front grinding / binding sometimes... hmm don't know how my truck actually works???

[budwich]

I have a 96 xl 4w. Of late, there seems to be situations (after a lot of stops... turn off, turn on... parking lot, to parking lot stuff), that I get a very coarse grinding at slow speeds from light turns either left or right just before straighting out or during the straightening out. It doesn't happen all time and I have figured out what the "kicker" is to predictably cause it to occur. It would appear that it is locked in some form of 4wd but the lights on the dash show no indication and I haven't engaged 4w auto or 4w lo for months. I got thinking about this and then wonder how things actually work???? The reason for this quandary, it that the grinding only occurs once for any start / travel sequence. Once it has happen, it will not happen again regardless of the number of turn or changes (forward or reverse) that have occur. So my questions are numerous and I hope someone will help direct me with some knowledge so that I can figure the problem before it is severely damaging.

First question: If you haven't engaged any 4w operation in a while, in general during any startup, is there some sort of "sequencing" that sets the transfer case / shift more into some "known" state.... hopefully 2wd?????

Second question: There are some vacuum lines associated with the front end / 4wd system, what do these actually operate on... ie what are they trying to engage / engage? Do they operate differently for 4w auto versus 4wd lo???

The reason for the "two parter" above.... is the

Third question: When I select 4w lo, I get a signicant "clunk" and the 4wd lo engage (light comes on) and I can move accordingly (ie. up ramps and stuff) which I can't seem to do in 4wd auto. In 4w auto, there is no "clunk" but there is a light.
I guess my question is... Is the "clunk" caused by the vacuum operation of something??? or is this the shift motor on the transfer case.... and if its the shift motor "clunking", then why isn't there a corresponding "clunk" for the 4w auto and is this a "normal" sound?

The grinding is very worrisome but overall when the truck moves down the road, the transmission appears to be / sounds OK in terms of shifting up down / step down etc.

thanks for any guidance.

PS. both hubs (auto) have been replaced over the past year (not at the same time) for bearing issues.

 

[budwich]

It would appear from some events of "grinding" that they occur if the truck has been used a bit (lots of restarts or a long drive) that if during a restart, I don't allow the "4w Hi, 4W lo" lights to cycle thru their "initialization sequence" before putting the vehicle into gear, then there is a good chance that I will get a "grinding" occurence during that particular trip sequence.... almost like something didn't initialize properly and the truck "thinks" its in some form of 4w drive.... but the lights on the dash are out indicating it should be in 2wd. So, does any one know what the truck is trying to do during the start sequence (after starting) and the 4w hi / 4w lo lights are on for some initial period???? Is it operating any transfer case gears / clutches / relays to put them in known states???? It would appear that if I don't allow that sequence to complete, then I have the "grinding" issue later on.

 

[budwich]

I have now found that I can stop having the "grind noise" IF I start out forward by manually shift the gear lever into "1"... then once going, placing it in "D"... from then on, regardless of whether I shift into reverse or otherwise stop or start, I don't have a problem. But after a "key startup" ( stop, turn off, startup and go), IF I choose "D", then there is a good possibility that I will have "grind noise" happen prior to the 1-> 2 shift... maybe hard to tell.

My guestion: what gets set differently on a manual shift into first versus a "auto" / "D" selection????? The "grind noise" doesn't happen all the time but often enough to be "frightening". I hope to drop the pan shortly but was hoping someone might have an idea of what to look for once I have dropped it. Thanks.

PS. It appears to operate "normally" thru most shifts including step down and OD on / off although occasionally I do get a "harsh" step down. Its got 234K km on it.

 

[jtison]

Automatic hubs, perhaps?

You never said where the noise was coming from. Is it from the front hub assemblies? Just because you recently replaced them doesn't mean the entire system is OK. If your noise really is coming from the transfer case or the tranny, my experience can't help you.

I had something similar happen in my '94, which turned out (after chasing wild geese for about a year) to be automatic locking hub failures. Related to this issue was a failed radius arm bushing (yeah, really ... it's a long story).

