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Thread: Recalibration of Speedometer

  1. #1
    Join Date
    Jan 2002
    Location
    BAKERSFIELD,CA,USA
    Posts
    27

    Post

    I've been carrying the Superlift TrueSpeed speedometer recalibration unit around in the truck for the last month and finally got around to installing it. It was a fairly simple install with the exception of the c2 connector on my 2002 California truck is clear instead of red. Any way we got it installed and after 3 or 4 stops to make fine adjustments the sppedometer / odometer are whithin .3 mph at 75 mph according to my GPS.

    I calibrated it according to the published tire sizes from Fireston/Bridgestone. Stock Steeltex 245/16 at 30.5 diameter and Bridgeston Dueler 285/15 at 32.9. These were obviously off either by stock being smaller or new tire bigger because I had to dial in more adjustment.

    I had always figured my fuel mileage at about an 8% difference. But last tank I used after the install showed it to be about a 10% difference. last tank was about 125 city 300 highway came in at 17.9 mpg.

    For all you guys out there that want to recalibrate the speedometer this thing works! It also has a switch so you can run a second size of tire wheel and have your speedometer be on with the flic of a switch.

    allamerican1
    2002 GMC DMAX 4X4, slt Ext cab, Short Bed, Summit White w/tan interior<br />Line X Bedliner<br />Westin SS Nerf Bars<br />Eagle Alloys w/Brigstone Duelers 285/75/16<br />4\" Diesel Dynamics Exhaust<br />Autometer Boost & Pyrometer<br />Amsoil Air Filter <br />Husky Liners and Mudflaps<br />GMC Underseat Storage<br />Kennedy head light Harness<br />Uniden CB<br />The Juice<br />Superlift Truespeed Speedo Recalibrator

  2. #2
    Join Date
    Mar 2002
    Location
    Mountain City, Texas
    Posts
    3

    Post

    Where did you get the recalibration unit from. Its the first one I've heard of for the Allison...
    2002 2500HD Crewcab 4x4 <br />Indigo Blue<br />Westin Nerf bars<br />Rhino spray in Liner

  3. #3
    Join Date
    Jan 2002
    Location
    BAKERSFIELD,CA,USA
    Posts
    27

    Post

    I ordered it from 4wheelparts in Southern CA. I guess it's been out for a while and they just got around to testing it on the Duramax/Allison. It goes inline with the vehicle speed sensor wire from the main PCM. It has two trim pots on it for 2 different tires sizes. You just turn the trim pots the correct number of times to adjust to your tire/gear size.

    allamerican1
    2002 GMC DMAX 4X4, slt Ext cab, Short Bed, Summit White w/tan interior<br />Line X Bedliner<br />Westin SS Nerf Bars<br />Eagle Alloys w/Brigstone Duelers 285/75/16<br />4\" Diesel Dynamics Exhaust<br />Autometer Boost & Pyrometer<br />Amsoil Air Filter <br />Husky Liners and Mudflaps<br />GMC Underseat Storage<br />Kennedy head light Harness<br />Uniden CB<br />The Juice<br />Superlift Truespeed Speedo Recalibrator

  4. #4
    Join Date
    Apr 2001
    Location
    Atlanta
    Posts
    21

    Post

    AllAmerican1,

    How much does this Speedo Recalibration unit cost?

  5. #5
    Join Date
    Jan 2002
    Location
    BAKERSFIELD,CA,USA
    Posts
    27

    Post

    With freight and CA sales tax (7.25%) It was right at $195.00. It seems to shift quicker now and shouldn't have any problems with ABS brakes either.

    allamerican1
    2002 GMC DMAX 4X4, slt Ext cab, Short Bed, Summit White w/tan interior<br />Line X Bedliner<br />Westin SS Nerf Bars<br />Eagle Alloys w/Brigstone Duelers 285/75/16<br />4\" Diesel Dynamics Exhaust<br />Autometer Boost & Pyrometer<br />Amsoil Air Filter <br />Husky Liners and Mudflaps<br />GMC Underseat Storage<br />Kennedy head light Harness<br />Uniden CB<br />The Juice<br />Superlift Truespeed Speedo Recalibrator

  6. #6
    Join Date
    Dec 2001
    Location
    Lexington Park, Md
    Posts
    137

    Post

    ALLAMERICAN1 - I assume you miss-typed and meant 285/16. I have been trying to inform people that even though the static calculation for these tires is 8%, the tires "grow" with speed. I've calculated doing measured miles and gps that they cause almost an exact 10% error. As an extreme example, watch a dragster on takeoff. The tires look like they "grow" more than 50%.
    02 GMC 2500HD D/A EC LB SLT
    FLAME RED! Charcoal Leather Buckets
    Pacer 16x8.5 Chrome Split Rims W/285R16 Goodyear MT/R'
    Weston Nerf Bars
    Fold-A-Cover
    Lund Bug Deflector
    Air lift Air Springs
    Gabriel HiJacker Air Shocks-all 4
    JUICED
    Elkhorn 11X slide-in
    Rinker 212 Captiva

  7. #7
    Join Date
    Nov 2001
    Location
    Muskego, Wisconsin, USA
    Posts
    76

    Post

    A question immediately came to mind when I read this post...What would prevent a person who purchased this item to program, at the very least, 225/75R16's into the recalibration unit, but wear 255/85R16's in order to add an additional 13K of warranty on the engine?

