Just going to ask the group,


So my D250 has always had some error in the spedometer. My truck has the RH47 transmission, so I don't know if the gear is different. It seems to me that @ indicated 65 mph I'm going about ~60mph, @ 74 ~70mph, and at 85 indicated it's 80 mph. So is the variation in the transducer (it's a 91.5). I did the RH46 to RH47 conversion. So the external part is what came on the truck. Then again, I wasn't the original owner- but the 3rd.


Michael

 

With that small of a MPH reading off, it is likely a different than stock sized tire on your truck.
The gear ratio options in the years 91.5 and '94/'95 [the years that came with 47 RH auto transmission] ran 3.54 and 4.10. If you where running the wrong speedo gear it would read more off than that.

What sized tire are you running on the back?

 

I'm running stock 235/85/16s which my door tag says are stock. They are BFGs. Rear end is a 3.54. I had assumed the transducer produces a square wave similar to a cps and it wouldn't have error. Does the signal go through the computer in a 1991.5?

What size tire would be stock on a 94/95? Maybe that's the difference?

Maybe it just needs to go out for calibration/service somewhere?

 

My stock tires on a 93 are 215 85 16s.

 

The '94/'95 2500s and the non dually 1st gens come with 235/85R16 tires.
Me personally I would not let my speedo reading 85 while I am doing only 80 bother me at all.

 

Thanks Oliver!

I was looking at the Wittrans page. It looks like there are a lot of tooth range available. I'll take it out and count teeth.. and order a different number.