HELP - DA,CC,LB with LAUNCH SHUDDER under load, is there a known fix

[jallen]

I took delivary of my DA,CC,LB on 10-25-01 & I love have 8,800 wonderful miles on it, I just took delivary of our 32ft.5er and Discovered the dreaded "LAUNCH SHUDDER". The service man @ the Dealership has not ran accross this he says & I don't remember seeing a post on this Forum. I guess I should have first mentioned that I have been monitoring this forum for about 10 mo. now & have found it most informative. This is my 3rd Gm Diesel 82,88 Both Suburbans & I have come to love & expect the good mileage & dependability of the Diesel Engine. I am one who does most of my mecanic work & don't like to take my vehicles to someone's shop. I HOPE some can shed some light on this subject.

[NutNbutGMC]

^...Where have you been? Living in an Afghan cave?.. D@mn it boy. Launch Shudder has been discussed here so much, everyone has theirs fixed and has forgotten all about it :D :D ... Search tool will give ya' what ya' need. smile.gif

[NEW2DMAX]

Took mine into the dealer today, launch shutter is what they call it and they are going to repair.
They will remove the 2 piece driveshaft when the replacement single shaft has come in.....
:confused:

[jallen]

Thanks for the reply NutNbutGMC
All the Shudder problems that I have Read all have been CC,SB or XT,LB But mine is CC & LB & I have not picked up on the problem on this looong model.
Thanks

2002 D/A K2500 4X4
Crew Cab
Long Box
DTA Ultra Boards
Jordan
R D S Mfg. 60gal. Tool /Tank
2002 31-5 Wilderness 5er

[NutNbutGMC]

^...Well, my friend, certainly you should know I mean no harm. I'm one of the misfit Diesel Heads with a tangent sense of humor. Welcome to the forum. Many here will help you out. Watch out for Mackin though. He's got an ace up his sleeve.

Here is some info. from the search function:

The Launch Shudder on Acceleration Bulletin (#01-04-17-001B) does NOT apply to 2WD or manual transmission trucks, nor does it apply to crew cab long bed trucks. The only models covered by the bulletin are: K25953, K35953, and K25743 with the MT1 (4L80E) or M74 (Allison) transmissions. Look for the model number on the door sticker.

A snip from the bulletin:

Launch Shudder On Acceleration (Install New One-Piece Propeller Shaft)

1999-2002 Chevrolet and GMC K2500/3500 Extended Cab Long Box and Crew Cab Short Box Pickup Models With Automatic Transmission.

Condition

Some customers may comment on a vibration during acceleration from 0-40 km/h (0-25 mph). This may also be referred to as launch shudder. This condition may be more noticeable when the vehicle is carrying cargo or is used for towing.

Correction

A new propeller shaft is available for service to correct this condition. This new propeller shaft is a one-piece design and will replace the current two-piece design.

Install a new one-piece propeller shaft on affected vehicles. Refer to the service procedure and the parts information listed below. Match the affected vehicle with the appropriate propeller shaft. Refer to the usage information below. This fix does not apply to the Chassis/Crew Cab Models (K35943).

The main point here, that is tied in with the cross member is this:
DO NOT.... DO NOT... allow them to use the first version of the TSB and misinterpret it, and cut the cross member. DO NOT cut the cross member. There is a revised TSB out to clarify the replacement procedure.

One more time for the disbelieving Service Managers, all across the country.

Please be aware of the cross-member issue. DO NOT ALLOW IT TO BE CUT. Remove ONLY the brackets for the carrier bearing. There is a revised TSB for the clear and concise procedure.

Again, welcome to the forum. smile.gif

[ 04-30-2002: Message edited by: NutNbutGMC ]</p>

[SHOPMAN426]

So the question remains, what do use folks that drive the big long school bus do? :confused: :confused: :confused:

Thanks, SHOPMAN426.

Mike.

[NutNbutGMC]

^...IMHO, I'd visit the Service Mgr. and discuss the issue, based on the revised TSB for Launch Shudder. Express the problem and have the SM either apply the TSB, based on his / her judgement or get a GMC Tech Rep involved and see if they will acknowledge the problem / fix, or if they resolve your concern with Not Applicable to the long bus. The main concern here is the issue of the application, even if shudder is acknowledged.

Just my dollars 0.02 worth.

[jallen]

Thanks Guys,
The Bulitin you refer to DOES NOT apply to the Crew Cab Long Box model # K35943 this is the truck I have. IF it did apply I would have had this done the first month I had the truck. THIS IS A CREW CAB LOOOOONG BED K35943
Thanks :( :confused:

[Tough Guy]

Add air bags to correct the driveline angle loaded and your shudder will cease....Your big ol' trailer is squatting the truck enough to shudder on launch....

[ndamico]

My 2002 CC SB D/A came with a 1 piece drive shaft. do some CC SB's come with 1 piece, or am i just retarded and can't tell the difference between a 1 and 2 piece drive shaft?

[Kennedy]

OK, I picked up a protractor Saturday, and have been playing around a bit. I should know more soon. The big thing I see is that the pinion to driveshaft working angle is only 1

[chipper]

DMAX/A&CAMP,
I too had the same problem. I added 2.5 degree caster wedges under the rear springs, but still had a smidgen of shudder when towing my 32' 5 er.
I had a set of Firestone air bags installed & with 50# of air all is well & the towing ride is much more stable.Try it,you will like it.

chipper

2001 GMC Ext Cab,Long Bed,DMAX
24,000 miles & still smiling

[Kennedy]

Air bags will be added too, but at a later time. Not sure if I can get them in prior to the Rendezvous. For now, I will be working out the driveshaft angles as that is the big key. Once there, the air bags will allow maintainance of these corrected angles.

