Can anyone please tell what tooth gear for the transmission that I need to purchase to make my speedometer acurate? Here are the details; 1969 Chevelle Malibu original 10 bolt posi, 3:73 ratio, original TH 350 transmission, tires P235/60 R15 tires. I have changed the gear ratio to 3:73 and of course the tires are larger. Ant information would be greatly appreciated! Thanks.

They have a calculator in the NPD book that shows how to figure out what you need.

LK

Try these out.

http://www.chevelles.com/shop/speedo.html

http://www.tciauto.com/Products/TechInfo/speedo_gears.asp

Tried a combination of both and think I have mine closer now. Find out tomorrow when I pick up my nephews "gps" for the weekend.

I have 3:73 with 275-60-15's on the back, and a 350th.
went from a 10 inside to a 8 and from a 25 that goes though the casing to a 21. I now seem to have 2800 at 60 mph.

Try these out.

http://www.chevelles.com/shop/speedo.html

http://www.tciauto.com/Products/TechInfo/speedo_gears.asp

Tried a combination of both and think I have mine closer now. Find out tomorrow when I pick up my nephews "gps" for the weekend.

I have 3:73 with 275-60-15's on the back, and a 350th.
went from a 10 inside to a 8 and from a 25 that goes though the casing to a 21. I now seem to have 2800 at 60 mph.

Great resources - thanks for the links!

Try this...go to a GM dealership parts counter and tell them your application (TH350, 3:73 and tire size). They have a chart that gives you the correct color of gear and associated housing. Cost me about 50 buck, but now my spedo is right:thumbsup:.

Oh ya...you will have to convert your metric tire size (275-60-15) to something close to the same overall diameter in the old US standard sizes for their chart. Found a converter online.

Here is another link, this is what I used to get my 700r4 right.
http://www.bgsoflex.com/speedo1.html

Can anyone please tell what tooth gear for the transmission that I need to purchase to make my speedometer acurate? Here are the details; 1969 Chevelle Malibu original 10 bolt posi, 3:73 ratio, original TH 350 transmission, tires P235/60 R15 tires. I have changed the gear ratio to 3:73 and of course the tires are larger. Ant information would be greatly appreciated! Thanks.

7 tooth (pink) drive gear, 20 tooth (blue) driven gear should work with your combo. If you change your driven gear make sure the bullet or driven gear housing matches the new tooth count.

BLT4FN

How do you run 12.3 in the quarter mile? My 60 foots are 1.7, my mph at the traps are 107.5 and my et's are 12.7. I am totally motor with a big block and have 4.11 gears.