Strange Lurching Diagnosis Help

[INHWMW]

Hey all, I need some help here. I've got a '96 4.0 4WD that's acting up and I don't know what to fix. I'll describe what's going on and maybe one of you could help me get a direction to go in.

The truck starts just fine, and when it's started cold the issue doesn't show. But if I start it an hour-ish after driving, I will put it into drive and it just won't move. I can throttle though it, but soon after it lurches to a stop again. After I push through it a little bit, whatever "it" is loosens up and it doesn't completely stop but turns into a lurching kind of motion. A stop-and-go kind of thing. As if something sticks at a certain point in the rotation of the axles, bakes, etc. As I continue driving (for a minute or so) it goes away completely and I can drive and brake just like normal. I should mention, engine RPMs stay the consistent through the surging motion. So it's not the engine causing it.

My only guess is maybe a warped brake rotor? That could explain the friction that only comes at a regular intervals, and perhaps the stopping at the beginning, but I don't understand how that would just go away after a minute. Perhaps an issue with the transmission?

I'm normally pretty handy at fixing 'im up, but I don't even know what to try to fix in this case. Any help would be greatly appreciated.

 

[Curious Hound]

Driving in 2wd or 4wd? What type of road surface? Tell us more about the vehicle? Manual or auto transmission? Open diffs or limited slip or lockers? Front hubs locked or unlocked?

 

[INHWMW]

4WD truck driving in 2W, hubs unlocked. Automatic transmission, driving on normal pavement. Ford 8.8 diff in the back, I believe it is limited slip but I'm not sure.

Just got back from a drive as well, and I must amend my earlier statement. It still did the stop-and-go motion even from the cold start, it just does it worse after I've driven and it's sat for a while. That's when it will completely stick and not move even with my foot off the brake. There's an occasional brake squeal as well, not often though.

 

[Uncle Gump]

I moved this to the 4.0L forum before I read the entire post. It seems to me your issue is more likely in the brakes forum.

If you put the truck on a incline... in neutral. .. will it roll from its own weight?

If not... you likely have a brake sticking.

I'll try to move this once we get a true direction to your problem.

 

[INHWMW]

No problem, I wasn't sure where to post this in because I don't know what's going on. There aren't an great hills to test that around here, but I could try just shifting to neutral and pushing. See if I can move it that way.

I suspect the brakes, the part that makes me doubt it though is that it loosens us within a minute or so of driving. I feel like if the brakes were sticking they would still all the time... thoughts?

 

[Uncle Gump]

No problem, I wasn't sure where to post this in because I don't know what's going on. There aren't an great hills to test that around here, but I could try just shifting to neutral and pushing. See if I can move it that way.

I suspect the brakes, the part that makes me doubt it though is that it loosens us within a minute or so of driving. I feel like if the brakes were sticking they would still all the time... thoughts?

Well... they likely free up a bit until you apply the brakes again.

You can also just do a slow roll... pop it in neutral... a see if it quickly comes to a stop.

 

[Uncle Gump]

And honestly... and automatic transmission should move forward in drive on level ground when you release the brake

 

[INHWMW]

I'm aware of that, that's why I'm here haha. Because it doesn't, and I don't know why.

 

[Uncle Gump]

Jack it up one corner at a time and spin the tire by hand...

 

[INHWMW]

I can go try that, anyone else have ideas?

Thanks for the help so far, by the way.

 

[Rick W]

Sounds like my ex-wife. Cranky when you first start, then goes kind of crazy, and then just digs in. Go to the thread on “divorce.” See if anything there makes sense.

 

[INHWMW]

I have more information. I jacked up both front tires (separately, all brakes off) and they both spun reasonably easily. I jacked the back up next (both at the same time, park brake disengaged, front wheels chocked) and one spun alright, the other one was really stiff. I put it into drive to see if they'd spin, and the pattern was repeated. One spun, the other didn't. And strangely, when in reverse they both spun fine.

Any guesses? Maybe the parking brake isn't disengaging all the way until it's rolled a bit?

 

[RobbieD]

The one that won't spin, I'd pull the wheel and then pull the drum next, to have a look-see.

If it's been a while since the brakes were done, it'll probably fight you.

But, if you're overdue on a brake job, that will be something that you'll really want to do anyway.

 

[Uncle Gump]

Look for fluid leakage around the back side of the drum.

 

[Uncle Gump]

A leaky axle seals or wheel cylinder will gum up the brakes.