Have a 93 Dodge Cummins, Getrag 360 manual trans. Replacing speedometer gear & pinion trans drive gear. PROBLEM: My book manual shows the index setting number for the speedometer adapter for an Automatic tranny but nothing for my 5 speed. Anyone know where I should set it? My speedo gears get messed up about every 50k miles (quit working).

 

I am confused. I i know the 727 and NP4500 have an eccentric(the sane one) but an unaware of on on the Getrag. but my only experience with the 360 is four wheel drives.

 

Not sure about the Getrag but the A-833 4 speed that I had had numbers cast into the speedometer gear eccentric housing and a "bump" cast into the tail shaft. The numbers corresponded with the number of teeth on the speedo gear and you had to line the number up with the bump to get the correct gear mesh with the tailshaft gear.
The idea being that the tailshaft gear has a certain number of teeth. Because the vehicles came with different gear ratios in the differential a different sized speedo drive gear was required to correct for this. The different speedo drive gears are different diameters hence the eccentric mount.
At a given rate of speed (for instance 35 MPH) the tailshaft will be spinning much more slowly with 3.07 diff gears that with 4.10 diff gears. This would give an incorrect speedo reading.
Clear as mud??

 

For the 2wd getrag, yes the speedo gear is the eccentric style found on the tailshaft housing. It uses the same gear as an auto. On 4wd the speedo is on the np205 output.