Very wierd clunk feeling

[SpaceHiker]

I'm a new owner of a 98 Ranger Supercab 4x4 manual tranny. I've read about the slip yoke issue and read the TSB about it, but the description in the TSB does not completely agree with what I am feeling, so I don't know if the slip yoke is my problem or not. I was hoping some of you might recognize this problem when I describe it and steer me in the right direction:

I think what I feel may technically be considered a "tip-in clunk", but it's very strange. If I am coasting along (for instance if I'm moving slowly in a traffic jam) and I give it a little throttle, it begins accelerating for about 1 second and then there is a strange type of clunk (not a sound, but a feeling) like something suddenly grabbing. I've driven trucks with a loose ring/pinion mesh before and this feeling is nothing like that, because in my case the truck does accelerate a little bit before the clunk occurs. It happens in both 2 and 4 wheel drive (and yes my 4 wheel drive does engage properly).

At first I thought the driver's seat was loose, because it is exactly that type of feeling, but I checked and that's not it. The cab and suspension seem tight, so I'm thinking it's something in the drivetrain. Then it began snowing here and hasn't really stopped, and I don't have an indoor place to work, so I'm not at liberty to jack it up right now and check around for drivetrain play. I was hoping you guys might have seen this before and could help me shorten my search.

Maybe it is the slip yoke problem, but the TSB mentions that it occurs during start/stop, and I don't feel this problem during start/stop. I only feel it on acceleration after coasting.

 

[4LO 4.O]

I know what your talkin about, taking off from a stop you give it it a little gas and start moving then a little clunk from the rear like the gears where catching up with the drive shaft. Mines done the same since Ive owned her. I replaced the u-joints and still it's there so i guess it's the slip yoke. It doesn't seem to do it when there's some weight in the bed.

 

[Chic N Stew]

does it do it when going from reverse to drive, if so, your drive shaft bolts maybe loose, it did it on mine, at the rear

 

[MAKG]

Look for something heavy but unconnected to the drivetrain to be loose. Like the exhaust pipe or the fuel tank or the spare tire.

When the engine is cool or cold, climb under the truck and start wiggling things.

 

[4x4junkie]

I'd still say it could be the slipyoke. Any time you accelerate, whether from a stop or not, the axle moves on the leafsprings, causing the slip to move.

There's also a possibility it's the engine missing slightly. My '94 4.0 started making a "noiseless" clunk sometimes when light throttle was applied at low RPMs, new plugs & wires cured the problem. (my brother's '98 4.0L seems to be doing the same thing as well, although no attempt has been made to replace the plugs & wires on it yet)


Hope that helps