'08 Tahoe 4x4 Motor Mount Education

[EddieC]

2008 Z71 Tahoe, 4x4

Started thread in suspension but moving here as it seems motor mount(s) issue may be the cause of out front end clunk on starting the truck moving.
What had been most noticible has been loud clunk when turning the steering wheel fully left and backing out of our turn around. There have been a few similar noises when going forward and turning. We have had the noise for a few months. Other things have been looked into and a ball joint changed.

I have seen several threads here and outside videos on motor mounts and it seems to be a jumble of hard to easy and major disassembly to barely any disassembly and a crazy range of proposed costs so I was hoping to try to refine the information.

Doing a power brake test as previously suggested in drive there is a noticible motion on the driver's side of the engine. In reverse there is significantly less, barely noticeable movement, on the passenger's side. Assuming the driver's mount is failing it seems odd that the loudest noise is when backing the vehicle up. Wouldn't this be opposite of what would be expected?

Does the noise and conditions mentioned sound like a failed motor mount?

Would that require immediate attention? (It's a tough season to be doing significant vehicle work outside)

If it does need replacing, does the 4wd complicate the replacement? How?

Is this possibly a do it at home on the pavement job?

Hoping those who have been through it can clarify what is actually really required in the process.

Thanks guys for anything offered.

 

[donjetman]

2008 Z71 Tahoe, 4x4

Started thread in suspension but moving here as it seems motor mount(s) issue may be the cause of out front end clunk on starting the truck moving.
What had been most noticible has been loud clunk when turning the steering wheel fully left and backing out of our turn around. There have been a few similar noises when going forward and turning. We have had the noise for a few months. Other things have been looked into and a ball joint changed.

I have seen several threads here and outside videos on motor mounts and it seems to be a jumble of hard to easy and major disassembly to barely any disassembly and a crazy range of proposed costs so I was hoping to try to refine the information.

Doing a power brake test as previously suggested in drive there is a noticible motion on the driver's side of the engine. In reverse there is significantly less, barely noticeable movement, on the passenger's side. Assuming the driver's mount is failing it seems odd that the loudest noise is when backing the vehicle up. Wouldn't this be opposite of what would be expected?

Does the noise and conditions mentioned sound like a failed motor mount?

Would that require immediate attention? (It's a tough season to be doing significant vehicle work outside)

If it does need replacing, does the 4wd complicate the replacement? How?

Is this possibly a do it at home on the pavement job?

Hoping those who have been through it can clarify what is actually really required in the process.

Thanks guys for anything offered.

https://www.tahoeyukonforum.com/threads/front-differential-mounts.120260/page-3#post-1676685

 

[Geotrash]

2008 Z71 Tahoe, 4x4

Started thread in suspension but moving here as it seems motor mount(s) issue may be the cause of out front end clunk on starting the truck moving.
What had been most noticible has been loud clunk when turning the steering wheel fully left and backing out of our turn around. There have been a few similar noises when going forward and turning. We have had the noise for a few months. Other things have been looked into and a ball joint changed.

I have seen several threads here and outside videos on motor mounts and it seems to be a jumble of hard to easy and major disassembly to barely any disassembly and a crazy range of proposed costs so I was hoping to try to refine the information.

Doing a power brake test as previously suggested in drive there is a noticible motion on the driver's side of the engine. In reverse there is significantly less, barely noticeable movement, on the passenger's side. Assuming the driver's mount is failing it seems odd that the loudest noise is when backing the vehicle up. Wouldn't this be opposite of what would be expected?

Does the noise and conditions mentioned sound like a failed motor mount?

Would that require immediate attention? (It's a tough season to be doing significant vehicle work outside)

If it does need replacing, does the 4wd complicate the replacement? How?

Is this possibly a do it at home on the pavement job?

Hoping those who have been through it can clarify what is actually really required in the process.

Thanks guys for anything offered.

Sounds like you've confirmed a bad mount with your tests. Not a fun job, but not terrible either.

I pulled the drivers side front wheel and fender liner, and also had to separate the steering shaft and the exhaust manifold heat shield to get enough clearance to work. While I was in there I also replaced the oil cooler lines. You might do the same if yours is so equipped.

Bad mount that came out:

What it looks like with everything out of the way:

New oil cooler lines installed:

New Hummer mount installed:

 

[Marky Dissod]

New Hummer mount installed: ...

Two questions, if you don't mind.
1. When you say 'Hummer mount', do you mean H2 or H3?
2. What year?

 

[EddieC]

Sounds like you've confirmed a bad mount with your tests. Not a fun job, but not terrible either.

I pulled the drivers side front wheel and fender liner, and also had to separate the steering shaft and the exhaust manifold heat shield to get enough clearance to work. While I was in there I also replaced the oil cooler lines. You might do the same if yours is so equipped.

