Significant vibration at 30-35 MPH

[Daniel]

While enjoying a drive today, I slowed to make a left hand turn while double clutching to try and save my 2nd gear downshift syncro, as I accelerated after making the corner, all of a sudden a major vibration presented itself at around 30 MPH. I thought maybe something came loose in the front end suspension, loose lug nuts or broken shock? I immediately pulled over and checked all I could. Nothing loose or hanging, shook all 4 corners with no funny noises. I babied it home at 25, luckily I was only a mile or so from home when this all took place. I'll get under it later to see if i can find anything out. Could the bad syncro have come loose inside the tranny? U-joints? If the car is rolling ie; clutch in or out, in neutral or in gear, it vibrates HARD at 30-35, but goes away above 40 or below 30. Opinions?
67 1600 with a transplanted 68 2L 5 spd and the rear end.

[jrusso07]

My guess, a tire defect...a broken band perhaps. Other than that, could be a bad ball joint or A arm spindle bushing.

[redroadster]

Shakes the whole car sounds like the drive shaft or in drive line loose wheel ....stay low speed really need it on a lift

[Bwk2000]

All good suggestions above. In addition, I would check the u-joints for a crack (since the vibration just started) and check the trans fluid level. I would then change it and run a magnet through the old fluid and then pour it through a clean shop towel (to catch any brass shavings) - That should be pretty definitive one way or the other.

[Daniel]

Mystery solved!
The 4 bolts that attach the driveline to the transmission yoke came loose. Not only loose, one was missing and the other three were only finger tight, hanging on by a couple threads each! Yikes!! Fortunately it didn't come apart on the freeway.
For the tech part, you can't really access them from underneath, as they are right above the X in the frame. I went through the top, at the shifter hole. New Grade 8 bolts, lock washers and nuts. Oh yeah, plenty of blue lock tight. It's too tight of a space for a socket and ratchet, gear wrench, or even a boxed end. The only wrench I could make fit was open ended, and my shortest one was a bit too long. So for me it was 1/4 turn, flip the wrench over, another 1/4 turn an so on....

[david premo]

You probably have the drive shaft out of time if it’s a 5 speed. There are alignment 0, on the shaft and yoke that have to match up or the shaft is out of timing and will vibrate until bolts come loose or something breaks.
Dave

[redroadster]

I've had more than a few like this and were thieves trying to make off with it , probably not as so hard to do but they lift with a tow truck

At a KIA dealer I worked briefly they had a methadone addict as a tech that would tear up cars so it would need work he liked to do

[jhayden]

You probably have the drive shaft out of time if it’s a 5 speed. There are alignment 0, on the shaft and yoke that have to match up or the shaft is out of timing and will vibrate until bolts come loose or something breaks.
Dave

Dave is right on point here (as usual). Many 2000 owners do not realise that the "0" marks to which he is referring are on both fore and aft yokes as well as both ends of the shaft, and all must line up for proper balance.

All that is assuming, of course, that the original shaft is mated to the original yokes. Unless that is absolutely certain, best to have a driveline shop rebalance using today's technology. And, yes, most will require installation of brand new ujoints to do the service. Still cost-effective.

Jon

[Florida Roadster]

I rebuilt a 4-speed driveshaft and the marks were clearly visible on both ends. See pic. I have a mark on the front yoke of the 5-speed driveshaft but I have no marks anywhere on the driveshaft itself. Are the marks usually always in the same position on the ends of the driveshaft?

IMG-4355.jpg

IMG-4356.jpg

[jhayden]

Probably the most comprehensive explanation you'll find on this topic:

https://www.youtube.com/watch?v=ljAkxZj3i1Q&t=5s

Jon

[Florida Roadster]

Probably the most comprehensive explanation you'll find on this topic:

https://www.youtube.com/watch?v=ljAkxZj3i1Q&t=5s

Jon

Thanks Jon. I'll have to do a little paint removal and exploration to find the marks on the driveshaft.

I heard KONESHEWA, and that's about all I could understand.

[Solex68]

Probably the most comprehensive explanation you'll find on this topic:

https://www.youtube.com/watch?v=ljAkxZj3i1Q&t=5s

Jon

Wow, What a great YouTuber.

[Gregs672000]

Translation unneeded!

[unklpat]

I can not agree more than that driveshaft should be gone thru by a shop. Pat

[Gregs672000]

So today I decided to do a brake and clutch fluid swap, and decided that I'd check my drive shaft since I was under there anyway. Took a while to scrape off the "patina" but I eventually found all the alignment marks and... oops, I'm off 45 degrees. So, a big THANK YOU to this post, group and our friends in Japan... drive shaft is now property aligned, and while I was not experiencing any issues, ya never know!