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Changed Transmission Mount(Anchor brand) and now......

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by palmer_df0130, Apr 30, 2012.

  1. palmer_df0130

    palmer_df0130 Rockstar

    I have a vibration when in gear at idle. Also, when I shift into reverse or drive, the RPM's drop and i get a shutter then the RPM's come back to normal and the vibration is there as stated earlier. The transmission did shift about 1/4" toward the drivers side when I lowered the tranny back down onto the new mount and I had to pull on it to line the holes up to get the bolts back in. Truck shifts and drives good, now I just have the problem described above. The old mount looked like the original mount. What's everyone's thoughts on this? Thanks in advance for any help on this.

    99 Chevy Silverado Z-71 5.3l
  2. shibby2oo8

    shibby2oo8 Member 2 Years 100 Posts

    While stopped or moving? Did the exhaust bolt to the mount or not on your truck? Will putting the old mount back stop the prob? Is the vibration more of a noise or feel? Just trying to narrow the field here.
  3. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    I would check your U-joints. The "Shutter" you describe can be play in the joints, along with any vibrations. Did you take the drive shaft off when you did the job? Make sure you put it back the exact same way it came off?
  4. palmer_df0130

    palmer_df0130 Rockstar

    The vibration is when I'm sitting still at idle and the "shudder" is when shifting to reverse or drive and the rpm's drop and come back to normal. To remove and replace it, I just unbolted it and lifted the transmission enough to get the old one out and put the new one in. I left the old mount in Tucson at my parents house and I'm in Yuma now.:grrrrrr: I just got done cleaning the MAF, throttle body, and idle air control valve with no luck. Thanks for the responses.
  5. shibby2oo8

    shibby2oo8 Member 2 Years 100 Posts

    Since it does it when stopped i would look at the motor mounts and the accesories on the front of the engine. Im thinking that the strain on the mounts when you lifted the drivetrain damaged them or something that spins while the engine is running hit something. I would check the fan and shroud then work around the belt and inspect everything.
  6. palmer_df0130

    palmer_df0130 Rockstar

    I did take the belt off and didn't notice anything unusual. I also noticed that when I do shift it into the gear, the lights on the dash dim and the voltmeter drops also, but that is a result of the the engine bogging down for a second or so. Could the vibration I feel at idle in gear just be the result of the new mount that has a stiffer rubber than the OEM one and also the angle that the drive shaft enters the rear of the transmission changed slightly and it's binding? Hell, I'm just taking wild guesses.
  7. palmer_df0130

    palmer_df0130 Rockstar

    I had a little bit more time to check on things again and noticed that when I am in gear with the brake on and I turn the wheel, the vibration gets worse and the engine bogs down. I took the belt off again to check things over and this time I noticed the power steering pump moves in and out some, but no movement up/down and side/side. Is there supposed to be any in and out movement on the pulley shaft? Also, can a bad idle air control valve make it do this? Vacuum problem?
  8. shibby2oo8

    shibby2oo8 Member 2 Years 100 Posts

    The ps pump can have about 1/8" play in and out but no play side to side up down etc. there were problems with the plastic intakes warping which was more common on the 6.0 engines but happens to the others too. The engine will strain some when turning the wheel while stopped but not alot. Check all of the intake tubing from the filter bc if there is a leak after the maf sensor it will cause a rough idle especially since the engine moved and could have separated the tubes. Also depending on year/engine the map sensor is mounted on the rear of the intake and that too may have been bumped and is leaking air. Check all sensors and hoses while running ( BE CAREFUL!) and see if the idle changes. The map is held on with plastic fingers and seals with an oring so if the engine kissed the firewall could have messed that up.
    Last edited: May 2, 2012
  9. palmer_df0130

    palmer_df0130 Rockstar

    Thanks Shibby for the input. I will give the engine a look over when I get home from work today and let you know the results.
  10. palmer_df0130

    palmer_df0130 Rockstar

    Checked for damaged lines, vacuum leaks, motor mounts, and tested the Idle Air Control Valve and everything looked good. The biggest thing I notice now is when turning the steering wheel when in gear it brings the idle down to 3-400 and does the shuddering I described originally. I put the parking brake on and placed it in gear and turned the steering wheel and it does the same thing as when my foot was on the brake. Kinda at my wits end on this problem. It's crazy how just changing a simple mount can jack up the trucks performance. Other thing I noticed is I do have a lot of up and down play on my drivers side axle shaft that goes in to the front diff and it is leaking some. If it ain't one thing, its another.:mad:

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