In reality IMHO, either the transfer case should go up (also helps the front shaft) or the support bearing should go down do eliminate the incorrect front shaft angle first, as there is no joint to "cancel it out" on the other end.

[jallen]

Thanks Kennedy & Guys for the sugestions. I will experiment with raising the pinion angle, b-4 I get the wedges & get back with you on this. However I will, along with others be interested in the results of your calculations, experimentation & what your fix is. This was exactly the kind of answer I was hopping for; not just the fix but why.

I don't know about the rest of folks, but mine does not sag (level) & while I have not weighed it for Pin Weight (which I intend to do)I believe I have only used ~90% or less of the capacity of this BAAD BOY.

thanks again :D :D :rolleyes:

[TimT]

While you're under there, take a look at the slip yoke and the u-joint alignment. I had an 89 Ext cab long bed witha 2 piece driveshaft and found that if I rotated the slip yoke away from what is assumed to be "correct", the shudder went away. This was a TSB for that year truck. Just 1 spline off from the "correct" alignment and no more shudder. 200K miles and 1 set of U-joints because the carrier bearing flat wore out. :cool:

[jallen]

Kennedy & the other guys,
Today I hooked up with the springs loaded between the bottom leaf & the H D monster leaf to give the effect of lowering the pinion (oops I did not mean to say raise in yesterdays post) & this did help the shudder. Took a long look under the D/A & the pinion angle is several degrees higher than the line of the rear section of d/s. Will be interested in knowing all the changes you make to yours to correct d/s angle & thus the Shudder.

This Forum is really great I am so glad I joined.

thanks everybody.

2002 K2500 4x4 Duramax / Allision
Crew Cab, Long Bed
Jordon Electric Brake
D T A Ultra Boards
R D S Mfg. 60gal. tool/tank
2002 Wilderness 32 foot 5er
ROYAL TRITEN 15/40 SEMI-Synthetic (76 lubricants) :rolleyes: :D :D

[Kennedy]

I am hoping to have a worksheet made to illustrate these angles as it makes life a lot easier. I'll confess, I have consulted Dennis (White Truck) as a tech advisor on this subject.

Basically, as my truck stood, the angles were this:

Allison/T-case = 4.5

[hoot]

I'm a little confused as to why these things haven't been engineered correctly by GM before putting the product out to market.

John,

I'm not sure what you mean by this. How does less fail a joint? Just curious.

"The desired angle here is .25

[Nels]

This is an excellent thread! I am reading with interest, although it doesn't apply to my truck. I have the ext. cab long box with the factory installed Alcoa aluminum single piece telephone pole revision (late 2001).

I am curious, as hoot was, about the 0 degree wear on the u-joint. The theory floating in the back of my head is that 0 degrees will not cause rotation of the needle bearings in the cups, thereby isolating the load to one spot on the bearings, whereas a slight angle will alow a slow rotation so the load distributes across all of the bearings? It sounds cool, even if it isn't quite on the mark.

And hoot, don't get me going on engineers. They are to many companies what an appendix is to the human body. There are some good an useful ones, but unfortunately there are many with no common sense.

[hoot]

Nels,

That explains it. I see where some movement is required to keep things moving and lubricated but I'll bet with suspension traveling going down the road, even at 0 degrees you would get plenty of movement. That spec is probably based on a static model (engineering lingo ;) )

Now up front between the Xfer case and the carrier there are no angle changes during suspension travel. That's where 0 degrees would be a problem if your theory is correct.

[ 05-03-2002: Message edited by: hoot ]</p>

[Kennedy]

Keep in mind, the front shaft will not move, and the front section of the rear 2 pc will only move as much as the support bearing rubber flexes...

[Kent Tuttle]

So John, will any of these changes you and others are working on help with what feels like drive line slop or a bump during stops and starts??

[Kennedy]

On the 1/2 tons they are swapping shafts left and right in favor of a new spline on the slip yoke. The new one is plated and supposed to slide more freely.

[Billy14]

John & others,

I've been all over the bump at stop & start with my dealer. SM called GM engineering & was told they have no plan to address this issue with the binding slip yoke on the HD's for now.

Could this also be the villain for all of the pinion brg. & leaky seals I read about on the forum? The constant thrust pounding on the diff. & output shaft of the tranny can't be good! Somethning eventually has to give.

They gave me some special sticky cherry colored grease & told me to pile it in the slip yoke after cleaning. Unbelievable results. So smooth & overall driving much better especially on rough roads. Said they had the same problem with Tahoes & same procedure lasted for over a year.

My question to them was: The grease has eventually got to wick it's way up the spline teeth into the transfer case mixing with the tranny fluid. They told me naw, don't worry about it. Oh Well, not until I have a problem with the Allison!

Billy

[jallen]

Kennedy & all other interested,

Today I (me & my son) placed 2 Degree wedges between spring & axle & it got rid of most of the SHUDDER, WOW I wish I had gotten the 4 degree wedges b-4 we did this project, because now it will have to be done over again. Many thanks to you john & others for this will fix the truck I am sure.

Took the D/A in to the dealer Thursday To get constant down-shift adjusted & while there asked them to fix the SHUDDER, their comment for this was "NO REPAIR FOR THIS" but I was not surprized because John you said "the general can't help with this problem".

After the Tech reprogramed the TCM the down-shift problem has been corrected, it will now pull down to 1800 RPM b-4 it shifts.

Thanks again
:rolleyes: smile.gif :D