Hi. Chasing a "pop" in my front end and would like to get some opinions, because I'm about at the end of my wits!
Van is '96 Aero AWD with 125K miles. Pop only occurs when backing up with the steering turned to one side... it will roll about 10 ft and then POP. Sounds like left side, but hard to tell because its so loud. I can feel it in the floorboard of the van right under my feet. When I turn the wheel the other way (as in backing out of a parking space and then moving forward) it will POP again... just once. Other than that, its perfect.
So far, I've replaced lower control arm, drivers side. Upper ball joints both sides. Upper control arm bushings drivers side. Sway bar bushings, front. Front shocks. Both front axles. Front diff mountings. and it still POPs.
Its definitely not the transfer case sensors. Only pops once going backwards (like something is moving or twisting) with the wheels turned hard over and only once when going forward again (like its popping back into position).
Everything is tight. Cannot make it pop any other way.
Ideas? I'm thinking front drive shaft joints or transfer case chain.
Thanks for any ideas.
KenP

 

> I can feel it in the floorboard of the van right under my feet

There is a bracket mounted to the Dana 28 that locates it, that breaks sometimes. Sorry I can't be more specific, it has been years since I have been under an AWD.

 

Hi KenP:

That sounds so similar to this gentleman's problem. I think the fix is near the end of the thread, and it requires a big impact wrench.

https://www.ford-trucks.com/forums/s...d.php?t=488369

 

I had a similar "pop" in my front end that happened in about the same way; usually from large changes of directions in the steering, like while parking. I also replaced my control arm bushings, checked that the ball joints were OK, and tried to find any kind of looseness in the steering system. Then earlier this week, I started to hear and feel rattles and shimmies when going over bumps. I found the left side outer tie rod end very loose, so I had to do an "emergency" tie rod replacement yesterday. Something that made that a lot easier than my previous jobs was a separator tool from Harbor Freight. (Having one of those down the street is really convenient.) I got Moog replacement parts, which looked to be about the same dimensions as the originals. But after the replacement, the wheel was still cocked a little, despite my best efforts to keep make the same number of turns on the rods, so I'll need to get it aligned before long. But now, it seems that the "pop" or "thump" has gone, so I think it must have been the loose tie rod end all this time.

Looking over the new and original tie rod ends, I see that the originals look almost as if the ball stud was encased in rubber, and has no provisions for lubing. The loose one looks like a chunk of the rubber fell out recently, which allowed it to flop around a lot more than before. This was probably what caused the rattling I suddenly started to hear and feel. The other one seems normal, but with the rubber casing, it's really hard to tell if it's worn. I replaced it anyway.

The new ends from Moog look like they have the ball stud sitting inside a steel shell, which in turn moves inside the body with the stud. Looks like a trick to give them greater range of motion but still have support. That's kind of refreshing to see; an upgrade designed to improve functionality, instead of just cutting cost.

 

Had the same type of "pop", not in my Aero but in a T-Bird, pop 1 time going forward and not pop again untill I would back up and then it would pop 1 time. Turnnedd out to be a dry rubber bushing on the front sway bar. Shot it with WD-40 and not more popping. Droveme nuts looking for it. Allen

 

Thanks all for the ideas. Yes, I've pulled the front diff and checked the mounts, they all look fine. New bushings. Tie rod ends are tight, but I haven't changed them... probably worth a try. I would think if it were a tie rod end, I'd feel it in the steering, but I don't.
Forgot to mention earlier that I also replaced both front wheel bearings... but no difference.
Checked the subframe mounts and bolts with a 3 ft bar. They are tight.
Drove it around a parking lot today... as long as I'm going forward, it is silent and smooth no matter how tight I turn the wheel. (I'm sure folks thought I was nuts making tight circles in the parking lot!) Either way is fine.
Put it in reverse, roll about 6-10 feet and POP! Put it back in drive, roll it about 10 feet and POP! Just once.
Hold the steering straight ahead, and it doesn't pop no matter what I do.
This has become a challenge now...
Thanks again, KenP

 

back to that parking lot for more testing, this time with an assistant to do the slow driving while you listen from outside and up close
if you can't pinpoint the "pop" to one wheel well and it sounds more under the van, remove the dog house hatch and lay in the passenger seat to listen to tranny and transfer case while assistant slowly rolls the rig

then disconnect AWD controller under seat or pull AWD fuse and see if POP is still there...since the noise involves tight turns, suspect either the AWD system or the CV joints

 

Thanks. Unfortuately, I've been there and done that.
Disconnecting AWD makes no difference at all. I've had the box under the driver's seat disconnected for the last week.
Having my spouse drive it slowly in a tight turn backing up, the pop seems to come from the left front hub.
Have replaced both front hub bearings in addition to installing my third front axle on the left side in two weeks. No change.
I agree about the C/V joint, which is why I've changed that axle three times in recent days. No change at all. Plus, only pops once... just once. And then again when going forward... just once. I am getting good at pulling axles though...
Strange, eh?
KenP

 

Have you put any lube in the sway bar rubbers? Like I said my T-bird did this, the dealer that I got the car from, their machanics could not find this and it took me 2 days with the car on jack stands to chase it down.

 

I replaced the end bar links/rubbers as part of my "diagnostic" chasing... it didn't change anything, but I'll admit I didn't put any lube of any kind on them. I'll try that this weekend.
Thanks, KenP

 

I just spent 20 minutes typing a reply and lost it! Anyway a thread posted way back suggested a lose transfer case chain. They had it replaced and it fixed the pop. It's about the only thing you haven't tried. I don't think it's that difficult to do, the transfer case isn't lite and working under a vehicle isn't on my fun list. My Aerostar ('91 AWD 87,000 miles) is popping also and everything seems tight. If I remember right the chain can be tested by raising the front end (in Park) and torguing the front wheels forward and backward which stresses the CV joints as well as the transfer case chain (I think). Of course you will have to lift one wheel at a time or the other wheel wil spin. Let us know how it turns out.

 

kenp,
Since this 'pop' is reproducible on turning situations only, I can't see how this would induce any pressure differential on the transfer case or chain. Since you've replaced everything, the obvious place to look is non-changed components. I'm wondering if your steering rack is loose?

 

Aerocolorado you are absolutley right. If it happens only when turning like he said (I read it to) then it wouldn't stress the transfer case chain. DUHH....what was I thinking!

 

RPin,
I've uttered the same words many times on this forum, so you're certainly not alone. When it comes to solving a problems, most of us are just throwing darts and hoping for a bulls eye, so the more opinions the better.

 

Yea, I thought about the steering rack too, but it seems to be pretty tight in there. I'm also pretty convinced that if the rack moved, I'd feel it in the steering wheel, but I do not.
Transfer case chain is indeed loaded differently when turning... when wheels are straight ahead, the front and rear driveshafts turn at the same rate, In a turn they don't. Whether that load is enough to cause a problem, its hard to say. Differential action in the transfer case should handle it under normal circumstances, except when the electric clutch is engaged. Which is why they pop if the case sensors go bad.
I wonder if the electric clutch in the case is dragging or otherwise not releasing all the way? Hmmm, will have think about that some more...

KenP