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Trying to get my speedometer to work. The cable is fine but does not turn when hooked up to the transmition. It must be the speedo gear. I can pull it out of the trany with out messing up any of the other gears right?
 

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Quick Question: Do you by chance have cruise control? If so, I know the transducer can bind up, and cause speedo cable failure. The tranny may turn the cable, but the transducer may be jammed, so replacing the cable alone will not suffice. Check this if applicable.

If no cruise, then I know on a TH 350 you can pull the sending unit out with only a few fluid drips. What kind of tranny do you have anyway?
 

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I have the same problem on an 88 IROC w/ 700R4, but for the life in me, I can’t find the transducer assembly. I have a repair manual that talks about it but it is not where it should be in the motor compartment of the car. I talked to a speedo shop a while back and they thought that I may not have one and the cruse control was being controlled via the computer. Any Ideas?
 

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David, GIve us some details on the year and transmission you are running. We may be able to give you a better answer.

If the Trans is a Muncie they can with two different diameter drive gears. You may have a combination that doesn't mesh.
 

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G.M. has 2 basic cruse system's. the one with a transduser mounted in-line and the electronic system that uses a sensor in the speedo.

the transducer is a big unit mounted on the iner fender on the driver's side. the speedo sensor is in the speedo.

if you have no transducer you have the electronic unit i bet. also if you have an eclectric speedo you will always have the electronic unit.

the trancduser has a cable from the tranny, then one going to the speedo. the tranduser is about the size of a fist.

the electronic type is used on all G.M car's and light truck's after around 1985 i belive. do not hold me to this i am racking my brain here but that is around the right year so say mid 80's.

i bet the 88 IROC is electronic. as for the other one you have not posted a year, so i have no idea.

on the electronic you will have a seperate harness coming out of the back of the speedo on the top side with a non-electric speedo. with a electric speedo it is controled by the ECU.

hope this help's! and a 700R4 tranny's speedo hook up is basicaly like a THM350's. you have a gear on the output shaft and a speedo gear at the end of the cable.

so you have 2 possable gear's that might be bad, or the cable has a rounded off end and is not spinning.
 
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Thanks. I’ll have to tear the dash apart, again, but that’s half the fun. Also have to take a look at the trany and check the cable and gear / plugs. Again, Thanks everybody!
Mark (A.K.A. Z28 Mark)
 
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