How To - Calibrate Speedometer - Diesel Place : Chevrolet and GMC Diesel Truck Forums
 
Home Forum Market Place Garage Tuning Library DTC Tool Register Vendors
Go Back   Diesel Place : Chevrolet and GMC Diesel Truck Forums > GM Diesel Engines > 6.5L Diesel Engine
Register FAQ Forum Rules My Replies My Threads Advertise

6.5L Diesel Engine Discuss the 6.5 GM diesel engine & associated components. Automatic transmission questions & problems belong in the 4L80/85 - 4L60E - 6L90 Transmission Forum


DieselPlace.com is the premier Duramax Diesel Forum on the internet. Registered Users do not see the above ads.
Like Tree1Likes

Reply
 
LinkBack Thread Tools
Old 01-17-2010, 09:31 PM   #1 (permalink)
Green Machine
She Don't Smoke!
 
Green Machine's Avatar
 
Join Date: Aug 2007
Location: Ohio
Posts: 4,689
iTrader Score: 1 reviews

Northeastern Ohio Diesel Crew Member

How To - Calibrate Speedometer

Calibrating Speedometer
Ability to adjust settings without using a programmer

This Guide should work on trucks from 1992-1999 (maybe 2000).

This mod is normally used for those people who run over sized tires or different rear end gears and want their speedometer to be accurate. I'm not sure if this will change what the PCM sees for the transmission but it will help correct your speedometer. You can also spend $150+ on a programmer or a preset VSSB which either way is a good way to go if you have the money. But, you can also calibrate your own VSSB (Vehicle Speed Sensor Buffer) for a few dollars.

*Caution* - I do not take any responsibility if you mess up your VSSB in any way.

Skills Needed:
  • Ability to use a tape measure
  • Ability to remove soldered devices
  • Ability to solder devices
  • Ability to put numbers in an equation and solve it
Items Needed:
  • Small Pliers
  • Soldering Iron
  • Solder
  • A paperclip or a straight pin
  • Tape Measure
  • Calculator
  • 6 position DIP Switch (2 switches for 14 position jumper board)
    • Can be found at an online switch vendor
    • I found mine on Ebay for a decent price
************************************************** ********

Vehicles Gear Ratio
  • If you are sure that the truck's gear ratio is stock, look at the RPO's in your glove box.
    • GU6 - 3.42:1
    • GT4 - 3.73:1
    • GT5 - 4.10:1
  • If you are really unsure of the gear ratio you can pope off the differential cover and normally you can see markings on the ring gear that tell you what ratio it is.
Determining Tire Size
  • There are a few ways you can do this... but the best way is the first way that will be explained.
  • Measuring one revolution of the tire
    • Mark one tire on the bottom and Mark the ground at the same spot.
    • Roll the tire one revolution.
    • Mark the spot on the ground where the tire ended up at and measure the distance between the two markings on the ground.
    • This is what you will use as your tire's rolling circumference.
  • Calculating one revolution of the tire
    • Measure the height of the tire and multiply that number by PI (3.14......).
    • This will give you an estimated tire rolling circumference
  • To show the difference in the two methods. My actual tire size was 99", but the calculated tire size was 103". So I prefer to actually measure the tire for an accurate jumper position.
Calculating your Input Ratio

