speedo question

[dman1982]

i swapped out my instrument cluster yesterday with a better looking one, the circuit board on the back was a lot better shape than mine so i switched it out, just the cluster and the only thing i kept from mine was the speedo so that way i could keep the mileage the same, now my speedo is jumping all over the place....what could be the cause of this? the circuit board was a little different than mine but from what i could tell it only affected the oil pressure gauge (the person before me rigged one in there)

[79 silverado]

On an 84... or 82 based on your name, if that is what your truck is, the speedo is cable driven, not electronic. (that didn't come until the later r/v series trucks)

If you speedo is bouncing I'd suspect something got messed up in a connection with your Speedometer cable when you were taking apart and putting back together.

[dman1982]

Connection? It's just the cable and three wires with a screw...anything in particular? Is the cable not all the way on?

[dman1982]

no ones got any input???

[rs74]

Did you just change the gauge face or the whole thing? I would say unhook the cable from speedo and put back on and make sure the cable trips the clip to hold it in.

[dman1982]

i changed out the whole thing minus the speedo, i used my original speedo

[87squarebody]

I've seen a few post about what year the speedo went electronic.Most say 86 on up.My truck is an 87 with 700r4 and it has a cable operated speedo.What year did they actually come out with electronic speedo.Can someone post a pic of the electronic speedo connection at the tail shaft of the trans.

[dman1982]

mines a 84 with the th350...also cable

[68Timber]

Originally Posted by rs74

Did you just change the gauge face or the whole thing? I would say unhook the cable from speedo and put back on and make sure the cable trips the clip to hold it in.

I'd be trying this first. It's all mechanical and sounds like it's not seated properly.

[dman1982]

Originally Posted by BRUISER

I'd be trying this first. It's all mechanical and sounds like it's not seated properly.

thanks man, after dinner ill get up under there and try to reseat it

[chevylover1654]

Originally Posted by 79 silverado

On an 84... or 82 based on your name, if that is what your truck is, the speedo is cable driven, not electronic. (that didn't come until the later r/v series trucks)

If you speedo is bouncing I'd suspect something got messed up in a connection with your Speedometer cable when you were taking apart and putting back together.

i have a 85 and all i did was pull it then left it out for a hour then put it back and i was good to go

[dman1982]

i pulled it out and put it back in and its worse, i pulled it out and going to let it out all night and hook it up tomorrow and see what happens

[chevylover1654]

i hope it work

[1981Stepside]

If the cable is plugged into the back of the speedometer properly it sounds like the Speedo is bad. It's strange but it happens. When I changed from a th350 to a 4l60 I didn't even touch my speedometer but it started bouncing the same as yours. Sure enough, I swapped with a different speedometer and the problem was resolved.

[RandyP]

Things go bad by coincidence all the time like this. Before I went and changed the speedo head unit I'd try greasing the cable, that's the usual suspect in a bouncing needle for me. Just remove the entire speedo cable from within the sheath and lube it up and reinsert it and hook everything back up and give it a whirl. Takes literally minutes to do.

And speedos did not go electric until mid 89 sometime. Some 80 burbs have electronic speedos and some don't. All 90 and up models do though. In the 80's sometime they started placing a speed sensor on the speedo, which is the little thing with a couple of wires held in place with a single screw on the back.

[motornut]

yup my 89 was cable....make sure it's under the clip back there might be hard to tell

[USArmyCombatMedic]

I have an 87 R10 700R4 and have the same problem. It was bugging the crap out of me so I replaced everything. New speedo, cable, electronic connection, new transmission (just cause not because the speedo bounced). It still bounces like no other. I just figured it was suppose to bounce. Do all of yours bounce?

[chevylover1654]

mine dont bounce and i have the stock 85 cable

[willett]

My truck has a mechanical cable, I replaced it a few years back and once in a while on the highway it starts going nuts like you mentioned

[USArmyCombatMedic]

Personally, I would check to make sure that the speedo cable is all the way on. If so, I would disconnect and lube the end of the cable. It is suppose to be pretty well lubed which thinking back to when I did mine, I forgot to lube the new cable which could explain my problem. Also, when you say jump all over the place, I assuming you mean it bounces as in your going 25MPH the needle will bounce from 15ish to 35ish? Or like random jumps from 5MPH to 85MPH to 30MPH?

[mpierce9]

Not an expert but my cable didn't have much slack so i really hard to put in the extra effort to get mine on. Once I did I held the cable in place and pushed in a bit on the face of the speedo. That seemed to get my cable plugged in.

[chevylover1654]

the cables are should last a lifetime but they dont and it sucks but is better the new age style

[oilmanpat]

I would say it's a lube problem. you should beard a faint click as the end goes on the speedo.

[USArmyCombatMedic]

At mpierce9 I had the same problem. I could not connect the cable to my speedo since it was too short. Then I remembered there was extra slack under the cab to allow for flex and what not. I threaded some of the slack into the firewall. The cable stuck out past my steering wheel which made it much easier to connect and here the distinct click oilman spoke of!

[f.monroe]

Lubricate the cable as mentioned above. It was probably a little dry and just moving it will cause a bouncing speedo sometimes. The cable binds and lets go causing the fluctuation you see. The inner cable comes out real easy. Do not over lube it.
Frank