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Discussion Starter · #1 ·
Just wondering if anyone has experience with this. I realized that my 2002 EP3 VSS won't work. I could have sworn that I had checked to make sure that the gear on the VSS meshed with the gear on the diff, but when I grab the mainshaft splines and turn the mainshaft with the transmission in gear, you can see the VSS flexing and then you hear a regular "POP" as the gear jumps teeth.

I did some looking on part numbers and I noticed that the 2002-2003 EP3 uses a different part number for the VSS gear. Note that by VSS gear I mean the little gear on the end of the VSS that can be purchases separate from the VSS itself.

VSS part # 78410-S5T-901
gear part # 78415-S5T-901
speedo drive gear # 41312-PE6-310

The 2004-2005 EP3 uses

VSS part # 78410-S6M-N01
gear part # 78415-S7A-G01
speedo drive gear # 41312-PPP-000

The 2004-2005 EP3 shares the same part #s with the 2002-2004 RSX-s. I ordered the VSS gear for the RSX-s since it's only like 2$. Hopefully that will work.

I'm curious to see what kind of speedo error I'll end up with after doing this. My guess is that the speedo will read high since the cars with the bigger overall diameter wheel seem to have a different part number.
 

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Discussion Starter · #3 ·
If you could report back on the number of teeth on the gear, that would be great!

Are the speedo ring gears different? Just wonder if there would be any issues with gear mesh.
Yeah, the speedo drive gears are different part numbers, so I assume they are different. I suppose I'll have to do a closer inspection when I get the new VSS gear.

The observed pattern thus far is that the 5-lug models, which use a bigger wheel, have a different speedo drive/vss gear than the 4-lug models which use a smaller wheel. It would make sense to alter the speedo gear ratio in that case.
 

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Discussion Starter · #5 ·
I would also suspect them to be different because of the different final drives. So I would make the assumption that you want the vss gear to correlate with the final drive that you have.
VSS has nothing to do with final drive. Not on the models where the speedo drive gear is on the diff. It turns at wheel speed, so changing the final drive does not alter the accuracy of the speed detected.
 

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Discussion Starter · #9 ·
If you have the same exact setup. Meaning wheels tires trans. One with a 4.4 FD and one with a 4.7. Your telling me that VSS will accurately display the speed of the car?
Yep, as long as the speed pickup is on the diff, any changes in gearing will be accounted for. The 2005+ type-s has a countershaft mounted speed pickup, so changing the final drive will throw off the speedo.

the base and type-s gears are the same but the ep3 is not, the resion is the size of the overal diamiter of the tires. i have looked at both and there is a different number of teeth so ya they are not the same
That's what I've been guessing.

SI speedo ring(on diff)has 23 teeth
its vss has 19
so 23/19 =1.21
Type-s speedo ring(on diff) has 26 teeth
its vss has 20.
so 26/20=1.3

I put the si combo in my crx, now the mph is really close with my 215/60/14 BFGs on the front. -Neal
Ahh, I knew there would be someone that had done the research on this. Looks like that's my issue. So now the question is, do I want to bother taking apart the transmission I just put together just to swap out the speedo drive gear. The current speedo setup will cause increased error in my speedo and odometer, but if I up the tire size to something like 225/50/16 from my current 225/50/15, I'll be fine.

decisions decisions.
 

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Discussion Starter · #11 ·
Correct me if I'm wrong but...

The VSS whether it is located on the diff or the counter shaft, reads rpm. It then sends a signal to the cluster of your speed. If your FD is 4.4 or 4.7 it will result in different rpms sending to your cluster. It may send the same speed, but your actual speed will be off.

If i'm wrong explain to me how a 4.4 and a 4.7 FD will yield accurate speeds shown on the cluster vs actual speed.
That statement is not entirely correct. For a fixed engine RPM, the output RPM through a 4.4 or 4.7 final drive will be different. However, engine rpm doesn't determine vehicle speed, wheel rpm does. Regardless of FD, the number of turns of the WHEEL for a particular speed will be the same. Since having the speed pickup on the diff gives you the WHEEL rpm, your speed will be correct regardless of final drive.

Just take a moment to think it through and you'll get it. :)
 

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Discussion Starter · #13 ·
Interesting observation.

The car is running now with the speed drive gear (on diff) and pickup gear (on speed sensor) for the 5-lug wheel/tire, which are about an inch larger in diameter than the 4-lug wheel/tire. However, the speedo is still 100% accurate. According to the datalogs, 3690 = 80mph which is spot on with the math.
 

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Discussion Starter · #15 ·
Do you have access to a GPS to compare speeds?
Yeah. I have a garmin Nuvi 650.

I do know that before, the speedo was also spot on with the theoretical numbers at cruise. I think wheel slip only becomes a major issue at very high speeds when things become traction limited.
 

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Discussion Starter · #17 ·
I'm curious if there is a speed difference.

Possible to check and compare?
Yeah, I've done this myself to check. There's usually a little error, not huge as honda speedos are reasonably accurate at sane speeds. The more important thing for me to verify was not the absolute accuracy of the sensor, but to see if there was any error introduced as a result of swapping the speedo drive/pickup gear. To my surprise, even though I changed the drive ratio of the speedo gear, the speedo is still accurate on my stock gauge and in Hondata.

The only compensation I made is that I entered in the correct gear ratios into my calibration, but that still doesn't account for the fact that the tires I'm running are about an inch smaller in rolling diameter than the tires that the speedo drive/pickup gears I swapped to were designed for.
 
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