(63360) x (Gear Ratio) x (40)
(tire rolling circumference) x (128000)
  • Equation Explanation
    • 63360 = inches per mile
    • Gear ratio = trucks gear ratio
    • 40 = Pulses per revolution or speed sensor, most GM speed sensors produce 40 pulses per revolution
    • Tire rolling circumference = measurement you did in Inches!
    • 128000 = pulses per mile
  • Once you have done the calculations look below for the "Jumper Settings". Find the closest value to your answer.
  • Read across the line of your value for the correct jumper settings.
    • 1 means there should be a jumper across the terminals (closed)
    • 0 means there should not be a jumper across the terminals (open)
  • Jumpers are not numbered on the board itself, but look at the picture attached for an example on how to read the VSSB board.
Finding & Removing your VSSB (Vehicle Speed Sensor Buffer)
  • For 1994 and Earlier, The VSSB/DRAC is located behind the glovebox. You must unscrew/unbolt the VSSB/DRAC unit to remove.
  • For 1995 and Later, See Below:
  • Remove Your Glovebox.
  • This Device is normally found in a white box right under the PCM.
  • You can try removing the VSSB by just unclipping it from the PCM tray.
  • Or, you can try what I did...
    • Remove the PCM, unclip all the connectors and undo the clamp(s) holding the PCM in place.
    • Unbolt the 4 bolts holding down the PCM tray, see pictures for exact locations.
    • Unclip the VSSB connector and remove the tray. The VSSB will be attached to the bottom of it.
    • Unclip the White VSSB box and take it into the house.
  • Open the white box and remove the VSSB unit.
  • WARNING - This device is very sensitive to electric shock (as with most computer electronics). Do not let this board get in contact with ESD (Electro-static Discharge), grease, oil, water, or any other liquids.
Removing Jumpers
  • There are a few ways to remove the jumpers, but here is what I found worked best.
  • *NOTE* Do not touch both #1 positions on the VSSB jumpers Jumper locations. These do not change and if you mess with them a 6 position DIP switch will not work for this project anymore.
  • Cut each jumper that you are going to remove in the middle.
  • Use your soldering iron to head up the connection and you should be able to pull the jumper out with the small pliers.
  • Do that for all the jumpers you are removing.
  • Next you must clean out each hole, you can do this by using a small straight pin (used for sewing) or using a small paper clip. I used both methods. Take care when you do this as you don't want to ruin the board or other devices.
  • All the holes must be open enough to fit the new DIP switches and most of the left over solder should be removed so you don't short out the board and cause incorrect readings.
Installing DIP Switches
  • You want to carefully place the DIP switches in the 2-7 positions on each side of the jumper set (Both #1's are not to be touched) see pictures for more detail.
  • Flip the board over *with switches installed* and make sure that all the switch leads are through the holes.
  • Carefully solder each connection making sure not to put to much solder on.
  • After that is done, you can set your switches to the correct settings.
  • Using the input ratio you got from the equation above, go to the Jumper Input Chart below and check for the input ratio that is closest to your answer.
  • The chart should give you an answer like 1-0-1-1-0-1-0, that is the right bank (or the entire code for the 7 jumper board). The left bank will be a mirrored image that gives the opposite answer of the other side (see picture).
    • The straight across answer will be 1-0-1-0-0-1-0-1-0-1-1-0-1-0
    • Remember, the switches are installed so that both jumper #1 are untouched. So your switches will read:
    • 1-0-1-0-0-1-*-*-0-1-1-0-1-0
    • Example:
Reinstalling your VSSB and Testing
  • Install your VSSB (in the white case) back into your truck. Installation is opposite of the removal procedure you used.
  • Plug in the VSSB and take your truck for a test drive.
  • To help check the accuracy of your speedometer, use a GPS or pace another vehicle.
  • If your speedometer is still not accurate, you will have to remeasure your tire and redo your calculations. Then pull your VSSB back out and adjust the DIP switches to the next jumper setting
************************************************** ********

Notes:
  • There are TWO different types of DRAC/VSSB Units in these trucks. You have a 7 position and a 14 position. The Steps above are for the 14 position switch.
    • The 7 position mod is very similar. The "codes" for the 7 position board is the same as the 14 position, but you just don't have to have the mirrored opposite on the left side of the board.
    • I believe only the earlier models (up to '92ish) have the 7 position boards. But not 100% sure.
  • I take No responsibility on what you do to your VSSB of anything else done to your truck.
  • This can be a difficult mod for those who have not soldered. I have not soldered on a board, and I ran into one problem but I found the problem and fixed it.
  • If you feel uncomfortable doing this you can most likely have an electronic repair shop solder the connections for you.
  • You can also probably take your VSSB to some automotive shops and have them reconfigure your VSSB for you. Not sure on the price of this though.
  • Here is my experience (speedo wise). Before my speedometer was about 5mph slow. After this mod my speedometer is about .5 to 1 mph to fast. I believe that is pretty good considering the accuracy from factory. This will probably help me get a little more accurate fuel mileage calculations too .
  • I will try an help all those who have questions, but I do not know "a lot" about these modules.
  • I got this information from a few different sites and added some more from my experience. Including this site.

For the next couple days I may rephrase some steps or correct any information that needs changed...

Attached Images
File Type: jpg DPJumperSides.jpg (179.5 KB, 1179 views)
File Type: jpg DPJumperPostion.jpg (183.5 KB, 601 views)
File Type: jpg DPGlove Box.jpg (226.5 KB, 6262 views)
File Type: jpg DPPCM&VSSB.jpg (210.9 KB, 5711 views)
File Type: jpg DPtop bolts.jpg (153.7 KB, 5034 views)
File Type: jpg DPbottom bolts.jpg (161.7 KB, 5333 views)
File Type: jpg DPpcmtray.jpg (231.2 KB, 5045 views)
File Type: jpg DPVSSB.jpg (222.7 KB, 5486 views)
File Type: jpg DPDIPInstalled.jpg (63.0 KB, 4813 views)
Attached Files
File Type: xlsx VSSB Input Ratio Chart.xlsx (12.9 KB, 785 views)
__________________
| 6.5L FAQs and Information | To Search within 6.5 Forum | 6.5L Diagnostic Checklist | Create/Edit Signature | My YouTube Channel |

Quote: "Mind over Matter - I don't mind cause you don't matter!"


