You guys may know by now that I performed a C60 swap into my 2zrVios last December, and have done a bunch of highway and autocross testing for the past 5 months. On the street the 6 speed was awesome, the only time it ever had traction issues was in the rain. Autocrossing with this gearbox was quite frustrating though, the 4.5 final drive and short ratios resulted in a ton of wheelspin. We knew we needed an LSD badly, so I contacted my friend Kenji at CuscoUSA and placed an order. Once the LSD arrived, we did an unboxing video HERE and pulled the gearbox from the Yaris to start the install.
During the disassembly process (VIDEO) is when we do a majority of the inspection and take measurements, this way we know what parts need to be ordered while the gearbox is completely torn down. I created a thorough blueprint booklet with images where you can log all of your measurements and gearbox details. If you want a copy just send me a message. Once you place the order for bearings and synchronizers, now is the perfect time to send parts to be WPC treated as well.
Now that you're waiting on parts, take this opportunity to strip the case down completely and clean it. You want to de-grease it and clean all of the tiny areas where metal debris and tarnish may accumulate. Once the case is completely clean of oils, you can scrape off the old sealant and chase the case bolts/threads with an 8mmx1.25 tap and die. This is to clean the threads providing consistent fastener torque. Next, I blow all of the debris out of the case with shop air then cover it to prevent dirt intrusion before assembly. Check out the video HERE
If you remember 2 years ago when I shared my C50 build, then the Cusco Type-RS LSD will sound familiar. Again I did a ton of research on every type and brand of LSD to make sure the right decision is made. The TRD helical LSD and the Quaife are nearly identical in design, and I passed on these after many reports of wheelspin and an "unloading" in race applications. So it came down to KAZZ and Cusco, and with how awesome the unit in the C50 did I went for the RS again. This time, however, Cusco and I agreed to increase the ramp to 45 degrees and try the 1.5 way. ALL THE GRIP!
The AR-Differential Install Kit
Since I've built several of these boxes now, I figured it would be easier for everyone else if I put together a kit including the bearings, seals, and instructions. This way you guys won't need to go to the dealership and point out the parts you need on a diagram(and likely the counter guys make a mistake), you'll have the correct Toyota part numbers! (VIDEO) Once you transfer the ring gear and speedometer drive, install new bearings, put the assembly in the case, torque the bolts, and check preload (VIDEO). Then if your preload measurement is out of specifications, this kit will have the numbers for the shims as well! Easy Peasy. I also recommend investing in one of these high-quality magnetic plugs from Mishimoto, I didn't want to risk buying a cheap part and have my gearbox destroyed if it detaches. Make sure to put the plug in the FILL port only, since there is not enough differential clearance at the drain port. The link is to this part is HERE.
There have been many instances where C60's have suffered a broken 3rd gear under drag racing conditions. I'm not the type that enjoys this straight line racing, but in the Pro-Solo environment we do have a drag-style start. I measured all of the gears and sent out the 3rd and 4th gearsets based on their tooth width being the lowest. I also decided to have the output shaft treated due to rare instances of tooth breakage. If you want to learn more about WPC treatment and see the friction test video check out my write-up here: leave nothing to chance.
Now it's time to put it all back together, make sure you pay close attention to the install direction of every single part. Gears, Synchros, shift hubs, and even clips must be installed in a specific orientation. One mistake during the assembly process and you could be missing a shift or even have an immediate failure. Pre-lubricate all of the parts and take your time, feel free to use my videos of the assembly process here:
Input Shaft Assembly
Output Shaft Assembly
Final Transmission Assembly
Fluid And The Break-in Procedure
Once you have the transmission back in the car, special attention needs to be given to the fluid you use. All clutch-type LSD's require a unique formula of friction modifiers in the fluid to prevent disc sticking and chatter. I know you can take the risk and use whatever fluid you want and add a modifier to it, but that's outside of my comfort zone. I always just pay more for the recommended Cusco Mission Oil. If you installed a Quaife or Torsion differential then no special fluid is required, since these differentials only contain gears. Once the gearbox is full of the correct oil, it's time to perform the break-in procedure. Break-in for clutch-type differentials is a process similar to breaking in your clutch or bedding brakes. You want to slip the friction surfaces in a manner that results in a surface conformity of the discs, while also maintaining optimum temperature. After the process you replace the fluid and carry on, as usual, you can watch my video on the whole process below.
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