Speedo Calibration Problem

[DA BIG ONE]

I have a 1999 Suburban 6.5 TD / 4L80E / Automatic 4WD. I changed out the 4.10s for 3.42s, thought that speedo calibration would be easy using Jet Performance SCU2000.

I installed the Jet unit, the speedo was good to go, but it shifted hard, and when returning to a stop there sould be a shudder and grinding noise, along with the motor's rpm's rising while stopped.

The tech people at Jet decided their SCU2000 was not compatable with my truck.

Went to get my ECM flashed thinking it could correct the gear ratio problem, but those who do the flashing say it is a problem with my truck, so can anyone of you maybe help, or point me to someone who can?

[MTTwister]

Isn't this where you need to dig into the VSSB? Or is that just for Tire Sizes?

[DA BIG ONE]

Originally posted by MTTwister:
Isn't this where you need to dig into the VSSB? Or is that just for Tire Sizes? Well, I had bought Jet's unit to hack the VSSB, but it is not compatable with my truck according to them.

[Dave C]

Originally posted by DA BIG ONE:
</font><blockquote>quote:</font><hr />Originally posted by MTTwister:
Isn't this where you need to dig into the VSSB? Or is that just for Tire Sizes? Well, I had bought Jet's unit to hack the VSSB, but it is not compatable with my truck according to them. </font>[/QUOTE]Recalibration of the VSSB is based on the tire size, rear diff gear, and the tranny sensor (always the same in the 4L80E). The 1999 Feature Articles and Product Reviews Volume (http://www.thedieselpage.com/back99.htm) will show you how to do it. The instructions and pictures are exactly like the VSSB in your 99. Also, you can check out this web site 614streets.com/drac.html (http://614streets.com/drac.html) for additional info. smile.gif

[DA BIG ONE]

Originally posted by Dave C:
</font><blockquote>quote:</font><hr />Originally posted by DA BIG ONE:
</font><blockquote>quote:</font><hr />Originally posted by MTTwister:
Isn't this where you need to dig into the VSSB? Or is that just for Tire Sizes? Well, I had bought Jet's unit to hack the VSSB, but it is not compatable with my truck according to them. </font>[/QUOTE]Recalibration of the VSSB is based on the tire size, rear diff gear, and the tranny sensor (always the same in the 4L80E). The 1999 Feature Articles and Product Reviews Volume (http://www.thedieselpage.com/back99.htm) will show you how to do it. The instructions and pictures are exactly like the VSSB in your 99. Also, you can check out this web site 614streets.com/drac.html (http://614streets.com/drac.html) for additional info. smile.gif </font>[/QUOTE]Thanks Dave, I'll get that info and dig into it!

[DA BIG ONE]

Ok, I have gone through the Jet VSSB unit, Jet SCU2000, and now the Abbott ERA, none of them work on my rig.

Superlift states to reflash ECU is the only way to correct the speedo calibration problem on my rig!

Z-industries in cali won't touch the ecu unit, for fear of being married to it after a reflash!

Problem: 1999 GMC SUB 6.4TD 2500 HD only had 2 ratio options 4.10 or 3.73, I have installed the 3.42 ratio front and back. However the GMC 1999 SUB 6.5TD 1500 1/2 ton had the 3.42 ratio option, anyone know how to get this ratio flash installed into my ecu?

Any help is welcome!

My rig: 1999 GMC SUB 6.5 TD, 2500HD, INTERCOOLED, 3" FREE FLOW EXHAUST, 4L80E, NVG 246 TRANSFER CASE.

HELP!

[DA BIG ONE]

David C, thanks!

Dumb me, I did not see the link for hacking the factory DRAC, after reading it my speedo is now correct.

Again thanks............

[Shotuscnc]

this is a better site for explaining mods to VSSB or DRAC

http://webpages.acs.ttu.edu/chdarby/DRAC.htm

worked for me...