Last edited by Green Machine; 01-23-2010 at 02:25 PM.
Offline  
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 01-17-2010, 10:10 PM   #2 (permalink)
94C1500
Diesel Specialist
 
94C1500's Avatar
 
Join Date: Mar 2009
Posts: 3,231
iTrader Score: 1 reviews

Could just post this source

http://www.tbichips.com/drac/

__________________
1994 C1500 - 4L80E & 3.42 rear; Custom Multi-Program Chip; L65 intake; "FTB", Walbro FRC-10 lift pump, pre-LP fuel filter & OPS relay mod; D-Tech FSD on heatsink; Big Turbo, 4" to 5" exhaust exits before axle, Cone air filter; "marine" injectors. Propane fumigation and WMI.
ENGINE DESIGN CALCULATORS
LIST OF RECOMMENDED MNX & MODS
HX40 or HX35 V-Band Exhaust Elbows
Offline   Reply With Quote Quick reply to this message
Old 01-17-2010, 10:15 PM   #3 (permalink)
Green Machine
She Don't Smoke!
 
Green Machine's Avatar
 
Join Date: Aug 2007
Location: Ohio
Posts: 4,689
iTrader Score: 1 reviews

Northeastern Ohio Diesel Crew Member

Quote:
Originally Posted by 94C1500 View Post
Could just post this source

http://www.tbichips.com/drac/
That was the main source (pretty much only the chart and equation), but I also used a couple other sites to confirm details and such.
__________________
| 6.5L FAQs and Information | To Search within 6.5 Forum | 6.5L Diagnostic Checklist | Create/Edit Signature | My YouTube Channel |

Quote: "Mind over Matter - I don't mind cause you don't matter!"


Last edited by Green Machine; 01-17-2010 at 10:18 PM.
Offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 01-17-2010, 10:20 PM   #4 (permalink)
94C1500
Diesel Specialist
 
94C1500's Avatar
 
Join Date: Mar 2009
Posts: 3,231
iTrader Score: 1 reviews

The 94 and earlier have the DRAC, and its not under the PCM, just behind the glove box, so things a little different in adjustment on the DRAC.
__________________
1994 C1500 - 4L80E & 3.42 rear; Custom Multi-Program Chip; L65 intake; "FTB", Walbro FRC-10 lift pump, pre-LP fuel filter & OPS relay mod; D-Tech FSD on heatsink; Big Turbo, 4" to 5" exhaust exits before axle, Cone air filter; "marine" injectors. Propane fumigation and WMI.
ENGINE DESIGN CALCULATORS
LIST OF RECOMMENDED MNX & MODS
HX40 or HX35 V-Band Exhaust Elbows
Offline   Reply With Quote Quick reply to this message
Old 01-17-2010, 10:30 PM   #5 (permalink)
Green Machine
She Don't Smoke!
 
Green Machine's Avatar
 
Join Date: Aug 2007
Location: Ohio
Posts: 4,689
iTrader Score: 1 reviews

Northeastern Ohio Diesel Crew Member

Quote:
Originally Posted by 94C1500 View Post
The 94 and earlier have the DRAC, and its not under the PCM, just behind the glove box, so things a little different in adjustment on the DRAC.
the vssb/drac positions i was going to add but forgot. I also believe that the units you are talking about are the 7 jumper board? It sets up basically the same way, but you don't have the mirrored image for the other 7 jumpers.
__________________
| 6.5L FAQs and Information | To Search within 6.5 Forum | 6.5L Diagnostic Checklist | Create/Edit Signature | My YouTube Channel |

Quote: "Mind over Matter - I don't mind cause you don't matter!"


