Front diff mount play

[dave91gt]

New Bronco owner- 24 OBX Sas 2.7 4 door. Since new, it has had a tire balance issue and what seems like a driveline vibration at higher speeds. Will eventually have dealer address both. I decided to do the first oil change at 1750 miles and while under there did the touch and feel test. The pass side diff mount has a lot of vertical play (bolt is tight). I grabbed the CV at the diff side and could move the diff (at the mount) quite a bit. Maybe normal?

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[RP80]

Totally normal to have some play here. No worries at all.

 

[PWillette]

Are you saying the FDU itself is moving?

 

[BigMeatsBronco]

New Bronco owner- 24 OBX Sas 2.7 4 door. Since new, it has had a tire balance issue and what seems like a driveline vibration at higher speeds. Will eventually have dealer address both. I decided to do the first oil change at 1750 miles and while under there did the touch and feel test. The pass side diff mount has a lot of vertical play (bolt is tight). I grabbed the CV at the diff side and could move the diff (at the mount) quite a bit. Maybe normal?

I've said it was too loose as well. I'm surprised someone hasn't ripped mounts clean out yet.

needs more support for sure.

 

[RP80]

I've said it was too loose as well. I'm surprised someone hasn't ripped mounts clean out yet.

needs more support for sure.

Interesting. Mine has always had play and I've attributed it to design, but this has me reconsidering. The assumption was a bit of wiggle room was designed in to allow the diff a kind of self-adjustment to any minor alignment imperfections. I wonder if fixing it very rigidly would effect anything? Since adding a diff drop bracket, we've been having issues with the new available "wiggle room" and have needed to add a spacer to limit diff uptravel. The play remains, but we could easily fix this down. Hmmm....thoughts?

 

[BigMeatsBronco]

Interesting. Mine has always had play and I've attributed it to design, but this has me reconsidering. The assumption was a bit of wiggle room was designed in to allow the diff a kind of self-adjustment to any minor alignment imperfections. I wonder if fixing it very rigidly would effect anything? Since adding a diff drop bracket, we've been having issues with the new available "wiggle room" and have needed to add a spacer to limit diff uptravel. The play remains, but we could easily fix this down. Hmmm....thoughts?

It's kind of like engine mounts....OEM is great untill you start doubling the hp/tq....then you need beefier engine mounts, and even possibly a "torque-bar" on one side of the engine to handle the extra loads...

With BIG tires and low gearing, the driveline rotational thrust wants to naturally push the pinion in the opposite direction the tires are rotating...in the front, accelerate forward the pinion is forcing down. Mine sits 1/8 (foam thickness) from the crossmember, so it actually pushes down on the crossmember.

UNLESS you are in reverse, then the pinion wants to go towards the plastic oil pan...

I think the passenger side mount could be beefed up... (spicer claims their Extreem HD FDU has SOLID rubber mounts) and it looks like they are slightly better than OEM.

Id prefer adding a 4th mount...a bolt on plate that mounts to the front passenger side forward crossmember (w/urethane)


How are you having compression travel issues????

 

[RP80]

How are you having compression travel issues????

What do you mean?

 

[BigMeatsBronco]

Interesting. Since adding a diff drop bracket, we've been having issues with the new available "wiggle room" and have needed to add a spacer to limit diff uptravel. The play remains, but we could easily fix this down. Hmmm....thoughts?

The post doesn't explain what's going on?

the diff doesn't have uptravel (except for maybe the degree of deflection in the rubber bushings) ...you added a spacer Where?

 

[RP80]

The drop bracket rotates the diff in a way that creates space above the mounting bolt. We initially did not increase the thickness of spacer/bushing which resulted in a bunch of diff movement.

Worked through a bunch of this stuff the guy who designed the system. @TeocaliMG, is this an appropriate description of the original issue?

 

[87-Z28]

The post doesn't explain what's going on?

the diff doesn't have uptravel (except for maybe the degree of deflection in the rubber bushings) ...you added a spacer Where?

agreed. displacement degrees of freedom are not very clear. Curious about the details here. Not really understanding.

 

[RP80]

agreed. displacement degrees of freedom are not very clear. Curious about the details here. Not really understanding.

Honestly not sure how to describe it more precisely. I tried above.
Maybe the designer of the bracket can comment—@TeocaliMG

 

[BigMeatsBronco]

Honestly not sure how to describe it more precisely. I tried above.
Maybe the designer of the bracket can comment—@TeocaliMG

@TeocaliMG

 

[TeocaliMG]

My understanding from a cursory read over here is the OP is talking about excessive motion in the rubber bushings. (Particularly the passenger side)

Something to check on the driver side though, regardless of whether or not the bolt is tight (and this goes for the OEM bracket, or my diff drop). Make sure that the steel core is pinched tight to the steel and cannot slide at all. The rubber should be able to flex, and as BigMeats pointed out that will be exacerbated by higher torque, but the steel core bushing within the rubber should have zero motion in the bracket, if it does, crank that bolt down more.

As for the passenger side mount, it does have a lot of flex/play but it can only move so far before it bottoms out on the washer or the bracket itself. As RP80 pointed out, my initial kit did not account for that bottoming out so the diff could over flex the rubber. We since oversized the spacer to act as a bottom-out for the diff just to maintain the OEM allowed flex. (and added a beefy washer to the bottom for the same purpose).

I would not recommend rigid mounting anything there. Aside from the NVH, the bushings provide important shock absorption between the different ends of the driveline which is good for everything involved durability wise.

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