Speedometer doesn't work and transmission doesn't shift gears.


Asked by dfrinzi Nov 25, 2011 at 07:33 PM about the 1999 GMC Sierra 1500 SLT 4WD Extended Cab LB

Question type: Maintenance & Repair

The speedometer stays at 0 all the time.  When the transmission is in drive it won't come out of 1st gear.  Reverse works fine, and if I manually put the transmission in 1st or 2nd it works fine.

1999, Auto 4wd, automatic, 5.3L

17 Answers

Dan Nash

Vehicles transmission output speed sensor faulty

9 out of 9 people think this is helpful.
Best Answer

I replaced both output speed sensors, and also swapped them around with the old ones, no luck. This problem started after I removed the transfer case to install the wear plate and replace the actuator motor, not sure if that has anything to do with it. The 4wd works fine. Thanks

8 out of 8 people think this is helpful.

It's Vacume or electrical is your problem or passing gear cable.If the passing gear cable is broke,unhooked at the throutle body or unhooked inside the transmission would cause that as well.Yep,Vacume could be if your 4wd works under vacume hoses or lines.If your 4wd is electric .You either got a vacume line crossed/wrong.Or leak in a vacume line or unhooked.It's not a speed sinser.Transmission Shifts either from Vacume or electrical.Sounds like to me from playing around with the transfer case you made a mistake.

3 out of 3 people think this is helpful.

2003 Sierra-My truck is doing the same thing- speedo reads zero and won't shift out of first. I cleaned the MAS, replaced shift sensor, made sure trans fluid was full, disconnected and reconnected the battery, and now I am thinking of replacing the stepper motors for the speedo but don't think that covers the shifting issue. ANY HELP welcome!

9 out of 9 people think this is helpful.
Joe Bartlett

vehicle speed sensor,on the rear of the transfer case ,if you got no speed o your truck wont change gears

8 out of 8 people think this is helpful.

I replaced the vehicle speed sensor VSS then unplugged the vehicle speed sensor buffer VSSB (a 3 inch square flat white plastic sensor box) located behind the glove box, I unplugged it and waited 5 minutes before plugging it back in. I also pulled the brake fuse and did the same thing, waited 5 minutes then plugged the fuse back in. The result was successful, the tranny and speedometer work correctly now!

3 out of 3 people think this is helpful.

I did what you said but n luck


replaced the vss then unplugged the buffer waited 5 minutes then pulled the brake fuse and waited 5 minutes but no luck transmission still not shifting and no speedometer.

Willie Gillispie

same for me no help at all


check the ignition switch harness for power drops across the white wire and the pink wire... it is a know problem for the harness to lose power there and causes loss of transmission shifting along with instrument cluster failures.

Raymond McNeil

My 2000 Tahoe LT 4×4 has that not changing gears issue. Put it in drive - nothing, go to 1stthe and it grabs, you manually shift it, works great, even drops down gears and then changes great. The main problem is after I manually shift it, I come to a COMPLETE stop, it goes right into basically neutral, but if I don't COMPLETELY stop it keeps pulling. Once that happens, I have to manually shift it out again. Does anyone have an idea of what themayis be? issue

1 out of 1 people think this is helpful.
Jeffrey Kill

its more then likely the seo ign 10 amp fuse in the fusebox next to driver door the fuse looses power causing instrument panel failure and transmission goes into a nuetral state

Terry Huffman

You said check the ignition switch harness for voltage drops I think that could be my problem because when I check the buffer voltage I only get five volts at the speedo buffer I thought I was supposed to have at least 12 volts is that correct? Do I possibly have a bad ignition switch ?

William Zierman

I just replaced my trans in 01 Yukon. I'm having the exact problem originally stated by dfrinzi. speedo not working and won't shift out of 1st in od but I can manually shift from first to second but not 3rd or fourth. Jw if this problem was resolved and how to go about it thanks.

1 out of 1 people think this is helpful.
Terry Huffman

I replaced my ignition switch and problem was solved I wasn't getting 12 volts to the speedo buffer behind glove box

Jeffrey Kill

Speedo sensor in transfer case I replaced it now it shifts fine speedometer works like it should and I haven't had any other problems

Richard Longacre

I had similar problem and mine turned out to be the safety neutral switch.

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