50mph shake

[norm]

At about 50 mph I am getting a little driveline shake - not "looseness" but a minor, tight "lugging" maybe. It does not feel/sound like engine missing or anything, but prob. tranny.
A bit after 45 mph, when easy cruising in 4th and TCC locked up, I get this shake when adding a little throttle. If I get into it and unlock converter or downshift, it goes away. It also does not show up under 45, when TCC is not locked.

Any ideas on this one?

[Turbine Doc]

Norm,

Not sure but lets see if this description fits; you are driving along and truck starts jerking with feel similar to a fish jerking on hook of a fishing pole, not really anything like wheel imbalance, something like power on/off & traction grab when operating on slick to dry pavement, nothing definative, but a jerking felt thru the driveline.

If that fits description of your problem, "fishbiting" is a term I haven't seen here in a while but was a common symptom description when I 1st showed on the site a few years back.

From my own experiences, it happens as result of intermittent loss of fuel to IP. Check fuel filter, lift pump, OPS, wiring faults, could be crank sensor but that usually gives a code, and lastly if all that checks out could be early indication of PMD/FSD fail, if you don't have one anyway look for a glovebox spare. Lot of debate which is best solution on that front; I've posted my opinion/results on that issue others differ read and make your own decision.

[HowieE]

I may have seen the same thing.
When traveling just above the TCC lockup speed, 50mph, and decelerating down through the TCC lockup speed, due to a slight hill, if I apply light throttle I will get a chatter just as the TCC unlocks. If under the same conditions I hit the throttle harder the TCC will unlock in one clean action.
Suprisingly just changing the tranny fluid in the pan has cleared this up twice in the past, and I need to do it again.
If by chance you change your fluid and not e a differance e mail me the results.

[Spindrift]

On rare occassions, fishbiting can be caused by the failure of the electronic filter harness. Failures are due to, you guessed it, heat-related issues. The EFH plugs into the back of the IP.

[norm]

I would say on the feel of it that it's not the engine. Also not realy a chattering. I only feel it in 4th gear with TCC locked and RPMs low [<2000rpm/45-50mph], and rolling on a little throttle. Once the speed [and RPMs] increase to >55mph, I do not experience the problem.
It's almost like a bouncing in the driveline. I think I will have a look at the driveshaft carrier bearing. I guess it could be some lockup chatter, but I don't think it is trying to unlock. The fluid was recently flushed/changed by dealer at last IP change.
I wonder if this has anything to do with the "warning" not to use OD when pulling loads???

[More Power]

I doubt there's an electronic component to this problem you're seeing.

A few years ago when we first covered DSG's Phaser gear drive timing set, Scott Boleman reported that a driveline vibration he had been experiencing mysteriously vanished after installing the gear drive. His truck was equipped with an NV4500, but the principles would be the same as a locked TC at just the right engine rpm.

So, we learned that a loose timing chain can contribute to engine roughness at specific engine rpms.

MP

[norm]

Thanks MP, that will be something to consider for sure.
Just had a look at the driveshaft carrier. The bearing seems tight but the whole rubber damper piece moves up and down a good bit in the (horseshoe shaped) retainer - nearly 1/4". That could be something, but might not explain the MPH/RPM relationship. (for example, at the same 45-50 mph, it won't show up in [D](3rd), only in [OD])

Merry Christmas, all!

[DmaxMaverick]

That could be something, but might not explain the MPH/RPM relationship. (for example, at the same 45-50 mph, it won't show up in [D](3rd), only in [OD]) Darn right, it can! The conditions that you are able to recreate the problem might just be at the right rpm/torque to cause the carrier to jump around. More torque and the carrier is forced to one extreme, and no chatter. Less torque might not be enough to cause the chatter. Worn carriers will cause the problem you describe, exactly.

I would suggest repairing the carrier and trying again. You might be pleasantly surprised. If it doesn't fix it, it was time for a new one anyway.

Good luck and Merry Christmas!

[norm]

Got it now:
particular condition=particular problem.

Will go after carrier post haste!

Thanks

[catmandoo]

well i've had this same problem for over a year,and it's not just confined to diesel pickups but what i have found is it does seem to be related to the ext or crew cabs,mine is a 92 c1500 6.5 nv4500 2wd with 420,000,friend has a 98 c1500 gasser with auto with 60,000 and his does it too,also they are both the short box's.his is also an ext cab,and i just had a u-joint go bad so i replaced all 3 and the hanger bearing assy and it still does it.it seems to be engine rpm (load) related as it does it at about 62-65 in 5th and at about 45-49 in 4th.

[eracers999]

Norm;

Sounds like torq converter shudder, had good results installing a 1 pint bottle of synthetic lubegard (red)bottle. After 500 mi or so the shudder subsides. Plain ole transmission fluid by it self can be transformed into a quality semi synthetic oil by adding the above. Cost is a bout 12$ at carquest or at any transmission parts supply house.

Kent

[Spindrift]

I'm experiencing some pretty noticeable "fishbiting" throughout the rpm range, but only when the truck is cold. Any ideas?