my speedometer is off about 15 to 20 mph slow took it to the dealer they checked everything and it look good ,but the dash speedo cluster looked like it had been changed at some time .is there some body out there that can tell me what is the right speedo for a 1991 firebird 305.or can it be recalibrated or just find another one.

 

The speedometer doesn't need to be calibrated, but your vehicle speed sensor might. There are different sensors for different rear end gears. It's located in the transmission tailshaft, and pretty easy to change. Since your speedo is off by that much, I'm betting it's the wrong sensor.

 

Are the trans and/or rear end original to the car? If not, your problem could easily lie there.

JamesC

 

changed my 2.73's to 3.43's and it threw the speedo off by around 10mph

 

as far as i know the trans.&rear are origenal,did not see a tag on the rear end for what gears it has.might need to spin aback wheel and count the drive shaft.the trans has a red gear,now the less teeth will speed up the speedo wright?might try that.