Well, the wobble is back... And now I'm concerned...

[Geom]

OK, so the wobble mentioned in an earlier post appears to be back.
I've taken some additional info and here's what it looks like


It appears to happen regardless of speed, but 55-65 mph is the spot it begins to happen.
Taking the trans out of gear stops the wobble
Revving the engine to similar rpm, but out of gear, and no wobble
Rolling down hill at >65 mph in neutral no wobble
Climbing a really hefty hill from a dead stop and no wobble
It appears to be somewhat related to "strain" because climbing small hills while at speed causes the wobble
Backing off of the throttle, even slightly, stops the wobble.

We've pulled over for now just to write this post, but we plan on getting back on the road.
It is drivable in its current condition, I just have to ease off the throttle when it begins to wobble.
I checked the trans fluid and it looked full. I added some anyway because... I have no idea what I'm doing and hoping it's something simple. That appears to have have no effect.

It kind of comes and goes. I can be driving 64 and be fine, but then 58 will cause a wobble depending on road.
It feels like it's shifting ok, but when it's wobbling it's more like a lurch? Like the trans can't quite decide on a gear?
Dropping it to second doesn't seem to make a difference, but I don't think it'll go into second above 55.
The trans fluid was clear and normal colored
All temps looked great and engine pressure is normal.
Took an IR gun to the bell housing and body of trans and it all appeared ok with the hotest being around 150 on the top of the housing and body. The rest was ~135.
I can't quite tell how many gears it going through because the lockup feels like a gear shift? I'll pay more attention and report that back as well.

Anyway, that's all the info I have for now. We're gonna try to limp a bit further.
Any help or advice is obviously greatly appreciated.

Also, if it's a really bad idea to keep driving, please let me know and we'll stop for the day.
Other than the wobble, everything appears ok.

Thanks in advance,
George

[luvrbus]

When the rear radius rod bushings are bad or a rod is broken a GM will do crazy stuff have you checked the radius rods on the rear for slack or a broken hanger.

It's usually the top rod that goes bad the one you cannot see if I recall RJ had a problem with his upper rod on his 4106

[Hobie]

Could it be a U joint in the driveline??

[Darkspeed]

Have you checked the retainer nuts on your rear wheel hubs?

[Geom]

Clifford, I looked at the radius rod (lower) and it doesn't appear to be physically broken or hand loose. It's possible the bushings could be bad, but I'm not sure how I'd test that. I grabbed it and tried to move it, and there was no slack.

Hobie, I looked at the u-Joint (or at least what I thought is the u-joint, extended from the end of the trans heading toward the differential) and it appears intact (as best as I could see of it) and nothing looks out of alignment (although I admittedly would have no idea what out of alignment would look like).

Some additional data,

It appears that 61 mph is particularly an issue. Although I've been able to easily hit 65 on occasion. So it's still intermittent. I can definitely cause it to happen if I push the throttle above a certain speed (variable).
I can sort of pre-sense it before it happens and I instinctively back off of the throttle and can feel it stop. Even the slightest backing off of the throttle makes it stop when it happens.
Mashing the throttle definitely makes it get worse if it has started.

But having the throttle down, rolling from a stop is no issue.
It seems to be somewhere between 2nd and 3rd (or at 3rd?), although I "think" I can feel it hitting 3rd.

We've stopped for lunch and to make sure nothing worse is happening back there.
We're gonna keep going. So far it (hopefully) doesn't sound like driving it is ridiculously or overly stupid so... onward and forward.

[gg04]

Normally upper bushing. But who did the engine conversion? Just a few degrees any way will cause the same after a few thousand miles of wear. rdw

[gumpy]

Sound like a u-joint. You're not looking for alignment. That's not going to change. You're looking for worn out and moving.

[Geom]

Well we've pulled into our destination for the week.

I'll check the u-joint again in the morning and see if I can pull on it to see if it gives or moves?
I'm not sure how else to check it, but I'll take any suggestions there.

It actually drove pretty well the rest of the way, considering. That 61mph seems to be pretty consistent, although I was able to get to 68 with no issue a few times, by accident mostly.
The throttle, or more appropriately throttle at speed, seems to be key. Back off a bit and it pretty much stops. So I made a point of keeping it at about 55ish and had no wobble.

I guess if it's the radius rod or the u-joint, there's not much I'm going to be able to do about it on the road, I assume?

Is it OK to drive further? Maybe to the mechanic? We were going to put on about 700 miles to make our way down to the mechanic we had intended to take it to, over the next few weeks. Would that be OK?
We could also make a point of detouring to a closer mechanic if necessary.

[skihor]

We once had a "wobble" feeling and I couldn't figure it out. The problem became clear when the last couple of nuts/bolts on the drive line flange broke and it became no longer attached. loud and scary @ 65 mph.
Don & Sheila

[Brassman]

Don't know if this applies to your transmission but I've had the same thing happen in a car due to worn out lock-up clutch pads. At 45 mph when the torque converter locked up it would shudder because of clutch slippage.

[Jim Eh.]

As a rule of thumb:

45 MPH +/- = driveline
62 MPH +/- = wheel balance

Unless something is really out of whack then all bets are off.

Do you use a liquid balance or pellets in the tires? Have you checked the wheel nuts (re-torqued to proper spec)?

[Darkspeed]

does he have the driveline hand brake drum?

could it be a loose drum??

[gus]

My 4104 did this, turned out to be badly worn splines in the driveshaft slip joint.

[chessie4905]

   You need to have the driveshaft pulled and dissassembled to check the u-joint trunnions and needles and also the slip joint for wear. Also be sure the joints are indexed to each other. Because it is so short, it is somewhat a pita to remove. Have the balance checked while you are at it.

[Geom]

Hmm interesting stuff, thanks all.

I'll definitely check the u-joint and all adjoining bolts as best as I can tomorrow. I've got the maint manual (although not the engine manual) and can use that as a guide. It has some useful graphics of the u-joint assembly.

It's possible it could be slippage. Hard to tell. Wobble is the best I can describe it, but it's almost like a hesitation. Like the transmission can't convert power to forward motion, backs off, and keeps trying. But it could probably be easily described as a shudder by others....
I'd say the frequency of wobble is about 4-5 per second? Rapidly slower when I back off the throttle, and somewhat (if at all) faster if I keep pushing it. Have not tried to ridiculously push it.

I DO have wheel balancers. They're only on the rear tires. They're centramatics and use ball bearings in a disk attached between the two wheels. I had suspected that maybe they're going bad? Or perhaps one of the bearings is seized? But I thought that if it was really out of balance, it would wobble all the time, or would do so at and above a certain speed. I can (sometimes) and have gone above 61, sometimes under power, others while I was rolling down hill. Not sure, would a balance issue behave this way? Does it make sense that the balancers are whacked and causing this?
Also these are relatively new tires, for this bus. When we bought it we had new tires, and the balancers installed. We've put, I'd say, about 4-5K miles on them.
I keep an eye on air and it's even all around (TPMS).

Not sure how I could diagnose the other suggestions, but would be willing to try whatever tests next time we roll.

Other than the u-joint sheering off or possibly the driveshaft slip-joint, it sounds like the other possibilities are manageable if I keep it controlled and under the trigger speeds?
I'll make sure to throughly check the u-joint.

So I definitely need to get someone looking at it, and already have/had plans to do so. I guess right now I need to decide how far (and how safe for the engine/trans/etc) to push it. Hmmm.........