Drivetrain jerk

[BABHUMV]

If this driveline slap occured after the service, I would suggest returning and having them make sure they have the proper amount of fluid. It is possible no/low fluid could cause this to happen.

[Kracker]

Mine has it too.

Speaking of dealer prescribed overmaintenance, my dealer tried to sell me a $399 15,000 service at 13,500 miles. I politely declined and stated that I order my service ala carte, per the specific services spelled out in the manual. I didn't bother to ask what type of crap was in the $399 15K service.


S.

[HummBebe]

Thanks guys (BABHUMV and UNO), I'll call in the am and check in with the service dept.

Ed, well......yeah, thanks

[DTHVLY]

It's probably axle wrap, its a frequent problem on trucks with leaf sprung rear ends. It's caused by the axle wrapping up on the rear springs and then kicking out while decelerating or accelerating. It is a clunk feeling and at first I thought it was the transmission also. It was a problem on my old Toy.
It can be fixed or reduced by getting stiffer springs or traction bars.

http://www.4x4wire.com/jeep/tech/susp/axlewrap/

[HummBebe]

Damm....that sounds serious.

[evldave]

I'd bet you my hummer it isn't axle wrap.

That's common on USED vehicles, with softer springs, and I honestly can't remember ever hearing of it on a axle-over-spring setup. I've got some experience lifting Jeeps and axle-wrap happens over time, mostly with cheapo budget lifts using lift blocks on stock springs after tens (or hundreds) of thousands of miles.

The reason is that lift blocks move the center line of torque (the axle) farther away from the springs, which puts much more torque at the point of contact on the springs (usually an area of 2x4" - the block). Over time, weakness builds at that point, and the springs start to S-coil. The taller the block, the sooner you will get axle wrap. The H3 setup (axle-over-spring) is significantly more stable related to this since the axle torque is inside the radius of the spring, not outside like SOA.

The best and cheapest way to get rid of axle wrap is an add-a-leaf. It will make your ride stiff as hell, but your axle won't wrap. Given the stiffness of the ride, I seriously doubt that anyone has enough (hard) miles on their rear springs to cause the # of issues that seem to be outlined on this thread. I'd even be willing to bet we could disconnect the rear swaybar and drive with no problems (I think there's another thread on that) - trust me, if you can disconnect the swaybar and drive around a corner, your springs are stiff enough to not have axle wrap as a problem.

Why do I (think I) know so much about this? Because my last off-road rig was a Cherokee and I spent the last year fuggin around trying to resolve a driveline/transfer case problem. It kept binding the driveline and trashing u-joints and one output shaft on the TCase. Well, my 5 year-old 120k mile 4" lift rear springs had pretty much failed and I was getting axle wrap. After spending all my time trying to diagnose the problem, I went out and bought some RE 3.5" springs, took out the rear swaybar and was a happy camper (and bought my H3 2 months later). The axle wrap as so bad, the pinion was pivoting up through centerline of the driveshaft at WOT in 1st gear, and then jamming when I went off throttle and it pivoted back down.

Originally posted by HummBebe:
Damm....that sounds serious.

Yea I don't think my H3 can generate enough torque for something that serious.


S.

[HummBebe]

Originally posted by DTHVLY:
It's probably axle wrap, its a frequent problem on trucks with leaf sprung rear ends. It's caused by the axle wrapping up on the rear springs and then kicking out while decelerating or accelerating. It is a clunk feeling and at first I thought it was the transmission also. It was a problem on my old Toy.
It can be fixed or reduced by getting stiffer springs or traction bars.

http://www.4x4wire.com/jeep/tech/susp/axlewrap/

I was just in furnace creek.......

[HummBebe]

Originally posted by evldave:
I'd bet you my hummer it isn't axle wrap.

That's common on USED vehicles, with softer springs, and I honestly can't remember ever hearing of it on a axle-over-spring setup. I've got some experience lifting Jeeps and axle-wrap happens over time, mostly with cheapo budget lifts using lift blocks on stock springs after tens (or hundreds) of thousands of miles.

The reason is that lift blocks move the center line of torque (the axle) farther away from the springs, which puts much more torque at the point of contact on the springs (usually an area of 2x4" - the block). Over time, weakness builds at that point, and the springs start to S-coil. The taller the block, the sooner you will get axle wrap. The H3 setup (axle-over-spring) is significantly more stable related to this since the axle torque is inside the radius of the spring, not outside like SOA.

The best and cheapest way to get rid of axle wrap is an add-a-leaf. It will make your ride stiff as hell, but your axle won't wrap. Given the stiffness of the ride, I seriously doubt that anyone has enough (hard) miles on their rear springs to cause the # of issues that seem to be outlined on this thread. I'd even be willing to bet we could disconnect the rear swaybar and drive with no problems (I think there's another thread on that) - trust me, if you can disconnect the swaybar and drive around a corner, your springs are stiff enough to not have axle wrap as a problem.

Why do I (think I) know so much about this? Because my last off-road rig was a Cherokee and I spent the last year fuggin around trying to resolve a driveline/transfer case problem. It kept binding the driveline and trashing u-joints and one output shaft on the TCase. Well, my 5 year-old 120k mile 4" lift rear springs had pretty much failed and I was getting axle wrap. After spending all my time trying to diagnose the problem, I went out and bought some RE 3.5" springs, took out the rear swaybar and was a happy camper (and bought my H3 2 months later). The axle wrap as so bad, the pinion was pivoting up through centerline of the driveshaft at WOT in 1st gear, and then jamming when I went off throttle and it pivoted back down.

Ok evil, say I believe you (and I do), what do you think it is????

[evldave]

Honestly, I don't have a reasonable idea (and so I don't spout off in the forums). Since I'm in a wordy mood today, I'll continue...

