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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29430
Experience:  GM Grand Master Technician 2007. 14 years experience.
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95 Chevy Tahoe: 4x4 to engage..automatic transmission..2wd /..solenoid

This answer was rated:

I cannot get the 4x4 to engage on my 95 Chevy Tahoe 5.7L with automatic transmission. This model uses a lever on the floor to switch from 2WD / 4WHI / 4WLO.

I have verified that I am getting 12v to the front axle actuator and to the transfer case switch when the level is in 4WHI. I have also verified that the solenoid in the front axle actuator extends when it is energized. Since these types of gas actuators have had so many problems, I replaced the actuator with a new one just in case the old one was leaky or something else was wrong. Still no luck.

Other clues that might help:
* 4x4 worked last year. No transmission work performed or any other problems since then.
* The 4x4 light on the lever in the cab does not come on.
* Transfer case fluid is fine. Doesn't appear to be very dirty.
* As I test, I unscrewed the actuator from the transfer case to see how far the solenoid extended. Both the new actuator and the old actuator extended the same distance. However, if I pressed really hard on it, I was able to push the solenoid back inside the actuator. Should this be possible if it is working correctly? Is it possible that the new actuator I purchased is also faulty?
* The stock-style gas actuator is still installed. The recommended Chevy upgrade to the electric motor has not been performed.

Thanks in advance for your help!

GM Tech (Cam) :

Hello, I'm Cam. Please include all the details about your issue so I can accurately advise you. I cannot see your vehicle so please be detailed.

GM Tech (Cam) :

Did you try pushing in the plunger that the actuator pushes to see if that engages the front end?

Customer:

hello

GM Tech (Cam) :

Hi,.

Customer:

this is not a manual actuator, so i don't know how i could manually push in the plunger

Customer:

i did verify that the solenoid is extending when i disconnect it from the transfer case

GM Tech (Cam) :

The plunger from the actuator extends into the front diff and pushes a sliding gear on a fork over. USe a screwdriver to do the same.

Customer:

oh ok

Customer:

so remove the actuator, then push the fork over with a screwdriver?

GM Tech (Cam) :

yes, see if the system engages.

Customer:

will it be obvious what i'm pushing on? if so, i'll go try that right now

GM Tech (Cam) :

It is the only thing in there.

Customer:

perfect.. i'll go try it right now

Customer:

i depressed the plunger, but I could not tell if front diff engaged... would i be able to hear something?

GM Tech (Cam) :

I have to go and shovel my walk, I will be back in 20 mins.

Customer:

ok thanks for your help

GM Tech (Cam) :

Unless you have results now? If not I will check back in when I get back in.

Customer:

i just tried... no luck

Customer:

i didn't hear anything engage... also had my neighbor verify that the indicator light in the cab did not illuminate

GM Tech (Cam) :

Ok, did the plunger go in about the same distance as the plunger extends?

Customer:

no, it only went in 3/4"

Customer:

the solenoid seemed like it could extend 1.5" when i energized it manually w/ 12v

GM Tech (Cam) :

Ok, try again but turn the front drive shaft by hand. IT may be that the gear is not lined up.

Customer:

sorry for dumb question... front drive shaft is the 2" pipe entering the front diff from behind?

Customer:

seems like i could only rotate that piece 1/4 turn

GM Tech (Cam) : IS that with the 4wd engaged?
Customer:

i can't remember... should it turn freely in 2WD? after you reply, i'll go check

Customer:

btw, i am not on a lift... i'm just crawling underneath the car

GM Tech (Cam) :

I understand .It should turn freely in 2wd.

Customer:

ok... turns freely in 2wd... i tried manually depressing the plunger w/ a screwdriver in both 2wd and 4wd modes and did not hear anything engage

GM Tech (Cam) :

Ok, then it sounds like you have a problem in that right axle tube.

Customer:

however, when i switched to 4wd, i was unable to turn the front drive shaft

GM Tech (Cam) :

Ok, that is normal as the front drive shaft is engaged in the transfer case.

Customer:

i'm looking for information on a right axle tube... do you have any suggestions?

GM Tech (Cam) :

What sort of info?

Customer:

trying to understand what it does, how it may have gone out since last time i used 4x4, and most importantly, if this is something i feel comfortable repairing myself

GM Tech (Cam) :

ok, the front diff is open and the axles to the wheels turn all the time. Inside that tube is a sliding fork and gear. When you engage 4wd, it locks the 2 parts of the axle together inside and closes the system. If that gear is not moving then the 2 parts of the right side axle tube are not locked and it is not transfering the torque.

Customer:

ok, i got it... i understand now, and i agree with your diagnosis

Customer:

thanks so much for your help... i will definitely "accept" you!

GM Tech (Cam) and 3 other Chevy Specialists are ready to help you