Engine Mount Replacement

[GeneralDisorder]

My engine mounts were shot. And every other truck I've looked at was in similar condition. Speaking with someone in the know - apparently even Acela doesn't change these.

2008 M1079 w/25,000 miles.

Before. You can see the "fretting" from vibrations that is causing that characteristic red "dusty" look. That's from constant abrasion of the metal that is shedding bits of iron and abrading the oxide layer. You can also see some cracking where the rubber is delaminating from the steel plates.



You can see that the safety sleeve that protects the bolt is eating it's way into the frame mounting bracket:



Changing these involves taking the upper fan shroud loose, unbolting the mounts, then lifting the engine up. I could only get about 1.5-2", and unlike the TM's suggestion of "remove the mounts" I had to unbolt the frame mounting bracket lower bolt, and loosen the upper bolt to rotate the bracket and allow removal of the rubber mount, sleeve, and bolt.





Old mounts and sleeves:







New mount installed:



And now we have an air gap!:



Fan to shroud clearance before and after. Seems to have raised the engine about 1/4-3/8"



And the difference is noticeable. Lower cab noise and vibration. Especially at and near idle and just off idle when accelerating. When coming to a stop in gear I would have varying amounts of vibration depending on how the truck was sitting and where gravity was putting the most load on the collapsed mounts and sleeves I assume. No longer get that and much less vibration overall under all conditions. Very worthwhile.

Look close. I bet you ALL find yours are essentially the same unless you have already changed them.

 

[Keith Knight]

I’ll take a closer look today. Where did you find the new mounts?

 

[hike]

Ours look like the passenger side was changed and the driver side is original?

passenger


driver


driver detail

 

[Keith Knight]

I can definitely see on both of mine where the steel bushing on the bolt is rubbing on the large clearance hole caused by the rubber compressing over time. So where did you find new motor mounts?

 

[GeneralDisorder]

They are out there. Be aware of manufacture dates as they are rubber - don't buy anything older than ~5 years if you can help it. There is a fellow on ebay that has sold them for $50 each a couple times now but he only lists two at a time - I'm assuming to promote the assumption of scarcity.

NSN:

5342-01-382-5021

 

[GeneralDisorder]

Ours look like the passenger side was changed and the driver side is original?

Looks like they are both collapsed to me. You can see where the metal is being rolled off the bracket in both pics I think (hard to see on the passenger one - need a close up with more light). Not as badly as mine but have put miles on mine in the 3 years I've owned it (7k a year) and it served in the desert in Kuwait and El-Paso with 1st Armored Division.

Sounds implausible that someone would have only done one. That would be a hell of a high speed soldier to even bother with these, and to stop at doing just one side? Seems unlikely to me. Mine were not evenly worn and I looked at @Lostchain's 2003 M1078 truck this last weekend when doing mine and his were also bad but one is worse.

Could have been done if/when the engine was changed out. That's plausible. Definitely can happen that the Army throws an engine at a truck. Would believe that and maybe one got swapped and the other didn't...... supply chain issues perhaps. Ordered two mounts and only got one by the time the job needed to get done or only had one on hand..... Maybe one failed entirely so Snuffy only changed the broken one..... Motorpool is often that kind of world.