I have a 8 inch lift with 37 inch tires. Throws my speedometer off about 10mph. Does this in the end affect my shift points to which I should buy a tool to recalibrate my speedometer to the bigger tires?

 

Larger tires are harder on a trans but does not necessarily mean the shift points are altered- ex: 48re shifts into OD at 55 mph- 55mph is 55mph whether you have 31s or 37s. I think Gearing is what you are hitting toward- different gears will provide some stress relief for you rig. To answer your question recalibrating your speedo will not effect your shifting at all. If you have an edge monitor then I would run your speed there- I just know how far off my speedo is and drive accordingly

 

I thought so but wasn't sure so figured I'd ask before I bought a tool.to recalibrate my speedometer. Thank you.