TRD Gearset
TRD offers two different gearsets for the Corolla's T50 transmission. The budget set (33030-AE851) replaces only first and second gear with numerically lower (i.e. taller) gears spaced evenly and closer to the stock third gear. Fourth has to remain the stock 1:1 and fifth gear also remains the same. This is the sports option of the gearsets as it keeps the lower gears tight enough for daily street driving while not shortening fifth gear. We opted for the more extensive and expensive gearset (33030-AE811), which replaces every gear in the box other than fourth. Because this kit replaces the stock third gear with a taller gear, first and second are now even taller than the sports kit so that gear spacing is still consistent. Fifth gear is also made just slightly shorter so it can be more useful on track for a power limited car. This gearset is intended for circuit cars and will benefit from high output engines that can take advantage of the taller gears.
The circuit set comes with each new gear, counter gear, a new counter shaft, spacers, and the snap rings necessary to convert the transmission.
Prep Work
As fun and interesting tearing down a transmission can be, it's not something to be taken lightly, or a one-night ordeal to just jump into. There's a couple things you're going to need, a factory repair manual, rebuild kit, hydraulic press, clip ring removal tools, solvent tank, and most importantly, the cell phone number to someone whose done it many times before so you can call at all hours of the night. Our go-to guy would be close friend, Corolla drifter, and guru Wes Hamachi.
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TRD's complete circuit gearset replaces every gear except fourth gear, which is a direct 1
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All Transmission Parts supplied a complete rebuild kit, with the all important brand new s
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The TRD main shaft (front) has visibly different gear ratios. Larger gears correlate to a
Prior to the big job, we ordered a complete transmission rebuild kit from All Transmission Parts. While they don't normally sell to the public, All Transmission specializes in rebuilding, refurbishing, and stocking transmissions and parts for all sorts of popular cars. The guys at All Trans put together a rebuild package that included all the new bearings, seals, gaskets, and synchros necessary for the rebuild at a fraction of the price of what you'd get raped for by paying OEM prices. Your local repair shop can probably set up an account with them to get the parts.
To be safe and to aid the preparation process, we borrowed a scrap transmission from Hamachi. The donor transmission, which came off of Hamachi's car, had imploded on a hot lap during our Motor Skills Challenge (May 2006 issue) and was missing its third gear. Lucky for us, all the gears going into the transmission would be new. The transmission was torn down to the last bolt, documented, completely cleaned over several nights using the solvent tank, and inspected. With all the parts cleaned, they, along with the new gears, synchros, and new final drive ring and pinion, were sent out for some pre-treatment.
Cryogenic Treatment
Spending all this money on building a new gearbox won't do us any good if it breaks under the track abuse we have planed. To avoid that, we decided to invest a little more time and effort to help ensure that the transmission lasts. Because the original T50 transmission was designed for a light car putting out less than 150bhp, it's fairly small and, thus, delicate compared to modern transmissions. To prolong the life, we decided to give the new gears and internal components a deep cryogenic treatment.