zxnazx

Hello s2k owners, out of many s2ks i have purchased and worked on i have never seen the issue i am dealing with now. I do apologize for my english, let me know if anyone has anything to say.

Recently bought an 05 s2k 40k miles with no history from the past. First time i drove noticed that the speedo is reading higher from the actual speed, compared it to the gps tracker and i was 11 to 12 miles over the actual speed on the highway. I did read that some people's cluster had issues and people recommend installing a yellow jacket to compensate for the issue. The car is stock ap2 with matching vin number on the block/tranny. I checked the ecu and it is an ap2, i swapped clusters, and speed sensors and nothing has changed. I did read about different gears being installed in the diff like the 4.44 all the way to 4.77 and from reading it seems that ap2 with 4.77 would be 700 to 800 rpm higher ( would that be enough to offset the speed by 11 to 12 miles?).
Does anyone here run an ap2 with different diff gears and had the same issue with the speed?
I had put the car on the lift and examined the rear diff,bolts, anything to tell me that the diff at some point was out and swapped out and everything looks too clean, no scratches no nothing indicating different gears inside. If we are to say that the car is fully stock, what else could be going on that would cause the RPMS to be at 4k at 60 and have 11 to 12 miles over the speed?
Is there any way of checking the diff manually? by lets say marking, spinning counting how many revolutions i get with the oposite side axle then compare that to a stock diff or another diff? anything to see if the gears are different?
I do apologize for my english, let me know if anyone has any input.

ISADE

You're english is great, don't worry about that so much!

Someone might know more about the differential and gearing, but what wheel and tire size are on the car at the moment? You'd have to be much smaller than stock but that could be the issue as well.

Billman250

Match mark the wheels to the backing plates, so you can determine one exact full turn.

Mark the driveshaft at 12 o’clock.

Slowly turn both rear wheels one full turn, counting the number of driveshaft turns.

If the driveshaft turns 4.1 turns, you are stock. 4.56 turns, 4:56 gears, etc.

This method is dead accurate.

RacerXI

Mark the rear tires and driveshaft. Spin the rear tires and count the revolutions. That'll get you close and you'll be able to estimate the gear based on that.

zxnazx

Thank you . Thank you Guys. Did the mark, figured out i have a 4.77 diff in there, dropped it, put a stock diff in there as i have 4 spare once sitting in the shop and the Speedo is back to normal, rpms are back to normal, yaaaaa. Now need to figure out what kind of gears in there and what is it worth on the used market as i need to sell it. Any suggestions as far who makes these and what they are worth assembled?

windhund116

You have 4 Honda S2000 diffs sitting around your shop? You set them up for specific track use?

Thanks!

zxnazx

no i dont track. Just had few parts cars over the years as i specialize in rebuilding s2k's. Collision repair. here is the s2k whos owner i found on the forum few days ago.
05 S2k by Dennis V. | Photobucket

jsaric

can you tell us the difference beetwen diferent ratios. as this is still fresh to you.

is it worth to put 4.77 on a daily car with 4-5 track days/year ?

thank you