Bad throw-out bearing?

[l75eya]

From what I've been told, it seems my 87 5 speed D/R GL may be developing a bad throw-out bearing. I was wondering if the gurus here think these are the correct symptoms;

 

rattling noise (loud) coming from front of car. Center. It will rattle if the following conditions are met

The car is in neutral with the clutch pedal in it's normal position (not pushed in)

The car is in gears 1 through 3, clutch engaged or disengaged.

 

If I'm stationary with the car in neutral and the clutch pedal fully depressed the rattle goes away.

If I'm in motion and I put the car in neutral and fully depress the clutch pedal the rattle still goes away, but takes longer.

 

I'm not quite noticing any rattling in gears 4 or 5 but that just may be due to road/wind noise interfering.

 

What do you guys think? If it *is* the throw-out bearing..is it something that really needs to be addressed quickly (ie will it lead to other failures if not corrected) or can it wait until my clutch wears out (which may be awhile).

[scoobiedubie]

The throw out bearing should only be working during the periods when the clutch disc is not engaged, because the transmission drive shaft would not be spinning at the same rate as the flywheel. Once the clutch engages, then the transmission drive shaft is spinning at the same rate as the flywheel, causing the bearing to be stationary. With the transmission in neutral, the clutch disc should be engaged with no spinning of the bearing. It appears that you have a bigger problem than the throw out bearing. It sounds like a front bearing for the transmission drive shaft has gone out, since whenever the transmission drive shaft is spinning at slower speeds, you can hear the rattle. Easiest fix is to replace with a low mileage transmission from a wrecking yard, so that you can see the odometer and the condition that the vehicle was maintained in prior to it ending at the yard. Ideally, you would want to see a stack of Bibles in the back seat, the ash trays empty, not a speck of dirt anywhere, and with less than say 120,000 miles.

[l75eya]

Thanks for the insight, I haven't quite grasped for myself how exactly everything works through the drive-train and that explanation both makes sense and clears it up a bit for me.

 

Would there be any way for me to be certain that is the issue? The only way I'm thinking there could be is to drop the transmission and check out the condition of the input shaft itself.

 

The rattling is very, for lack of a better way to describe it, bouncy

sounding. It sounds a little bit like a percolator coffee pot, steadily making noise and occasionally catching something and making a bit more noise very briefly and then going back to it's steady rattling.

 

 

Either way, thanks for your advice!

[l75eya]

Okay, a couple of new findings, trying to post up everything I can to help you guys help me

 

The rattle does not make itself evident in 4th or 5th gears.

As I mentioned before, the rattle will occur while stationary in neutral with my foot off the clutch. If I push in the clutch, the rattle will slowly dissipate, like pushing in the clutch ceases motion on whatever it is that's making the noise and it slowly freewheels itself until it stops.

Now;

If I push in the clutch and then attempt to put the car in to 1st, 2nd, or 3rd gear, the rattle will abruptly stop. Also, with light pressure on the shifter it is only until the rattle stops that it will actually go in to 1st gear.

 

I've also noticed that it has been popping out of 1st gear lately, though very rarely.

 

As mentioned before, I'm not too knowledgable in this area, so excuse my ignorance but my gut wants to throw out

synchros?. But if that's the case, why only 1st, 2nd, and 3rd. Maybe because they are the most used gears driving around town? Lots (LOTS) of speedbumps, stop signs, traffic lights, and dumb-asses in my town..

 

Food for thought.

Either way, it doesn't seem like it's something simple =\

 

Till we figure it out, I'm rattling on.

[scoobiedubie]

The transmission drain plug may be magnetic from the factory. Remove it and be prepared to replace the 2 qts of transmission oil, and inspect that plug. If you have metal bits hanging onto it, then you just found the cause.

[l75eya]

Looks like that's in the queue now then. Couldn't hurt to change the gear oil anyway.

 

Thanks again for the ideas