Mechanics

SHIFT ISSUES

1999 Chevrolet Blazer • 4.3L V6 4WD Automatic • 124,000 miles

When driving today in ice and snow I pulled into a lot parked car for a few min. After starting the car to continue my drive I noticed my shift indicator lights were not lighting up on certain gears. Getting on the road again I noticed the truck was not shifting into third or OD. I continued at a slower speed to my destination. Returning to my vehicle to begin my drive home I noticed the truck was now not shifting from first into any gear. I can shift down to first and up through the gears only to get a top speed of 15 mph. When down shifting from drive I feel it go down through the gears. I have 4 wheel drive disabled due to un-related problems I believe. I replaced all the shift solenoids about a year ago and when those failed I got a c.E.L. I pulled codes today only to have o2 heater circuit bad. I believe its in limp mode for some reason. Or some how a chain or something in the damaged T-case has allowed it to get into granny gear? Any help would be great
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Frankie_mcgrew
December 22, 2013.



The first thing I would check is called the range sensor. Since the light isn't coming on to tell you what gear you are in, something is telling me that is the issue. Also, has the check engine light come on?

Yes. It came on last night after I changed the bank 1 sensor 1 o2 sensor. For c.E.L. That was on previous to this but still came on after new o2 installed. When I bought the truck it had shift solenoid problems and those were picked up by the pcm and caused a c.E.L down to which solenoid was the culprit I just replaced them both. I have had no issues till today. Also when I bought it the lights on the 4wd engagement switch did not work and truck was stuck in 4wd and damage was caused to the T-case something in the T-case broke and cracked the housing from with in. So I unplugged the harness on the T-case and removed the front driveshaft again a year ago and no issues till this. Is this range sensor can it also be known as the neutral safety switch or gear positioning switch. Also, can the trans itself go into a limp mode or should the whole truck like when there are major misfire issues? Cause the engine runs fine no registered c.E.L other than o2 heater circuit. It seems like I am getting first and second in granny gear no third or O.D with a 2.72 granny gear red line first gear is like 10mph so if Im getting second and maybe even third at 3,500 rpm id get about 15mph

Tiny
Frankie_mcgrew
Dec 22, 2013.
I keep fluid in t-case topped off and fluid in trans is clean and where it should be

Tiny
Frankie_mcgrew
Dec 22, 2013.
Since the check engine light is on, I would check to see if there are any trans trouble codes stored in it at this time.

Yes. I pulled codes when this happened and only stored code is 02 sensor bank 1 sensor 1 heater circuit. No trans codes were stored. I also have performed a drive cycle and no codes registered while I was driving. The o2 sensor code is being thrown due to a clogged catalytic converter I believe.

I tried driving again today and the gear shift selector is now lining up with the gear that is selected. But, truck still is not driving correctly. I have to start in first. Shift at 3,500@4 mph to second to get the truck to run at
15 mph@3500rpm and that seems to be all she has in her at the moment.

Tiny
Frankie_mcgrew
Dec 24, 2013.
I layered up and went out to get a visual of what the ice was looking like under the truck noticed on the tcc solenoid was a bunch of ice, chiseled it out and cleaned the connector and plugged it in, started the truck in neutral and hit 2 hi, heard a disengagement I turned truck off and unplugged the tcc solenoid now I am no longer in 4-low. Got all my forward potential back thanks for your time. Also the range sensor is intermittently acting up so ill head in that route soon thanks again.

Tiny
Frankie_mcgrew
Dec 24, 2013.
Glad you got it going. Chances are water got in the connection and froze. Hope you had a great Christmas.