Speedo gear

[TheMaster]

Today they put my 4:10s in the car and a 23tooth speedo gear and my speedo seems to me about 10mph off at 40mph (When my dads car was going 40mph my speedo read 50mph.) I went back to the shop that did the installation and they said their was nothing i could do about it. Is their any way i can correct my speedo or do i have to just live with it. The car is a 1992 Gt vert with and AOD trans On a better note the 4:10s are great and i love the performance

 

[shallto]

Are you sure he put the right gear in? I have a 92 hatch, AOD , and 4.10's. With the 23 tooth gear I am dead on at 50 .

 

[_jb_]

Don't know if this will help, but I found this on here at some point in time.

http://www.geocities.com/mgnedell/notchback/tech/speedo.html

 

[TheMaster]

stallto want color was the gear they put in your car the one they used on mine appeared to be black

 

[gt90stang]

Put the 21 tooth or original back in and take it to a speedo shop. They can put a little gear box between the transmission output and speedo input and calibrate it in about 45 min. It will cost you $100 or so. Ford went to a 7 tooth drive gear instead of the older 8 tooth on the tranny output shaft. So anything higher that 3.55s and you've got to do this or live with the error.

Good Luck, Don

 

[Biggeley]

A 23-tooth will only read accureately on an AOD with a 7-tooth gear on the other end, which was installed in mustang AOD's prior to 1990.. Therefore with the 8-tooth deal you have in your tranny -- you're pretty much screwed until you get a speedo reclibration box.

 

[jrichker]

Put the 21 tooth or original back in and take it to a speedo shop. They can put a little gear box between the transmission output and speedo input and calibrate it in about 45 min. It will cost you $100 or so. Ford went to a 7 tooth drive gear instead of the older 8 tooth on the tranny output shaft. So anything higher that 3.55s and you've got to do this or live with the error.

Good Luck, Don

Right on target...

Check to see if there is a speedometer shop in your area. If there is, ask about the Stewart-Warner speedometer gearbox. I believe it is either a 777 Series Drive Joint Kits and Parts or 666 Series Drive Joint Kits and Parts. It is a small gear box that fits between the speedo pickup gear on the transmission and the speedometer. It has quick change gears that allow you to choose almost any tire and rear end gear ratio you want. This will allow you to get the accuracy with within 2%-3%. The drawback is that it isn't cheap.