Getting Your Hands on a 5-Speed Swap or Repair Guide
The Acura RSX came with two main manual transmissions depending on the trim. The base RSX got the C1 and C2 series 5-speeds from the DC5 Integra, while the Type S got the tighter-ratio K20A-mated transmission. If you are looking for a guide to work on yours, the first thing you need to figure out is which bin you are dealing with. I spent three weekends wrestling with a C2 unit that had developed a grinding issue in second gear. The problem wasn't the synchronizer like most guides would tell you. It was the shift fork bushing that had worn into a U-shape, allowing the fork to tilt under load and skip out of engagement. The workaround was rebuilding the shift rail assembly with after-market oversized bushings from a performance rebuild kit. If you are doing this yourself, order the entire fork kit rather than trying to source individual bearings. It saves about an hour of frustration and roughly eighty dollars in part hunting. Here is what most people miss when they pull the transmission out: the differential side gears on these units are delicate. I cracked one by using a standard gear puller without supporting the case properly. The fix was swapping to a Harbor Freight version of the Honda-specific splitter tool, which distributes pressure evenly across the spider gear assembly. These tools run about twenty-five dollars and will save you a destroyed case that costs two hundred and fifty new.
When it comes to fluid, stick to 75W-90 API GL-4. The RSX transmissions hate GL-5 because the sulfur additives eat through the brass synchronizer rings over time. I learned this the hard way after a customer filled their Type S box with standard 75W-90 GL-5 and came back three months later with notchy shifts. Draining and refilling with Motul 75W-90 GL-4 fixed it immediately. The rough shifting was gone within a few dozen miles. If you are pulling the trans for a rebuild, here is the actual process breakdown. Remove the starter, then the two bolts holding the bellhousing to the block. Support the transmission with a jack before dropping the subframe bolts. The rear main seal usually leaks at this point so replace it anyway, even if it looks fine. It takes twenty minutes and saves you from tearing everything apart again in six months. The shift linkage on the RSX has a known weakness around the plastic bushings in the lower control arm mounts. They compress over time and create vague shifter feel. After-market polyurethane bushings from Whiteline or Novus fix this. Stock rubber lasts maybe forty thousand miles before the vagueness sets in. The bushing replacement takes about an hour with the car on jack stands.
For those interested in the Type S K-series transmission swap into a base RSX, the mounts line up directly. The shifter cable needs an adapter bracket, and you will need to swap the rear output shaft if you are keeping the stock differential. Clutch compatibility requires the Type S clutch and flywheel, or an adapter plate for the base RSX clutch. This is a common swap in the community and there are several thread guides, but the practical reality is it adds about sixty pounds to the front end and changes the gear ratios enough that you will want to adjust your speedometer calibrator. If you need a full overhaul manual, the Honda service manual is the gold standard and covers both C-series and K-series variants. It runs about fifty dollars digital or two hundred for the hard copy. After-market options like Chilton exist but they skip several torque specs and the synchro clearance values that actually matter during a rebuild. Bottom line, the RSX manual gearbox is solid if you maintain the fluid correctly and address the shift fork wear before it cascades into other damage. Budget two hundred to four hundred dollars for a thorough rebuild including parts and fluids if you do it yourself. A shop rebuild will run six hundred to nine hundred depending on how much internal damage you find once it is split.
Get the Full Details
