Thumping in a BW4405 ?

[MarkVIII]

Calling all you Transfer Case gurus. I'm trying in vain to determine the cause of a thumping noise coming from under the drivers floorbaord. It happens under acceleration, coasting and braking. I have replaced u-joints, ball joints, brakes & shocks - with no improvement. I have also swapped out the front shaft - and while this made some difference, it has not eliminated the problem. I have had the tires rebalanced and aligned and the front bearings checked by 2 shops. The truck runs awesome save for this noise. All 3 of the 4x4 settings (4auto, 4H & 4L) work. I pulled the transfer case skid plate and noticed there is a slight in & out movement on the front output shaft mount - maybe 1/4". I can also rotate the front mount about 1/8 to 1/4 of a turn each way, the rear shaft moutn is tight. Is this play normal? Would this be the cause of the noise? and more importantly can this be rectified at a reasonable cost by me?

I'm not affriad to get my hands dirty. Not that I'm a Ford mechanic by any stretch but I've done my share of J-mods and rebuilt many a small block. so I should be able to handle it (hopefully). Its a '98 XLT 4L SOHC with 168kilometers (105k miles). Thanks very much in advance guys.

 

[IZwack]

Clunking during acceleration, deceleration and braking can sometimes be due to a loose pinion in the rear axle.

Disconnect the rear driveshaft from the rear axle and check the rear axle's input flange for any up-down play (a bit of rotational play is fine).

 

[MarkVIII]

thanks IZwack.
I was able to get under the explorer and pull the drivershaft yesterday, no movement at the rear differential mount. Is play on the front mount of the transfer case normal? I'm not familiar with 4x4's enough to know if the rotation play and in/out play is normal? the only other thought i had was bad front hubs. Altough i would imagine some other noise/sypmtons of a bad hub would be present? I have done the "s" turns in a flat lot hoping to discover a bad bearing - but no luck. all seems well -other than the thumping from below my feet.

I'm still thinking the transfer case play is the culprit. Its just a lot of money to replace a transfer case that i "think" is the problem. wish i knew for certain. cheers.

 

[CDW6212R]

Welcome, and try to replace that trans mount if it's that loose. It may still be the TC, but things like the mount cloud the issue. Check the torsion bar pads also, 95-97's have a kevlar pad which wears out with some mileage. That might be more of a squeak though. Regards,

 

[MarkVIII]

CDW,

I'll check on the trans mount next -probably wont be able to get under the Ex again till next weekend due to my schedule.

While discussing Traction bars. I took a look at them but didnt notice any kevlar pads? I take it these should be at the adjustment block? When looking at the bars from the front or rear (i.e looking down the bar) - both ends have a hexagon style head. Like a bolt or nut - and those ends fit into a matching reciever. Both ends of mine look like there slipping. Meaning there is not solid contact all the way around between the receiver and the "bolt head" end of the bar. However the bar is crazy tight in there and has no play that I can detect.
Thanks again guys - I'll figure this truck out yet (and if i dont spend too much, the wife has given the green light for a flash tuner - although she doesnt quite understand what it is )

 

[CDW6212R]

The torsion bar is under constant load(twist), that is what holds the entire weight of the front end. The adjustment key is a lever attached to the bar at its back, which is resting on the adjustment bolt. That key is about 8" long or so, and the large end has a kevlar pad on the top side which rests against the truck frame.

The 98-01 trucks have a special pocket built into the frame where a special pad(isolator) is that the key rests against. Those keys have no kevlar material on them, it's a better design. The 95-97 trucks will need their keys replaced at some time, like at 100k miles.
Here's my 99 torsion key/pad area with the cover plate removed.

 

[MarkVIII]

Thanks CDW,

When I'm under there, I'll check on those pads. The end of your torsion bars, seem to fit much more snug than mine. The hex head part on yours looks tight all the way around. Mine looks likes look a wrench on a bolt thats about to strip.

 

[CDW6212R]

The keys are made of cast iron, and cost under $100 I believe.