Scary noise and thump when engaging torque, tranny/clutch/engine??? please read.

[rnln]

This is too complex for me. I hope someone know my new problem… please read
I recently experience scary noise and thump feeling when I engage torque. When I say “engage torque”, I meant when I lift the clutch pedal after shift into gear, and also when I hit the gas pedal after shift into gear.

One afternoon, couple days ago, I heard terrible noise every time I release my clutch and hit the gas pedal after a shifted. I thought something is wrong with my pedal cluster since I felt the vibration there at my feet. The noise is like a bunch of gears were turning and they were loose, and their teeth were not fit well together and they were going to through everything apart. It is in the rear around the engine or tranny area. Each time it last about a second or two, after shift and accelerate. At cruising, it drove normal, nothing happen. I did some tests slowly and precisely. What I did was, after getting up to 3000 rpm on first gear…
1- step in the clutch, pause
2- shift out of first, pause
3- shift into second, pause
4- lift up clutch pedal, pause (without touching gas pedal)
5- depress gas pedal, pause (without touching the clutch pedal)

I did all single steps careful with a pause to reproduce the terrible noise so I can be able to tell which action create this noise. Finally, I found that the noise can be recreate at step (4) and (5) above. If I do it very slow, very very slow and careful, then the noise and thump is less. Note: shifting is very smooth. Cruising is perfect, so the whole time driving is perfect except accelerating after shift, and sudden releasing gas pedal.

Another action can produce the hard thump feeling (very strong thump, without the noise) is lifting up the gas pedal while cruising on highway, then depress the gas pedal again (both action without touching the clutch pedal). When lifting the pedal, everything is normal, but when depressing the gas pedal again, the car jerk and a hard thump as you lug it very hard.

I spent all day today to check tranny fluid and refilled it. I am using redline 75/90NS. This fluid is new, replaced only 2 weeks ago. I also adjust the clutch pedal to raise the pedal up high, still same problem. Then I tried to adjust it 5 or 6 times from all the way high to very low, still same problem.

I also checked engine mounts and tranny mounts. They all look ok. The tranny mounts have some normal wear, but the big notch where it fit into the transmission has bad worn, probably do to the shake/thump. Please look at the picture below.

I have talked some friends and there are several opinions. Some think it’s the tranny gears. But if something wrong with the tranny, then shouldn’t it happen even while cruising? even though I don’t shift or applying torque? Some think it’s the clutch. But if it’s the clutch, or even bearing or anything related, then shouldn’t I be able to shift smoothly? At least it should grind, right?

Anyone experience this problem?

[ChkbookMechanic]

I'll take a W.A.G. but have you thought about the synchros in the transmission since it seems to come on with the clutch pedal? What gears does it make the noise in? Just 1->2 or does it do it in any of the other gears?

[MARTIN AIDE]

do you have a rubber centered clutch?sounds like the rubber has broken free

[Grady Clay]

I will second the rubber center clutch idea. Check above the transmission. You can get your fingers to the top hole into the bell housing on the side opposite the starter (sorta like half of a bear hug.) You are looking for little chards of rubber. Occasionally you can find some in the bell housing drain notch.

While you are under there, check that all the CV joint bolts are tight. Broken and loose bolts can give similar symptoms – just before very bad things can happen.
Check rcecale’s thread. While very long, it is worth studying in its entirety.
Reconstructing Constant Velocity (CV) Joints
Reconstructing Constant Velocity (CV) Joints

Best,
Grady

[rnln]

It doesn't sound like the syncro to me, since the syncro problem is to preventing you from shifting in gear (grind). My shifting is perfectly smooth. The problem I have is after shirting. It is when I accelerate (releasign clutcvh and hitting the gas pedal) right after shifted.

Originally Posted by ChkbookMechanic

I'll take a W.A.G. but have you thought about the synchros in the transmission since it seems to come on with the clutch pedal? What gears does it make the noise in? Just 1->2 or does it do it in any of the other gears?

[rnln]

I don't know what is in there. I have a question about this. If the rubber is broken, would you still be able to shift smoothly?

Originally Posted by MARTIN AIDE

do you have a rubber centered clutch?sounds like the rubber has broken free

[rnln]

I found that little hole with a piece of rubber seal but it's on top. THe only way to look from there is if I can take the tranny down, right? I did check around the 1/2 sharp but everything looks normal to me, bolts are tight.

Originally Posted by Grady Clay

I will second the rubber center clutch idea. Check above the transmission. You can get your fingers to the top hole into the bell housing on the side opposite the starter (sorta like half of a bear hug.) You are looking for little chards of rubber. Occasionally you can find some in the bell housing drain notch.

While you are under there, check that all the CV joint bolts are tight. Broken and loose bolts can give similar symptoms – just before very bad things can happen.
Check rcecale’s thread. While very long, it is worth studying in its entirety.
Reconstructing Constant Velocity (CV) Joints
Reconstructing Constant Velocity (CV) Joints

Best,
Grady

[rnln]

I went out and while wandering around my baby, I remember I saw some tiny rubber pieces laying on the ground under the tranny while I was taking off the tranny mounts yesterday. The material look like ruber from tire without thread (my tires are still perfect). Please look at the pic below. It's kind of shiny in the pic, but it's not in real. Do they look like they are part of the ruber clutch disk?
The blue pin is not from my car

I did some driving late yesterday. I didn't ahve any problem the first couple miles. The problem started to show after driving around for proximately 15 or 20 mins. I started the car today again and moved it around a little bit, no problem at all. Seem like heat related?

Grady,
the thread about the CV join is interesting. But I guess my problem might be different? since I can still have power as nomral and moving as normal. The problem is only when I accelerate. Or maybe mine is still in tack but loose therefore it still moving but thump when more torque applied? arghh... too much guesses for me.

What chances do I have on the ruber clutch disk problem? My car is an 87 with 88 engine, notsure 87 or 88 tranny though. I think they are the same aren't they?

[rnln]

Thanks all for opinions. I brought my car to AASE in Fullerton. After around 5 mins sitting on my passenger seat, he said it's my ruber clutch disc is separate fromt he clutch pads. I asked several questions and Jeff seem to know everything about it. I got a quote of $1,3xx quoted for clutch disc, spring center, some oil/filter, and labor.
What do you guys think?

[Christien]

Seems like a fair price. Clutch kit from Pelican is about $650, which includes disc, throw-out bearing and pressure plate. Labour is intensive on this job - even for a pro, one hour for engine out, one hour for engine in, plus time to replace the clutch components, and that would be lightning speed.