OK guys I need some quick advice. Here's the situation. After a very long year of work, this fulltime military howitzer mechanic finally gets a chance to go on vacation to MN Friday for some fishing and low impact offroading (or so I thought) After a long process of internet truck buying and title fun and games, I finally got my 94 Bronco, 351W, E40D, 8.8 limited Slip, Dana 44, 3.55 gears on the road today. 85K miles. I have driven it 50 miles tops since I bought it.

Runs super but it has a nasty double clunk when you take off forward in 2WD. Definitely two distinct noises separated by a quarter second maybe. There is no gear whine, grinds or any noises when you go down the road at any speed. I have frantically tried to service it before leaving on a 600 mile one way run with a 17ft Alumacraft in tow. The boat is fairly light, but it ain’t a jon boat either. It catches some wind. Here is what little I know after changing all the fluids. The transfer case Mercon fluid was clean as can be. No metal whatsoever. The 8.8 Ring and pinion look fine, the spiders and side gears look worn (wear lines the same direction the gears run, you can catch them with a fingernail). The differential fluids were black and probably never changed, no sign of metal shavings at all though. The U-joints are stock but appear tight. The diffs have more slack than I think is correct when up on the jackstands. The transmission seems to be pretty much OK. No slipping, it shifts OK as far as I know. Electronic trannies all seem a little weird to me.

I would have time to change out the spider and side gears, assuming I could get them tomorrow. I guess my question is how likely is it that the transfer case is acting up and am I likely to have catastrophic failure blowing down the interstate all day if I drive it gently. I am a pretty experienced mechanic but 4x4 drivetrains are a definite weak area of mine.

 

On my 87 when it drops into gear it makes a big clunk that sounds like a ujoint fixing to drop, but there all tight, a reputable local transmision,transfer case shop here told my it was coming from play in the shafts where the transmision an TC bolt together, it was par the age and not to worry bout it ? i dont know if this is the same as what your experiencing, but i'd like to know what you find wrong, GOOD LUCK! DW

 

I have a 90 bronco, same clunk. I have done the same as you. I have searched high and low for what ever is making the noise, but to no avail. I have come to the conclusion that if it runs good, drives good and isn't broken, don't screw with it. My only other hope is to strap myself to the bottom of my bronco and have my wife drive around till I can see what is making the clunk.

 

Separate the halves of the rear drive shaft, pack the splines with heavy grease, reassemble. Situation cured. Common problem..... lots of posts on the boards regarding this.

 

RESTORIT - Thats a very interesting, would have never considered that, but will definately try it, i couldn't hurt !! Thnx DW

 

Thanks guys. Tracked down a distant relative of mine has been working in a rear end/driveline shop and managed to get him over tonight. He has considerable experience with these model components. He told me the first light clunk was almost certainly slack in the transfer case chain. Not to sweat it and we'll rebuild it at our convenience for cheap.

I believe he correctly diagnosed the second noise before we removed the 8.8 cover. He told me the side gears were probably smoked along with the clutch packs. The clutch packs were just starting to come apart and I doubt any noise can be attributed to that. The side gears and spiders were torn up bad upon removal for closer inspection. The spiders are climbing around from the severe clearances. You could see them crawling up the pin and rocking real bad up when the driveshaft was turned (I should have bothered to put the thing in neutral while the cover was off a few days ago). Thrust washers wiped out etc. Amazing to me that the ring and pinion look fine with no excess gear lash, discoloration or pitting.

Anyway, she goes back together late tomorrow night after work. Looks like about $200. I don't want to know what a Ford dealer gets from an out of state vacationer pulling a boat.

 

Sorry you had a problem but glad you found it at home!! Good luck DW

 

I assume your cruise control does not work either? If what you say about the gears is correct, then you must have a lot of shavings in your rear-end lube, and some of it must have built up on the ABS/speed sensor. If not, then something else is causing the clunk-clunk or your gears are disolving instead of wearing away.

 

Seabisquit

No problems with any accessories yet. Like I said, it has only been on the road 50 miles or so. Cruise etc worked fine. Gears apparently wore slowly over time as I saw no signs of shavings, chips etc when I changed the lube. Lube was probably factory if I had to guess. Previous owner was probably tugging a decent size trailer around or something, with little maintenance. Who knows.

You can look at the differential in motion and it's very obvious it's not right. I should have noticed this three days ago. I'm lucky the carrier and R&P aren't hurt.

 

Got the side gears, spiders and clutches replaced tonight. The loud nasty clunk is completely gone now. I have the minor noise that sounds like it is upstream from the diff. I'll grease the driveshaft slipjoint as recommended here before I go tearing into the transfer for no good reason. The shaft looks like it has never been touched. Thanks

 

Have the same clunking problem, and after reading many posts on it, many members have said to grease the spline, so tomorrow I have something to do, thanks.

 

Yes slipshaft on my driveshaft was definitely making a racket too. Greasing that, and getting the 60 degrees of slap out of the rear differential did the trick. I believe my T-case is just fine. We'll see I guess.