please read entire post 4x4 system

[cyberpunk]

ok so here it goes.
working at a dealership i have access to a lot seeing that we used to be a pontiac dealership a isuzu. i.e gm tech 2 so on and so on. a long with isuzu parts catalogue. isuzu ascender = chevy trailblazer.

the problem.
4x4 does not engage.
2004 Trailblazer LT 4.2 with 2hi, aw4d, 4hi and 4lo, 110,000 miles/current
i put the truck on a lift the other day and i can hear the transfer case encoder and the actuator moving. the front wheels do not get power at all. i can see the front drive shaft (propeller) moving and hear what sound like 2 gears barely making contact with each other. i can not pinpoint the sounds location on the differential or the what gm calls a intermediate shaft bearing assembly (i would just call it an axle disconnect) being that they are right next to each other. according to gm (see pciture below) #56 is discontinued. #57 does not even show part information.



the real problem is i have no idea what i need to do to see if that is bad or not and i can not afford to be down my vehicle as i have no other right now. can someone please point me in a direction.

 

[Playsinsnow]

http://gmtnation.com/f79/4wd-not-working-step-inside-107/

I bought my disconnect on ebay, for $350ish shipped. Seems like it's your culprit. You can order the parts for a rebuild if you want to but buying the whole assembly was a sure thing to me. The collar fork can break and shear and/or the gears worn down due to past use. The grease is cheap and dries out over time.

If you can get the axle off the hub, you can take the four bolts to get the disconnect off. It took "us" 4 hours comfortably.

 

[cyberpunk]

All you need to know is right here.

http://gmtnation.com/f79/4wd-not-working-step-inside-107/

I bought my disconnect on ebay, ATP, for $350ish shipped. Seems like it's your culprit. You can order the parts for a rebuild if you want to but buying the whole assembly was a sure thing to me.

If you can get the axle off the hub, you can take the four bolts to get the disconnect off. It took "us" 4 hours comfortably.

being that the part numbers are the same for the ascender i can rebuild the entire unit for under $300 i don't mind rebuilding it i just have no warm place at home to do this (apartments). ebay's cheapest price was $388. same with amazon. and others as well. guess a rebuild is what i am doing. i will get a tut up of the rebuild with pictures. any idea what grease i should use?
also i will see about maybe getting a part number list together.

 

[Playsinsnow]

Offroadtb.com Front Axle 4WD Disconnect

Sorry should have posted this as well. It has your part numbers. This is the write up I used to replace it. Mobil1 synthetic grease is a favorite.

 

[cyberpunk]

Offroadtb.com Front Axle 4WD Disconnect

Sorry should have posted this as well. This is the write up I used to replace it. Mobil1 synthetic grease is a favorite.

woot! :wootwoot: you are awesome! i wont be able to order the stuff till Friday and then it will be at least three days till i get the items. i am going to replace that cv axle while i am at it since i can get the reman cv axle for $50 plus 19.00 core charge and also the front stab link also. i think this will actually be kinda fun.

why do they not recommend them to be greased? seems like it should be part of a service.

 

[Playsinsnow]

woot! :wootwoot: you are awesome! i wont be able to order the stuff till Friday and then it will be at least three days till i get the items. i am going to replace that cv axle while i am at it since i can get the reman cv axle for $50 plus 19.00 core charge and also the front stab link also. i think this will actually be kinda fun.

why do they not recommend them to be greased? seems like it should be part of a service.

I will never be able to return what these folks have done for me. Can only try.

You're right. It should be. Some of the offroad crowd uses the awd collar instead of the fork. They service it too, more than through the actuator hole.

PS searching is your friend. Checkout www.offroadtb.com too

 

[BoldAdventure]

Before you even order anything, please repost this on ORTB, becuase I think you're going to find a different answer.

 

[cyberpunk]

Before you even order anything, please repost this on ORTB, becuase I think you're going to find a different answer.

You seem like you have another thought in mind....

 

[Playsinsnow]

Only thing I can think of is they can be "harsh" to some that haven't read what's already been posted. Or you will get a Roadie answer full of detail that will surpass just about anyone in that shop

 

[BoldAdventure]

Only thing I can think of is they can be "harsh" to some that haven't read what's already been posted. Or you will get a Roadie answer full of detail that will surpass just about anyone in that shop

That really only applies to guys who ask a question right above a thread with the same question and answer in it. Like there are literally 4 threads in a row asking the same question about gears.

I do have an idea that it's something else. Something that is pretty common with the 4WD not engaging. A matter of fact I know you'll get 10 detailed trouble shooting replies if asked there. and some better opinions and advice about those reman CVs.

 

[cyberpunk]

That really only applies to guys who ask a question right above a thread with the same question and answer in it. Like there are literally 4 threads in a row asking the same question about gears.

I do have an idea that it's something else. Something that is pretty common with the 4WD not engaging. A matter of fact I know you'll get 10 detailed trouble shooting replies if asked there. and some better opinions and advice about those reman CVs.

The reman cv I am talking about is through isuzu (ascender) it is the same as the chevy trailblazer. I did a little further trouble shooting and I took a pry bar to the axle shaft and the four wheel drive did engage and I took the actuator off and manually could not get lever to engage uless I pushed up on cv with pry bar.

 

[seanpooh]

I had the same problem as you mentioned. It turned out to be the actuator that engaged the axle disconnect. Replaced both and I can drive in the snow without my heart popping out my chest.

