Topic: Solved: Shimmy-shake on take off

[Plainview]

Well if it ain't one thing it's another.  Drove the Xtra cab tonight and it has a strong shimmy right when starting off.  Fine once rolling.  If I slow to a crawl in 1st gear then give it gas I can feel it but it's not as strong as starting from a dead stop.  Feels like something in the drivetrain. The shifter really shakes but you can f feel it strongly in the whole truck. The engine runs smooth and strong and isn't missing.  It's not clutch chatter.

It was fine the last time I drove it.  I've done the following things since then:

Installed rebuilt rear section of rear driveshaft. (See my build thread linked in my signature.)

Installed OME springs and shocks with new bushings.

When I was installing the front springs I lowered the axle to far and the front driveshaft separated.  Don't know if I got it v back together the same way it was but that shouldn't affect anything in 2wd should it?

Is there something funky about that two piece rear driveshaft that could cause this?  I only replaced the rear section.

Any other ideas?  I'm baffled and not sure what to look at first.

[Willard]

Did you get the shaft balanced?


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[emsvitil]

Make sure all the driveshaft u-joints are lined up correctly.......

[Plainview [OP]]

Did you get the shaft balanced?


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Well, it came with a big 'ol sticker on it that said "Dynamically Balanced" and has two arrows pointing to each other at each end of the slip joint.   See the picture of it in the last post of my Xtra Cab build thread linked in my signature.  For what I paid those guys it better be good from 0-10,000 RPM...!

Wouldn't a balance issue appear at higher speeds?  This only happens at very slow speeds (strongest when taking off from a dead stop but can be felt if I slow to almost a stop in gear then give it gas.)  It goes away by 15-20 MPH depending on how hard I'm on the gas.

It does not happen under engine braking, it does not happen when coasting at a steady speed.  Only when applying power and only at very slow speeds. Strongest in 1st gear but can be felt less intensely when starting out in reverse or if I lug it down to about 1000-1100 RPM in 2nd gear.

Make sure all the driveshaft u-joints are lined up correctly.......

Hmmm.... Check out the picture of the new shaft in my build thread.  Are those lined up correctly?  The bolt holes in the flanges only line up two ways - 180 degrees apart.  Guess I could try rotating the rear section 180 degrees relative to the front section and see what happens.

[emsvitil]

Please post link (or picture) of new shaft........

[YooperYota]

Mine does the same thing, it's just an "Hey I'm about to stall" vibe that the engine is giving off. If you give it more gas on take off or are easier on the clutch you shouldn't experience it.

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[Plainview [OP]]

Please post link (or picture) of new shaft........

DSC_8150 by Will Baker, on Flickr

Mine does the same thing, it's just an "Hey I'm about to stall" vibe that the engine is giving off. If you give it more gas on take off or are easier on the clutch you shouldn't experience it.

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Thanks, but it's definitely NOT the engine.  I can keep the RPMS up and ride the clutch and you'll still feel it just as strongly as if you try to keep the RPMs down and engage the clutch more quickly.  Also, this is new behavior since the changes listed in the original post.  It was fine right after the new clutch went in but before the driveshaft was replaced and the new suspension went in.

[toyodaaddict]

The front driveshaft should have have no effect when in 2wd hubs unlocked. I would focus on rear driveshaft and pinion angle, also maybe a quick look at engine/trans mount and double check that ubolts are tight.  kind of a strange one right on take off like that 

[Willard]

Are the u joints fully rotating? I have seen I joints seize in one position causing a shutter and basically a hop of the vehicle at take off. As stated above check all drivetrain/power train mounts.


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[emsvitil]

http://jniolon.classicpickup.com/drivelinephasing/drivelinephasing.html

[Plainview [OP]]

Woohoo!  Problem solved.

The rear section of the rear 2-piece driveshaft (the part I replaced) was 90 degrees out of phase with the front section.  I saw it as soon as I knew what to look for and it took all of ten minutes to fix it.

Thanks for all the input everyone, much appreciated, I don't think I'd have figured it out without your help.  I've dumped a bunch of money and time into this truck over the last month and to have some weird shiz like that happening was beyond frustrating.

I knew about driveline angles - what is discussed in the link emsvitil posted as I've had some experience with that.  But, I've never had to deal with u-joint phasing as I've never worked on anything with more than a single piece driveshaft where the slip joint is in the tailshaft of the transmission.  I've owned a few different 4x4 rigs in the past but never had to deal with their driveshafts.  Cool, learned something new today.

Cheers everyone, enjoy the rest of your long weekend!