4.3 Motor Mounts

When I had my 03 S10 4.3 I couldnt keep motor mounts in it for longer than a few months....I drove it pretty hard & towed jet skis & boats with it so that means pulling them out at the boat ramps which puts a lot of torque on the drivers side mount causing it to rip.

So I went to the JTR mounts which are really awesome but it has a vibration at idle not real bad but just annoying.

So now I have the 04 Blazer & it had ripped mounts when I got it so I went with the JTR mounts & sure enough same vibration & its starting to get annoying as well so I was thinking about getting some stock mounts to stop the vibration & put a torque strap or chain to keep the motor from ripping the driver side motor mount.

Anybody know of a good brand of stock style motor mounts that last

It's a fault in the design that can't be overcome without doing something different, so all your reproductions are going to have the same issue.

I designed up an engine plate for the 4.3 that would use the same lower as the LSx mounts I designed. I chose a tube/bushing size that could also use a rubber Control Arm bushing in case I or anyone wanted a softer bushing material instead of the common poly used. I've never had a set of the 4.3 mounts cut, but they're similar to most the LSx mounts out there.

This is my 5.3 mount in CAD. Top engine plate is at a bit different height and has a different bolt pattern for the 4.3.

Nice work  !!  I wish I had the ability to make stuff like that.

The JTR mounts are like that with rubber clam shell mounts & I thought the rubber would get better with time but its not still has a vibration just like the day I installed them. My sons 02 has JTR mounts & his vib is hardly noticeable.

That makes me wonder if for some reason his body mounts are better at isolating than yours?

Those 2.8 mounts have a bunch of rubber, so seems like they would isolate better than you're seeing.

What trans mount are you running? Is it blown?

Something out of whack with the clutch/flywheel or torque converter? U Joints slightly worn?

Just trying to think of what else could be causing or transmitting the vibration.

Thanx for your input !!

The vib is only at dead idle....if I raise the idle with my foot to like 750-800 rpm it gets better it's worse when the ac is on cus it lowers the idle slightly. My 03 ext cab did it & the 04 Blazer X does it but my sons 02 ext cab is not as bad.

The vib is just getting to me & seems like everything is starting to rattle,door panels,console,crap in the console,passenger side seat belt rattles if nobody is using it so I have to pull it out & tuck it in between the cushions to stop the rattle.

My Blazer aint clapped out either,it is a no rust,no accident well taken care of Fla truck & I fix EVERYTHING that even shows a slight issue.

My 03 did it with the 4.3 & the JTR mounts & when I did the LS swap & I used CPW poly mounts & I was thinking the LS was gonna vibe the truck but it was total opposite the LS was smooth as glass.

IMO its the crappy ass 4.3 why else would GM put those double rubber motor mounts & put a balance shaft in it ??  Dont get me wrong I love how this thing runs. I miss my LS swapped S10 but the 4.3 keeps me under control as far as getting tickets. LOL

That makes me wonder if for some reason his body mounts are better at isolating than yours?

Those 2.8 mounts have a bunch of rubber, so seems like they would isolate better than you're seeing.

What trans mount are you running? Is it blown?

Something out of whack with the clutch/flywheel or torque converter? U Joints slightly worn?

Just trying to think of what else could be causing or transmitting the vibration.

My sons 02 has almost 300,000 on the chassis poor thing just keeps running (with the help of dad).

Yeah I fiqured over time & heat that the 2.8 clamshell style mounts would "soften" uo a bit & the vib would go away. The trans mount is a stock rubber style & new. 

Flex plate  & converter have been changed when I was looking for a clicking noise when I would accelerate away from a light but go away when driving......long story short ended up being the starter,the spring checked out & the bendix would hit the flywheel when I would accelerate. Banged my head on the wall with that one.

