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Left: This is the rosette weld that holds the axle tubes in place. Right: Lots of time with the angle grinder/wire wheel cleaned it all up
So our guys cleaned the rust off, which it took more time than I care to admit. With power tools it goes pretty quickly, but it makes a huge mess and you probably shouldn't breathe the "rust dust".
With all of the steel bracketry cleaned of any rust and grease, our fabricator Ryan then welded the Whiteline LCA relocation brackets to the housing. This is common to do, even when the designs are made to be a "bolt-on". There are a lot of forces going through these brackets and welding them on is another piece of "insurance". This was purely steel-to-steel plate welding, and TIG'd with ER-70 rod, so nothing too controversial.
Once all the welding was done, Olof cleaned the housing again with degreaser and got to painting. He used a semi-flat black engine paint in spray enamel, which is holding up well after two track weekends and loading onto trailers with axle straps. Once the paint was dry (overnight) it went back into the car.
Torsen T-2R Differential Upgrade
With the rearend housing back in the car (no, it wasn't weighed - we forgot, by damn!) it was re-attached to the various control arms and the swaybar was reinstalled with the new Whiteline brackets. Now it was time to install the new Torsen T-2R differential with the original 3.31:1 gearset, as the rebuilt TractionLok LSD wasn't lasting 2-3 track days with the current power level and high grip tires, even with the carbon clutch disc upgrade.
The Torsen LSD design doesn't use any internal clutches. Therefore it doesn't have some of the negative handling interactions that a clutch-style differential has from somewhat locking the inside and outside wheels together under all circumstances (push on corner entry, loose on corner exit), but it doesn't work if one of the driven tires becomes airborne. How it works is more complicated - it involves worm gears, thrust forces and... some form of black magic. Read the links below to learn more:
One thing to note was that the Torsen units (both the T-2 and T-2R we purchased for this and another project) weigh a solid 5 pounds more than the OEM diff. If you see them side by side (middle pic above) you can see why, as the Torsen is full of worm gears and not an "S-spring" and a bunch of air in the middle. Our guys set-up the gears, backlash and installed new bearings on the Torsen and the old 3.31 gearset. It went in and works very quietly, with only some normal "Torsen noise" in a tight parking lot turn.
Damned Upper Control Arm Set-up, Test 4
So we've put 4 or 5 iterations of Rear Upper Control Arms (UCA) in this car and have been happy with none of them. No matter what brand or style we try it always eventually comes loose, then clanks and bangs around on any bump. Very frustrating. The various designs have also taken their toll on the axle-side UCA bushing, that is press-fit into the axle. Our techs noticed that this rubber OEM bushing was cracked and completely shot, so while the axle was being refurb'd they pressed it out and in went a fresh new one. Why not poly, you ask? Well this is one of those "terrible places for a poly bushing"... as it needs to both
rotate and twist in 2 axis. Polyurethane rarely has the material properties for this task - it should be rubber or a spherical bushing.
After a quick glance we couldn't find a spherical set-up for the axle-side bushing (yet) so we just went back with the OEM rubber to replace the cracked and failed unit, for now. If you have an aftermarket UCA, especially if it is a poly bushing on the chassis side, check out the OEM rubber bushing in the axle at the top to see if it has cracked and failed. Click the high rez versions of the above two pics to see what to look for.
With that axle-side bushing replaced I wanted to look at the UCA itself. The Whiteline unit was fine but the adjustment method was a bit unusual and it wasn't exactly silent in use. Everything else they make for this car has been perfect, but I dunno.... I really wanted to keep the bushings able to rotate freely on the UCA, as both of these joints need to pivot smoothly when the car is loaded in corners. At first I wanted to attempt to go back to the "Del-sphere" bushed, adjustable length UCA we tried earlier from Spohn. That thing had some of the worst clanking and banging of any UCA we had tried but it did have the right style bushing at the foreward UCA mount... a Delrin-encased metal spehercial end, called "Del-Sphere". This is the right type of joint, I just didn't agree with the execution of the entire arm and mount.
We thought the problem was with the over-sized bushings that came in the Spohn UCA kit. The kit is made to work with the factory UCA bolt, which is a 14mm OD bolt. The ID of the Del-Spehre end is much larger, as were the holes in the UPR fabricated upper mount. It was as if these companies made something without checking the factory bolt diameter. What the...? So we upped the size of the UCA bolt to a 5/8" and made bushings to fit snug around the OD of the bolt and inside the ID of the Del-Sphere bushing. It took a little time on the lathe, some careful drilling, and some drilling of the UCA mount, but it all goes in and out smoothly now. No more slop to the bolt and hopefully no more banging around.
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