i need to ajust the speedo to account for my new tire size on my 1993 C3500.
How?
Is the an ODB reader/tuner that will adjust this?

Thanks

 

need to pull the speed sensor and see if you have gears in there. http://www.transmissioncenter.net/sp...n_______va.htm

 

I could not image a computer controlled tranny having a gear, but I checked anyway.
It does not... it is computer controlled

I should have mentioned I have the 4LE80 not the TH400.

 

Really not sure how that plug comes out of there. i dont want to break it.
But I have found nothing on there ever being a manual 4LE80

 

There should be some ridges on either side of the plug, just give it a squeeze and it should come out.

 

lol dont have a book for the 93, mine is a 97, 93 would be obd1 so im thinking it would have a trans control module of some sort. ahh here is something on it. How to Recalibrate/adjust your speedometer

 

I saw that article. That is a little above what I want. I would rather just buy a device to tweak it.

 

there is a electronic ratio adapter about 1/4 way down the page in the first link i gave. not sure but i dont think obd1 electronic speedo can be tuned.

 

You have to pull the inst cluster out and install a chip into a socket on the back of the inst cluster.
Any GM dealer will have it, Speedometer Calibration Kit, does two vehicles.
Comes in a package, two chips, a harness to literally 'burn out' a solder run on the board, and instructions on total usage of the kit and in clipping off the supplied chip legs to a corresponding gear ratio and tire size, all of them being OE size, of course.

 

Chevy wanted $350 to do it.

Actually one deal said sure no problem, will will reprogram it for $95. They never asked me the year. The just assumed it was ODBII

One told me it was impossible... and one told me they could replace the drac unit.

I just bought one of these. Superlift Part No. 33003 - Truspeed Speed Sensor Calibrator Kits
It is a superlift TruSpeed calibrator.
I remember these coming out in the 90's
I heard they worked.