Bill, make this a sticky!!!!
Originally post on AS.com
Posted by Lockdoc on May 15 2006,3:31
Here is some of the info I used to recalibrate my DRAC modules for different tire and gear sizes.
http://www.tbichips.com/drac
This is a nice calculator for calculating your input ratio.
DO NOT USE THE INFO FOR THE JUMPER SETTINGS ON THIS PAGE. I FOUND THEM TO BE WRONG MOST OF THE TIME. Use the chart on the TBIchips page
Input Ratio Calculator .....
http://www.philter.com/cgi-bin/drac.pl
This is a calculator I used for tire circumference. Fill in your known values in the "Calculate tire diameter" fields. Then click "calculate". Use the circumference found here and enter it into the "Input Ratio" calculator above instead of using your tire size.
How to calculate tire diameter.....
http://www.5speedtransmissions.com/calculators.html
Hope this helps others who need to recalibrate.
.......................................................................................................
Posted by LiftedAWDAstro on June 02 2006,12:15
I just pulled my DRAC and re-soldered the jumpers according to the posted links. My DRAC looked just like this one:
Speedo/DRAC recalibration
I installed two six pin dip switches on my VSSB to make it easy to change settings.. It only needs them on jumper positions 2-7. Jumper position 1 stays the same no matter what.
One of the websites listed was ambiguous regarding the differences between a DRAC (digital ratio adapter controller) and a VSSB (vehicle speed sensor buffer). A DRAC has only one set of jumpers. A VSSB has two sets. The second set is for the 4L60E and will be set as a mirror image of the other set that provides signal outputs for the speedometer, cruise control and ABS controller for the rear wheel speed signal.
One of the websites listed was ambiguous regarding the differences between a DRAC (digital ratio adapter controller) and a VSSB (vehicle speed sensor buffer). A DRAC has only one set of jumpers. A VSSB has two sets. The second set is for the 4L60E and will be set as a mirror image of the other set that provides signal outputs for the speedometer, cruise control and ABS controller for the rear wheel speed signal.
95 Astro 4.3 4L60E 3.42 Bilsteins/Timbrens
410,000 miles and counting
65 Chevy van 90" WB 305 700R4 3.36
garage queen rescued from the crusher many years ago
410,000 miles and counting
65 Chevy van 90" WB 305 700R4 3.36
garage queen rescued from the crusher many years ago
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Re: Speedo/DRAC recalibration
Dean, here are a couple of pics I was able to find...LiftedAWDAstro wrote:Bill, I don't have the pics of the DIP switches we did on zam's van. If you send me the spare DRAC module, I will solder the switches in. I will PM my address.
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Re: Speedo/DRAC recalibration
Here is snapples spare DRAC module with the 2 new 6 pin DIP switches installed.
Here is the bag, with part numbers, the DIP switches were in.
I removed the solder with a solder sucker and then removed all jumpers except for #1 on the right (no pic of this). #1 on the left is always going to be left a "0" or open so nothing is put there.
Now all Bill needs to do is compute the correct DIP switch settings based on gears and tire size and plug it right in and instant speedo re-calibration is done! I installed the switches upside down from each other so that when the switches on the right are selected according to the calculations, the switch on the left will be switched opposite based on the same switch number.
Here is the bag, with part numbers, the DIP switches were in.
I removed the solder with a solder sucker and then removed all jumpers except for #1 on the right (no pic of this). #1 on the left is always going to be left a "0" or open so nothing is put there.
Now all Bill needs to do is compute the correct DIP switch settings based on gears and tire size and plug it right in and instant speedo re-calibration is done! I installed the switches upside down from each other so that when the switches on the right are selected according to the calculations, the switch on the left will be switched opposite based on the same switch number.
Current rides:
2013 Toyota Tundra DC 4x4
2008 Dodge Nitro 4x4
2005 Nissan Sentra 1.8S Special Edition
Mileage spreadsheet
Vans owned:
1986 Safari 2.5L 4 speed manual - scrapped
1995 Astro 2WD conversion 4.11 posi, shift kit, DHC rock rails - sold to Skippy
1998 Astro 4x4 D44, D60, NP231, full hydraulic system with 9k# Milemarker winch and snow plow - sold to Lockdoc
2003 Astro AWD all stock - traded for a 3/4 ton truck
2005 AWD, 4.10's - sold to skippy
2013 Toyota Tundra DC 4x4
2008 Dodge Nitro 4x4
2005 Nissan Sentra 1.8S Special Edition
Mileage spreadsheet
Vans owned:
1986 Safari 2.5L 4 speed manual - scrapped
1995 Astro 2WD conversion 4.11 posi, shift kit, DHC rock rails - sold to Skippy
1998 Astro 4x4 D44, D60, NP231, full hydraulic system with 9k# Milemarker winch and snow plow - sold to Lockdoc
2003 Astro AWD all stock - traded for a 3/4 ton truck
2005 AWD, 4.10's - sold to skippy
Re: Speedo/DRAC recalibration
Thanks Dean!
Another step towards getting my van ready for it's Adirondack voyage this coming Labor day weekend!
Another step towards getting my van ready for it's Adirondack voyage this coming Labor day weekend!
'94 Astro AWD EXT LT - Over 211,000 ,parts van now!
DHC Rock rails
Overland Vans 4" lift kit and bumper w/grille guard
Fiamma awning
'95 Astro AWD EXT CS - Just over 99,000 miles
DHC Rock rails
Overland Vans 4" lift kit and bumper w/grille guard
Fiamma awning
'95 Astro AWD EXT CS - Just over 99,000 miles
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Re: Speedo/DRAC recalibration
It would be awesome to do a DIY recal on my van. Is there a similar hack for post-'95 models?BLAZER wrote:http://www.tbichips.com/drac
1990-1995 GM Truck/SUV DRAC/VSSB Calibration
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Re: Speedo/DRAC recalibration
OBDII vehicles you can adjust the computer using a programmer my jet programmer does it i'm sure a garage with a good scan tool can do it too. I know i've seen other hand held devices that do it too but for the life of me i can't remember them, the jet ones biggest down fall is it binds to your vehicles computer and will not work on another vehicle not even just to pull codes
1998 GMC Safari AWD, BFGoodrich AllTerrain T/A
Jet performance tuner 91 octane preset, Jet under-drive pulleys
Rancho 999000 series shock, on-board controller to be installed later
DHC rock rails and skid plate Add-A-Leaf
G3500 front calipers
Zexel Torsen Diff
11" drums
180 amp Alternator
Long tru-cool 4590 trans cooler
1997 gone
Jet performance tuner 91 octane preset, Jet under-drive pulleys
Rancho 999000 series shock, on-board controller to be installed later
DHC rock rails and skid plate Add-A-Leaf
G3500 front calipers
Zexel Torsen Diff
11" drums
180 amp Alternator
Long tru-cool 4590 trans cooler
1997 gone
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