafts and all the other bits (prop, drums, etc). When I repeated the above test I was a little disappointed to get high 20's readings. I suspect this was down to the extra drag of the brakes and oil. I would test it when the car was back on the road and if an improvement was felt, but not enough I could always do it again - it wasn't very hard to do.

With all my mapping and misfire issues I almost forgot that I had done anything to effect the handling when I started driving it again. The difference was great, it was back to how it was before the LSD, very neutral turn-in with a rear that just followed where the front went. As the mapping was improved and the misfire issue was fixed (all it needed was new leads) the rear end has started to be much more fun. I softened the front anti-roll bar as I felt the ride was too stiff (I think the 032's have too stiff sidewalls) and as a result the front has more grip, and the rear proportionally less. It made it quite good fun on roundabouts as you can just apply a bit more power and prevoke the back to start to slide slightly, very predictably. The next plan is to change the 032's to some CR500's which are almost as grippy but with softer sidewalls which I think will suit the live axle setup as otherwise you bounce over every bump!

 
 
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