Put 31's on my 01 blazer and I know the speedometer and other things like shift points will be affected and my question is who has the tool to recalibrate the PCM? Is this a tool most garages have?
Also I have read on here that the larger tires will cause the trans and engine to wear faster. My ZR2 has the same size tires and 200,000 on it and has been no issue so is that just a myth?

 

Do you know someone who works at a GM dealer? If so they can use the tech II and change your tire size. I did it on my blazer as it came with 70's and I switched to the 75s' for more variety.

 

I know of one guy but not sure he can get the toll out. Wonder if any of the better local shops would have one or s this something that a GM tech would have?

 

It is mostly a GM dealer item.

 

That's what I was afraid of.

 

I believe that most high end OBD-II tools can correct for the different tire size, but to get the shift points changed you might need to have your PCM flashed. I believe that most decent performance tuner chips like Hypertech will also allow you to correct for different tire sizes and gear changes. Some also change shift firmness, but I don't really know that they actually change shift points to match different tires or gears.

 

Maybe I am missing something but if it is now going into OD say at 45 to 50 MPH with stock tires if the speedometer was corrected wouldn't that also trick the PCM into changing again at those speeds? Looks like yours has oversize tires, what did you do?
By the way I like those SS rims on yours. I have found some but the darn tires are so expensive these days and mine are still to good to part with.

 

I have 32's (265/70/17's) and with my Hypertech programmer I've corrected for the gear change and different tires so my speedometer is exactly on. I've verified it with GPS as well as the radar warning signs my community posts to encourage people to keep the speed limit. I feel that my shift points are not ideal though. It certainly goes into OD a bit earlier than I'd like it to, especially in the city. Once the transmission is warmed up it will drop into OD at 25-30mph, which is annoying in town. I usually shift into D to prevent the OD from kicking in. Like I've said many times: I'm not an expert and don't have any direct knowledge in this area. I'm just going on information from others online and from my own experiences.

I think the ideal situation would be to have your PCM flashed by a competent tuner shop, but I also think that a decent quality programmer like the Hypertech is a good alternative. I'm satisfied with how my truck drives given how thin my wallet is.

 

Looks like I could find someone with one of those. I would like to get one myself but you know how it is with the thin wallet, especially with this economy. What's one of those Hypertechs run roughly? Noticed in your picture there you said 3.73 with G80. I noticed in my RPO codes my 01 LS has G80. Is G80 posi-traction?

 

Contact this guy:
Wait4me Performance
Jesse Bubb
JesseBub@yahoo.com
574-267-3630
He does PCM tunes for gears, tires, turbos, SCs, and stuff. Never used him but he was recommended by a Blazer tech that I bought some parts from once.