speed sensor

[JMullens]

Have a friend with a '93 ctd 350 dually. He is having trouble with the transmission. Jim Jessup says that the speed sensor is bad and it is not allowing the transmission to shift into overdrive. Does anyone have a used speed sensor, It mounts on top of the fuel pump.

 

[nascar mark]

Before swapping out old senser or buying new one, take off TPS and turn upside down. Spray with contact cleaner and let soak. Many times its just bad contact. Another fix is to take apart with dremmel by cutting top of TPS were you can see its glue ring. Clean with contact spray and reglue with electic glue. Try cleaning as above first before taking apart.



mark

PDR - Black Sheep Racing

 

[formula]

Originally posted by JMullens

Have a friend with a '93 ctd 350 dually. He is having trouble with the transmission. Jim Jessup says that the speed sensor is bad and it is not allowing the transmission to shift into overdrive. Does anyone have a used speed sensor, It mounts on top of the fuel pump.

Just to clarify something here:

The Throttle Position Sensor (TPS) is mounted on top of the injector pump. The TPS is most likely causing the shift problems, I've fried 2 of 'em and the third has been hangin' on for over 5 years now. The speed sensor is mounted next to the output shaft on the transmission or transfer case if you have 4wd. I've never had any trouble with my speed sensor, but I've heard that it can cause some shift problems too.



Have a look at this thread:

https://www.turbodieselregister.com/forums/showthread.php?threadid=57835



SP

 

[BushWakr - RIP]

I just had problems with mine and replaced it.

I'd also like to confirm what formula said..... the thing on the injection pump is the TPS, not the speed sensor. It is located just were formula said, on the transmission or the transfer case on a 4X4.

In my case the speedo would spazz like crazy if I 'got on the throttle' but was ok if I did "granny driving".

Every time the speedo went wacky, the transmission would drop out of OD.

So far, the new speed sensor seems to have fixed the problem.

As for the TPS, mark is right on... . that thing is the bane of our existence.

When the TPS acts up, it causes the 3-4, 4-3 shift to get wierd.

The truck will "hang" and not want to go into OD, then it'll drop out seemingly for no reason and on it goes... .

I have a detailed "how to" on my 'puter here, its in text format I think so if you want it, I can email it too you. I finally typed it out and saved it after posting it about 50 times...



Let me know.

 

[JMullens]

Oops!!! That was my mistake. I was in such a hurry to get this on that speed sensor just sounded right, but instead it is the TPS.

Talked to my buddy again today and he said that there is some type of drive between the sensor and pump that is missing. Anybody got one?

 

[BushWakr - RIP]

I don't know what kind of "drive" he's talking about. The TPS controls your 3-4, 4-3 shift on an auto trans.

The TPS has a shaft ending in a hex head which in turn goes into a hex socket (female). This is rotated by your throttle, as the socket is rotated by the throttle, the shaft is turned. This in turn, causes the TPS to rotate internally. This rotation send a signal which is used, in part, to determine when to upshift into OD, or when to downshift into 3rd. There is no other "drive" that I am aware of, and I've messed with mine plenty... lord help me

I'll attach a pic of the TPS. Find your's and take a look at it. Look on the underside of it and you'll see the shaft coming out, and also were it enters the little socket I mentioned. I don't know how you could possibly be missing a "drive" for it.



Now, the speed sensor on the transmission has the sensor part with the electrical connection, and it has a mount/coupling that goes onto the transmission. That is connected to the drive gear, which is inside the transmission and can be removed by undoing the nut at the very face of the transfer case housing, and sliding the drive gear assembly out. This will also affect your OD shift.

When mine went out on me the speedo would thrash around and the truck would drop out of OD. Then after the speedo settled down for a few seconds, it would go back up, into OD.



Is this helping any????



Bob.

 

[boatpuller]

Maybe he's missing the little plastic(if memory is corect,maybe part metal) that has the tangs that go up into the TPS and mate with the plastic piece you adjust it with. If that was gone the TPS wouldn't sense the throttle position. If so that is probably a Cummins or stealer part.

Just trying to help fill in the blanks,

Caleb

 

[BushWakr - RIP]

Boatpuller, you have a point... ...

JMullens, look under the TPS and see if that shaft I mentioned is there. The bottom of the shaft will have a hex head, then a very short metal shaft like a bolt (not very long) then a round plastic piece with two "flats" on it, for a an open end wrench.

If you take the TPS off the bracket itself, there is a plastic "tang" that fits into a slot inside (bottom) the TPS as well. Did they disassemble the thing to make this diagnosis???

Boatpuller may be right, referring to those parts. I've never heard of anyone have them break off, but it's possible I suppose.



Let us know, now you got me curious as heck too... ... .



Bob.

 

[JMullens]

Hey guys, thanks for the responses. I will give my buddy a holler and see if anything helps.