Hey Rich,
I think this was covered in a recent thread on speedometers and rear ends. I don't remember if it was in Diesel, vintage or tech discussion but you should be able to find it with a search.

Good Luck

__________________
Ncnetman
1978 300cd fresh paint
1965 Mustang
1968 Torino GT fastback
2015 VW Passat TDI
1969 Ranchero- project
1974 240d 4-speed -for sale
1976 240d - for sale
1990 6.2 Suburban 194k-getting a 6.5 turbo
2008 Duramax Silverado-totaled
1959 Chev 3100 Fleetside - sold