Shifting points seem to be off after lift/tires and JSCAN recalibration.

[kris77]

Long story short here. 3" teraflex lift. 315/70/17 KO2s. Used JSCAN to change tire size to 34.75" My shifting points seem to still be off a bit. Seems to hang in 2nd and 3rd way too long. Mainly 3rd for some reason. Anything I can do differently on JSCAN to try and correct?

Sponsored

 

[rkwfxd]

Put a tape measure on those tires. They are prob only 33.5” at most.

 

[kris77]

Ok, I'll try that. I went by some calculator online that said they were 34.5. That's what I used, not 34.75. I just went and double checked myself. So them being a bit smaller than I entered will keep me in gear a little longer than usual?

 

[58Willys]

Your shift points will be off due to the larger tires effectively changing your overall gearing.

 

[unsavory]

FYI, the JLUR XR, comes with those tires from the factory, and is set at 34.88 from the factory.

I thought this was wrong, so I changed the setting to 34.5", and my speedometer was off, as measured with GPS. So I used JScan to set them back to 34.75, which is as close to 34.88 as it can get. My speedo is now correct again.

So the tires may not actually be 34.88 inches, but that setting from the factory is indeed the correct setting for those tires if you want your speedo to be accurate.

 

[El Zilcho]

I used 34 inches for 315 KO2's on my Sport. Speedo is close enough and it shifts good.

 

[J0E]

Put a tape measure on those tires. They are prob only 33.5” at most.

That's a start but use a GPS app to compare actual to speedo.

 

[aldo98229]

Your shift points will be off due to the larger tires effectively changing your overall gearing.

^^^ This!

Depending on what gearing your Jeep came with, 315 tires might be too much for the stock gears.

My Sahara came with 3.45 gears. After I mounted 35x12.5 General ATs on it, the automatic transmission refused to shift beyond 6th speed. Even after I recalibrated the speedometer.

I ended regearing to 4.88 last winter; I now have use of all 8 speeds again.

 

[mwilk012]

Recalibrating tire size doesn’t change shift points. Actual load on the engine does.

Sponsored