I have a 1992 RS. It has a 305 TBI and a TH700R4. I just replaced had the rear rebuilt with 3.73 gears. This is an increase from the 2.73 gears. So, my speedometer is way off. I want to fix this and I am not sure about the whole thing.

Does my car have a VSS (Vehicle Speed Sensor)? If so, do I need to do anything with this?

Does the car use a “DRIVE” and “DRIVEN” gear? If so, what do I need to do to fix this?

I have read that I need to know the outside diameter of the tire and the color of the drive gear. The tire is easy to get, the other I am not able to do right now. I know that everything in the tranny and speedometer is stock as if it was 2.73 gears.

If there is anything I am missing, feel free to tell me. If there are parts need to buy, tell me… HELP IS NEEDED!!!!

I cannot merge into traffic because when the speedo get to about 115 the motor shuts down. I know that is the limiter in the EPROM.

 

Go to http://www.transmissioncenter.net/sp...er_calibration they can help you out. Know your tire size, drive gear and driven gear. You may just need to replace the driven gear which is behind the cover on the drivers side of trans. Hope this helps, they helped me with mine.

 

Yes, you have an in-trans. VSS. It is driven by drive and driven gears. You need to ask the dealer what gears were in a 1984 Z28 with 3.73 rear gears and a 700-R4. You need to get that # tooth count drive gear (it will fit your trans) and a VSS driven gear with the same tooth count as the driven gear for the 1984 Z28.

You will need to unbolt the tailhousing to change the drive gear. It will be relatively easy. But not as easy as my car since I don't have a tq. arm on my 700-R4.

All online speedometer gear calculators are wrong. Every single one I have ever seen. Trust the combinations GM installed in cars: they will make your speedo correct. Transmission Centre .net will make it wrong.

 

Thanks.. You mentioned 84. Is that going to be the same as a 92. If so, I need to call the dealership and get the driven gear.

 

I gave you an app. which came with 3.73 rear gears. The drive gear from an 84 works for you. The driven does not, but you need the correct tooth count.

 

The 84 came with 15 drive and 45 driven for a 215/65/15 tire and 3.73 rear. Assuming you have that size,a 235/55/16, or equivalent diameter tire, the ratio will work. You will need to change the gear in the trans to a 15 tooth one GM part # 8642620 ($6.24). The 45 tooth gear for the sensor should be GM part# 25513052 ($6.24). You should also change the sensor to GM part# 10456089 ($46.19). For some reason it takes a different sensor if the driven gear has over 40 teeth. For reference, the ones in your car should be 17 and 37.