When I did my LS swap I sold & installed my old 4.3 in another Blazer & it vibed at idle with the JTR mounts & it was well discussed at S10 Planet & I think Rented Mule was shocked at first when he installed JTR mounts back when IIRC

I cant bring myself to install $12 Rock Auto motor mounts only to have to do them again (lesson learned) so I check with Chevrolet dealer today & they wanted $110 each for stock GM mounts & my buddy can get them for me for $64 each which is a little better & probably the way I will go & "chain down" the drivers side so it doesnt rip the mount.

I want to point the finger at the 4.3 too. haha It seems something in the rotating assembly is out of balance.

My thought on the U joints is the drive angle wasn't great with the blown mounts and now the u joints are showing signs of wear.

Which makes me wonder if the driveline angles are off with the JTR mounts and somehow your son's truck got lucky. That would be worth measuring too. If the mounts are a different height than stock that could throw things off. Hopefully a spacer under the transmission can fix the problem if it is there.

But U joints are stationary at idle, so I'm back to the first thought above.

Could it be a slight miss at idle?

Another option would be to raise the idle. When we first setup my 5.3 tune the idle was pretty low and along with other problems it did vibrate things a bit more. It's set around 800 now, which was pretty much copied from the Z06 tune we had on hand.

I have the basically solid Baja Customs mounts. IIRC, I raised the idle speed about 100 rpm in the tune and it made a world of difference. The MSD box also smoothed out the idle noticeably, even with the rest of the ignition being almost new.

I have the JTR mounts in my truck along with a poly trans mount. There is a slight vibration at idle, other than that it's smooth. Maybe I'm just used to it, but the vibration isn't that unbearable. The 4.3 isn't known to be a smooth engine lol. Both of my stock mounts were broken when I replaced that at around 194k. The JTR mounts are a far superior design IMO. I'd rather deal with a slight vibration than continually replacing the stock mounts that tear.

Another thing to check is your body mounts. Most trucks I see in the junkyard around here have completely worn cab mounts. I used to have poly ones but got tired of the vibrations so I went back to rubber mounts.

I want to point the finger at the 4.3 too. haha It seems something in the rotating assembly is out of balance.

My thought on the U joints is the drive angle wasn't great with the blown mounts and now the u joints are showing signs of wear.

Which makes me wonder if the driveline angles are off with the JTR mounts and somehow your son's truck got lucky. That would be worth measuring too. If the mounts are a different height than stock that could throw things off. Hopefully a spacer under the transmission can fix the problem if it is there.

But U joints are stationary at idle, so I'm back to the first thought above.

Could it be a slight miss at idle?

Another option would be to raise the idle. When we first setup my 5.3 tune the idle was pretty low and along with other problems it did vibrate things a bit more. It's set around 800 now, which was pretty much copied from the Z06 tune we had on hand.

All my trucks & my sons have the JTR driveline alignment kit & it made a world of difference. When I got my 03 it was a stock height ZQ8 truck & when you got to 80 mph the driveline shook so bad I thought it was gonna come apart. Installed JTR driveline kit the imbalance was gone. Had it to 142 mph with the LS. LOL  Smooth as glass.

No miss as all the trucks did it. Its the combo of the 4.3 & the stiffer JTR mounts. The vib is not unbearable as I have been driving it for 3 years like this. I guess I am just getting older & getting tired of the vib.  Maybe a idle raise as I was looking to get a different tune anyway Hmmmm

I will mess with raising it with my foot & see what that does.....     Once I get moving its smooth as glass & I love how the motor is anchored & not moving around during hard braking & cornering.

Today I messed around with raising the idle by stepping on the pedal....the sweet spot is right around 750-800 rpm & everything is smooth so instead of changing the mounts for $140 & a bunch of work I am gonna send my stock PCM out to PCMforless & get it tuned.

The PCM thats in it now was done by wait4me & I think it could be better & I am having a issue with acceleration from a dead stop anyway & have been wanting PCMforless to do one for me.

Is Shawn (xtreme80) still around the forums somewhere? He did a killer tune on my truck and tested it on his own truck before sending it to me. 

I wish he was around....I miss the Planet.