Knocking/Vibration through shifter

[boostfrk]

UPDATE, POST #11

1990 LX 5.0, 115,000 miles, I've had the car about 3 weeks.

Predominately in first or second gear when I'm either coasting to a stop (clutch in but still in gear) or slowing down (clutch not in and still in gear) I get an audible and easily felt knock/vibration through the shifter that is speed dependent (from about 20-25mph until I stop). If I have the clutch in and rev the engine the vibration does not change.

The T5 has about 100 miles on it. I got a brand new rebuilt one and put it in after I bought the car. I've checked the driveshaft and even rotated it 180 degrees with respect to the tranny yoke just to be sure. No change. Both u-joints are also brand new.

If this is normal (which I don't think it is) I can just live with the noise and move on. But, I don't want to ignore it and cause damage or excessive premature wear.

Any idea what this could be?

 

[Kdubslugga]

Did you install the transmission or did somebody else? A lot of time guys will get the trans up in the bellhousing, slide the input shaft in, and a lot of times there is a 1/2" gap between the trans and bellhousing. Ive seen it a lot where they put the trans bolts in and use an impact to tighten the trans to the bellhousing. What that does is basically "PRESS" the pilot bearing out. The transmission should be flush or very dang close to the bellhousing before you tighten the bolts down. That could def cause a vibration.

 

[boostfrk]

I installed the transmission myself, and the transmission was flush against the bellhousing before any bolts were tightened. All bolts were also tightened finger tight, then I used a ratchet to snug them down, so everything was done by hand.

Interesting thought, it wasn't something that crossed my mind. Thanks for the input.

I took it back by the guy who built the transmission yesterday and he rode along so he could hear and feel what it was doing. He doesn't think it's anything to be concerned about. I am pretty picky when it comes to noises, rattles, vibrations, etc.

 

[boostfrk]

When I took it to my transmission guy, he's about 45 mins away. Well after driving that far and having things get warmed up the noise and vibration seemed much less noticeable. It's definitely the worst when the car is cold and in the first 15-20 minutes of driving or so.

 

[boostfrk]

So this problem is still present, and I've since replaced the throwout and pilot bearings. Put everything back together carefully, and no change. I also swapped the wheels front to back in case one of them was out of balance, no change.

I've noticed I also get a similar audible knocking when at idle and I let out on the clutch. I had thought replacing the throwout bearing would fix this but it didn't.

The only thing I can think of left to mess with is the driveshaft (which wouldn't fix the knock at idle with the clutch out). I suppose I'll start by trying the balance procedure using the hose clamps and see if it changes at all.

Any other ideas?

 

[5.0TailPipeHump]

I'd have a look at the motor mounts along with the balancer, i'm having the same problem and hopefully diagnose it when i get off my lazy ass.

 

[boostfrk]

Problem appears to be solved.

I swapped in a driveshaft from a 94 GT and the vibration is pretty much gone. I suspect the original driveshaft was bent or out of balance.

 

[rbonella]

I replaced my driveshaft with an aluminum FRPP shaft and it vibrated just like you have mentioned.....drove me bonkers for a few months. Replaced it with the factory shaft and my problems went away.

 

[boostfrk]

That's odd...seems like a lot of people buy the FRPP aluminum shaft to get rid of a vibration.

Besides the vibration, did you notice any difference with the aluminum shaft? Was it worth the $270 price tag?

 

[betke76]

could also try a "bob's shifter gasket" i personally never tried one but a couple of buddies say they are great.

 

[boostfrk]

So I thought this problem was gone, but it's clearly not. I still get the vibration/knocking. Seems to happen under these conditions:

Low speed <25mph
1st or 2nd gear
Most noticeable with clutch engaged

Oddly enough, if I push the clutch in and pull it out of gear, I can't feel the vibration anymore. I wonder if it's coming from the rear end somehow (wheels out of balance, some bearing in the rear end) and it's just transmitted through the shifter when it's in gear and the clutch is engaged.

I don't want to rip apart the rear end and start replacing stuff but this is driving me bonkers.