I have just joined the ranks of Cummins owners. We bought a 99 3500 4x4 with a 6 speed in place of the factory 5. The tires have also been changed from the 215 to the 235/85r16. when we went to bring home the ebay purchase I was asked by the wife on a radio if I was trying to run away from her. I thought I had set the cruise at about 70mph. She said she was showing 82 and was falling behind at that rate. The dealer claims to know of NO fix for that. I cannot believe I am the only one with this problem. I tried a search and found mention of truespeed. I may have not used the right search words, but I never saw any description of what that is or how it works or where to get one
Oh by the way, this is our fourth diesel. The other 3 are 6.5 electronics. At least one of them has been lowered to grocery-getter status.

 

There is also this one:

http://www.abbott-tach.com/era.htm

 

I have the truspeed. Very satisfied, now I am not tied to a tire size. Took a few mintues to put on, is flawless.

 

marlelectric: The difference you see is caused by the tire size difference. There are two possible ways to go. First there are boxes like the truespeed that modify the VSS (vehicle speed sensor) signal and then there is the possibility that the dealer sets your PCM to the different tire size.

HTH

AlpineRAM

 

The dealer claims there is no way to make any adjustments. I have looked at the two possibilities listed above and the truespeed looks interesting. I now need to see if I can get a price on one. At first look at the price of those two (websites) it would appear to be another bite out of my wallet. I think I am DONE with ebay.
Thanks for the help!

 

try another dealer first or a speedometer shop mine was adjusted at the dealer in kocamo (sp) Indiana.

 

To Helicopter Dan; What year is your truck? Any possibility the dealer in Kokomo is more on the ball having the trans plant in town? The ******* in Columbus has 975 finance plans to sell a truck but was not interested in fixing one he did not sell.

 

Find the right dealer he can recalibrate it with the scanner thingy...
there was a big post on this awhile back and some reserched it all out...most dealers do not know that thir machine will do it so you will probly have to do the reserch here and teach them how!

 

I did a search, Probably didnt hit the right words or phrase. Any ideas of how to label the search? Anyone remember the title?

 

try' recalibrate' I think you will find it there

 

well I have three but the one I was refering too is a 98 12v 4x4 quad cab sport before I bought it it was owned by a police officer in Kocamo Indiana. He had it done by the dealer so it was right on as far as speed indication go's.

 

how much does this cost? I imagine the dealer is going to rip me for about 1 hour of tech work $80. I know that JET has one I can get for about $140-150... May be worth it for the ability to modify when swapping tires especially if you have an auto.