The noise and "grabbing sensations" I experienced happened on one side at a time (never did both hubs scream at once) and only when turning slowly with any kind of thrust/axial load. It was worse when I turned to the left, but sometimes happened on R turns, too. The noise was loud, embarrassing, and turned heads in a parking lot, where it seemed to happen the most.

I can explain why this happened to me; but it's a long explanation and may have nothing to do with how your '96 works. If we share symptoms, respond, and I'll go into the theory of how these noises happened and how I fixed them in my case (YMMV). My problem had nothing to do with neither the transfer case nor the tranny ... the fix was keeping the front axle absolutely perpendicular to the drive line in a turn (as in radius arm bushings <sigh>).

How the auto hub-based 4WD system works: When you push the 4x4 hi or lo button on the inside of the cabin, an electric motor engages the transfer case, which starts turning the front differential, and causes the axle half-shafts to push outward a little bit due to centrifugal force. This motion pushes the lockring outward, which has 3 or 4 sharp, steep teeth on it. These teeth engage with corresponding tabs in the auto hub housing, which stops the housing's innards (which have splines on them) from freewheeling. At the same time, the half-shafts themselves push into those splines, and voila, you have 4WD.

 

[budwich]

I recently dropped the transmission pan to check for "things" in the there..... Nothing but fluid.... great... . I continue to do the "start in 1st manual shift" work around and haven't heard any "disparaging" noise. I can't afford to have any major work done. Don't know what to say as to where the noise is coming from when it does happen.... certainly from the "front" part of the vehicle and not from the rear (ie. back axle / differential). Your comment about it being the "auto locks" is a good possibility as initially that's what I thought as the "grind" seemed to last about "one wheel rotation". I guess I need to look at your hint about the radius arm bushings... heck I don't even know what those are. Thanks again for the ideas / comments.

 

[jtison]

Bushings are at the ends of the arms

Find a front shock absorber, either side. Its bottom bushing is attached to the radius arm with a nut on a stud. Follow the radius arm rearwards. It ends at a black sheet metal bracket just behind the front wheel, fastened with a 23 mm nut.

The radius arm bushing (rubber) is hidden inside that bracket (actually, half-in, half-out) -- you should be able to see half of it close to the RA nut & washer; but that's not the business part of the bushing. You have to remove the bushing to inspect it (kinda sucky, but that's Ford's engineers for ya).

The passenger side RABs fail most often because they're located so close to the catalytic converter (heat kills rubber). AFAIK, 1996 was the last model year with this design error. If you replace your RABs, I suggest Moog thermoplastic replacement bushings -- so far (1 year), mine don't seem to be melting

There are many, many threads on this board about RAB removal and replacement. Search is your friend

 

[budwich]

thanks...yep the search was the plan....this morning. Anyways, in my search "travels", there was links to "partsamerica" site to look at pictures. However, when I entered my 96 vehicle in the site, it responded that the radius arm "stuff" was not part of the "target vehicle" but that I could "highlight" the parts if I choose different vehicle.... so I choose a 94 and sure enough they became "viewable".... sooooo, this would appear to indicate that "perhaps" 96's don't use the same system... ?????? (actually 95 doesn't appear to have them either). So I am not sure where that leaves me.... I guess further "study" / suggestions.

 

[BLKLTDV8]

94 was the last year for that antiquated swing-arm front suspension. 95 and up all have independent front suspension. You will not find the bushings the others are talking about. Your noise sounds like it has to do with the transfer case.

 

[budwich]

that doesn't sound good... although I only used 4wd a couple times at best (during snow conditions).... so maybe just leave well enough alone???? Are there any "inspection plates" or equivalent or does it involve a more "rigorous effort" (ie. removal and bench effort) to see what might be a problem with xfer case????

 

[budwich]

It looks like this is more transmission than xfer case as recently, it appears to be worsening in terms of transmission function with the cold weather. It now appears to be very slow to shift out of park to drive or 1st (manually selected). And recently the O/D started flashing which is a "sign of bad news". Could this be as simple as a weak / dying shift solenoid or something worse????.... when it doesn warm up, it seems to run normal. Of course, I don't need a transmission xmas present... :-( most shops are on reduced hours so I don't know when I can get some one to at least read the codes to see if there is a "hint".