my name is Bradley. my wife has a 2001 Tahoe and the speedometer is off.... we got it used (nearly 300,000 miles) and I suspect the rear differential has been swapped. I need to find out how to get it back on track...… it reads 87mph when we are actually going 75mph.
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2001 tahoe
- Thread starter bmiller
- Start date
Will L.
Well-Known Member
Ahh, the teenager mod. Keeps the kids from speeding too much...
Take a look at the VSSB modification for adjustable dip switches. It’s a little 2” square white plastic unit hiding behind your glovebox area that takes in the signal and converts it to output for speedometer.
If you can solder, you can diy. Otherwise get ahold of John at Unique Diesel. iirc he has them done and in stock.
Take a look at the VSSB modification for adjustable dip switches. It’s a little 2” square white plastic unit hiding behind your glovebox area that takes in the signal and converts it to output for speedometer.
If you can solder, you can diy. Otherwise get ahold of John at Unique Diesel. iirc he has them done and in stock.
- Staff
- #3
Does not apply to a 2001 tahoe. Gassers went pcm controlled in 96.
As to the op's problem, you need to get a scanner on it and see what the pcm is seeing for speed. The problem with adjusting the speedo in these is the trans shift points are all based on mph, so if you alter the speedometer, then you have to change all the shift points to match. What could have happened is your pcm(most call it an ecm) probably failed, somebody swapped it with a used one, and it's programmed differently than yours, or else the gear ratio was changed in the axle(s). If it has a stock ratio in the rear axle(3.42, 3.73, or 4.10), then you can probably find somebody to reprogram your pcm with a stock flash cheaply. Otherwise you'll need a custom tune flashed into your pcm to correct the speedo, or install one of the correction boxes that alters the pcm's signal to the cluster to correct it that way. If you're close to central Florida I could set you up.
- Staff
- #4
Was just crunching some numbers. If your Tahoe originally had 3.42 gears(pretty common ratio for a 2 wheel drive Tahoe with a 5.3l), 87 mph showing on the speedo would have you running 80 with 3.73 gears, or 73 with 4.10 gears. I've never seen a tahoe with 4.10 gears, but Suburban's did get them early on. Out of curiosity, what tire size is on it, and how many rpm's is it turning at 75 actual speed(not indicated)? This will help to determine what gear ratio is currently in it.