4x4 question works in 4auto/ not in 4hi / 4 lo

[bradhaight]

1999 blazer - 4 x 4 is only engaged when I am in the 4 auto. I push 4hi and I loose the front axel. This is also same with the 4 lo.. But as soon as I push the 4 auto/ i get the front axel back again.. ? What is going on.. I replaced the cable actuator behind the battery tray last year.. and thought I solved the problem then.. I have good vaccuum off the solenoid on the fire wall to the actuator behind the battery tray. check for vaccuum leek on the actuator, an negative.. any help??

brad

[BlazerLT]

Reset your computer by pulling the negative cable for 10 minutes to reset the computer.

This more often than not will fix the problem.

[bradhaight]

Originally Posted by BlazerLT

Reset your computer by pulling the negative cable for 10 minutes to reset the computer.

This more often than not will fix the problem.

Tried the disconnect twice, and did not solve the problem... This is strange.. my drive way has slight grade with snow/ I can only go up in 4 auto/ switch to 4hi, and the back right rear is the only movement.

need help in ohio, thanks brad

[BlazerLT]

Does the 4hi light illuminate when you switch from 2hi to 4hi?

Do you hear any clicking?

Have you tried going from 2hi directly to 4hi?

[bradhaight]

Originally Posted by BlazerLT

Does the 4hi light illuminate when you switch from 2hi to 4hi?

Do you hear any clicking?

Have you tried going from 2hi directly to 4hi?

yes, have tried going 2hi to 4hi and still no luck.. the light stays on in 4hi / put vehicle in park switchout to 4hi from 4hi and here a slight hum in a motor under the vehicle.. no clunking noise at all.. I gone thru 9 pages of threads, and still have not seen this problem yet...

[BlazerLT]

Hmmm....

[rlith]

Originally Posted by bradhaight

yes, have tried going 2hi to 4hi and still no luck.. the light stays on in 4hi / put vehicle in park switchout to 4hi from 4hi and here a slight hum in a motor under the vehicle.. no clunking noise at all.. I gone thru 9 pages of threads, and still have not seen this problem yet...

Sounds like the vac diaphram under the battery isn't being pulled to engage the front axel. Check it for tears. Also check that the little spring clip that holds the actuator onto the cable hasn't slipped (common) You can do this by carefully squeezing the servo and feeling the pull of the cable (you'll hear clicking in the front end) If both those are ok, start following the hose from the servo to the abs fix, then from the abs fix to the vac switch on the transfer case. Make sure there are no cracks or leaks. (When my 4wd had the same symptoms as yours I found that my vac hose from the servo has rubbed against the header and burned off, we ended up re-routing along the firewall then behind the brake booster...) Check these things and you will find your issue.

[Mikado14]

If the front axle is engaging in 4auto, the actuator cannot be bad for it is working in that position. He has another problem.

[bradhaight]

Originally Posted by Mikado14

If the front axle is engaging in 4auto, the actuator cannot be bad for it is working in that position. He has another problem.

I have another problem as you stated.. I spent two hours and verified that the actuator is working correctly... It is engaging and disengaging as it is supposed to do... now I can not find the vaccuum line to the transaxel, could my be electrical..

[bradhaight]

Originally Posted by rlith

Sounds like the vac diaphram under the battery isn't being pulled to engage the front axel. Check it for tears. Also check that the little spring clip that holds the actuator onto the cable hasn't slipped (common) You can do this by carefully squeezing the servo and feeling the pull of the cable (you'll hear clicking in the front end) If both those are ok, start following the hose from the servo to the abs fix, then from the abs fix to the vac switch on the transfer case. Make sure there are no cracks or leaks. (When my 4wd had the same symptoms as yours I found that my vac hose from the servo has rubbed against the header and burned off, we ended up re-routing along the firewall then behind the brake booster...) Check these things and you will find your issue.

okay. it is not the first problem, I have removed the battery, and verified that everything on the actuaAtor is working correctly.

I am having trouble finding the vac switch on the transfer case to the abs fix, I am not seeing any vaccuum lines, just electrical connections.

[rlith]

you should have a hose that runs from the vacume actuator (under the battery) up towards the abs fix (culinder looking thing either attached at the fender next to your water bottle or on the waterbottle itself (this is provided you had the ABS recall done on your truck) It will be on a T fitting, if you dind't have that done, the hose will go from the vac actuator direct to the transfercase switch...

[bradhaight]

Originally Posted by rlith

you should have a hose that runs from the vacume actuator (under the battery) up towards the abs fix (culinder looking thing either attached at the fender next to your water bottle or on the waterbottle itself (this is provided you had the ABS recall done on your truck) It will be on a T fitting, if you dind't have that done, the hose will go from the vac actuator direct to the transfercase switch...

Thanks.. appears now that I did not have the recalled done, and that caused that confusion. I am thinking that the encoder motor, or the transfer case control module tccm is the problem...

Encoder motor is shifting into 4hi from 2hi, but is it locking? how can you test the unit..

Same with the tccm, could this also cause the problem, and is there a way to test for failuure with buying new units//

[bradhaight]

Originally Posted by bradhaight

Thanks.. appears now that I did not have the recalled done, and that caused that confusion. I am thinking that the encoder motor, or the transfer case control module tccm is the problem...

Encoder motor is shifting into 4hi from 2hi, but is it locking? how can you test the unit..

Same with the tccm, could this also cause the problem, and is there a way to test for failuure with buying new units//

The encoder motor was the failure for the 4hi 4lo not engaging.. Thanks for the useful information on this problem.. Hopefully this thread will help others.

best reguards

brad

[bradhaight]

the encoder motor failed to engauge the 4 hi and 4 low..

[BlazerLT]

Yea, I thought so, very common.