4 whl lo clunk

[gthawus]

99 Ford Ranger 4 whl drive manual trans

Hi! Can anyone help to identify the source of this clunk? I use 2nd gear, 4 whl drive lo daily going up and down a track on my property. Recently, but only periodically, I get a big metallic CLUNK going either up or down the grade. And only in 2nd lo. Have never had it happen in 1st low or 1st high, the only other 4 whl dr gears I use. I'm going very slow and it seems to always happen when speed is consistent and there is no jarring motion from dips or bumps. The track it happens on is about 1/4 mile and it might happen only once along the way and I'm able to continue on in the same gear in a normal manner. Because it happens only in 2nd lo and it does feel like the source is directly below me, I'm inclined to think it's coming from the transfer case. Perhaps some sort of a momentary skip or slip? Thanks

 

[mdixon]

I just did a live axle swap from a 2000 and the same thing has been happening, but it's not isolated to 4lo it happens in 2nd gear on a grade and only intermittent. I'm thinking its excessive driveline play or a shift fork issue in the transfer case. Have to do a little digging an see if I can find anything binding up front.

 

[ab_slack]

Just a thought, but this wouldn't apply if you been doing this regularly for a long time before this started happening without problems. Unless you got a new tire or two.

You said it happens when there isn't any jarring from dips or bumps. Do you feel anything in the wheel when it clunks? I am just wondering if there is enough wheel slip to prevent winding up front to rear tension. While normally this only happens on dry paved surfaces, I've been on some hard packed dirt/stones on a couple occasions where I have experienced this. Bumps and stuff can give opportunity for slippage to release the tension on a surface that is otherwise not so giving of slip. So your saying this happens only when there isn't bumps makes me wonder.

Usually there also needs to be some amount of turning (even a slow amount) to cause front/rear speed difference that will wind up tension. If your tires are not matched it can happen in a strait line. This is why I mentioned that if you recently replaced a single tire or even just a pair this could explain why it has started recently.

As for why it happens in second and not first, tension should be able to build up either way if the surface is hard enough, but in first gear there is a higher likelihood of delivering more torque to the wheels. More torque at the wheels has more likelihood of generating slip at points that allow the tension to be released before it builds up and makes a clunk. More likely than when in second.

These are just a thought and would occur without anything being wrong mechanically except perhaps different size tires. I am sure there are mechanical issues that might explain it too.


What kind of surface is it?

 

[gthawus]

Hi ab_slack & mdixon! Your idea of a front/rear tension slip sounds plausible. But it brings more questions into my mind. Tires are good and equal. This track is graded with a light layer of rock. It's a little uneven from people driving up it with only 2 whl drive. Rock is expensive and my idea is to add it as needed. Anyway, I've been driving up and down it for over 10 yrs and this has only started happening in the last couple months. Currently to avoid the clunk only 1st gear 4whl Hi is used but this makes me go faster than I'd like to, but it there's never been a clunk in it. Couldn't you get a tension build-up here too? I don't feel anything in the steering wheel and the amount of turning is slight. Thanks for your help. gthawus

 

[ab_slack]

You are right, 1st gear in 4H would be similar. I can't explain that.

Only other thing that occurred is maybe a slipping locking hub? But again don't know why specific to second gear.

Unless it is speed related and combination of 4L and 2nd gets you in that speed and rotations

maybe a u-joint starting to go?

 

[mdixon]

turns out my pinion gear started hitting thr pinion shaft in the rear end. idk how but thats it. pulled a chevy out of a pit yesterday and on my way home the rear bound up until the pinion gear sheared pieces off the pinion shaft.... OH NOOOOOOO!!!!!

luckily theres a donor in my front yard so rear end swap then a rebuild on the other.

 

[mdixon]

btw when i bought my truck it was terribly neglected... ive been fixing every weak link as i find it... first hubs then springs now driveline slop... i really hate people, especially when they dont take care of their stufff.... errrrr