4wd not working

[hangontight]

Hello all, new member here, first time post.

So, I have an '02 Suburban LS and the 4WD has not been working for some time. The buttons all function properly, I know this because when I push them I can hear the transfer case shift motor and the front differential actuator operate. Even though I can hear the motors doing something, I'm not getting power to the front wheels (or at least not getting much);

I put the truck up on 4 jack stands. When in 2WD, I put the truck in drive and both the front and rear driveshafts turn. The rear wheels turn, but the fronts do not.

When I switch to 4 high, I can hear the transfer case shift motor make noise, as well as the front diff actuator. When up on the stands, the front wheels DO turn when I put the truck in drive. However, when on pavement, they don't bind going around corners on dry pavement and they don't hook up when driving on snow covered road....thus I don't think they're getting any power (even though they were turning when up on jack stands). This same situation holds true in the 4 AUTO setting as well as 4 LOW.

I guess my question is this: Even thought the front driveshaft is turning (in both 2WD and 4WD), is there a chance that it's not getting any useful power to it? Is this the reason it also turns in 2WD?

 

[Ac19513]

I am having a similar problem. as far as the computer system is concerned the truck is in 4x4 but its really not. haven't put on jack stands yet to confirm but i am pretty sure the TC is shot.

 

[Ac19513]

i replaced my front actuator thinking maybe it was weak, but didn't change anything still no 4wd,no codes,lights indicate its in 4wd.

 

[hangontight]

i replaced my front actuator thinking maybe it was weak, but didn't change anything still no 4wd,no codes,lights indicate its in 4wd.

I am fairly confident mine is a worn out transfer case. The only other thing that I thought it could be is the transfer case control module. I believe the TCCM sends a signal to the TC (after that actuators have locked in the front half shafts) to tell the TC to supply full power to the front driveshaft....If this is somehow not happening it could be the culprit.

 

[YukonandtheHOE]

Your certin the front diff is locking in? With the front end in the air, KOEO in 4x4 do both front wheels spin when you turn one tire?

 

[Ac19513]

wont be able to check that till friday. i am leaning away from my case. it makes no weird noises and no leaks. should the front shaft be locked in also at this time?

 

[YukonandtheHOE]

Nodoubt, their is a clutch pack in their for the autotrac.. and they do fail, have you looked at your fluid by any chance?
Burnt smelling? The color?

 

[Ac19513]

Sorry hangontight not trying to jack your thread.

was planning on doing that this weekend also. will also look for any metal. what fluid is best to put back in and how much?

 

[YukonandtheHOE]

Sorry hangontight not trying to jack your thread.

was planning on doing that this weekend also. will also look for any metal. what fluid is best to put back in and how much?

Depends on the tcase. the autotrac ones require acdelco autoTrac fluid, blue in color. floor shift and non "auto" button tcases use Dextron3 ATF.

You will want to grab 3qt

 

[Ac19513]

I have auto 4wd so the ac Delco is what I'll need. thanks so much. will post results by the end of the weekend

 

[Ac19513]

So i had the opportunity to lift the front end of the hoe today here is what i found
2hi-each wheel spins freely drive shaft does not turn, i can turn it freely by hand
4hi-wheels turn together and drive shaft is locked into the tcase and not the front end
seems like something in the front dif is not right

 

[YukonandtheHOE]

So i had the opportunity to lift the front end of the hoe today here is what i found
2hi-each wheel spins freely drive shaft does not turn, i can turn it freely by hand
4hi-wheels turn together and drive shaft is locked into the tcase and not the front end
seems like something in the front dif is not right

So with the front end in the air in 4hi your wheels spin in opposite directions with out the pinion moving? Thats normal operation of the spider gears and your actuator is working buy connecting the RH to the Diff, What you want to try is having the wheels spin in the same direction. If it spins the shaft against the tcase in park the clutch pack has gone bad in the T-case. Maybe not bad enough to spin freely by hand but with the gear reduction though the diff it may show

 

[Ac19513]

yes they spin opposite. i tried to get both wheels to turn the same way when in 4hi but couldnt. i tried this when i had it in the air and it was in park. i thought that even in 2hi the driveshaft would rotate with the front wheels?

 

[YukonandtheHOE]

the drive shaft will free wheel because the LH wheel is connected to the diff full time, so when moving forward its spinning the pinion. Mechanically it sounds like everything is doing what it should. I wonder if the actuator isn't doing its job? Try cycling it through 4 and lo and mash the pedal on a slippery surface

 

[Ac19513]

i will try that again as soon as i can. but like i said in previous post i replaced the front actuator.

 

[YukonandtheHOE]

I ment the tcase selector

 

[Ac19513]

any idea if the front driveshaft should be locked into the front differential at all times?

 

[YukonandtheHOE]

The left hand wheel is full time in the diff, when you spin the front shaft by hand in 2wd it should spin the front left wheel. But if you spin the wheel it wont turn the drive shaft because spider gears rotate inside the ring gear carrier.

 

[Ac19513]

when i spin the shaft the wheel doesnt turn

 

[YukonandtheHOE]

My bad man, the diff will spin around the side gears its not a locker diff lol, it needs both sides to make engagement on the carrier. Try taking the shaft off the front pinion and putting it in 4x4 then see what happens.