somethin' ain't right
Thread Starter
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Junior User
Joined: Aug 2002
Posts: 54
Likes: 0
From: Colorado
somethin' ain't right
Okay, gurus. After following the posts on the speedometer calibrations, I decided to check mine since when I bought the vehicle (used) it was running 33x12.5 15's and I'd been told that my speedometer appeared off by about 5 mph low(don't ask). Stock tires with the vehicle, according to the factory door sticker, were 265x75 15's with the axle code at H9 ( 8.8"355 LS). When I brought up the conversion constant, it was set at 9.18 with six changes still to go, which I assume means this was the factory setting. I'd already noted that the constant should be changed to 8.59 after following some of the earlier threads. I shut off the ignition, grounded the PSOM wire, brought the constant back up to change and found that the constant changed down instead of up when pressing the select button. I went ahead and brought the constant down to 8.59 and locked it in, pulled the ground wire, rechecked, and it sure enough took, with 5 more changes available.HOWEVER, my speedometer is now reading about 12 mph to high, and I've lost some of the perfomance(of course).
What's going on? Is it:
a. bad PSOM since it changed the constant down instead of up.
b. different rear end. Yes it has been opened, because I don't think the factory uses permatex high temp sealer.
c. something totaly unimaginable
The only tag on the axle itself is an adhesive plastic band on the right axle tube, with the numbers 873B on it. I know this could be irrelevant, since swapping a rear doesn't necessarily mean changing the entire assembly.
Thanks, Yelrihseam
What's going on? Is it:
a. bad PSOM since it changed the constant down instead of up.
b. different rear end. Yes it has been opened, because I don't think the factory uses permatex high temp sealer.
c. something totaly unimaginable
The only tag on the axle itself is an adhesive plastic band on the right axle tube, with the numbers 873B on it. I know this could be irrelevant, since swapping a rear doesn't necessarily mean changing the entire assembly.
Thanks, Yelrihseam
Post Fiend
Joined: Nov 2002
Posts: 9,987
Likes: 7
From: Memphis, TN
somethin' ain't right
I haven't reposted all my PSOM info on this BBS yet, but you can read it in this thread.
The constant is supposed to decrease by 001 each time you press the button, so yours is fine. I'm guessing someone has added an aftermarket calibration module somewhere in your wiring harness & it's what's messing things up. You may have to open the dash to find it.
This site shows how. In any case, trace the wires from the sensor on the rear axle all the way up to the speedo.
The constant is supposed to decrease by 001 each time you press the button, so yours is fine. I'm guessing someone has added an aftermarket calibration module somewhere in your wiring harness & it's what's messing things up. You may have to open the dash to find it.
This site shows how. In any case, trace the wires from the sensor on the rear axle all the way up to the speedo.
