Honda Tuning reveals the blood, sweat and tears that go into creating a competitive all-motor drag car by building our own CRX racer. This month we turn our attention to the drivetrain, sending our JDM Y1 transmission to GearSpeed Hi-Performance for a rebuild that includes a CircuitWorX spool.
So you probably giggled a little when you saw which transmission we chose for our all-motor CRX project in the May issue. For the record, the LS tranny was all we could get our hands on at the time. We knew even then that we had to get something better. Thus project leader Thai Nguyen from Serenity Sound & Performance searched until he got his mitts on a salvaged trans from an '88-'91 JDM Civic SiR. The gearbox was a little dated but boasts a respectable 4.27:1 final drive ratio.
The final drive ratio is critical when formulating a tranny for competition. It's the gear ratio in a vehicle's differential, and on a front-wheel-drive car the figures express the number of turns required by the countershaft gear to turn the ring gear of the differential. A higher number means a lower, or shorter, gear, and short gearing gives quicker acceleration. But because the engine must turn faster, gas mileage and top speed are lower. Tall gears, on the other hand, give longer acceleration and a higher top speed at the expense of quickness.
Our 4.27 final drive was fine for what we wanted, certainly better than the 4.21 that came stock in the LS transmission. Unfortunately, the rest of the rescued gearbox was pretty beat up: bad synchros, chipped gears, a hole in the case. It needed help, and help it got from Honda transmission specialists GearSpeed Inc. in Rancho Cucamonga, Calif.
GearSpeed is an offshoot of thriving transmission rebuilding outfit H&A Transmissions, which got its start in the late '70s rebuilding Honda slushboxes for wholesale, a practice it still keeps today. At the time Honda transmissions couldn't be easily identified from the outside, even though most other automobile manufacturers typically used case numbers for identification (in '96 Honda began placing VINs on its cases). The transmissions did come with a gold tag that American Honda could use to determine where and when they were assembled and what was inside, but dealers didn't have this information available to them.
Figuring out what was inside wasn't simple. Essentially, the owners of H&A learned gear ratios by physically counting each tooth on every gear of every unit they cracked open and documenting it. The immersion into Honda gearing led them to invent a system of charts for identifying different Honda transaxles. The charts also helped to determine which parts overlapped with other model years and platforms. After a short time the owners of H&A realized they could build high-performance trannies using different combinations of stock gears from varying platforms, and from this realization GearSpeed was born to service the needs of the manual transmission crowd.
We took our SiR box to GearSpeed and had the techs there freshen it up for us. Right off the bat, the guys identified the Y1 tranny and said we'd do much better with a different final drive, like the one from a J1 transmission. The J1 is found in '90-'91 JDM Integra XSi/RSi's and features a 4.40:1 final drive, which is the highest FDR we can get with stock Honda parts in our transaxle. To alter the final drive, the techs had to change the ring gear on the differential as well as the countershaft. And since the ring gear is getting swapped, the O.E. diff is also booted for a solid race spool from CircuitWorx, which you might recognize a little more by its previous incarnation, ProDrive USA (not to be confused with the Subaru rally tuners.)