someone972

iTrader: (2)

So the speedo is reading wrong in my Firebird, it shows 65 when going about 55, and around 90 when going 75. So the gear ratio has probably been messed with at some point since the tires are stock size. Is there a way to fix this without getting speedo gears? Isn't there a buffer box somewhere that can be calibrated like this link shows: http://www.tbichips.com/drac/?

JunJun

If the needle of the speedo is not stable, I would replace VSS.

someone972

iTrader: (2)

The needle is very stable, it's just off by a certain amount. It's 0 at 0 mph and then gradually gets farther away from the actual speed as speed increases. I'd love to get this fixed since it's racking up my odometer faster than it should be. I don't know how long it's been like this, so I don't know the actual miles my car has.

visceris

I have this exact same issue. If you found a fix for it please share. Thanks

someone972

iTrader: (2)

I ended up doing it properly and changing the speedo gear combination. I started off by using a gear calculator like this site: http://www.tciauto.com/tc/speedometer-gear-calculator/ There is also a sticky on the site somewhere that has a good equation. After coming up with the closest gear ratios for my car, I went looking for the gears. If you go this route, you may have trouble finding the gears locally. I needed a 15 tooth gray drive gear which nowhere local had; I got lucky and it was in a junk-yard third-gen Camaro that I was getting some parts off. Be aware that there are two different housings for the driven gears. I forget the exact range, but the lower tooth count driven gears fit on one style, and the higher tooth count fit on the other style. For me it just so happened that I could re-use my old driven gear and housing and just put in a "new" drive gear to get the correct ratio.

Replacing the gear isn't very hard, you just need the right tools. You'll need a jack and some jack-stands to get the car up, then you just unbolt the driveshaft from the diff and then there are four bolts holding the end of the tail-housing onto the transmission. You don't need to drop the transmission, although some wobble extensions might be helpful. The driven gear housing is only held on by one bolt. Remove the driven gear housing before removing the tail-housing. The drive gear is sort-of pressed on. There is a small clip on one side that you have to hold down to remove the gear, which is somewhat tricky, but can be done. The junkyard gear I got off by using a crescent wrench behind the gear and then hitting the bottom of the wrench against the transmission bracket with a hammer to act as a sort of lever. The one in my car was a bit trickier and I ended up using a screw-type bearing puller that I had, but it could be done without it. When putting the new gear on, make sure it's lined up with the clip or else it won't go on. I had to put it on and off a couple times before I got it right. After that, just bolt everything back up and top off the transmission fluid that you may have lost while doing the swap. If you are paranoid like me then you can use a torque wrench to tighten the tail housing bolts and the bolts holding the drive shaft to the yoke.

Alternatively if you don't have the tools for swapping the gears, there are electronic converter boxes that go somewhere near the dash I think. Last I saw they were around $80, but I could be misremembering. I didn't go up going this route so I don't have any instructions, but it will work just as well.