[waffles]

Alright, here we have a 1999 5700 Vortec Chevy Tahoe 4x4. It has about 170,000 miles on it (it was a workhorse for a local grading company) that's suffering from three distinct and seemingly unrelated problems, but they all occur at the same time.
It started with the anti-lock brakes kicking in at low speeds. I was advised to remove the wheel sensors, clean and re-grease them with an anti-rust grease. I did this despite the sensors and the housings being seemingly immaculate. This did however seem to stop the problem.
Only two days after that though, I braked and the ABS light turned on. The transmission went into what I can only guess is limp mode. When in the normal overdrive selection, it starts out in third and gets no acceleration after about 3000 rpms. Same thing if you manually shift it into second or first. 4-wheel drive will engage but the vehicle will not move. Also, the speedometer would move seemingly randomly even when the Tahoe is stationary, and now will not move from zero.
The problem seems to also start randomly. Normal operating temperature can be reached and exceeded without any problems normally, all though the problem will not start with the vehicle cold. Any ideas?

 

[TrailLeadr]

I would try replacing the speed sensor in the transfer case to start.

 

[waffles]

Where is this located on the transfer case?

 

[unplugged]

Have you checked for DTC codes? If so what are they?

 

[waffles]

Yeah we had the service light come on when the transmission first went haywire the DTC codes we got were:
P0327
Knock sensor 1
Circuit Low Input Bank 1 or 1 sensors
and
P0420
Catalyst Efficiency below threshold.

The knock sensor was replaced and the codes were cleared, the service light has not come on since, although I haven't had it rescanned since they were cleared.

 

[TrailLeadr]

The sensor should be near the tail end of the transfer case.

 

[84fiero123]

Any problem with the engine, brakes or anything else that is attached or has the transition run threw that system can give false trany problems.

Once you reset the codes after the repair did the problem go away?

By the way codes are just helpers to the technician. They are not always the problem.

If for example it says you have a MAP sensor problem it could just have a dirty intake filter, or dirty throttle body. Don’t just expect them to tell you all, it still can take a GOOD diagnostician to find the problem.

A few years ago a friend with a ford F150 that had been revving on start up took it to the dealer several times. They hooked it to the computer, checked it out, never could figure out the problem.

I looked under the hood and saw it with out even a computer. It had a carburetor, and the float was sticking.

A light tap on the carb over the float bowel fixed the problem.

He called me the next time he brought it in to have the carb fixed and told me that non of the dealers techs even knew how to fix a carburetor.

Read my signature. Technology is not always good. Sometimes you just need a HAMMER.

 

[chevyloverss]

Alright, here we have a 1999 5700 Vortec Chevy Tahoe 4x4. It has about 170,000 miles on it (it was a workhorse for a local grading company) that's suffering from three distinct and seemingly unrelated problems, but they all occur at the same time.
It started with the anti-lock brakes kicking in at low speeds. I was advised to remove the wheel sensors, clean and re-grease them with an anti-rust grease. I did this despite the sensors and the housings being seemingly immaculate. This did however seem to stop the problem.
Only two days after that though, I braked and the ABS light turned on. The transmission went into what I can only guess is limp mode. When in the normal overdrive selection, it starts out in third and gets no acceleration after about 3000 rpms. Same thing if you manually shift it into second or first. 4-wheel drive will engage but the vehicle will not move. Also, the speedometer would move seemingly randomly even when the Tahoe is stationary, and now will not move from zero.
The problem seems to also start randomly. Normal operating temperature can be reached and exceeded without any problems normally, all though the problem will not start with the vehicle cold. Any ideas?

I agree with Fiero you need someone that knows how to diagnose the problem because it sounds like an electrical problem. Good luck keep us posted what happens