If I were to conjecture (only because you lived up here and you asked) - I'd follow the same thing I always do when diagnosing - start with the cheapest stuff first.

You wheel hard, put a lot of stress on the driveline. Check the u-joint. Reach down, try and move it perpendicular to the joints. Does it move left right (not rotationally)? If so, spend the $30 and have the u-joint R&R'd - or take it in for warranty service. Get a Spicer (sp?).

Does the driveline rotate and have some play in and out? There should be some movement in the parallel direction and rotated (not much, but a little). If none, there's binding somewhere. It could a number of things, but it's under warranty and tell the service tech.

Do you have an older rear end? If so, there was a gear lube issue with the supplier and that may have caused an issue w/the gears in the rearend, but not enough to blow it up. Since this seems to have happened when you had the service done, putting new fluids may have made it easier to feel. Might want to look up mfr date and see if it was back w/that lot of parts.

In my completely uneducated guess, I'd say the torque converter isn't unlocking quickly and so the drivetrain is under locked load when you are stepping on the gas. I don't know all this fancy computerized stuff, but a torque converter is supposed to let the engine 'throttle up' without having the drivetrain acccelerate at the same rate (it's essentially slipping to let the motor spool up without spinning the tires at the same time - it builds power faster so you can put more oomph to the wheels when it finally does engage).

There is lost efficiency in this design because of the slipping, but it's required in automatic transmissions (otherwise the engine would stall when the rear wheels stop). Most modern transmissions have a 'lockup' converter that locks in either 3 or D to maximize the power transmission between the motor and...well...the transmission. When decelerating, the converter usually locks to help with slowing (you can feel this on a lot of vehicles) - when you accelerate, it should immediately unlock and slip a little.

On the H3, the converter locks when driving normally in D. When you step on the gas on the highway, it actually unlocks (check your RPM, they will increase quite a bit but it won't actually downshift - that's the converter unlocking and hitting it's stall speed). IF (big if) it doesn't unlock and you put too much gas on, it can bog down - the equivalent of being in 5th gear in a stick driving at slow speeds. This can cause all kinds of wierd clunking and bogging.

On my H3, I noticed when I first got it that it had a significant amount of slip at lower speed - to the point of annoyance that I couldn't use engine compression to keep the rig slow on downhills. As I've now got 8k miles on it, I've noticed the converter locks up much sooner and better at low speed - it may be a design or trait of the H3 - the older the tranny, the more it locks up? I don't know, but it's noticeable to me because I've been paying attention to it.

Is this an issue? I have no idea, but I wouldn't worry about it. I'd go beat the hell out of it right now to see if it breaks - if it does, going to MOAB is a bad idea, if it doesn't, don't worry about it.

I'm sure other more edumicated people will fix any of my factually inaccurate statements - a lot of that going on lately...

And a note on axle wrap - it happens on all rigs and is expected to a small degree, however EXCESS axle wrap (that would cause this sort of problem) should only be present on older springs.

[HummBebe]

Evil, thanks, you seem to have a good logic going on here.....you know your beer too

I appreciate you taking the time. Kiss kiss.

[DTHVLY]

Originally posted by evldave:
I'd bet you my hummer it isn't axle wrap.

That's common on USED vehicles, with softer springs, and I honestly can't remember ever hearing of it on a axle-over-spring setup. I've got some experience lifting Jeeps and axle-wrap happens over time, mostly with cheapo budget lifts using lift blocks on stock springs after tens (or hundreds) of thousands of miles.

The best and cheapest way to get rid of axle wrap is an add-a-leaf. It will make your ride stiff as hell, but your axle won't wrap. Given the stiffness of the ride, I seriously doubt that anyone has enough (hard) miles on their rear springs to cause the # of issues that seem to be outlined on this thread. I'd even be willing to bet we could disconnect the rear swaybar and drive with no problems (I think there's another thread on that) - trust me, if you can disconnect the swaybar and drive around a corner, your springs are stiff enough to not have axle wrap as a problem.

While axle wrap is more likely with old springs it does occur on new vehicles. Ask anyone with a Tacoma they come straight from the factory with it bad and they only have 190hp. After driving a Tacoma I swore I would never buy a leaf spung offroad rig. I really like the Toy 4 link coilover rear suspensions a lot better than the leafs, that's one of the main reasons I want't to check out the FJ.

While it's less likely on a axle-over-spring setup it does still happen but the swaybar disconnect would be a good test.

Don't you think a traction bar would be a better cure because it dousn't stiffen the ride like an AAL and won't soften like the AAL eventually will.

Is your name "evldave" taken from Evil Dave on the Stern show?

[evldave]

evldave was a nickname I got in college for being a dick. Now that I'm older and wiser, I'm just a more experienced dick.

That said, I agree traction bars are much better for traction control (that's why they are used on drag cars) but their cost and setup can be tricky (and are usually more $$ than an AAL).

Interesting to hear about Tacoma's, just goes to show we don't always know everything. I'm familiar w/the axle-over-spring Comanchees and they never had (new) spring axle wrap issues.

I'm still curious as to the resolution on this - I wonder if it's one of those 'annoyance' things or if it's going to be something that is a real issue...

yea but at least now we understand the origin of "evildick" or whatever the name is...

S.

[evldave]

oh, man, that's cold

If I cared what you thought, I'd be hurt

I must of mispelled evldave. Sorry

That's why I have to wear those big bullit-proof sunglasses.

S.

[wannabeH3]

mine had it and now they are replacing my transfer case

[Edspad]

Originally posted by wannabeH3:
mine had it and now they are replacing my transfer case

Dont Cry HummBebe, its going to be ok...really!!

[HummBebe]

I just might....