So I just regeared my truck and I went in and changed ratio in tune. However speedo seems way off and abs and brake light keep comin on. What is goin on
Gears and tune
- Thread starter dracing70
- Start date
No tires were set prior to gear change. I just changed gear ratio. Is the gear swap what is setting off brake lights. And it has to b changed with a tech 2?? What exactly has to b changed???
Nope. All you need to do is change h103 and h105 which should be tire size and gear ratio.
try backing down the tire size to 34.0 and see if the lights stay off longer. i had to find a sweet spot for my 37s to keep the ABS light off and a correct speed. 34.35 works perfect for me, no lights have come on in three months and my speedo is only 1 mph slower throughout the entire speed range than actual
I have had that problem before with real large tires I would just use 34.5 however my 35 s have been on for years and I have never had a problem
but you have re-geared now, it changes everything. you may try puttin 4.10 in instead of 4.56 and see what it does. Your gunna have to play with it unless you go to a shop and get a tech 2
this may help http://www.duramaxdiesels.com/forum/showthread.php?t=944
this may help http://www.duramaxdiesels.com/forum/showthread.php?t=944
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Its not the tire size thats messin with you, its the fact that the driveline speed and axle speed don't match what the computer is expecting. For some reason, GM saw fit to make this area of tuning not make any sense, my truck has 4.10 gears, and the value set in the programming is 3.73. The only thing that changing the tire size will do is correct or throw off your speedo. That has nothing to do with the ABS/brake light. Move the gear ratio value around untill the light stays off.
Are you sure they were 4.56? I have 33's and 4.56 and don't have any issues. Are you putting the metric numbers or standard numbers for your 35's.
its h0101 and h0103. Do not change h0102 That will really mess with your ABS, it should read 40.0000. Play with h0103 (gear ratio) untill the ABS light stays off, and then make your speedo read correctly after that (h0101).
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you can also try leaving the gear ratio alone in the tune, and just compensate the tire size for the difference. Sometimes that works too.
In my expirience this will not correct the ABS light, only the speedo. The ecm reads transfer case output speed, and compares it to axle shaft speed. Naturally these speeds will be different due to the ring and pinion gears...that is why the ecm needs to know what the ring and pinion gear ratio is. The problem is that for whatever reason, it isn't always just plug in the ratio and go. Mine for example, runs 4.10 gears, but isn't happy unless the value is entered as 3.73. If I put in the actual gear ratio the ABS system freaks out. Your results may vary, but this is what I have run into.
so can you explain how the ECM reads axle shaft speed if there aint one sensor back there to read it??
the ecm only uses these parameters (h0101, h0103) that you put in as a calculation in comparison to output shaft speed and what the front wheel speed sensors are showing. When the ECM sees a big enough difference in what the front WSS are showing in comparison to rear d-shaft it throws the code and kills the abs. By changing one of the two tables one at a time and slowly adjusting up or down by so much you can make the equations the ECM is using equal out to what the front WSS sensors are showing, thus keepin the ABS.
Now this is my theroy behind it as i have no way i seeing how this actually works but its been workin for me on a few trucks ive changed the speedo/gear ratio on and its what makes the most sense to me seeing as how there is no other sensors for WS on the back of our trucks
