Not going in reverse?

When I'm in 4wd and try to reverse it makes a really bad grinding noise but doesn't do it when I'm in 2wd and doesn't do it when going forward

Does the PCM control the reverse in the transmission. The vehicle won't go in reverse. Won't shift out of 2nd. Gear until you release the throttle.

Drove to work no problem at all, backed into spot and at end of the day pulled out of spot and it started making a whirring sound. I put truck into reverse to back into spot, and nothing no reverse. All forward gears seem to work, whirring noise is only in park neutral and reverse it goes away when in drive. It is showing a vehicle speed sensor code also.

2002 Chev Trailblazer LT, 136,000 miles
When shift into reverse it does not engage and it makes a loud grinding noise.
After approx. One hour, symptom disappeared. Reverse ok. Then had transmission work done.
5,000 miles later, symptom appeared again. After letting car sit for a couple of hours, symptom disappeared. Returned to Transmission shop. They test drove... Worked fine. They dropped the pan, took a look at transmission again and said it was totally clean and no apparent problem that they could see.
Approx 5,000 miles later, symptom appeared again. This time I drove on highway. While gliding down hill, if over 50mph, the similar grinding noise heard. When I gave it a small amount of gas, noise disappeared. I pulled over, on downhill grade, put it in park, and the car glided forward (park did not engage). I stepped on the brake and the car stopped and park engaged. Reverse was still not working. Park engaged ok after that.
Drove 60 miles to destination. Parked, tested the reverse and all symptoms gone... Engaged in reverse properly.
Took to Transmission shop again. They test drove for long time... Could not get symptoms to reappear. Transmission fluid ok. They baffelled and now recommend to have cable replaced that runs from shifter to transmission.... No promises.
Are we missing something?

Could that also cause that grinding/whirring sound upon deceleration?

Transmission problem
2002 Chevy Trailblazer 6 cyl Two Wheel Drive Automatic 60.100 miles

My car drove fine all the way to work, I went to leave and it won't go in reverse. I had someone push me out of the parking spot and I put it in drive and it worked fine, it just wont go in reverse. When I go frome drive to reverse it makes a whinning noise. Help

I have a 1999 S-10 Blazer, 4WD, 4.3L V6 engine, Auto.

While driving tonight, I noticed that the rpm's were higher than normal at highway speeds. I stopped at the store and upon restarting the engine, I had no reverse. I had forward gears to get home luckily.

The rest of the trip home, I noticed that it revved VERY high before shifting from first to second.

Are the rough shifts and lack of reverse related? If so, does anyone know what the problem could be?

PLEASE don't tell me I need a new tranny.

Any idea how EXPENSIVE that could be?
Now I am going to cry :cry:

LOL