Spinning93

recently bought a 2001 ford svt cobra. When I got the car the miles nor the speedo worked. The clutch went out a couple weeks after. I bought a 10 spline clutch but when the shop was trying to install it they told me it was the wrong one because the car has a upgraded tranny with a 26 spline input shaft and its a tr3550 so I got the right clutch over nighted. My dad did something in the wiring to fix the miles so the miles work now. After he did that and got the miles to work the speedo worked but now it only goes to 20 what might be wrong?

dawson1112

Because your transmission is an earlier year 3550, your car uses a magnetic pickup to read a reluctor ring in side the trans mission. The 3550 has a speedo gear. Your miles may be reading but they are not accurate.

The only way I know to solve it on the 3550 is to get a dallas speedcal. It allows you to convert the gear driven signal into magnetic or digital signal. The PCM looks for about 30,000 pulses per mile, but your gear driven VSS only generates about 8,000 so essentially the PCM thinks your going a lot slower and traveling a lot less miles.

I am not real familiar with the TKO , but on the old T45 transmissions you could swap the tail housing for a later model T45 and replace the gear with a reluctor ring and a magnetic VSS. I don't know if you could use a TKO tail housing with the 3550 or not.

Spinning93

Thanks a lot I'll probably go the Dallas speedcal route for now. So it has somewhat of a signal but it just isn't reading it correctly? Could it be the VSS, wiring harness, or the cluster itself?

dawson1112

No its not in the wiring, It has to do with the way the 99+ cars read the VSS.

The early year models, like 94-98 used a speedo gear. The 99+ use a magnetic pick up, so it does not calculate the same way. From what I know of the 3550 it uses a gear driven VSS. I had the same issue with my 2000, someone put a 97 T45 in it. It would not read past about 20mph going 100+ . I bought a speedcal for it to use temporarily , then I just rebuilt a 2000 tremec T45 to replace the one that was in it. You may also notice that the car tries to idle down to soon when you let off of the gas.

You can pull the VSS and look at it , if it has a gear its wrong for that year car. If it has a magnetic pick up then the problem is elsewhere.

I have a dallas speedcal that I would sell for $50.00+shipping. Its only about 2 months old I believe, they cost about 110 new. Pm me if your interested. I have a paypal you could send the money to and Id ship it out right away.

The only other way I know of is to get a chip and have the car tuned.

Spinning93

Thanks a lot man I really appreciate it. I'll probably send you a pm within a week or so still have to buy some other things for it first this is my first v8 so I'm pretty excited.