Shadow_S14

I'm having this strange thumping noise whenever I engage the clutch while in motion, tap the throttle, and shift; usually in lower gears (1,2,3). It happens every time I shift and it has been bugging me since I can't seem to find the problem. I changed the diff and sub frame bushings, motor/trans mounts, 1pc. drive shaft already and only other thing I could think is the diff itself just being worn out (J30 VLSD). The noise wasn't there when my car was Automatic, it began making the noise after the 5-speed swap. I have searched many threads, but haven't found a solution. Would be great if someone could add some insight to my problem. Thanks.

Sforteen

The noise is pretty normal.. when you have the clutch in there is slack in the drivetrain.. when you put the car into gear the tranny is likely still freewheeling.. when the synchro trys to match said gear to the same speed as the main shaft it clunks from the slack that gets taken up momentarily.. the synchro abruptly stopping the trannys internals sends a jump thru the drivetrain. as things wear, the noise worsens... The noise is from the pinion slapping the ring gear.. Autos don't have this issue as there is always a preload on the drivetrain, having solid bushings will for sure make this noise more evident

shookproof red line might help with the noise if your looking to make it less notable.

mechanicalmoron

If you replaced those bushings with something stiffer, you probably made it a lot worse. The noise comes into the passenger compartment by way of the subframe bushings, mostly.

Shadow_S14

I don't think the noise is normal. I was driving in my buddies s14 and it was a lot smoother compared to mine.
Nothing too stiff, I just used Energy bushings for the sub...

nextproject

Mine is the same way. Although i have solid subframe riser bushings. Also i have had the noise with both the stock and 1-pc aluminum driveshafts. Possible the noise could be from worn out traction arms? Possibly, excessive backlash in the diff, i dont know a whole lot about the audible effects of that. I plan on upgrading my diff soon and will likely go the extra mile to rebuild the unit with new bearings and properly set up. If the noise persists then i'll consider it likely to be normal.

Sforteen

try shifting slower and see if it goes away, like... push clutch in, wait..... ok next gear.. that will give time for the tranny to slow down after being disengaged from the running engine..

Understand??

mechanicalmoron

Yeah, it's the fact that you just multiplied the bushing stiffness by like, ten times? you're going to be transmitting a whole lot more vibration.


Try driving a bit more pro? Time your clutching and rowing better. You should go through the gate a fraction of a second before rpm's reach the new gear's speed, and you almost needn't slip the clutch at all, for a perfect, clunk-free shift. You also won't get that chunky feeling like your gears are not grinding, but they're sure as hell not synchronized either.

Also, try driving enough for your transmission to actually warm up. I bet after 20 miles, it goes away, and all your shifts feel better.

You're hearing it in the differential (and I'm sure there's some from there, too) but manuals gears are also just different than automatics, which have (very smooth, strong) planetary gears. If you put the shifter in that gear, you're forcing it to synchronize the transmission to the speed the wheels are turning, in that gear - and that backlash noise coming down the driveshaft and through your subframe, into the car, is what you hear. This is also why you have a whining/roaring (depending on the gear) gear noise when you engine brake at various (lower) RPMs, but it goes away when you clutch, and it changes pitch when you shift. It's gear noise.

turboS14kid

I had a similar problem end up being subframe busing I replaced the with energy suspension busing. Not solid bushing.

Mikester

Re-check the nuts/bolts holding your axles to the diff.

__________________

Shadow_S14

Hey thank you for this insightful response. Your right, the diff and transmission are worn out. I've been trying out different ways to shift, and I found that catching the next gear as soon as possible lessens the noise. Quick shifts do seem to work. Also after the tranny warms up the noise does disappear. And yes I double checked diff to axle bolts; they are all tight and torqued. I couldn't find a way to fix it, but I found a way to work with it. Thanks!