Speedometer bouncing

[Hooptybass]

My 94 GMC K2500 Suburban the speedo is acting up . Its wont work right , or its bouncing all over the place and then sometimes it just stays on 0 mph
Anyone have any ideas on where to start chasing this down ?

Thanks Brian

[a5150nut]

Check your plug going to the sending unit on transfer case. If it is good go ahead and pull sending unit to see if it is full of filings on the bottom end.

Might check connections at VSB too. Pull glove box out and it will be a white plastic box about the size of a cigarette pack just left of the opening where the glove box was.

[CoyleJR]

If it is cable driven remove the cable from the back of the speedometer. Put some wheel bearing grease on the tip of your finger and put it on the cable behind the speedometer and put it back on to the speedometer snug. If the cable is loose at the back of the speedometer it causes the needle to jump around. If it is electric check for a bad ground or bad sending unit.
Good luck
John

[a5150nut]

If it is cable driven remove the cable from the back of the speedometer. Put some wheel bearing grease on the tip of your finger and put it on the cable behind the speedometer and put it back on to the speedometer snug. If the cable is loose at the back of the speedometer it causes the needle to jump around. If it is electric check for a bad ground or bad sending unit.
Good luck
John

94 is electronic not cable driven.

[Hooptybass]

ok thanks ill give that stuff a try this weekend ....

[john8662]

Sounds like speed sensor, wiring, or VSSB/DRAC Module behind glove box near the PCM.

If you need a new VSSB you can get one at www.uniquediesel.com/drac

Thanks,

John

[jggiedeman]

I had a similar issue. Turned out to be the male plug connector on the rear pickup. It was removed previously by someone who had the tranny replaced. Probably yanked on it to hard and broke one of the two arms. Was inserted but not tightly which led to sporadic speedo bouncing around.

[Hooptybass]

Ok ive cleaned the plugin on the transfer case and pulled it and cleaned the sensor . I will try the box int he dash next . Are these boxes the same on the gas trucks and burbs of the same body style ? if so i may goto my local pick n pull and get one . those new ones are pricey

Thanks Brian

[a5150nut]

Little white case just inside the dash. Pull glove box and its in the lip of the dash to your left. About the size of a cigarette pack.

[Hooptybass]

Anyone know if the little white box on these are the same on the gasser trucks and burbs ? I took the one out of my 94 Chevy 1/2 ton with a 305 and I'm still getting the same thing . I may try taking the sensor back and get a warranty one and try that before i invest in a new box

Thanks Brian

[a5150nut]

Can't remember if it was bouncing or just quit all together on my 94. But it was filings built up on sending unit in transfer case where it reads the reluctor wheel. Just pull it out and see if its all covered in metal.

[Hooptybass]

I will have to try and pull it and clean it . I tried that when i first posted and it didnt seem to do any good . Ill clean it and if it dont help ill replace it