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Discussion Starter · #1 ·
That time of the year I guess. Trying to get back into the driveline shop. Being told no appointments till Jan '22.

I have a front end issue!

When I purchased my AWD van last March, there was no front drive shaft.

I recently sourced one and popped 'er in. No serious noises and felt good right off the bat.

Began to feel a small clunk towards center/rear upon hard acceleration (takes a second for the clunk to come after pressing on the gas) Slow acceleration - no clunk.

Now beginning to feel a forward momentum sound (similar to bad brakes) upon deceleration, coming to a stop. Thought initially it was the brakes, but my mechanic was able to rule out. Its a deeper wooshing type sound, louder upon a harder brake. Keyword here likely: "PLAY."

Ball joints recently redone. The front drive shaft was recently put in and greased up, but no fluids or anything replaced or checked on. Rear end was redone in April by this same shop (KM Driveline, Brooklyn NY), inclduing new rear drive shaft.

I've convinced them to pop into the van tomorrow morning at shop opening time for a ride along to diagnose...

But anyone got any thoughts? Transfer case? Transmission? Idler arms? Motor mounts? Lack of clean fluids in tcase, tranny or front diff? Something broken, snapped, rusted that I should specifically look for when I get home from work?

I am moving to Colorado (driving) in 5 days...fun times!!!
 

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2002 so np136

Without hearing it, and looking it would be a hard diagnoses but hopefully your shop can help.

could be a simple as the transfer case fluids need to be flushed or have the wrong stuff in there. needs to be autotrac. Should be blue. if in good shape it's usually a pretty clear blue.

You can pull the plug and take a look. if it's any other color, or if it's real "dirty" flush it, run the figure 8's. Drive it about 100-500 miles, and flush it again.

Even if it doesn't fix your specific problem if the fluids are not correct or clean, it would need to be done soon.
 

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Technical Service Bulletin.

Transfer Case Shudder (Flush and Replace Transfer Case Fluid) #99-04-21-005B - (Sep 10, 2002)
Transfer Case Shudder (Flush and Replace Transfer Case Fluid)

1999-2003 Chevrolet Astro (AWD)

1999-2003 GMC Safari (AWD)

1999-2001 Oldsmobile Bravada

with All-Wheel Drive (NV136) Transfer Case (RPO NP4)

This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 99-04-21-005A (Section 04 -- Driveline/Axle).
Condition

Some customers may comment about a vibration (shudder) during tight turning maneuvers on dry pavement at vehicle speeds less than 8 km/h (5 mph).
Cause

This condition may be caused by a slip-stick of the clutch plates in the transfer case clutch pack. On 1999 and newer models, the preload that is designed into the clutch pack may contribute to the condition. In addition, contamination of the fluid may interfere with the friction modifiers.
Correction

Flush and replace the transfer case fluid on affected vehicles using the following procedure and the part number listed below.

Perform the following diagnosis prior to flushing and replacing the transfer case fluid in order to properly identify the shudder.
Diagnosis

1. Verify the shudder in the vehicle. The vehicle needs to be at operating temperature (driven at least 5 miles) for proper diagnosis. After the vehicle is at operating temperature, drive in a tight circle just short of steering wheel lock, at a speed less than 8 km/h (5 mph) in order to identify the shudder.
2. Identify what rear axle type the vehicle has.
  • If the vehicle has a standard rear axle, then proceed to step 3.
  • If the vehicle has a locking rear axle, remove the front propeller shaft. Refer to the Propeller Shaft subsection in the Service Manual. Drive the vehicle as outlined in step 1.
o If the shudder goes away, install the front propeller shaft and proceed to step 3. Refer to the Propeller Shaft subsection in the Service Manual.
o If the shudder does not go away, the locking rear axle may be the cause. Review the owner's records and determine if the rear axle was serviced at the first scheduled oil change. If records indicate that the axle service was done, then revaluate the condition using diagnostic information in the appropriate Service Manual. If the rear axle was not serviced, service the rear axle. INFORM THE CUSTOMER THAT THE AXLE SERVICE IS AN OWNER'S MAINTENANCE ITEM NOT COVERED UNDER THE VEHICLE'S WARRANTY.
o Install the front propeller shaft. Refer to the Propeller Shaft subsection in the Service Manual.
3. Flush the transfer case with the blue colored fluid (AUTO-TRAK II) using the procedure and part number listed below. Perform the flush procedure even if the transfer case contains the blue colored AUTO-TRAK II fluid in order to remove any possible contaminants. The AUTO-TRAK II fluid contains an improved friction modifier that should correct the slip-stick condition. Refer to the Transfer Case subsection in the Service Manual for information on draining and filling the transfer case.

