Basic Info

You can tell a DX/CX/VX tranny from a EX/Si by numbers cast into the housing. Just above the filler plug is a set of numbers.
P20/A000 is for DX/CX/VX
P20/B000 is for EX/Si
Other than that, tranny must be split apart to know for sure which one you have.

Available Stock Ratios

EX/Si
1st-----3.250
2nd-----1.900
3rd-----1.250
4th-----0.909
5th-----0.750 for Si HB and Del sol Si
or------0.702 for 2 dr or 4 dr sedan
Final Drive---4.250

DX/LX
1st-----3.250
2nd-----1.762
3rd-----1.172
4th-----0.909
5th-----0.702
Final Drive---4.058

CX /VX
1st-----3.250
2nd-----1.761
3rd-----1.066
4th-----0.853
5th-----0.702
Final Drive---3.250

Internal Differences

There are some minor differences, mainly with the bearings inside the trannys. The diff bearings, countershaft bearings, and input shaft bearings are different between the DX/CX/VX casings and the EX/Si casings. If you are putting a EX/Si gearset into a DX/CX/VX casing, you have to use the second countershaft bearing and the differential of the case you are swapping into.
NOTE The bolts for the ring gear are lefthanded thread.

Weak Points

The major weak points are the shifter forks and the diff. gears. The shifter forks are made out of cast aluminum. They are prone to rapid wear, so be cafeful when downsshifting into first gear, esp. when racing. DO NOT force it into first gear. The fork will break! Another weak point is the gears inside the differential. They are cast steel and prone to failure. If a HD clutch or slicks are used, the diff. will fail sooner or later. The best thing is to install a quality LSD (Limited Slip Differential) as I've broke two trannys from this. Beware of the Phantom Grip LSD as it uses stock gears. It might be OK for autoxing, but AVOID it for drag racing.

5th gears

You can swap any of the 5th gearsets for cruising at a higher/lower rpm. This is a simple swap, once your inside the tranny. The 0.771 from the 4g Civic/CRX L3 trannys fit perfectly and is a nice swap to a DX/EX/Si 0.702 5th. Make sure you keep the gearsets with each other. It is very easy to get the 27 tooth gears mixed up. They are very close in size, but will not interchange. You have the following choices.
0.878---??/??---CRX ZC JDM
0.771---35/27---Civic/CRX 88-91 DX/Si
0.750---36/27
0.702---37/26
0.694---36/25---Civic/CRX 88-91 HF
The mysterious VX 5th of 0.673 was a misprint in the 1994 Honda Service Manual. It was the 4th gear ratio of the automatic tranny. It is best to use either the 0.771 or 0.750 with stock or lightly modified engines. You can get by with the 0.702 but mileage will be about the same.

RPM vs. MPH of various 5th gears

5th gear-----FD------45------60------80------100---
0.702------4.058---1898---2530---3373---4217--
0.702------4.250---1988---2650---3533---4417--
0.750------4.250---2123---2831---3775---4718--
0.771------4.250---2183---2910---3880---4850--
0.878------4.250---2486---3314---4419---5523--

Multiply RPM's by 1.135 if using 20" slicks
Multiply RPM's by 1.032 if using 22" slicks

RPM shift tables

These tables will tell you how much your rpm's will drop when shifting. These numbers are for a steady speed shift. If you are accelerating they will be slightly higher due to clutch slippage and continued acceleration. Hybrid trannys also included. MPH numbers are for stock size tires, 22.7" overall diameter. MPH numbers for 5th gear are assuming enough power to overcome wind drag.
How to use these tables...If you shift at 6800 rpm using the DX tranny as an example, your rpm will fall to 3685 in 2nd, 4526 in 3rd, on so on.

DX
1st----3.250---0000/6800---34.8mph
2nd---1.761---3685/6800---64.3mph
3rd----1.172---4526/6800---96.9mph
4th----0.909---5274/6800---124.5mph
5th----0.702---5251/6800---161.3mph

Si/EX
1st----3.250---0000/7200---35.2mph
2nd---1.900---4209/7200---60.2mph
3rd----1.250---4739/7200---91.6mph
4th----0.909---5236/7200---125.9mph
Choose your 5th
5th----0.702---5560/7200---163.0mph
5th----0.750---5941/7200---152.6mph
5th----0.771---6107/7200---148.4mph

Hybrid using ZC 3rd and 4th gears
1st----3.250---0000/7200---35.2mph
2nd---1.900---4209/7200---60.2mph
3rd----1.346---5101/7200---85.0mph
4th----1.033---5526/7200---110.7mph
5th----0.750---5228/7200---152.5mph

For 92-95 trannys it is best to use the HF/STD 3rd gear of 1.033 for 4th gear.
If you use the ZC 4th gear it will require grinding to fit the synchro hub.