Issues with 2001 gmc sierra...any ideas?

[Bullshop Junior]

I have a 2001 GMC sierra 1500 5.3L 4x4 with the 4l60e in it. Today it started acting wierd. The speedo started bouncing. Just a little at first, but by the time I got home it was a constant bouncing back and fourth up to 20mph. It only does it in drive. If you shift down it works fine. Towards the very end of the drive it started randomly shifting and then everyonce in a while the rpm would just jump about 200. The whole time the parking brake light was randomly flashing. Not in a pattern. Just random. Where should I start looking to fix this? Wanna get it fixed before i mess something up....

[Ford SD]

I have a 2001 GMC sierra 1500 5.3L 4x4 with the 4l60e in it. Today it started acting wierd. The speedo started bouncing. Just a little at first, but by the time I got home it was a constant bouncing back and fourth up to 20mph. It only does it in drive. If you shift down it works fine. Towards the very end of the drive it started randomly shifting and then everyonce in a while the rpm would just jump about 200. The whole time the parking brake light was randomly flashing. Not in a pattern. Just random. Where should I start looking to fix this? Wanna get it fixed before i mess something up....

Not a GM fan Drive a Ford
Might not solve problem
How many coils Does it have (one per cylinder)

Have had problems rpm jump when have a bad coil

Water / corrosion have gotten in and corroded one of the terminals on the coil connections
Fixed it by using an old spark plug file (fine app 1/4w x 1/32 thick 6inch long) to file the corroded terminal --blow dirt out and reconnect wire

Just be carefull you don't brake anything

Might not be your problem?
Flash light and good vision and a bit of time and you can check connections

[SP5315]

Check the connector from the speed sensor wire harness at the transmission. This was my exact issue in my GMC Savana, caused speedo to jump around along with an intermittent ABS light.

[Mod42]

Check the alternator, doesn't sound like the problem but low output can make the inst cluster crazy, should be about 14 volts.
This is about the correct vintage for bad inst clusters, however the normal failure is the odometer goes out then the the speedo, or the gauges read incorrectly.
What I would look for in my shop would be a torque converter not locking up properly. Get the truck to a GOOD scan tool to see if the are tranny codes! from your description I fear transmission problems!

[smokeywolf]

Start by scanning for error codes.

[Bullshop Junior]

Check the alternator, doesn't sound like the problem but low output can make the inst cluster crazy, should be about 14 volts.
This is about the correct vintage for bad inst clusters, however the normal failure is the odometer goes out then the the speedo, or the gauges read incorrectly.
What I would look for in my shop would be a torque converter not locking up properly. Get the truck to a GOOD scan tool to see if the are tranny codes! from your description I fear transmission problems!

I was wondering about the tourqe converter but its puzzling it only does it with the shifter in drive. If you shift the shifter to 3 it stops. If you have it in drive and push the gas down to shift down it doesn't go away though...

[MTtimberline]

Sounds like the instrument cluster assembly is failing.

[freebullet]

I would check all grounds and both battery terminals for cleanliness. If you have to clean anything disconnect the - terminal fer a couple minutes before driving again. Then getter scanned if it persist.

Bad grounds
Tranny solenoids
Torque converter-not unlocking can cause surges at idle and an overly rich running condition. To the point your oil will smell like gas as it progresses.
Speedo cluster

Does it do anything strange at idle in drive?

[texassako]

Check the connector from the speed sensor wire harness at the transmission. This was my exact issue in my GMC Savana, caused speedo to jump around along with an intermittent ABS light.

I would definitely check this first, especially since it is in the transfer case you just replaced I think. Electrical gremlins can be a pain.

[geargnasher]

The small gauge, single ground wire that attaches to the back of the engine block, WAYYYYY back behind the plastic intake manifold and just above the tranny bellhousing where you can't see it without a mirror and flashlight, is broken inside the insulation right at the base of the crimp on the ring terminal. Remove the ground bolt, splice on about six inches of new wire and a new, 3/8" diameter ring terminal, clean the grounding area to bare metal, and reinstall the bolt and ground wire.

You're welcome.

Gear

[smokeywolf]

Good to know gear. I have a 2001 Yukon.

[Bullshop Junior]

Wasnt the problem gear. Just lost 3rd and forth on the way home from work

[Mod42]

Wasnt the problem gear. Just lost 3rd and forth on the way home from work

Get to a shop and have it scanned!! When you know what the codes are you can start to look in the right places, until then all of the free advice you are getting is worth exactly what you have paid for it!!

[Bullshop Junior]

Doesnt show any codes. I know what's wrong with it. Now just have to come up with the money for a tranny

[Fishman]

I have a 2000 model with the 5.3 and auto. I lost gear 1 and 4 and it was just a shift solenoid so you may not need a tranny. Pay no attention to the Ford loving Chevy basher, he's used to having to replace coils on each cylinder LOL . I'm just shy of a quarter million miles on my z71 with only the aforementioned solenoid issue with the powertrain.

[Bullshop Junior]

Mine isn't a solenoid. Most of the time tht just causes it to not shift. This shifts into 3rd and then there is just nothing there. It's happened to several of te Chevys I have had, so nothing new. All the other ones just went clank and quit working, so the speedo thing threw me off.

[TXGunNut]

Sounds like the instrument cluster assembly is failing.

We have a winner!

[Bullshop Junior]

We have a winner!

I'm pretty sure not. The speedo sensor is on the input shaft. All other gauges work fine. Now that I have lost third and fourth the speedo does not work at all.

[tomme boy]

Didn't you just have a transfer case problem with this truck? Does the transfer case and trany share the same fluid? I thought some did?????

[Bullshop Junior]

This one does not.