A big piece from the donor going in now.
One Chrysler rear axle with a 8.3" ring gear, electronic limited slip diff with a 3.73:1 ratio. 12.6" discs with ABS.
Centred the axle under the coil mounts by placing a level vertically each side of the axle housing and measuring back to the centre of the coil hat. Can only do this if you were careful with the placement of those in the first place of coarse.
The panhard rod bolted right in and placed the axle within a millimetre of dead centre, which surprised me actually. My XJ Jeep was about 10 mm out while still stock from new.
Now for the lower control arm mounts. After carefully removing the stock one a while ago, was not able to use it. This frame starts kicking up much earlier at a shallower angle than the donor, so misses by a lot.
With the axle sitting at the exact height in relationship to the other suspension points already mounted to the frame, I could set the arm angles up the same as factory. This will give me the correct roll centre, anti dive etc as the Jeep engineers worked out in relation to the front end arrangement.
When I laid out the frame rail spacing, I also took into account that the inner frame rail would line up with the inside of the lower control arm bush. I will just have to step out the outside of the mount to line up.
Just did a rough layout using taped pieces of recycled A4 paper. I left a 10mm-3/8" extra around the control arm end. I'd rather that if it ever hits something, that the bracket takes the weight rather than the arm and bush.
The outside angles of the bracket is set at 22.5*. Very common angle used in engineering and even my house roof is at this pitch. It also worked out that it would cover the upper control arm mount as well. The extra V taken out of the top is for a few reasons. One is that it then makes the weld length on the top and bottom of the rail the same. The top would have been 50% longer otherwise if fully welded and that would have caused the frame to bend upwards after welding. It also allows welds in the middle of the bracket increasing its strength. Lastly it reduces the weight of the bracket both physically and visually. Can also see the fold I will be putting in to accept the extra width the bush has over the frame width.
Time to start cutting out the new brackets from some of the left over 4mm plate I bought for boxing the rails. There is a inner and outer template due to needing extra length for the fold that goes into the outer one. The curved bit at the bottom of the V was first cut out using a hole saw. Then the rest just using a 9" cutoff wheel.
Now the lower arms do not run exactly parallel with the frame and skew outwards by 3*. This is common and helps reduce binding during axle articulation. The way they set the original mounts up was to press the 3* around the mounting hole.
I decided to do simulate the factory way by cutting out a 2" disc using a hole saw around the mounting point, tacking it in top and bottom, then tilting it to 3*.
Then fully welding it back in again. It is not much of a tilt, but means the bush wont be under constant tension if it had not been done and will therefore last a lot longer.