I rebuilt the front driveshaft two or three months ago, and initially everything seemed to work fine. About a week ago, though, I started to notice a vibration under acceleration between 40-80kph, a typical out-of-balance symptom. I lubed up the shaft just in case (not that it needed it), which doesn't seem to have done anything.

I'm planning to take it to get balanced tomorrow, but I don't get how it could go out of balance like this, which worries me. My only theory is that maybe one of the balancing plates came off, but I don't see any evidence of that. I'm thinking about taking the zerk off the main shaft and plugging it with something to see if that has any effect. Is any of this normal?

 

i suppose you could put the yolk on 180 degrees off

 

Rear shaft another possibility unless recently serviced.
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Very true about the rear shaft possibility. I've always been a little wary of that rubber thing.

I just did some tooling around it and noticed one of the bolts on the front flange wasn't tight :/

I torqued it to spec when I put it in. Am going to put in a new bolt. I'm hoping this resolves the issue, but all the other bolts are very tight, so I'm not totally sure.

 

This didn't solve it and it looks like I'll need to get the thing balanced. Weird problem, though: I just undid all the nuts and took all the bolts out of the shaft where it connects to the front diff, leaving it loose. But the flange connecting to the transfer case won't budge. I tried hammering it gently with no luck, then sprayed it with penetrating oil. I don't remember this being a problem when I dropped it before. Any idea what's up here or what I should do? It's almost as if the metal plates are fused together. The bolts are all loose in their holes but it won't budge.

Edit: looks like others have had this issue—I stupidly didn't put any anti-seize between the two pieces of metal. Regretting that one about now.

 

Would have done that myself in the near future if not for you. Thanks.
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Here's another thing I'm noticing: it's also shaking a bit on idle, definitely noticeably. From reading up various places, people say rough idle could be a sign of a misfire or bad spark plug. Could this also cause the kind of shaking I'm getting on acceleration perhaps?

Thing is, I have no codes that would indicate a misfire. No codes at all, in fact.

 

No, you don't need codes for a misfire. I had a fried #8 wire and would misfire with no codes. Basically, parked and in neutral, your shaft should not move to vibrate or have torque, so a misfire could be a culprit sitting still. Also engine mounts that have dropped can vibrate. Vibration from a shaft usually resonates with rpm, in my experience. Slow shaft slow vibrate, faster spinning shaft, faster vibrate. Also when driving at speed, I don't notice a misfire like at idle.

 

The vibration I'm feeling while driving only appears at around 70-ish kph and then disappears again at about 100kph. It also shakes side-to-side on idle (not hitting the accelerator).

Funny thing is, the guy who did the detailing work on the car said he'd do a quick mechanical check and told me I needed new plugs. I said no because I had them done not too long ago, but I now wonder if he might have screwed something up.

 

Have you checked tires lately. There are quite a few threads online from vibration in the range you mention. If it only started after the shaft rebuild, might need to re-check balance of the shaft. I doubt a vibration from tires would suddenly appear out of nowhere - but could be.