4 weel drive problems

i purchesed a 92 blazer s-10(cpi) ..... not too long after i started to have troubles with my transfer case. i took it into a local transmission place (a very dumb idea) they ended up replacing the entire transfer case........ the problem went away and now about 3 months later i have the same problem. the truck goes into 4 weel drive, then all of sudden it will make a loung grinding noise...... after stoping the truck and putting it into park i can get it to come out of 4 weel drive....... the guy at the transmission place says he thinks it is something to do with the computer?? and isn't covered by the warentee

any ideas what it could be?

well if you are mechanically inclined maybe you could start doing some checks on it yourself. I am not that advanced to know where much is but afetr doing research on here numerous times for 4 wheel drive problems I believe what you might wanna check is the vacum. But if it is a computer problem once you have it stuck in 4 get somewhere that you can sit for a couple minutes and disconnect the negative side of the battery for about 10 mins than reconnect that would reset the computer if it would be that. I am thinking maybe it is not fully engaging your 4 wheel drive sicne it is grinding. I am not sure but are there hubs behidn your wheels which actually engage to make the wheel turn? I know other trucks do b/c I have had other classmates have to replace but I really am not too positive on that. If there is a hub or soemthing than maybe it is shaved down or the teeth aren't catching and might need replaced.

id check under the battery for the actuator and see if the vacuum hoses there are kinked or disconnected.follow them accordingly and repair them and hook them back up and then try it.

i took it out and got the 4 weel drive to make the loud grinding noise..... i then put it into park(the noise stoped) and shut it off. I waited about 10 mintues with the negative side of the battery off. It did not help and i manged to get it to make the noise again......... when i got home i took a look at the actuator and the vacum hoses and didn't notice any damage...... what should i look for on the actuator that would tell me it is faluty?? I also took a look at the front differitional fluid....... it was gray and very dark. is this normal? could this be an indication that the grinding noise is coming from there?

Is it an electronic 4x4 or the floor manual one.

it is electronic

I you replace your differential lubricants.

It should be light brown to honey color when new.

I would look for a bad wire going to the encoder motor on the transfer case.

is there any easy way to drain all the differantial lubercant??

I believe the fron has a top fill and lower drain plug.

I may be wrong. If not, you will have to buy one of those pumps to extract it yourself.

I have my diff fluids changed at the local jiffy lube seeing it was a lot more convenient than doing it in the driveway.

They handle the mess.

thanks i will try that. I still would like to know how to tell if the actuator is faluty? any sugesitions would be great.

well i am still having poblems....... i changed the front differental oil..... and traces all the vacume lines back and they all look ok. i don't know what else to check could any one help??

start looking at your vacuum actuator and encoder motor.

well all the vacume hoses look fine....... and the encoder motor wires look ok?? it seems to go into 4 weel drive fine it is just when it is in it wants to jumb out

I had the exact problem. It was a humming/grinding noise when driving and during deceleration. Turned out to be a worn drive axle joint. I jacked the front up, put in 4x4 to lock the front axle and differential, and turned each front wheel and looked to see each front axle turn. The upper and lower cv joints should turn together on the axle if not, you have just found your problem.

well all the vacume hoses look fine....... and the encoder motor wires look ok?? it seems to go into 4 weel drive fine it is just when it is in it wants to jumb out

Sounds like you are having a vacuum leak caused by a bad vacuum actuator.

This problem has nothing to do with worn drive axles.

sould i try replacing the actuator?? is there any way to tell if it is leaking?

i also checked the front CV joints..... when i turn turn the weels both upper and lower cv boots turn.... i noticed there was some play. is this normal?

Some play is normal.

I would recheck all vacuum lines in the engine area and then replace the vacuum switch.

where is the vacuum switch located? after doing some research i found the vacuum actuator is worth 150 at the dealer! so i want to be sure that this is the problem. i was reading another fourm and was wondering if clamping the actuator with a c-clamp and try running it in 4 weel drive would tell me if the actuator is at fault??

First off when you say it jumps out of 4 wheel drive do you mean the front diff is disengaged but the transfer case is still in 4 wheel drive or the transfer case jumps out all the way??
I have the GM Training manual in front of me so that is the first info i need.

Front diff disengages out of 4wd model 233 cases
First go the the battery just under it is a vacuum actuator that controls the front diff engagement.
When put into 4wd there must be 12 inches of vacuum at the actuator,if not trace lines for leak if no leak found check the transfer case vacuum switch on the transfer case, it has 3 vacuum lines on it. They go bad a lot remove that switch and at the end that goes into the transfer case is a ball switch that gets stuck half way out causing low vacuum to the front diff. If stuck replace it with a new 1
If you have good vacuum at the front actuator(use a vacuum gauge to get this reading) see if the actuator rubber blader is sucked all the way in. If not see if you can push it all the way in by hand and if it does will it stay there.
Post what you find and we will go on from there

the transfere case is 233. i do not belive that the transfere case is slipping out. i think it is trying to jump out in the front diff. i installed the new vacuum switch on the transfere case...... the old one was not stuck it just seemed to stick while depressing the ball valve. I tryed this and ended up with the same problem.
i then removed my battery and proped it up so i could see the vacuum aculator. with the truck runing, by putting it into 4 weel drive the aculator would pull in. after shutting the truck off (still in 4 weel drive) the aculator would return to it's normal position........????

i found out that the acuator does not leak
i started the truck then putting it into 4 weel drive, i then pintched the vacuum line with a c clamp. i shut the truck off and waited about 10 mintues and the acuator did not come out......... is there any other places that i could lose vacuum?? i am also having some problems with my abs..... when i lock up the brakes(on snow or something) i hear a whinning noise, it is not that big of a deal i was just wondering if these problems are related??

