Mystery Noise when Braking

[ratdude747]

Here's a head scratcher:

My '95 RWD Ranger has a noise when braking. It's a one-off tap sound, which I can feel in the floor and sounds like it's coming from the front. It's had it for a while, here's what I've done over the past several months:

-Winter 2015/2016: Replaced worn radius arm bushings. Old brackets reused due to a lack of bracket wear. Also replaced my front stabilizer link bushings.

-Spring 2016 (may be unrelated): Swapped transmission crossmembers (used a solid one off a 1994 B3000) and replaced a split transmission mount. Also added a rear stabilizer bar from the same B3000 using new links.

-Yesterday: Replaced outer Radius arm bushings because moron here got the plastic ring in the wrong spot, resulting in the bracket flange cutting the inner bushing. Lots of play too. Also saw that once again my transmission mount is splitting (Energy Poly one on order).

Both times I used Moog Radius arm bushings which I torqued to 120 Ft-Lb with the truck on the ground. No play after the most recent swap. I still have the noise (less pronounced).

I only hear it when I brake, most often after changing direction but some times it will do it multiple times in a row.

There isn't any shake in the steering or noise going over bumps. No ball joints are split. The pivot bushings are old but not visibly bad. The shock bushings are old and rotted a bit but again, no play.

At some point I also replaced my front brake pads and redid my rear brake hardware. AFAIK the calipers are tight (unlike prior incident where they were not and I had a front wheel lock up).

Where should I look next to nail down this noise?

 

[RonD]

I would start by jacking up a front tire(one at a time) and get it spinning then apply the brake, test in both directions, just to take those parts off the table.
If you feel it in the floor then probably not brake related, but easy test to eliminate it.

Suspension parts are harder to test.
You can use the weight of the vehicle on a steeper hill to mimic stopping weight but at very slow speed.
Need a helper though.
Just roll and stop on the hill, uphill and downhill directions, to see if you can repeat the sound and localize it

 

[black_demon69]

is radius arm cross member bolted or riveted? check for movement there

might also check body mounts

 

[Mark_88]

One of the guys on here (think it was 85Ranger_4x4) put a camera under his truck and filmed at various and assorted angles. It was actually pretty interesting to watch as he caught the suspension doing it's various and assorted things it does...

If you have one it might be worthwhile to try to fasten on under there in different locations and maybe catch what it is.

I'm leaning towards it being one of the radius arms like black_demon69 mentioned...had a bushing come loose on my 88 and it made a bumping noise every time I came to a stop.

 

[ratdude747]

is radius arm cross member bolted or riveted? check for movement there

might also check body mounts

The brackets used to be riveted but are now bolted. No movement AFAIK but that is a place to check. I'll look again and see if there is any signs of movement.

Body mounts are saggy with badly rusted hardware (the frame brackets are fine) but not rotted to the point of obvious play. I was wondering about that though. They've been on the list for a while but the Duff hardware kit pricing has kept me away.

One of the guys on here (think it was 85Ranger_4x4) put a camera under his truck and filmed at various and assorted angles. It was actually pretty interesting to watch as he caught the suspension doing it's various and assorted things it does...

If you have one it might be worthwhile to try to fasten on under there in different locations and maybe catch what it is.

I'm leaning towards it being one of the radius arms like black_demon69 mentioned...had a bushing come loose on my 88 and it made a bumping noise every time I came to a stop.

If I had such a camera in working shape I would. I actually have a couple of GoPro Hero 1's some place but they're missing batteries.

The radius arm bushings were the obvious issue but they're fixed now, so not likely the issue

 

[ratdude747]

I decided to inspect some and take pics. Here's a tour of the places asked about, starting at the Left Rear body mount and moving around clockwise:

First, the rear mount:

I noticed a witness mark (less dirt) around the mount bracket. The bushing was also soft to the touch as were the others. Makes me think that it's compressing (and expanding) a lot, which might be part of the problem?

Next, the center left mount:

This one is the worst, note the rusted away washer. Also note that I angle grinder'd the bolt, in order to improve access when I had to grind the radius arm bracket rivets.

Here's the left radius arm bracket:

The witness marks are from the now corrected issue. All the bolts seem tight so I don't think this is the issue.

Left front body mount:

Nothing to say here. Right front body mount:

Again, nothing to say. Right radius arm bracket:

No evidence of bracket movement. Also, before the fix that bushing wasn't against the bracket like it is now (and should have been).

Right center body mount:

Probably the 2nd worst one here. Like it's brother on the left, rusted out washer.

Finally, the right rear body mount:

Same old thing as before.

I'll also note my leaf spring bushings, at least the three stock ones, are dry rotted pretty bad but don't seem to have any play (yet). I say three because while the same shop did both of my shackles and rear leaf mounts, it was at different times and on only one of them did they also do the spring eye bushing. I have replacements but I don't have access to tall enough jackstands to support the frame high enough to remove the springs.

So, maybe the body mounts are the culprit?

 

[Mark_88]

I've actually had body mounts disintegrate and they do add a bit of music to the ride. The surface rust doesn't always indicate problems with those unless you want to remove them...then they can be a pita.

You might be able to check them with the help of a strong friend...just get into the position you took the pic and have them rock the body...fairly strongly might be needed though.

I can't see your images for some reason...they appear and then they vanish and I can only get them back by relaunching them...but...probably just my computer...

 

[ratdude747]

I've actually had body mounts disintegrate and they do add a bit of music to the ride. The surface rust doesn't always indicate problems with those unless you want to remove them...then they can be a pita.

You might be able to check them with the help of a strong friend...just get into the position you took the pic and have them rock the body...fairly strongly might be needed though.

I can't see your images for some reason...they appear and then they vanish and I can only get them back by relaunching them...but...probably just my computer...

I did try moving the body. No noise but the bushings were expanding and contracting. I'm suspecting that the rubber has degraded as IIRC they aren't supposed to be like marshmallows?

Tinypic may be having problems. Normally I'm against offsite hosting but I'd chew through the storage cap way too quick.

 

[ratdude747]

Swapped the tranny mount, no change (as expected).

I'm hearing it on bumps a bit too. Would bad I beam pivot bushings do that?