    Allison Jettester,
    Why wouldn't the 8% (I calculate 7.2%) circumferential difference of 245's vs. 285's be the same statically and dynamically? Is there that much difference in the "grow ratio" of the 245's vs. the 285's?
    2002 Chevrolet Silverado K2500HD
    Crew Cab 153"WB LS Duramax/Allison

  8. #8
    Join Date
    Mar 2002
    Location
    Mountain City, Texas
    Posts
    3

    Talking

    Allamerican1,

    Thanks for the info. I also found it on the superlift website but didn't see a price. I wanted to put a lift on my truck but didn't want to do it because of the speedo calibration issue with the Allison tranny. Guess I can do it now.
    Thanks.....
    2002 2500HD Crewcab 4x4 <br />Indigo Blue<br />Westin Nerf bars<br />Rhino spray in Liner

  9. #9
    Join Date
    Dec 2001
    Location
    Eugene, OR
    Posts
    107

    Post

    How difficult was the install? I have one on order it should be here tommorrow. Are the instructions detailed enough? Which wire is the speed sensor wire (description)? I have nightmares when it comes to wiring!! I want to make sure I have the right one
    Do you have any tips or secrets?

    Thanks in advance
    Kyle

  10. #10
    Join Date
    Jan 2002
    Location
    BAKERSFIELD,CA,USA
    Posts
    27

    Post

    Install was not that difficult with the exception of their directions refer to 2001. My truck is a 2002 and the red connector to the PCM they refer to in their instructions is clear on my truck. Luckily I purchased a full set of GM manuals and was able to figure it out. The wire color for the vehicle speed sensor was the same (Pin 50 and green and white I believe). Basically it was just cut that wire and solder in the Tru-speed, then hook up a hot wire and a ground and adjust it. After playing with the adjustment according to my GPS I'm within 3/10ths of a mile at 75.
    2002 GMC DMAX 4X4, slt Ext cab, Short Bed, Summit White w/tan interior<br />Line X Bedliner<br />Westin SS Nerf Bars<br />Eagle Alloys w/Brigstone Duelers 285/75/16<br />4\" Diesel Dynamics Exhaust<br />Autometer Boost & Pyrometer<br />Amsoil Air Filter <br />Husky Liners and Mudflaps<br />GMC Underseat Storage<br />Kennedy head light Harness<br />Uniden CB<br />The Juice<br />Superlift Truespeed Speedo Recalibrator

  11. #11
    Join Date
    Dec 2001
    Location
    Eugene, OR
    Posts
    107

    Thumbs up

    I installed the module yesterday. Fairly easy and straight forward, just time consuming. I also wanted to make sure I did not make any mistakes With 315/75 tires my gps reads about 0.2 under to about 0.2 mph over what the speedo says. I don't think it gets much better than this. With my stock tires my speedo was fast about 1-2 mph compared with the gps. So far I am pretty happy

  12. #12
    Join Date
    Feb 2000
    Location
    Montana
    Posts
    11,382

    Arrow

    Moved to "2500HD/3500 Trucks & Drivetrain"

  13. #13
    Join Date
    Jun 2002
    Location
    Oregon & Texas
    Posts
    340

    Post

    Wouldn't the best bet be to measure actual loaded runout of the tire, and use that instead of tire diameter?

    Blaine
    2002 Crew Cab Short Bed 2500 HD 4x4, Duramax, Allison, Amsoil, Magnaflow 4\" x 20\" muffler, Juice,; Fold-a-Cover, nerf bars, Husky mats, Weather Tech windo vent shades; bed mat, tailgate protector, bulkhead protector, wheel-well protectors; mud flaps, Leveling kit, Frontier front end replacement

  14. #14
    Join Date
    Aug 2002
    Location
    Charlottesville, Virginia
    Posts
    331

    Question

    Isn't it possible to recalibrate the speedometer via PCM programming like on late model f-bodies and corvettes?
    \'02 Pewter 3500 LT CC LB 4x4 D/A G80<br /><br />Predator v1.11, Warn M15000, BFG 235-85-16 ATs, Crimestopper Remote Start, 2.5\" Front Leveling Cams, Prodigy Brake Controller, Nasta Nerf Bars, UNI Foam Air Filter, Fumoto Valve

  15. #15
    Join Date
    Oct 2001
    Location
    Jackson, MI,USA
    Posts
    67

    Post

    allamerican1,

    Do you have the Allison Transmission? If so, how are things going with the calibrator?

    Mike
    2001 Silverado Crew Cab 4X4 Duramax<br />Check out my NEW SS Pics and Truck at - <a href=\"http://www.mikebroughman.com\" target=\"_blank\">www.mikebroughman.com</a>

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