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another vibration thread

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i usually dont post with my problems cause it's too easy to search and find similar postings to fix it but my search ends here with this thread. this is going to drive me crazy. it already is or i wouldn't be asking.


i've done a few things to my 71 521 over the last couple months that may be suspect to my vibration problem. put in another l16 and kept the same trans.


let me tell you it only vibrates while stepping on the gas. i have no vibration in the steering wheel at all. there is a oscillating vibration til i get to about 40 mph then its a constant vibration. as soon as i step on the clutch and coast the vibration goes away.


does a bad rod or crank bearing cause vibrating?

will a loose pressure plate or flywheel cause vibrating. (recently replaced)

changed rear trans seal with a thinner body? (grabbing at straws here)


i have a new rear tire but i think it would vibrate with the engine engaged or not. i'll check with my known good spare to make sure.


the first thing i thought it was is the drive shaft. crap this is going to be a longer post than i want. i know what a drive shaft wooble feels like and this feels more like a vibration. BUT after i swapped engines i noticed the engine sitting forward more slightly and had a clanking slap sound when i hit the gas at all speeds. come to find out i'm looking at the rear spline and i see fresh metal as the yolk (behind the carrier bearing) has moved forward about an 1/8 of an inch after the engine/trans being installed. so i lubed the yolk and the slapping noise went away. could that small lengthening of the drive really cause my vibration? i wish i had a 1/8 to 1/4 spacer to stick in the back of the drive line to check.


then i thought carrier bearing but when i grab the drive line on my other truck it feels the same. i'd hate to start swapping out drive lines and carrier bearings but i suppose the process of elimination has to start somewhere.:mad:


i also noticed my u-joints don't have zerk fittings. whats up with that?


any advice, tricks, tips, sympathy would be appreciated.:)

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Is the exhaust pipe rubbing on anything? When the engine torques to one side under acceleration could the pipe touch anything. Is the motor mount or tranny mount loose or damaged as this would allow even more movement?


When you removed the motor/tranny did you remove or disassemble the drive shaft. Did you mark the U joints so they were put back in their original positions on the differential?

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Ok... When going coasting does your car vibrate when you do this?!?!?!


So if you coast at 40 mph with the engine off and it shakes "leave the car in neutral"... Its the suspension and or wheels


If you drive it until you hit 40 and press the clutch and it stop vibrating, then its the tranny and or engine...


Too see if its the engine or tranny then you drive till 40 and press the clutch in... Then you floor the gas.... If the engine shakes at high rpms with the clutch pressed in, then its the engine... If it doesn't and only shakes when the clutch is in. Then its the tranny or the drive shaft or something similar...

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i know its not the exhaust pipe cause i'm anal bout that thing. i checked the motor mounts. i didn't take out the drive shaft but didn't mark it to the trans flange to the drive line. i did notice the trans flange large nut was loose when i took it apart. i haven't checked the trans mount yet. well i half ass did by grabbing and trying to jiggle the trans but haven't looked at the actual mount yet. i know i'll find the problem eventually but hope it doesn't take forever. freakin mirrors shake while driving.:mad:

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  • 3 months later...

found it. i was screwing with the muffler and found this. REPLACE THAT U-JOINT BEFORE IT SMOKES YOU! so true. i should have looked closer when it first started vibrating. 3 months later, done deal. made me feel better after i ripped my mirror off with a recycle bin today. damn it.





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found it. i was screwing with the muffler and found this. REPLACE THAT U-JOINT BEFORE IT SMOKES YOU! so true. i should have looked closer when it first started vibrating. 3 months later, done deal. made me feel better after i ripped my mirror off with a recycle bin today. damn it.

I was just going to suggest u-joint but thought I better read all the posts, but alas you found it.

Good job.

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how hard is it to replace the u-joints, im in a 70 521 and im have the same problem... tips and tricks will help...




Remember: "Don't Bogart that joint" get it replaced before it smokes you!



Hard to tell if the trunnion hasn't worn onto the yoke an damaged it yet. As long as it's not damaged a new joint should fix that right up.


Edited by datzenmike
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wow, that coulda hurt!! i just replaced my half shaft u joint on the z, i had a vibration. the only thing differnt with mine is it had worn out the needle bearings, but also cracked one leg off the spyder!! i should post pix. well here are some






Edited by SHADY280
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mike that was the phrase i was looking for!. i had another drive shaft laying around so i just installed it. i'll replace the joint on the bad one soon. my bad one didn't have a zirk grease fitting but the one i put on yesterday did so i lubed the hell out of it. i notice the front joint has no zirk either.

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