SOLVED: Shudder from full stop

[tooleyondeck]

I have narrowed this down to what I believe is the drivers side engine mount.

Pop the hood, start the truck, peek through the gap between your dash and hood and rev the engine a bit, you can typically see the engine moving if it's a bad mount.

 

[alvocado]

Should there be any movement? When I had the broken mount in, the engine heaved noticeably. I can still see movement up and down with revving although much less.

 

[donjetman]

with the hood up, put it in Drive then power brake it. If the mount is bad you will SEE it.

 

[Dustin Jackson]

@alvocado It should move very little, since you've seen a bad mount in the past you know what it looks like when the mount is broken.

What makes you think it's the drivers side mount again? Have you tried disabling traction control and stabilitrac and see if the problem persists?

 

[alvocado]

@alvocado It should move very little, since you've seen a bad mount in the past you know what it looks like when the mount is broken.

What makes you think it's the drivers side mount again? Have you tried disabling traction control and stabilitrac and see if the problem persists?

I can repeat the shudder by power braking with the truck in park so that points me to a mount. Since most of the engine movement when revving is constrained by the driver side mount, I've been focused there. I understood that the passenger side mounts don't typically wear as quickly or even at all vs. drivers side.

With the said, if anyone has experience with a passenger side mount failing and can comment on the symptoms, it would be helpful to compare. The passenger side is factory and is not leaking. It's hard to assess the rubber condition with the heat shield in place.

A new mount is arriving today so I'll have to decide if I swap the driver's side and compare or go straight to the passenger side. 50/50 chance I'm doing mounts twice later today.

 

[Fless]

Inspect the transmission mount, too.

 

[Dustin Jackson]

@alvocado My theory is when the driver side fails the passenger side begins to wear faster from the excessive movement of the motor so go ahead and do the other side as well. Interesting the problem happens in park. Can you maybe take a video showing the problem?

 

[alvocado]

Update: I think it's solved. I decided to install the additional engine mount I ordered on the passenger side under the assumption that a new GM mount on the driver side is most likely good. I also swapped the transmission mount while I was under there since it's inexpensive. Both mounts didn't show any signs of wear like cracks, etc. but the shudder is completely gone upon test drive.

If I had to put my money on it, I'd say the passenger side engine mount was the culprit. It's 74% humidity in SW OH and I lost 6 lbs in sweat over 5 hours in the garage but it was worth it.

One question: the exhaust clamp just forward of the flex pipe always gives me fits trying to get it tight and quiet. I loosened it trying to drop the cross member when changing the transmission mount but there still wasn't enough clearance to get the cross member bolt out. I just lifted the tcase and slipped the mount out from above. What's the right way to make that exhaust connection so it's sealed up? I try to pull the exhaust forward as far as it will go then zip the clamp with an impact. Sometimes I'm lucky and sometimes I just can't get a good seal. It's definitely louder than when I started so I have to take another crack at it.

 

[PG01]

For future forum readers…. peeking through hood gap whlie power braking in drive you can see if driver side mount is bad and power braking it while in reverse and you can see if the passenger side is bad. Drivers side will lift in drive and passenger side will lift in reverse. Power braking is holding your foot on the brake while giving it gas.

 

[blondie70]

For that exhaust clamp, I used an old rachet strap to pull the flex joint forward....it did it easily and plugged the pipes together nicely. Then I clamped that baby down.

 

[alvocado]

For that exhaust clamp, I used an old rachet strap to pull the flex joint forward....it did it easily and plugged the pipes together nicely. Then I clamped that baby down.

Good tip. I think that's the issue, not getting the pipe pulled forward far enough.