"final drive ratio" of a GMC 2500 vandura

This chart might help you:.. https://www.gearvendors.com/cg2wdt.html

Could you please check your VIN and come back? In 1981, before your Van was assigned a VIN, the DOT had already mandated that a VIN not contain the letter 'O' or 'Q' or 'I' and no 0 (Zero) I tried to run it every way but then it dawns on me you have a 1986 which should not have those characters, but it does, Something is not quite right 1981 was the same year 17-digit VIN numbers were used

sorry the correct vin is 1GDEG25HOJ7512227

http://www.vindecoder.net/?vin=+1GDEG25HOJ7512227+&submit=Decode ..that says the same as the rest. Invalid http://www.vindecoder.net/

Still something not right. First the 10th digit, in your case the 'J' id the model year, and that is for 1988. Then there is still either an O or 0, I think it's letter O but still should not be there. Please believe be, friend... I am trying to help but that one shows 'invalid VIN' also

But none of the matters just find out what transmission you have and use the chart link above

i found that final drive ratio is: 10.16