What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

99 6.0 Silverado....common brake line blowout

76zimmer

76zimmer

Flyin Rat
Staff member
Moderator
GMOTM Winner
Joined
Nov 14, 2005
Posts
33,036
Reaction score
34,918
Location
Kzoo, Mi
99 6.0 w/ Autotrac t/c... have been feeling a slight vibration for a couple months, thought it was a newly installed tire, but after rotation of the tires the vibe is still in the front.
Also have had a few issues with getting 4WD to unlock and go back to 2WD this winter.
The "Service 4WD" light came on while on my road trip of 1500 mi.
The vibration starts to be noticeable at 50mph and up.
I unplugged the motor on the axle and the motor on the t/c. The only improvement that made was the vibration wasn't noticeable when decelerating...at cruise and under accel it was still noticeable.
So anyone dealt with the "service 4WD" problem before?
 
Last edited:
I thought that also Jeremy, I've checked them both, and they seem fine, and the vibration started when the unlocking issue started w/ the t/c/axle system.
 
Have you looked to see if the t c is unlocking. You could see if the front drive shaft is lock in or not, should be free. Some times they can vib a little. if ya need a little help I have been off work, so have some time.
 
If you've got some time maybe Friday we could check it out more?

I've found that the dash switch can be culprit, as well as a programming issue, a module issue, or control motor issues....I feel my system is at least partially engaged for the last 2 months as I have encountered a vibration in that time span @ 50+mph.
 
Ive replaced a bunch of encoder motors for the service 4wd light. You need to get the codes pulled so your not just throwing parts at it but my money is on an encoder
 
Have you ever had that T-case checked out or the pump rub issue fixed? Thats 246HD in there. The vibration could be caused by a bearing failure from lack of lube. That Tcase is our number one seller from that issue. The pump rattles back and forth inside the case and rubs a hole in the tailhousing then shoot the fluid out while your driving down the road and you wont see any drips in the driveway. And those Tcases have plastic cages in the bearings that like to explode. If you need any help with it just shoot me a PM. I've built quite a few of em.
 
MTChevy said:
Ive replaced a bunch of encoder motors for the service 4wd light. You need to get the codes pulled so your not just throwing parts at it but my money is on an encoder
Click to expand...


we tried to pull codes but nothing is showing up (Equus 3030 Innova reader)...I only have the "service 4WD" light that comes on in the information block on the left of the dash cluster...:dunno:
And I'm not even sure what an encoder is:confused:...is that the module I've heard mention of needing an update?

GMC1977 said:
Have you ever had that T-case checked out or the pump rub issue fixed? Thats 246HD in there. The vibration could be caused by a bearing failure from lack of lube. That Tcase is our number one seller from that issue. The pump rattles back and forth inside the case and rubs a hole in the tailhousing then shoot the fluid out while your driving down the road and you wont see any drips in the driveway. And those Tcases have plastic cages in the bearings that like to explode. If you need any help with it just shoot me a PM. I've built quite a few of em.
Click to expand...

I don't know what model the t/c is....this is NOT a HD designated 2500, just a Silverado 2500...6.0/4L80E/14bsf at any rate, in the 2 years I've had it, I have not had any 4wd problems until this started a couple months ago. I changed fluid in it 2 years ago when I got it (would have to look to be sure what I put in it) but it seems quiet no matter what mode I've had it in...even now I get no t/c noise, just up front where it seems like its locked in, and won't release. I did try a dash switch on it today to no avail. I can hear the motor on the t/c engaging/dis-engaging, and I can feel the front axle motor moving, but it doesn't seem to unlock the axle.
The underrbody area around the trans/transfercase area is all dry...

A little more troubleshooting from today...
I unplugged the supply to the t/c motor and the front axle motor, then disconnected the batt....no change...feels like the front axle is engaged all the time, as it pushes harder the tighter the turning gets. Tomorrow I will try to take the front motor off and see if I can find anything there?

Thanks for the input guys.
So far 3 hours and 60$ spent.
 
You'll need to get a more specialized scan tool to read the transfer case module codes. I wouldn't spend any more time on it until you get the codes, most likely is the transfer case shift (encoder) motor. Those parts are so expensive that you don't want to guess.
 
I don't know what model the t/c is....this is NOT a HD designated 2500, just a Silverado 2500...6.0/4L80E/14bsf at any rate, in the 2 years I've had it, I have not had any 4wd problems until this started a couple months ago.


