Driveline Clunk

[michibronc]

I'm new to the world o' Bronco (bought a 96 xl last week and I'm lovin' it!). It's got only 86k on it and runs beautifully. I've got the 351W and when I accelerate from a stop or when I come to a stop I get a dull sounding clunk and I can feel it. It seems to only happen when there's a decent change in speed and the suspension rocks back or forth. Barely accelerating or braking from a slow speed gently doesn't cause the problem. I've laid under the truck while my brother pushes down on the rear bumper repeatedly and it seems that the rear driveshaft slides in and out of the transfer case about 1/8 inch (normal?) and I can hear a slight clunk coming from the transfer case.

Everything works fine in terms of 4wd. I seem to only get the clunk when the suspension travels. I'm wondering if anyone else has experienced this problem and if they have any insight into how to fix it. It seems as though the driveshaft is supposed to be able to slide longitudinally because it has a black rubber accordian shaped boot right in the middle of it. Is that supposed to slide and could that be the clunk? I'm really at a loss here. Any help would be GREATLY appreciated as I'm in the heart of Chevy country (Flint, MI) and a good FORD mechanic is hard to find!

 

[firelt90bronco]

Mine had a klunking noise from the driveline, turned out the truck had locked itself in 4 low and the dash display didn't show it.

 

[madmax]

Mine had a klunking noise from the driveline, turned out the truck had locked itself in 4 low and the dash display didn't show it.

I had a clunk in my driveline too, seemed to be a delay from when i let off the gas to when you feel it engin brake, kinda like downshifting to engin brake and sidestepping the clutch only worse. then when you'de hit the gas again it'd again slam forward.

At first i thought the trans was coming unbolted from the cross member but i checked over the entire drive train and nothing is working loose. Nothing was making any strange noises so i couldn't find the exact source of the problem. A couple of garages i talked to thought it was the tcase so i threw in the np208 i had laying around. I'm not too concerned if its the rear cause im changing that too, just hope it isn't coming from the tranny. It's not the strongest unit out there, the aluminum housing 4 speed overdrive tremec RTS. i ripped it out of an 83 F150 that i bought as a parts truck.

I have yet to get it on the road because I jumped right into body work after swapping the Tcase, so I don't know if I fixed it yet. Any suggestions would be greatly appreciated.

 

[Seabronc]

One source of start and stop clunks is the radius arm bracket getting egged so the arm moves up and down.

Good luck,

>-

 

[madmax]

One source of start and stop clunks is the radius arm bracket getting egged so the arm moves up and down.
Good luck,

>-

Hrmm, nobody suggested that yet, I'll have to check it, guess if it's good I will put my BW1356E and my NP208 up for sale. The 205 should basically last forever.

 

[sbveenker]

yes i had pretty much the same thing with my 94. my neighbor told me to try greasing the driveshaft splines and it went right away!!! try that

 

[Mike @ Tracy]

Have you checked the U-joints? Sometimes the obvious gets overlooked

 

[michibronc]

Thanks to all! I appreciate you taking the time to fill me in. I haven't checked the radius arm bushings yet - that could well be it. The U-joints seem to have no slop. Is there another way to check for bad universals other than looking for slop?

for sbveenker (or anyone else!), is the driveshaft spline within the accordian shaped boot in the middle of the driveshaft? If so, how do you go about replacing it once you cut into it?

 

[Justbust1n]

Thanks to all! I appreciate you taking the time to fill me in. I haven't checked the radius arm bushings yet - that could well be it. The U-joints seem to have no slop. Is there another way to check for bad universals other than looking for slop?
for sbveenker (or anyone else!), is the driveshaft spline within the accordian shaped boot in the middle of the driveshaft? If so, how do you go about replacing it once you cut into it?

yeah if it gets tight in any spots when you rotate it or if the is a squeak while doing so , this either means that you need to grease them if possible or they are going bad, i didnt have the greasable kind but now after i got mine rebuilt i have the greasable u joints, definatly worth the money

 

[madmax]

Have you checked the U-joints? Sometimes the obvious gets overlooked

yep

 

[Mike @ Tracy]

I had a jeep with a bad trans mount and under hard excelleration the t-case would bump against the floor board.

 

[Roadkill]

for sbveenker (or anyone else!), is the driveshaft spline within the accordian shaped boot in the middle of the driveshaft? If so, how do you go about replacing it once you cut into it?

Yes it's inside the boot. To grease the splines, just remove the drive shaft and slide the two halfs apart. Before doing this, mark all the parts (including where the ends mount to the t-case and rear diff) so that you can put it all back together the exact same way. This is important to ensure that everything stays balanced and you do not get vibrations when its back together. Once its apart, grease it up, slide it back together, and re-install on the truck.

 

[Sarahs85Bronco]

LOL AFTER my t case went lol i broke my yoke on the rear drive shaft the part connected to the t case. i went to pick in pull grabed another whole drive line as they dont just sell the yoke (no one does!) it was $45 and its perfectly fine now. my t case ~sigh~ on other hands is still not!

 

[michibronc]

Thanks for the knowhow, Roadkill. I'll give it a shot this weekend - that seems like the most likely source to me. Good time to check the U-joints more closely anyways.

Yes it's inside the boot. To grease the splines, just remove the drive shaft and slide the two halfs apart. Before doing this, mark all the parts (including where the ends mount to the t-case and rear diff) so that you can put it all back together the exact same way. This is important to ensure that everything stays balanced and you do not get vibrations when its back together. Once its apart, grease it up, slide it back together, and re-install on the truck.

 

[motoxscott]

I just picked up a '95 and have the same issue. I'll let you know what I come up with as well. It really sounds like its coming from the rear of the truck.

- Scott

 

[sbveenker]

Thanks to all! I appreciate you taking the time to fill me in. I haven't checked the radius arm bushings yet - that could well be it. The U-joints seem to have no slop. Is there another way to check for bad universals other than looking for slop?
for sbveenker (or anyone else!), is the driveshaft spline within the accordian shaped boot in the middle of the driveshaft? If so, how do you go about replacing it once you cut into it?

Hey sorry i was slow. but i didn't take my drive shaft out. i just un did the little clamps holding that acorndian shape boot then i just shoved the grease gun in and greased it up. then after a little driving it went right away sorry if i was too late but o well hope it works

 

[Refalova]

I had the same problem. Mine ended up being a worn leaf spring.

 

[Big_Ford_POS]

Thanks to all! I appreciate you taking the time to fill me in. I haven't checked the radius arm bushings yet - that could well be it. The U-joints seem to have no slop. Is there another way to check for bad universals other than looking for slop?
for sbveenker (or anyone else!), is the driveshaft spline within the accordian shaped boot in the middle of the driveshaft? If so, how do you go about replacing it once you cut into it?

the u-joints might be good but the centering ball between the front two u-joints (cv joint) could be taking a $h%&. I had a 89 ranger with the same joint, a clunk and a bad vibe, the u-joints were soild, i checked them looking for the vibe. a week after i bought the truck, i was pulling away from a toll house and after a bang and a pop and a shake so bad i couldn't see straight, i found out that the joint broke, but the u-joints held drive shaft together. Thus destroying my transfer case and bending the output shaft in the tranny. It was bad. Now i always take apart that joint and inspect it when i buy a truck with it.

 

[motoxscott]

I checked the driveshaft and the slip joint was fine. Sounds like its either coming from the rear end or transfer case like they have too much play in them.

- Scott