Loose motor mounts? Please help

[Fjordlander]

Hello all,

Lately, my 76 K10 has been "klunking" when shifting from reverse to forward or vise versa. It also will occasionally rumble and shake after I turn the truck off. The only thing I can think is that something could be up with the motor mounts but I would greatly appreciate everyone's suggestions.
I also have no idea what to look for when assessing thr motor mounts so any input there would be great

 

[CalSgt]

Reverse to forward clunk can be loss of motion in the differential too.

You can put a floor jack under the oil pan and gently lift the engine while looking at the mounts. Also, under the trans pan and look at the trans mounts.

 

[scrap--metal]

Bad U joints or a bad transmission mount are more likely to cause clunking in my opinion.

Do what @CalSgt suggested, and look for sloppy u joints while you're under the truck.

Rumble or shaking after turning off the truck could be unrelated.

 

[Fjordlander]

Reverse to forward clunk can be loss of motion in the differential too.

You can put a floor jack under the oil pan and gently lift the engine while looking at the mounts. Also, under the trans pan and look at the trans mounts.

Without jacking it up I just climbed underneath and felt the motor mount and a chunk of crispy rubber fell off. So whether or not that's my issue I'm definitely going to replace them.
Will I be able to replace the motor mounts just by jacking it up by the oil pan?

 

[DoubleDingo]

Without jacking it up I just climbed underneath and felt the motor mount and a chunk of crispy rubber fell off. So whether or not that's my issue I'm definitely going to replace them.
Will I be able to replace the motor mounts just by jacking it up by the oil pan?

Yep. Just need to get the tension off the mounts, not jack up the engine real high. And make sure to put a block of wood between the jack and pan

 

[Fjordlander]

Yep. Just need to get the tension off the mounts, not jack up the engine real high. And make sure to put a block of wood between the jack and pan

Thanks!

 

[idahovette]

One side at a time, please!!!!

 

[Fjordlander]

One side at a time, please!!!!

Copy that!

 

[Trucksareforwork]

On your rumbling on, just do a search for “dieseling” and you should find a lot of causes and cures. Usually it’s excessive air leaking into the engine via throttle plates or another vacuum leak.

 

[DoubleDingo]

One side at a time, please!!!!

I forgot to mention that, thanks for telling him.

Definitely one side at a time, don't need to fight the whole assembly when bolting in the new mounts.