Last edited by Green Machine; 01-17-2010 at 10:32 PM.
Offline   Reply With Quote Quick reply to this message
Old 01-17-2010, 10:47 PM   #6 (permalink)
94C1500
Diesel Specialist
 
94C1500's Avatar
 
Join Date: Mar 2009
Posts: 3,231
iTrader Score: 1 reviews

Yep, that link explains the difference.
__________________
1994 C1500 - 4L80E & 3.42 rear; Custom Multi-Program Chip; L65 intake; "FTB", Walbro FRC-10 lift pump, pre-LP fuel filter & OPS relay mod; D-Tech FSD on heatsink; Big Turbo, 4" to 5" exhaust exits before axle, Cone air filter; "marine" injectors. Propane fumigation and WMI.
ENGINE DESIGN CALCULATORS
LIST OF RECOMMENDED MNX & MODS
HX40 or HX35 V-Band Exhaust Elbows
Offline   Reply With Quote Quick reply to this message
Old 01-18-2010, 03:36 PM   #7 (permalink)
jetech1
Diesel Apprentice
 
Join Date: Oct 2005
Location: San Antonio, Florida
Posts: 364
iTrader Score: 0 reviews

Do the gas powered trucks have the "same" VSSB unit? If so we could get one or two from the salvage yard to try the surgery on
I'd like to do this on mine but just a little "skerd" to hack it up
__________________
1995 Chevy Z71 EXT.CAB 6.5l S code.Shift improver kit 4L80E Trans 195,000 miles.remote PMD. intake plenum mod. 18.5 average mpg
1996 GMC 3500 dump truck "F" code.remote PMD
Offline   Reply With Quote Quick reply to this message
Old 01-18-2010, 04:12 PM   #8 (permalink)
Rafedial1
Diesel Nut
 
Rafedial1's Avatar
 
Join Date: Apr 2007
Location: OH
Posts: 835
iTrader Score: 1 reviews

nice work Mike! very clear and straightforward writeup
__________________
#2) 94 Camaro-(L33 5.3L/4L80E) LS1 intake/243 heads/aluminum block
Hptuners+me, LC1 wideband
3.42 10-bolt/Auburn Posi/LS1 brakes
UMI suspension/TCI trans controller, M+H Radials
http://www.ls1tech.com/forums/conver...5-3-4l80e.html
#1) 94 Camaro V6 body-(6.5L/4L80E) L65 ported intake/567 heads, stock 506 longblock
stock injectors/Db2 4911 turned/ 3800 rpm
Holset He351 vgt turbo, non IC, 15 psi
Snow WMI kit, TCI trans controller, 3.23 10-bolt/LS1 brakes
rod let go, parted out:RIP 8-15-10
https://www.dieselplace.com/forum/sho...297673&page=28
Offline   Reply With Quote Quick reply to this message
Old 01-18-2010, 04:25 PM   #9 (permalink)
dustyvinyl
 
Join Date: Jan 2010
Posts: 3
iTrader Score: 0 reviews

that's some good advice, thanks
Offline   Reply With Quote Quick reply to this message
Old 01-18-2010, 06:44 PM   #10 (permalink)
Green Machine
She Don't Smoke!
 
Green Machine's Avatar
 
Join Date: Aug 2007
Location: Ohio
Posts: 4,689
iTrader Score: 1 reviews

Northeastern Ohio Diesel Crew Member

Quote:
Originally Posted by jetech1 View Post
Do the gas powered trucks have the "same" VSSB unit? If so we could get one or two from the salvage yard to try the surgery on
I'd like to do this on mine but just a little "skerd" to hack it up
Gassers should use the same VSSB. May want to find one with the same gear ratio, although I'm not 100% sure that really matters. I know one way to find out lol, and thats try it and see what happens .

__________________
| 6.5L FAQs and Information | To Search within 6.5 Forum | 6.5L Diagnostic Checklist | Create/Edit Signature | My YouTube Channel |

Quote: "Mind over Matter - I don't mind cause you don't matter!"

Offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Diesel Place : Chevrolet and GMC Diesel Truck Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

PLEASE READ! You must check your email inbox for the confirmation link to complete registration. Please check your spam box if you do not see the email in your inbox.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Insurance
Please select your insurance company (Optional)

Log-in



Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Calibrate for tire size my1stduramax Third Generation Duramax Electronics/Tuners 3 04-26-2008 11:11 PM
08 lmm will not download factory ecm says cannot calibrate with E38 please help Attention Deficit EFILive Tuning Software 4 11-05-2007 12:49 PM
Re-Calibrate ECM/TCM tire size Cougar281 Second Generation Duramax Electronics/Tuners 11 09-13-2006 05:55 PM
Can dealers Re-calibrate your Speedometer?? truckee274 Wheels & Tires 23 06-21-2006 10:28 AM
Re-calibrate? ColoradoCummins Any Other Vehicles 2 04-01-2005 04:06 PM


All times are GMT -4. The time now is 05:03 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Shoutbox provided by vBShout v6.2.1 (Lite) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd. Runs best on HiVelocity Hosting.
© AutoGuide