The transfer case itself is the HD model. They make a LD for the 1500 pickups. If anything they are extremely easy to pull and go thru. 2 drivesafts, 6 nuts and some plugs. Try pulling the front shaft and see if the front end still feels locked up. There is also an encoder under the dash that goes out on these trucks and give you some 4wd issues. I have an artivle on it from Transmission Digest i can scan and email or fax to you if you would like.
 
thanks for the help guys.

Today I jacked it up, turned the driver side tire, and the pass spins in the opposite direction at an equal amount.
I pulled the axle housing apart at the center section, and put it on the bench. The output gear to the pass side was toward the pass side about an inch, so I pushed that back in, and retracted the coupler sleeve in the axle tube portion, but the engagement motor on the axle tube wants to push it back towards engagement.

Here is the pic of the gear towards the pass side..

HPIM3549800x600.jpg


and pushed back toward the center section (like it would be if not engaged)

HPIM3550800x600.jpg



The pass side tube with engagement collar:

HPIM3548800x600.jpg


And removed the collar:

HPIM3551800x600.jpg


That plunger from the motor doesn't seem to want to retract any farther than it shows in the pic, and I believe that is what is engaging the axles...when I put it back together both tires seem engaged and spinning in opposite directions....
Ryan I will check the encoder motor under the dash to see what if anything I can find tomorrow...headed to work right now.
thanks guys!
 
I pulled the article back out from transmission digest.
" 1998-2002 models of the 246 have a 100lb preload on the clutch pack, and the front prop shaft will turn in 2WD. In 2WD the front- axle dissconect will prevent torque transfer to the front wheels and will engage in any of the 4WD ranfes if it is working correctly. A failed front dissconect that does not release will have the front axle under power even in 2WD." And it goes on to say " Another problem with the magnesium case is the elongation of the sector shaft hole, again beacuse of the clutch torque application and steel on magnesium issues where the rear bearing has excess endplay. The common problem is that the case wears and the unit cannot shift into 4WD or out of 4WD Low."
 
I haven't tried 4LO, because I don't want it stuck there...but that sounds like my situation...it won't come out of 4WD no matter what is selected.
push 2HI it goes to 4HI...push Auto4WD it stays in Auto4wd, which is only slightly better that 4HI...I will try to pull the motor off the front tomorrow and drive it like that to see what happens, if still a problem would pulling the front driveshaft do any good?
 
pull the shift motor off the transfer case completely and maunally put it in 2wd. The early 246 like the one you have has a shift detent that will hold it in gear. and i dont think that pulling the DS would matter after talking to you. the front end would still be locked in just now recieveing power.
 
Should I try that before anything else?

thanks again Ryan...
 
GMC1977 said:
pull the shift motor off the transfer case completely and maunally put it in 2wd. The early 246 like the one you have has a shift detent that will hold it in gear. and i dont think that pulling the DS would matter after talking to you. the front end would still be locked in just now recieveing power.
Click to expand...

I pulled the shift motor off (after removing the front driveshaft)
and manually selected Hi range, with a wrench...but at this time I'm not sure if its still driving the front output, haven't got a helper to look yet.
the binding in the front is gone now also, so things up there must be ok as you suggested.
I have an appt on Tuesday to have the codes read, and we'll see where we go from there. At least now the front isn't locked in anymore.
 
well at least thats one step in the right direction. It seems like a electrical issue to me for sure. Im willing to bet its the encoder under the dash thats giving you all the issues.
 
I (think) hope so...the t/case is stuck in 4wd today, and now the shifting of the trans has moved up to about 3000 instead of its usual 22-2500...it won't shift into OD unless I completely let off the throttle???? This reafirms my belief that all electronics are voodoo!
 
Codes read today..CO327 and CO323. could not test due to me taking off the encoder motor.
Encoder motor has a 2" crack around it, that he explained as being caused by corrosion between the encoder housing and the gasket between the housing and the t/c itself...corrosion makes the metal expand and with it being bolted down, the housing cracks.
So with that being the case, I'll get a new encoder motor tomorrow and put that and the front driveshaft back on, and he said to try the system after putting it back together, and he would clear the codes and see if anything else comes up.

A Napa motor is about 175, so I'll go with that, and see what happens next.
 
You must log in or register to reply here.

Latest Posts

Top Bottom