Okay, 91 d250. The speedometer drive gear was stripped out so after searching for about 3 days, i finally found one. Installed it and it still reads alot faster than i'm actually going. Wannadiesel mentioned something about a L shaped piece between the vss and the drive gear. I dont see anything that looks like that. Where can i find this, and anyone know a part #? Also, is it possible that even the old drive gear was not the right tooth count, and that be causing it? The old one was 31 teeth so that is what i put back in. I also replaced the gears in the odometer, and it still does not work. Is the incorrect speed causing this, or do i need to take the odometer back apart?

 

Need to know what transmission you have. My manual trannies have always had the L-shaped adaptor; Mom's auto just plugs right into the tranny. 4x4s had the offset adaptor coming out of the t-case.

Daniel

 

2wd with 5 speed

 

There should be an adaptor in there. I have one from a set of 4.10s, I think. Dealer wanted $100+ 5 years ago.

DP

 

i found them on transmissioncenter.net for 62.00, but it asks what percentage you want to slow down. 26.7%, 17.6%, 10%, or 2.56%. how do you calculate that. when mine says 55mph, i'm actually going 35mph. when it says 100mph, i'm really going 65-70mph. i'm guessing maybe the 26.7%?

 

if the numbers you gave are right, you are more like 35% off.

 

That is pretty far off.

I dont know why, but when my truck was stock, it read a little more than 10% fast, but when I put 35" tires on it is now only about 1% off. Dumb luck I guess.

 

I think Ma Mopar wanted to keep CTD drivers from killing themselves by making them think they were going alot faster that they really were.

 

Mine is off a little at low speeds and high speeds... but the Garmin street pilot is right on...

 

jeramy125- you got it right.

Take 100 and multiply by .633 (the number you get when you subtract 26.75 from 100%). Gives you 63mph, which is right in the range he needs to be.

Take 55mph and multiply by the same figure (.663)- you get 34.815mph; within the range of accuracy the factory adaptor was.

Diesel Junkie- when you went with bigger tires, your actual tire revolutions per mile decreased. That made your tires catch up to your speedometer.
At 2050 RPM, I am going 70mph in 5th gear (235/85-16; 31" tall). With 35" tires, that same 2050 engine RPM would speed me up to 79mph; with 70mph being only 1816RPM.

Daniel