Final Gear Change from 4.764 to 4.052
As we discussed, we would like to move out the 2nd gear shiftpoint up to around 70mph. In addition, the final gearing is just too short for this car, being designed for the heavier ITR and CTR. 1st gear is ridiculous, you just burn rubber, and expensive tires. The highway cruise RPM is not great either at 4000 RPM at 70 MPH. So, after some research, we found Club RSX offers a final gear set of 4.052. Of course, to change the gear set in a Honda transmission you have to totally break down the tranny and replace the countershaft as the pinion gear is integral to the countershaft, and of course you need to change the ring gear as well.
In the CRX swap, to remove the tranny you need to remove the engine as a there is not enough room in the engine bay to pull the tranny with the engine in place. So you need to remove fuel lines, radiator, hoses, shift cables, throttle, etc. etc.. We did cheat a bit, we did not remove the engine from the car completely, we just lowered it down to the ground (using a set of wooden blocks and a hydraulic jack) so we could yank the tranny. We didn't even have to disconnect the electrical harness. At the same time, we removed the Hasport mounts to send them to Hasport for stiffer Urethane.
This was also a good time to inspect the clutch and flywheel, we expected no surprises after only 6000 miles, but we were quite surprised to find some bad news, see Clutch and Flywheel for the details.
Just follow the Honda service manual and remove the tranny from the engine, set it up on a work bench and unbolt what the manual says. What the manual does not tell you, or at least is not obvious to the novice, is some detail in undoing the countershaft snap ring, and the fact you need to us a substantial pry bar to get the case apart. When you expand the countershaft snap ring, the countershaft should drop slightly. Look closely and you will see it is out of the groove, it's not obvious. Now to remove the case, you will see the pry points (3) on the tranny case but only one that has a surface to easily pry against. Start at this one till you just break the seal, then pry around the other points so the case comes off straight and just pull it straight off. Again, follow the manual and you pull the entire main shaft/countershaft/shift fork assembly off as a whole. It pays to be clean and organized, you don't want to put things back together incorrectly, it could be a costly and time consuming blunder.
At this point, I hope you have a hydraulic press, or you are in trouble. There are so many uses for a hydraulic press when working on a Honda that it becomes an essential tool. You can get a decent one for a couple hundred bucks, a worth while investment is you plan on working on cars a lot. Use the press and follow the instructions to disaasemble the countershaft. When all the gears are off, they then get pressed on the new countershaft with the different pinion gear. Honda has a bunch of special tools for pressing the gears on, but you can get by using a piece of pipe of the right length and diameter along with assorted random sockets etc. It is not clear in the manual, but it implies you need to replace both the "special" bolt at the top of the countershaft and the bearing as well. Check the clearances as they describe and shim as necessary.
Finally, unbolt the old ring gear from the differental. In the manual, they say they are left hand threads, on my K20A they are normal right hand threads, so be careful, this one threw us for a loop. The pictures below show the old and new gears. You will also need to change the countershaft bearing in the clutch housing, as the new countershaft end is a larger diameter, the Honda part number for this bearing is 91003-PPT-004. Finally, put is all back together and reinstall the tranny and engine. Not a bad idea to check the condition of the clutch and flywheel when you have it all apart.
It has been suggest to us, that a clutch type LSD is the way to go and will make a big difference. Now would be a good time to consider such an upgrade. The K20A uses a helical gear LSD which seems to work well, and is virtually maintanence free. I have talked to at least one person who has had both installed on the same car, and claims that there is not much difference. So we will stick with the gear type LSD.