Bad mount that came out:

View attachment 421246

What it looks like with everything out of the way:

View attachment 421248

New oil cooler lines installed:

View attachment 421249

New Hummer mount installed:

View attachment 421247

Dave,

Am I right in thinking the motor mount you show is not supposed to have the joint midway across, that being the failure point?
Presuming you have 4wd, did you have to remove the axle shaft?
Yes, I have a weeping crimped connector on my upper oil cooler line that is another thing on my list.

 

[EddieC]

https://www.tahoeyukonforum.com/threads/front-differential-mounts.120260/page-3#post-1676685

What symptoms pointed you to the front differential mounts?

 

[j91z28d1]

of course I. need to do mine too. it's kinda brutal the price has tripled for the hummer mounts.

almost 600$ for mounts feels crazy, but I don't really see any other solid rubber ones to use.

if the job didn't look so hard, I'd try some cheaper auto parts store ones for like 40$ and see how they do

 

[donjetman]

What symptoms pointed you to the front differential mounts?

The infamous clunk/klunk sound when transitioning off then on the throttle quickly
and
getting under it and prying/pushing/pulling on the front differential/driveshaft etc.

The next task I'll do to reduce the clunk/klunk will be rebuilding the transfer case, a <$300 DIY job.

 

[EddieC]

The infamous clunk/klunk sound when transitioning off then on the throttle quickly
and
getting under it and prying/pushing/pulling on the front differential/driveshaft etc.

The next task I'll do to reduce the clunk/klunk will be rebuilding the transfer case, a <$300 DIY job.

So when you handled the front driveshaft you got movement or noise?

 

[gooffeyguy]

Sounds like you've confirmed a bad mount with your tests. Not a fun job, but not terrible either.

I pulled the drivers side front wheel and fender liner, and also had to separate the steering shaft and the exhaust manifold heat shield to get enough clearance to work. While I was in there I also replaced the oil cooler lines. You might do the same if yours is so equipped.

Bad mount that came out:

View attachment 421246

What it looks like with everything out of the way:

View attachment 421248

New oil cooler lines installed:

View attachment 421249

New Hummer mount installed:

View attachment 421247

Quick question...going in that way from the top/side, were you able to get to the two 10mm bolts that hold the cooler line block to the side of the pan above the filter without dropping the front driveshaft?

I replaced the cooler line gasket about a year ago and did it from underneath but I unbolted the front U joint and let the driveshaft rest on the swaybar.

This summer when I replace my cooler lines I plan on doing it like you did by removing the motor mount and I'll also be removing the exhaust manifold to remove the broken rear bolt.

 

[donjetman]

So when you handled the front driveshaft you got movement or noise?

easy movement at the bushings of the front differential mounts.

 

[donjetman]

So when you handled the front driveshaft you got movement or noise?

twist the driveshafts back and forth to see how much slop is in the transfer case

 

[Geotrash]

Quick question...going in that way from the top/side, were you able to get to the two 10mm bolts that hold the cooler line block to the side of the pan above the filter without dropping the front driveshaft?

I replaced the cooler line gasket about a year ago and did it from underneath but I unbolted the front U joint and let the driveshaft rest on the swaybar.

This summer when I replace my cooler lines I plan on doing it like you did by removing the motor mount and I'll also be removing the exhaust manifold to remove the broken rear bolt.

Yes, I was. In fact I had to get a helicoil into one of the cooler line bolt holes from underneath, previously. Never dropped the front driveshaft.

 

[EddieC]

twist the driveshafts back and forth to see how much slop is in the transfer case

A bit confusing. I thought you were describing diagnosis of the differential mounts, not the transfer case.

 

[donjetman]

A bit confusing. I thought you were describing diagnosis of the differential mounts, not the transfer case.

with the front tires off the ground, get under the vehicle and pull/push up and down on the front pinion and see if there is any movement at the front differential mount bushings.

 

[EddieC]

Well, we've chased this sound around and finally found it. It is a suspension issue after all and not motor mount.
The sound changed from occasional to always when backing and braking and as a mild clunk.
Having someone watch the driver's side top control arm while doing that it turned out that the 20,000 mile old top control arm bushings had enough play to allow the bolts to move enough to make noise.
New control arm and no more noise.

 

[petethepug]

Nice follow up & follow through. Add Solved or Fixed to the title and watch the likes go crazy

 

[jrobie79]

The next task I'll do to reduce the clunk/klunk will be rebuilding the transfer case, a <$300 DIY job.

Have a writeup for this?

 

[donjetman]

Have a writeup for this?

No, I might tackle this project this summer if it floats to the top of my lists