In need of a problem diagnosis... completly lost

[Marahutay]

Alright.

Since i bought my 1991 240sx fastback in late april last year with 164XXX miles on it it has been making a rather weird noise that causes the entire car to shake from side to side (laterally). the noise sounds like something clunking like it is trying to engage into something but is being forced out.... the best way i can relate it to something is it reminds me of stripping the top of a screw with a power drill (drill bit bouncing up and down on screw). Guessing from the noise being made, i assume there must be something wrong with the clutch.

BUT

the clutch was replaced in september 07 and has not been abused.

it only makes this noise when starting in first, second, third, or reverse. I havent tried starting from a dead stop in fourth (yet... ) . it is not due to the engine moving at low rpms either, the shaking and the noise has occured as high as 2k rpm when starting from a stop and finally goes away when the clutch is fully engaged. when the noise and shaking occur after i get rolling in first sometimes, i push the clutch in (fast) to go to take it out of first and put it into second and its almost like it throws itself out of first gear once i start pulling on first towards second and has been so bad at times that it has almost shifted into second for me.

if the noise/shaking starts to occur and i do not fully engage the clutch (stop n go traffic), and i DO NOT try to take it out of first to try to go to second, it feels like every time i push the clutch back in. it feels like something is not disengaging correctly, it is very hard to explain.

oddly enough, it made a very similar feeling to the one i am trying to describe when i was driving in the snow cruzin at abt 4300 RPMS in first gear (to warm the car up) and i suddenly took my foot off the gas and i did not have enough grip through the snow to be able to turn my engine over at that speed and the car lurched in a way that was very similar......

i really hope someone knows whats up. i just rolled over to 185000 a few days ago with all original parts cept for a starter and some tie rods.

if i ride the s*** outta my clutch (2400RPM +) it does not happen.

It has been doing this since before i bought the car(good friends with previous owner and original owner), and has gone through a legitimate PA inspection and passed, and still it continues to clunk.

it sounds like something is going seriously wrong, but, nothing bad has happened for the past year and a half involving the clutch/transmission except for my slowly dieing reverse gear.

Modified by Marahutay at 8:04 PM 3/15/2009
Modified by Marahutay at 8:08 PM 3/15/2009

[liquid_cool]

check both your motor mounts to see if there broken and the engine is sloppin around in the bay..and get back to us after you look.

[Marahutay]

have not checked the motor mounts yet, but i have seen the engine moving quite a bit when moving my car slightly with the hood open. ill check the mounts when i get off work. Thanks liquidcool.

[Marahutay]

the mounts seemed to be in good condition.any other suggestions?also, it does not happen all the time, it hasent happened in about 2 days now. but usually doesnt go more than a week without doing it once.

[-RJ-]

does the transmission make a wierd noise in 1st 2nd 3rd and 5th but quiet on 4th gear?

[Marahutay]

it only makes the noise when starting from a stop. i assume it would do it in every gear if i could start out in fourth or 5th.

also.the gear popping out of first, it also does this when i push the clutch in at the EXACT same time i take my foot off the gas, even when the noise and lateral shaking DOES NOT OCCUR. it is almost impossible to recreate it on purpose though, it happens by accident every now and then.

[USMCgetsome]

sounds like your synchro gear is busted and swirling around in your transmission. time to change the oil and fish it out of the drain plug with your finger.

[Marahutay]

correct me if i am wrong, but, I was under the impression that first and reverse gears did not come with synchros

thanks for the info though.and how may this be affecting my engine/transmission if this is the case?

[00ryancody]

I would do as he said and check for the synchros. anyone could be busted out and around in it. if it shakes side to side then i would just make sure your driveshaft struts and the alignment is fine then see whats going on.