38s with 4.88. Is recalibration a must?

 

You have to know what was on it before. What is it calibrated for now. So you can calculate the change.

 

What ratio and tire size did it come with?

 

Stock gearing which was 3.55 I do believe and I had 275/70R18s on it

 

Was that the stock size the truck came from the factory with? If so, those are 33's.

Yes, you need to recalibrate. Your speedo is more than 10 mph off at 70 mph. The dealer can't compensate that much, so you are going to need a programmer. The PCM is getting the wrong data from the speed sensor, which will affect how it runs and how the transmission shifts.

 

Ok whats a good programmer to go with to do just that? To many threads bout this one or that one and this does this and this etc. Just something to get it back on track

 

I think you should get a SCT or a Edge/Gryphon and some custom tunes. If you are going to buy anything, do it right. If you bought 38 inch tires and 4.88 gears, you already have a decent investment and you should optimize that.