Speedo Not Working

[ericstreich]

Hi, I have a 74 FJ40 which has had the engine converted to a 350 small block and 700r4 auto trans. Recently my speedo stopped working and I have troubleshot the situation and determined that the speedo and cable are just fine. What I do know is that there seems to be some sort of an electrical device between the speedo cable and the transfer case. This device has a plug that as far as I can tell connects to the transmission. The reason for my speedo no longer working is that the brass fitting which threads on to the transfer case appears to be broken which causes the chuck to not come in contact with the gear inside. Can anyone tell me what this is? The part has a name "MassTech" with what I assume is a part number "TR9-AA-2". I cannot find anything on this when I search by name or part number. Thanks so much to everyone who responds. This is my 16 year old son's car and now that he has his license it is killing him and my wife and I when he does not know how fast he is traveling. Thanks again!

Eric

 

[reddingcruiser]

It's the VSS and provides a pulse signal for the ECM. It's unusual that this would affect the speedo because its pretty much and straight through shot for the speedo cable. Though a stripped gear would affect the VSS function, have you taken the speedo drive off the back of the t-case and checked the drive gear?

 

[reddingcruiser]

Look up 'Jags That Run' on the Internet, they stock the VSS, sometimes.

Do you have a short length of speedo cable between the VSS and t-case?

 

[ericstreich]

It's the VSS and provides a pulse signal for the ECM. It's unusual that this would affect the speedo because its pretty much and straight through shot for the speedo cable. Though a stripped gear would affect the VSS function, have you taken the speedo drive off the back of the t-case and checked the drive gear?

I don't think the VSS is bad as the vehicle is having no driving issues. My biggest issue is that the brass fitting on the VSS has broken and will not allow the chuck to come in contact with the gear. The brass fitting on the VSS is fixed and will not come off. The small ring spun freely inside the brass nut. I have tried O'reily with no luck. Could not seem to find anything on Cool Cruiser or Specter.

 

[ericstreich]

Look up 'Jags That Run' on the Internet, they stock the VSS, sometimes.

Do you have a short length of speedo cable between the VSS and t-case?

There is no short length cable between the VSS. The brass fitting mounted directly to the transfer case and I am guessing the vibration over time. If I could find the fitting with the small ring which swivels inside the brass nut I would most likely be fine.

 

[reddingcruiser]

Like I said, take a look at the JTR website an give them a call. They are familiar with that VSS and may be able to offer some solutions. My 700R4 conversion kit that originally came from @Downey had a 12" piece of speedo cable, I've not seen the VSS hooked up direct to the drive gear ass'y.

 

[pjohnson]

Jags that run makes that particular VSS. It provides a signal to the TBI ECM that primarily prevents stalling when coming to a stop. Some say it's required, some say it isn't... Search for VSS if you want to read the debate.

If you're not having any drivability issues, such as stalling when coming to stop , then maybe you don't need it. You're statement below indicates it wasn't working anyway since the unit wouldn't connect to the transfer case.

The brass fitting mounted directly to the transfer case

Connect the cable to the t-case directly. If it's not long enough, contact @Downey or Trail Gear sells an extension cable.

 

[bentzb02]

Did any of you find that part? Im looking for the exact same part by MassTech TR9-AA-2. Im told it is a speed sensor and Ive looked for it at that site JagsThatRun. The people at that company told me that I needed a part labeled a 2PRS. I bought it ($120) and they sent it to me and its entirely wrong part. I really need to find the correct part if anyone can steer me to it. Thanks in advance.