Flush Procedure

Important

Refer to Corporate Bulletin Number 99-04-21-001, dated April 1999, for important information on removing the transfer case drain and fill plugs.
1. Drain the transfer case fluid.
2. Refill the transfer case with 2 L (2 qts) of new fluid, P/N 12378508 (Canadian P/N 10953626).
3. After refilling the transfer case, drive the vehicle a minimum of 8 km (5 mi).
4. With the transfer case at operating temperature, drain the transfer case fluid again.
5. Refill the transfer case with new fluid.

Important

The vehicle may require approximately 160 km (100 miles) of driving before the condition is completely corrected.
6. If this procedure does not correct the shudder condition, please call the Technical Assistance Center for further instructions.

Parts Information

Part Number

Description

Qty

12378508 (Canadian P/N 10953626)

AUTO-TRAK II Transfer Case Fluid

4 (1 L) containers
 

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I've found that when this first starts to happen in my van, it feels almost like the brakes are not releasing when you start accelerating, then it feels like they just "Pop" loose.

and when decelerating, it's almost like someone is dragging on the brakes.
 

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Discussion Starter · #7 ·
I've found that when this first starts to happen in my van, it feels almost like the brakes are not releasing when you start accelerating, then it feels like they just "Pop" loose.

and when decelerating, it's almost like someone is dragging on the brakes.
yes, sounds about right! thanks for passing along the bulletin. will certainly give it a whirl to see if it improves,

got the driveline team to take a ride in the van this morning. clunking coming from transfer case, the "pop" does come just a second after accelerating. can hear when shifting from park to drive, reverse to drive, drive to reverse, etc.

they recomended pulling the shaft for the drive and then figuring out when i'm there next step.

If the fluid aint the cause, maybe time for a np233!
 

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Discussion Starter · #8 ·
Hi All - thanks for reading through. Just posted this snippit in another post, but would like to start a new thread for more visiblity.

I just got van back from the tansmission/t-case shop last night. Took van there to rebuild t-case due to leaks and suspected internal damage from previous owner - "clunk."

Clutches were fried, rusty water inside t-case. No good. They took apart and rebuilt. Great!

Once t-case was put back together and working, other issue began occurring. They kept mentioning keywords - "binding" and "shudder"

We discussed proper fluid, multiple flushes and figure 8's. They mentioned issues are beyond that.

Here are my notes from everything they tried:

2 different t-cases rebuilt and installed
Tried different drive shafts, including a new one
TCCM - found a good used one, were then able to pull codes and data, flowed
EBCM mod re soder
Brake lines, front left caliper. 2 brake lines were rusted and they had to replace.
Could not get bleeder screw out on one or two of the lines.

Other notes:
Transmission and t-case full of fluid.
Found corrosion in fuse block. Fuse 19 or 13.
Removed ABS fuse. problem stopped.
Removed AWD fuse, still had issue.
AWD light now displays when starting the van, was not showing prior.
ABS and brake light are no longer showing on dash, they would both show up a few minutes into driving.

They believe issue is within ABS - something is telling the van that there is slippage when there is not.

They were hopeful a resoder would fix - it did not.

They could not solve my issue - they could have _____ed me with all of the hours spent and parts they purchased and tried. I am very thankful they charged me nothing - including for the t-case rebuild. They were disappointed they couldn't solve. They certainly helped to cross off a bunch of boxes.

Getting into the van leaving the shop - felt like me as a scared little kid coming home from school after being bullied. Whimpering.

The front drive shaft is now removed from the vehicle. I believe it is important that I now pull the ATC fuse to stop any unnecessary spinning?

This weekend I will check t-case fluid myself to be 100% sure it's blue inside. I feel like I need to have brake lines checked over, they claimed one disintegrated in their hands due to rust.

They were pulling C0265. No longer reading that. Front wheel bearing hubs w/ sensors were installed a month ago.

Any other thoughts of where to look? I am b.u.m.m.e.d.o.u.t but not flat broke through this......yet!
 

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Clutches were fried, rusty water inside t-case. No good. They took apart and rebuilt. Great!

Once t-case was put back together and working, other issue began occurring. They kept mentioning keywords - "binding" and "shudder"

The front drive shaft is now removed from the vehicle. I believe it is important that I now pull the ATC fuse to stop any unnecessary spinning?
Driving without the driveshaft in place... how do you suppose the water got in there in the first place.

Pulling the ATC fuse won't stop "unnecessary spinning"... the clutch packs have a certain amount of "pre-load" which means they spin whether AWD is engaged or not.

Pulling the fuse however, will reduce or prevent wheel-bind in turns (assuming system works). But it doesn't have any affect on clutch pack pre-load.
 

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Discussion Starter · #11 ·
With SO many people having SO many complex issues with the AWD system... it's NO WONDER the simple manual 4x4 option is SO popular! Sorry.. no help
for sure - but if abs is the culprit - would that problem still remain?
 

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AWD is a much better option for snow, 100%. I wouldn't even consider a case without AWD if my main usage was snow.
I'm kinda confused with them being combined together, what are the symptoms you are currently having? Is it the binding and shudder? That is going to be an AWD issue. Not an ABS issue.