Does your truck have a plastic vacuum ball on the right front fender. If so that is where the transfer case vacuum switch gets it vacuum from.

i bought a vacuum guage today and when i went to test the vacuum on the aucator i noticed oil in the line......... i have read other forms and know that i have to get it all out...... how should i do this. i am planning on replacing the vacuum line that goes from the transfercase to the acuator....... how do i drain the acuator and the reat of the vacuum system??

well....... this is really starting to bother me! I replaced all the vacuum lines, drained the vacuum ball and the acuator. i was getting 11.5 to 12 inches of vacuum at the acuator. and i am still having the same problem??? i can get it into 4 weel drive but after a mintue of so it will start grinding....... very loundly?

does your 4 wheel drive lite come on and stay on while its in 4wd??? the only other thing you can check would be to see if when 4wd is called for that the front vacuum actuator is pulled all the way in and it is pulling the actuator cable all the waybecause it sounds like itsnot pulling the slide shifter fork all the way to lock the front axles. Remove the cable and see if it moves ok thats the cable that runs from the vacuum actuator to the front diff.

yes the 4weel drive light goes on and stays on. when the cable is attached to the acuator, i can move the cable in a bit with my hand....... should i be able to pull it in all the way with my hand?? when the engine is running and in 4 weel drive the acuator does go in. should i remove the entire cable back to the front differantial?? if so any thing i need to know before disconnecting it??

Thanks guys for your help ... I looked at the actuator under the battery and found that it was working fine .. but upon further inspection I noticed that it would not maintain vaccume and found that I never needed to remove battery as there was a split in the vaccume line that connected to the "T" just before going to the actuator .. I trimed the line at the split, reconected everything and now it all works great again .. Thanks for your help I really apprieciate it.

Excellent! :D

i took the acuator out again and noticed it had oil in it. Why would this happen with a new vacuum switch? ....... at the acuator it is only drawing 10 inches after a couple of mintues it went up to about 11. i then wrapped some wire around the end of the shifter cable and tightened it so that the pin was out, it made the same noies when i took it for a test drive. why is it doing this??????????????

is my front differental shot??? because if it is fine i was thinking of installing an after market, manual shifter to lock my front hubs. any comments would be greatly appreaticed.

are there any tests i can do to see if it is the differental or if my problem is else where?

I copied the following from s-10 forum. I see a lot of member having problems with their electronic transfer cases not allowing their 4 wheel drive to work.


All this info helps as well that I wrote on another forum:

Well, through everything I have gone through with this electronic 4x4, I figured I would share my knowledge as best as I can. If anyone thinks something should be added, feel free to. This is also from gathered information on other posts.

***HOW TO CHECK WHAT IS WRONG***

You will probably know when your 4x4 has failed when you needed it in the mud pit. Mine, for instance, failed by not doing anything when I hit the 4HI button. However, it would go into 4LO.

To read the codes for the 4x4 with electric shift transfer case, install a jumper wire from terminals "J" and "A" on the ALDL (12 pin connector under the driver's side dash)

The lights on the 4x4 indicator (switch) will flash in a pattern, there are only 4 codes, one flash is code one, 2 flashes is a code 2, and so on...

Code "1" is "RAM standby power" and is considered normal, may be caused by clearing the codes.
Code "2" is "Encoder fault"
Code "3" is "TCCM motor circuit"
Code "4" is "RAM/ROM failure"

If you have the codes 2 or 3 check all the encoder motor connections at the transfer case, if OK it will need a new encoder motor assembly.
If you have code 4, replace the TCCM.

Make sure all connections are good and no corrosion, and then it's either an encoder or TCCM.

***TO FIX THE TCCM***

The TCCM is located behind the glove box, and is accessed from underneath the dash. To remove, the kick panel and black cover come off. Then a 1/4" screw holds the "brains" in the dash. The middle computer is the Truck's brain, the one on the backside is the TCCM, and on the front is the small ABS computer. Simply loosen the 2 10mm nuts on each side, and they will separate.


***WAYS TO FIX THE ENCODER MOTOR PROBLEM.***

This is the most common problem, and was my problem.

Cheap way - To clear the codes and reset the computer, pull the 5 amp TCCM fuse, located at the bottom of the fuse box. Wait at least a half hour, and then replace the fuse. Turn the ignition key to run, wait for the 4x4 lights to blink, and then turn off. Repeat 5 times, and then start the truck.

Decent price way - I just went and bought a rebuilt encoder motor from a company off of Ebay. Their company is www.northernautoparts.com The part cost me around $140 with a 1 year warranty and $38 core refund when I send the old one back.

Expensive way - buy a brand new one from GM for over $300.

***HOW TO INSTALL THE NEW ENCODER MOTOR***

Lucky way - Only thing that needs to be removed is the encoder motor itself. Tools needed are a 10mm hand wrench and a 8mm and 10mm socket wrench. The 10mm socket will work on the upper and lower bolts, while the regular wrench is needed for the middle bolt. (Tight squeeze). The 8mm socket is for the electric plug.
Then, just pull out, and wiggle it out of the truck. Install in reverse order.

Unlucky way - This means the encoder motor did not just wiggle out. Now the front drive shaft will have to be removed at the transfer case. Then, a yolk puller is needed in order to remove the yolk from the transfer case. Once this is done, go to the directions in lucky way.

This is as much knowledge as I have at the moment about the beautiful setup called the electronic pushbutton 4x4. Thank you to all that have helped me, and hopefully this will help others in fixing the future.

-=Glenn=-

I wish to Thank Glenn aka gmshades from s-10forum.com


I followed everything and I finally figured out what was wrong.
Thanks Glenn