 

[The_Roadie]

I did a little further trouble shooting and I took a pry bar to the axle shaft and the four wheel drive did engage and I took the actuator off and manually could not get lever to engage uless I pushed up on cv with pry bar.

That sounds clearly like the sliding collar isn't able to engage because the CV bearing is shot and doesn't hold the shaft centered. The outer seals often go bad, then grit gets into the bearing, and when you have up/down CV shaft movement, it's rebuild time.

GM didn't put in a Zerk because they outsourced the unique system design to AAM, who totally underestimated how badly the internal grease would congeal and shrink over 5-10 years. As usual, "permanently lubricated" is a huge lie.

Working backwards, this sort of mechanical failure, along with broken forks that move the sliding collar, go undetected because the actuator has a spring behind its plunger, so a jammed disconnect assembly won't stall the actuator's motor and break the high-ratio step-down gear train. The actuator THINKS its button is extended, its position feedback sensor reports success back to the TCCM, but the sliding collar fails to connect the intermediate shaft to the CV output shaft and voila - you're still in 2WD with no blinking diagnostic lights on the mode switch to tell you you're screwed.

 

[cyberpunk]

That sounds clearly like the sliding collar isn't able to engage because the CV bearing is shot and doesn't hold the shaft centered. The outer seals often go bad, then grit gets into the bearing, and when you have up/down CV shaft movement, it's rebuild time.

GM didn't put in a Zerk because they outsourced the unique system design to AAM, who totally underestimated how badly the internal grease would congeal and shrink over 5-10 years. As usual, "permanently lubricated" is a huge lie.

Working backwards, this sort of mechanical failure, along with broken forks that move the sliding collar, go undetected because the actuator has a spring behind its plunger, so a jammed disconnect assembly won't stall the actuator's motor and break the high-ratio step-down gear train. The actuator THINKS its button is extended, its position feedback sensor reports success back to the TCCM, but the sliding collar fails to connect the intermediate shaft to the CV output shaft and voila - you're still in 2WD with no blinking diagnostic lights on the mode switch to tell you you're screwed.

Thank you roadie. I have looked at other posts from you and I have to say all have been helpful. Including what was on the other sites from you. Also an update as well as to rebuild I was thinking entire guts of disconnect but that turns out that might not be the case looks like I will only need seals and bearings, race or collar depending on what you want to call it and maybe along with 2 or 3 more items. In your opinions(yes plural)should I replace the 2 gears if I do not see any broken teeth?
Also thank you playsinsnow (not meant to be an after thought)

 

[The_Roadie]

I would leave the gears alone, depending on any visible wear, and the condition of the grease. I rebuilt mine with Mobil1 red synthetic around 50-60K miles and never had an issue. Hope to never have one now.

 

[cyberpunk]

Well I got everything apart on saturday. Replaced bearings, seals, washers, and axle since that was shot. And guess what my 4x4 works now. So this means problem is solved
:wootwoot:

Would like to thank everyone who helped out on here I have a few modifications that I plan on posting here for electronics i need to finish first though.

 

[The_Roadie]

Cool. Thanks for the report. Don't suppose you took pics?

It's so refreshing to get a new member who doesn't ask for an illustrated "How To" article for removing a wheel or adding fuel to the gas tank.

 

[cyberpunk]

Cool. Thanks for the report. Don't suppose you took pics?

It's so refreshing to get a new member who doesn't ask for an illustrated "How To" article for removing a wheel or adding fuel to the gas tank.

Due to time constraints I did not seeing that I live in an apartment complex. I went to a buddies house to work on it since he has a garage. sorry roadie. The hardest part was getting the axle and housing out. Everything else was easy as pie. And a little future fyi the unit is not properly greased from the manufacturer. When I cracked open the case the only lubrication to be found was in the unit itself. The bearing had literally a minimum amount of grease and the bearings had a rather cruddy lubrication job or rather lack of lubrication. The bearings in all were not that bad honestly though, but again due to the manufacturer being rather skimpy they are destined to fail.

 

[cyberpunk]

Due to time constraints I did not seeing that I live in an apartment complex. I went to a buddies house to work on it since he has a garage. sorry roadie. The hardest part was getting the axle and housing out. Everything else was easy as pie. And a little future fyi the unit is not properly greased from the manufacturer. When I cracked open the case the only lubrication to be found was in the unit itself. The bearing had literally a minimum amount of grease and the bearings had a rather cruddy lubrication job or rather lack of lubrication. The bearings in all were not that bad honestly though, but again due to the manufacturer being rather skimpy they are destined to fail.

to add to what I said in my case the fork and seals were not bad but I replaced them anyways.:wootwoot:

 

[cyberpunk]

So the next thing I am going to do is the ball joints upper and lower.
Also look for me in the mods and electronics section were I will be posting a tut on how to replace cluster lamps with leds.. That will be over the weekend though. Also how to build an invertor into your car along with how to add bluetooth streaming with a stereo that only has audio auxilary. I think I have found my favorite past time here now

 

[cyberpunk]

Cool. Thanks for the report. Don't suppose you took pics?

It's so refreshing to get a new member who doesn't ask for an illustrated "How To" article for removing a wheel or adding fuel to the gas tank.

to add to your comment i deal with that daily. so i am aware of what that can be like. i was just looking for diag. ideas to help me figure out what was wrong.
it is much appreciated to find such awesome people on a site that are willing to help