ABS and AWD are separate issues, and should be separated as such when trying to diagnose IMO.
The ABS uses the front wheel sensors and the speed from the PCM to determine if either of the front wheels or rear wheels are locked up.
The AWD unit uses two sensors on the TC to determine if the prop shafts are spinning at the same speed.

If removing the front prop shaft takes care of the symptom, then it's definitely an AWD issue.
Read through Astro-Safari-Info - AWD Transfer Cases and see if you have checked the issues there, including checking gear ratios, tires, and removing the encoder motor.

Should at least give a shout out to the shop that did you right, even though they couldn't fix the problem, that is a shop I would definitely go to if I needed something.
 

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Discussion Starter · #13 ·
Driving without the driveshaft in place... how do you suppose the water got in there in the first place.

Pulling the ATC fuse won't stop "unnecessary spinning"... the clutch packs have a certain amount of "pre-load" which means they spin whether AWD is engaged or not.

Pulling the fuse however, will reduce or prevent wheel-bind in turns (assuming system works). But it doesn't have any affect on clutch pack pre-load.
copy! makes sense
 

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Discussion Starter · #14 ·
AWD is a much better option for snow, 100%. I wouldn't even consider a case without AWD if my main usage was snow.
I'm kinda confused with them being combined together, what are the symptoms you are currently having? Is it the binding and shudder? That is going to be an AWD issue. Not an ABS issue.

ABS and AWD are separate issues, and should be separated as such when trying to diagnose IMO.
The ABS uses the front wheel sensors and the speed from the PCM to determine if either of the front wheels or rear wheels are locked up.
The AWD unit uses two sensors on the TC to determine if they are spinning at the same speed.

If removing the front prop shaft takes care of the symptom, then it's definitely and AWD issue.
Read through Astro-Safari-Info - AWD Transfer Cases and see if you have checked the issues there, including checking gear ratios, tires, and removing the encoder motor.

Should at least give a shout out to the shop that did you right, even though they couldn't fix the problem, that is a shop I would definitely go to if I needed something.
Astro will, thanks for stopping by! yes, binding and shudder, according to the shop. i have yet to experience it for myself, so this weekend i'll pop the front driveshaft in and see how it feels.

before going to shop:
1.) refilled t-case fluid, clunk stopped
2.) questionable if awd was engaging at all, but drove great with both drive shafts
3.) drove 3k miles to denver, no issues at all. great road trip!

took to shop in denver - list it out in steps with how they explained their work to me:
1.) transfer case out and rebuilt, reinstalled
2.) unresponsive tccm, found good used one, dashboard awd now working at startup
3.) binding/shudder bad. pulling c0265
4.) tried different, rebuilt transfer case and new front drive shaft - same issue
5.) attempted ebcm mod re soder, no more c0265
6.) broke brake lines in process, made new lines
7.) abs light and brake light now gone
8.) binding/shudder issue persists, so pulled front drive shaft.

how about encoder motor? all tires same size.

I'll keep reading through, any thoughts please let me know!!

And yes - HUGE shoutout to A-Affordable Transmissions Center in Sheridan, Colorado. Family owned, father/son running the ship.
 

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Here's some simple AWD food for thought...

If the front drive-shaft is spinning at any speed different from rear shaft, the AWD will engage.

Binding in turns (and shutter) are typically from AWD engagement with front/rear working at slightly different speeds... but may also come from pre-load.

As stated, pulling the ATC fuse prevents engagement, but does not prevent pre-load.
I used to have my ATC fuse on an under-dash toggle switch.
Cluch pre-load chatter is solved with correct special AutoTrac II fluid and break-in procedure.
My solution was to pull the unit and install a manual system (not preferred option for snow).. although I actually did it for other reasons.

Pulling the drive-shaft could potentially still cause damage ...
(in my opinion... which I've already speculated why).
 

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Discussion Starter · #18 ·
Here's some simple AWD food for thought...

If the front drive-shaft is spinning at any speed different from rear shaft, the AWD will engage.

Binding in turns (and shutter) are typically from AWD engagement with front/rear working at slightly different speeds... but may also come from pre-load.

As stated, pulling the ATC fuse prevents engagement, but does not prevent pre-load.
I used to have my ATC fuse on an under-dash toggle switch.
Cluch pre-load chatter is solved with correct special AutoTrac II fluid and break-in procedure.
My solution was to pull the unit and install a manual system (not preferred option for snow).. although I actually did it for other reasons.

Pulling the drive-shaft could potentially still cause damage ...
(in my opinion... which I've already speculated why).
makes sense, def need to check fluid and make sure it's correct
 

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Discussion Starter · #19 ·
Took to chevy dealership this morning upon recommendation from the transmission shop.

Front drive shaft still out.

Pulled codes:
C0221 - Right front antilock braking system channel in release too long
C0265 - Valve relay coil circuit open

Thoughts?

Charged me nothing. When will my luck run out?
 
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