Speedometer Gears

[David A Young]

Hello. I have a 1985 GMC C1500 2WD LWB 2.73 10 bolt rear end. I recently swapped in a later model 700R4 (came from a 91 Silverado). It has the electric speed sensor for a speedometer and I need to swap to mechanical speedometer but I have no idea where to start. Is there a numerical method on how to figure BOTH drive and driven gears? Since the transmission has electric guts they'll have to be removed to install the plastic gears. I have cruised the web trying to find a method on how to figure both gears and haven't found anything yet. Any help would be greatly appreciated. Thanks.

[Irish_Alley]

one option would be put a cluster from a 89-91 blazer burb or crew with the electric speedo. another option is to get a dakota digital  ecd-100
http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=886/category_id=287/mode=prod/prd886.htm
the owner of this site is a dealer for them but i want to say it might be around $300. me personally im running my cell phone for a speedo

[Jakethesnake73]

one option would be put a cluster from a 89-91 blazer burb or crew with the electric speedo. another option is to get a dakota digital  ecd-100
http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=886/category_id=287/mode=prod/prd886.htm
the owner of this site is a dealer for them but i want to say it might be around $300. me personally im running my cell phone for a speedo

Cell phone works great!

Sent from my SAMSUNG-SM-G891A using Tapatalk

[David A Young]

I can convert it for 95$ but I need to know where to go with the gears. I found a website that gave me the driven gear and I just plugged it into the formula on the site and came up with a 19 tooth drive and a 34 tooth driven. So maybe that will give me a close readout. The reluctor wheel can be removed with a puller and the gear will clip in its place. But because it has a reluctor wheel in place of the gear, I don't know where to start. I have an older tailshaft housing as well if it needs to be changed too.