Jump to content

The *thunk* when stopping

Laurence
 Share

Recommended Posts

Laurence Enthusiast

Laurence

Posted
Posted

I have a 2006 2500 Duramax 4x4. It has 100k miles on it. Occasionally when I come to a stop, it feels like someone is bumping in to me in the rear. This could be happening at the final downshift but I can't tell. The Allison is so smooth. I have no signs of any trans problems at all. Fluids are up. Temps are normal.

Any idea what this could be?

txab Senior Enthusiast

txab

Posted
Posted (edited)

Generally it can be a slip yoke sticking issue at the trans. Removing the shaft, lubricating the splines, will generally take car of the issue. They developed an upgraded slip yoke, out of nickel that was supposed to reduce this issue. If you search the site a bit, you'll find more about this

 

https://www.google.com/search?hl=en&as_q=slip+yoke+clunk&as_epq=&as_oq=&as_eq=&as_nlo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=www.gm-trucks.com&as_occt=any&safe=images&as_filetype=&tbs=

Edited by txab
  • Thanks 1
Colossus Senior Enthusiast

Colossus

Posted
Posted

Slip yoke clunk was a common issue on the GMT-800 1/2 tons, and the solution was replacing it with a nickle plated slip yoke.  Did the 2500s have the same issues?  I don't recall that back in the day just on the 1500s..

Laurence Enthusiast

Laurence

Posted
  • Author
Posted

I have been doing some reading on this issue. Lubricating the splines is a GM recommended procedure for 4x2s only. GM does not permit this for 4x4s. ( Bulletin # 09-04-21-003B). The grease will migrate into the transfer case and contaminate the oil. Transmission fluid is supposed to lube the splines in this case.

I'll have to pull the yoke out and see if it is dry. What has been the experience of you 4x4 guys? Thanks for pointing me in the right direction.

 

  • 3 years later...
Laurence Enthusiast

Laurence

Posted
  • Author
Posted

The yoke is in great shape. No rust; nice and shiny. The splines had a thin film of oil in them.

I had the dealer look at it, thinking they would know what to do, All they could come up with is to use the GM special lubricant #12345879. It is a PTFE filled high temp grease. What will that do to the transfer case oil?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Latest Articles

  • Posts

    • Aimatdeer
      Ac not keeping up

      By Aimatdeer · Posted

      Anyone have any info about backorder time? It's classic 4th of July hot here in ohio.
    • Chuck FB
      Fluid Change Questions

      By Chuck FB · Posted

      There would be one way of determining the quality of the factory oil although probably more than a typical oil lab test, and that would be to draw out some oil from a new truck and send a sample to a lab that could do a more elaborate test of the oil. The issue with too little oil in the diff may not be the lack of lubrication of the diff bearings and gears themselves ( although a lack of oil volume for cooling ) but the wheel bearings because at some point the oil would be too low to properly get onto the spinning axle or fed along the axle tube. That was the claim by the local dealer from a couple of trucks in recent years that had the wheel bearings fail and they figured from lack of sufficient oil due to a severe underfilled diff and some of the bearing material made its way to the diff and it got damaged as well so the axle housings were just replaced on warranty. But your right that if the diff is over filled by whatever margin that it causes more churning of the oil than is desirable and that is no good either and can cause a pinion seal to leak. Also old oil I believe can tend to loose some of its properties like antifoaming and another good reason to change the diff oil every so often. 
    • Z45
      Fluid Change Questions

      By Z45 · Posted

      I would be surprised if the diff's were not filled (with the cheapest gear lube) at the axle factory before being shipped to GM.  If you ever watched them building trucks they install the axles and all suspension parts with the frame upside down and then turn it over before its time to install the engine.     Too much gear lube in a axle can be worse than not enough especially with a lower quality GL where is get whipped up with entrained air (foam)  weakening its ability to lubricate.        
    • MORSNO
      Oil Consumption

      By MORSNO · Posted

      This is the 6.6 gasser section of the forum, you should either delete or modify your previous post as it is misleading for anyone looking for factual information on their 6.6 gas engine.
    • Atlas
      Wow I'm in a pickle. (Broke down truck) and a story.

      By Atlas · Posted

      Well....I've done my first intake gasket. Probably wrong, but...we'll see?   Ultra black on the china walls and 1/4" up onto the sides of the intake gaskets. Permatex High Tack (couldn't find Gaskachinch) on the head side of the intake gasket. I read wrong and it says you're supposed to put it on the mating surface of the head, not the gasket. Hoping it's like a PB&J sandwich where it doesn't matter what side the PB goes on so long as there's jelly. That crap is messy/sticky and I got a dab or two on the intake port openings, tried to wipe it off. Hopefully it won't be a big deal and will only aid in sealing.   Per instructions I left the intake (top side) of the gasket dry except for a light smear of RTV around the coolant ports. Wiggling the intake in there was a bear but I had help to free me of surrounding wiring/stuff but I was basically able to set it straight down lined up with the bolt holes.   I did not think to wait until the RTV skinned over but there probably was 5-10 minutes while it sat before installing the intake.   Bolts finger tight first. Then, followed the Chilton's manual pattern to snug them to 15 lb-ft.   Waited a little over an hour, and then did the final torque in sequence again to 35 lb-ft.   Yesterday I replaced the fuel pressure regulator and got my new "nut and bolt kit" (fuel lines) installed. Damn GM used security torx on the spider, which I don't have, so I got scammed at the local HW store for an off-brand security Torx bit set.   The new driver's door mirror arrived yesterday, so, there's a chance this thing could be running and road legal tomorrow? I don't want to get my hopes up.   This will be my first time stabbing a distributor, too. Although, lucky me, someone else marked the old distributor for removal previously, I did see that. (Someone's been here before!!). Engine is still at TDC so it *should* be just a matter of transferring the mark to the new dizzy and rotating it into place.

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...