VSS's different?

So I was sitting at home pondering about my car. I noticed on the highway, when my speedo says Im doing 75, cars are still passing me. Im at 75 MPH @ 3200 or so RPMS (stock 92-93 LS transmission w/14" wheels on 195/60/14’s).

So I decided to check part numbers on VSS’s… and I came up with this.
56500-PR3-901 90 at
56500-PR3-010 90 mt

56500-PR3-901 93 at
56500-PR3-010 93 mt

So could my speedo be off becuase of the different part numbers? Whats going on, should I swap it out for a manual unit (my car is AT-MT w/AT VSS and AT Starter)

that RPM seems low, I’m at 3500 at 70 MPH with my A1 tranny 91 LS. So you might indeed be going slower than indicated, can try timing yourself between mile markers and see how long it takes to go a mile, and calculate true speed from that.

Yea, I don’t know if anyone has compared the 2 different VSS gears from the AT and MT. It sounds reasonable from your RPM & speed that you are in fact going slower than you think. I want to say I am doing 3500-3700 for 70 to 80MPH.

i am doing a auto to manual swap and put a 98 itr spec tranny. can i use my at vss or do i need a mt vss???

hey guys i still waiting for some help here ???

Im not sure its going to fit.

You can use an auto VSS but I believe your speedo will be off by about 5mph at freeway speeds. I put a hydro gsr in my 90 auto da. I used my OEM auto VSS. I’ve noticed that my speedo is about 5mph fast. I’m not sure if it’s because I’m using a hydro tranny or my auto VSS.

Ng