tanman_2006
Just a farm kid...
A buddy of mine just bought an 87 5/4 ton that has been swapped to 4.10's from the 4.56, what does he need to do to adjust the speedometer?
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1987 5/4 ton Speedometer adjustment
- Thread starter tanman_2006
- Start date
83GMCK2500
Active Member
I'd suggest downloading a copy of the parts catalog that covers that year (it's the 85-86 C/K & 87-91 R/V series book), refer to group 4.000 where trans/tcase section is, there are speedometer gear charts. It also depends on what tire size he has.
FellowTraveler
Well-Known Member
The drive gear for 4.56 & 4.10 should be the same "15 tooth", then tire diameter is needed to determine driven gear required. Note tire diameter is measured 2 ways 1st is what the manufacture label's the tire with say 33.5" however at proper air pressure it may only be 31.5" in diameter this is the 2nd method called loaded diameter so some tinker between the two diameters will calibrate more accurately.
Post the tire diameter being used.
Post the tire diameter being used.