'92 - '95 Civic CX tranny swap and VSS clarification

[cems70]

Hello all,

I've been planning to swap a VX/CX tranny into my '95 DX hatchback ever since i bought my DX several weeks ago. I finally bought a CX tranny w/ low miles and will do the swap in the next 2 - 3 weeks and have a couple of questions:

1) One of my main concerns is the possibility of altering the odometer/speedometer readings. By installing a CX tranny and keeping the standard 175/70/13 tires, it would seem that this would cause the odometer to read too few miles because the tires are about 2.5% larger diameter than the correct size 165/70/13 tires for a CX tranny. Given this theory, it would be logical to assume that I should swap the VSS from my DX tranny into the CX tranny. When I checked the Honda part # for a DX VSS and CX VSS, the part number is exactly the same. Now I'm confused. A DX w/ standard 175/70/13 tires is somehow calibrated for an accurate odometer/speedo reading. A CX w/ standard 165/70/13 tres is also calibrated for an accurate odometer/speedo reading. Yet both use the same VSS. So any ideas what other part is different in the tranny or speedo to give them their distinctive calibrations with their different standard tire sizes? I've read various posts on this issue, but can't make sense of what to do.

2) The used CX tranny has 60k miles on it, but has been sitting around in a junkyard (inside a weatherproof bus) for quite a few years. Are there any specific parts (seals etc.) that should be replaced w/ new parts or with existing parts on my DX tranny (that has only 70k miles) before swapping into my DX?

Many thanks for any insight.

[Matt Timion]

concerning the VSS... they ARE the same part. I think that automakers are allowed up to a 5% discrepancy when it comes to speed.

[cems70]

So basically Honda made three car models w/ the same VSS and two different tire sizes. And either the VX/CX w/ its 165/70/13 tires or the DX w/ the 170/70/13 tires registers the correct # of miles on the speedometer. That means that the VX/CX model or DX model odometer and MPG is off by up to 2.5% (either high or low). I guess I'll measure my odometer against 20 miles of highway mile markers to see if it's off.

[GasSavers_Ryland]

when I replace trannys I replace the axle seals, when you have the tranny out they are extreamly easy to work on, and about $20 each, replace the clutch too, along with getting the fly wheel reserficed.

[GasSavers_scostanz]

Originally Posted by cems70

So basically Honda made three car models w/ the same VSS and two different tire sizes. And either the VX/CX w/ its 165/70/13 tires or the DX w/ the 170/70/13 tires registers the correct # of miles on the speedometer. That means that the VX/CX model or DX model odometer and MPG is off by up to 2.5% (either high or low). I guess I'll measure my odometer against 20 miles of highway mile markers to see if it's off.

There is just a little over 1 1/4% difference in diameter of the two sizes you've mentioned so you'll be close either way. I think you'll find that you're going to be off to some level.

Before I did my CX tranny swap, I was registering 2.79% more indicated miles than actual miles. After the swap I was registering 2.34% less indicated miles than actual. The funny thing is, my speedometer was reading about 6 mph fast with the old tranny and now it's reading about 1 mph slow. I think there are variences within the VSS sensors as well. My take away from all this is anyone who hasn't dialed in their odometer is probably not reporting accurate mileage.

-- Scott

[imzjustplayin]

Sorry to necro but... I think you guys don't know what you're doing.. First of all, you shouldn't be using the speedometer itself as the acid test but actually the Odometer itself. Why do I know this? Because on my '98 Civic I have a scan gauge hooked up and it tells me what MPH the ECU is detecting. The Speedometer was reading 2MPH faster than what the ECU was reading and what the ECU was reading was actually accurate! How do I know the ECU reading was accurate? Because I used my friend's GPS and the numbers corresponded nearly perfectly between the GPS and the Scan Gauge yet the speedometer was fast by 2MPH.. So if there is a way to read the MPH from the ECU, do it that way because playing around with the VSS and whatnot because of what the speedometer is saying is a poor way of doing it.

[cems70]

Originally Posted by *************

Sorry to necro but... I think you guys don't know what you're doing.. First of all, you shouldn't be using the speedometer itself as the acid test but actually the Odometer itself. Why do I know this? Because on my '98 Civic I have a scan gauge hooked up and it tells me what MPH the ECU is detecting. The Speedometer was reading 2MPH faster than what the ECU was reading and what the ECU was reading was actually accurate! How do I know the ECU reading was accurate? Because I used my friend's GPS and the numbers corresponded nearly perfectly between the GPS and the Scan Gauge yet the speedometer was fast by 2MPH.. So if there is a way to read the MPH from the ECU, do it that way because playing around with the VSS and whatnot because of what the speedometer is saying is a poor way of doing it.

After swapping the CX tranny into my DX 3 years ago, I checked the speed on the GPS versus my speedometer and my speedometer is perfectly accurate. The indicated miles on my odometer are nearly 4% less than the actual miles on the GPS.

[jmaze]

how many mpg improvement? any drawbacks?

[imzjustplayin]

Originally Posted by jmaze

how many mpg improvement? any drawbacks?

lulz... look at his gas log! He's got a civic DX and is averaging 56mpg...that transmission definitely has something going for it!!

[jmaze]

sorry, was not paying attention.