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Old 12-17-2007, 12:09 AM   #1
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Thumbs up honda civic tranny Question

civic P20 VX/CX trannys compared to P20 EX/SI trannys? is there anything on the casing that you can identify that the gears are longer? i ive looked in to it a bit about them, and all i can find is people telling me just to Throw it in and find out??!!?? im trying to get the best MPG's out of my tranny.

also dose anyone have any suggestions about the gears i should use on a VX motor in a 93 4door lx? is the extra weight going hurt my MPG's sense the car weights 2-300lbs more.

i can build trannys so if any one has a good hybrid tranny gear setups let me know! thanks!!
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Old 12-17-2007, 01:43 AM   #2
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I know that with cable transmissions, there is no way to tell the difference between the various transmissions based on the numbers on the cases. I would guess that the situatio is the same with hydraulic transmissions. The only way to really know is to see how many rotations of the input shaft are required to produce a given number of rotations of the differential carrier in, say, fifth gear. As for the proper gear ratios to use for best economy, this can be somewhat tricky. Based on my experience of swapping an HF transmission into a 1989 Civic DX, taller is not always better. BUT, since you are actually using a motor that was designed to be used with tall gears, yo would probably get good results if you used a staight VX/CX transmission. On the other hand, you could compromise by using a DX/LX transmission. This way, RPMs would be lower on the freeway than the EX, and the car would not feel so doggy around town (and force you to go heavy on the throttle, wasting gas).

I should add that gear swapping won't help with 1992-1995 transmissions like 1988-1991 transmissions. The CX/VX, DX/LX, and EX transmissions all have fifth gear ratios of .702:1. The VX/CX and DX/LX transmissions actually both have the same ratios in gears 1-5. And the ratios on the EX are not much different from the others. They only differ by the final drive ratios (4.250 on the EX, 4.058 on the DX/LX, and 3.25 on the VX/CX).
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Old 12-17-2007, 05:22 AM   #3
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The best way to find out is to shift the transmission into any gear and turn the input shaft. Count the revs you turn the input shaft to make the diff turn one full revolution. Then you can back out the gear ratio. Some trannys have the same ratio for first, so your best bet is to back out the FD ratio. It takes some finagling because you're trying to back out two ratios (the gear you're in and FD).
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Old 12-17-2007, 06:30 AM   #4
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I'm also fairly sure the stampings/castings on the case mean nothing and that spinning it is the only way to tell.
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