Here is a question I have been trying to find the answer to by going through the old post( using th esearch feature). I didn't want to get berrated for asking a question that may have been covered in a past post, like maybe 2 years ago. Anyway, does the VSS only affect the speedo or does it have an affect on the trans shifting characteristics?

 

both

 

Dirtydog, My truck seems to be short shifting since I went to 285's.(33's). If I swap the VSS gear to one that is 2 teeth smaller, I wonder if this will improve or return my truck to its previous shift pattern. I also noticed when at speed over 40 if I want to down shift to say pass someone sometimes it will not down shift fast enough. I know the tires are playing a large role in this, but it does not happen all the times.

 

What size were your stock tires? What count gear is in your truck now? What size are your new tires? What rearend gear do you have? What transmission is in it?
Alan

 

I went from a 245 to a 285. I think I have a 3.55 rear. and I have an auto trans.

 

Which auto trans?

 

How do I tell which trans?

 

I may be wrong but this is what I understand...

You will only have to change the speedometer gear. On the earlier F150's ('97, '98) there is still a speedometer gear used. I believe that it was in the '99 model year that the speedometer is controlled by the vehicle speed sensor. There are other componants besides the transmission that use input from the VSS, like the antilock brakes.

I have to change the speedometer gear in my transmission because I went from the stock 17" wheels to 18" Lightning wheels with farily tall tires. Well taller than the F1's. I haven't done the gear change yet but I believe it's necessary to remove the speedometer gear to count the teeth. I think you also need to calculate the difference in outside diameter. You can check out a site like Tire Rack, they have calculators, though I don't know how accurate thay are.

I don't know the code for the 4R100 but the code for the 4R70W is U. This will be on the sticker on the drivers side door jamb.

If this doesn't help, maybe it can at least help to point the direction.