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Drivetrain issue: Noise and jerking and shifter movement
I think my issues started 3 years ago. Or at least that's when i first noticed anything. I bought my 94 FD with 46.000km (28.500 miles) on the odo. It was a great cared for car, but as you guess not used much. I have put 15.000km on it while owning it. Driving nice and not abusing it.
As part of the “get her in to shape” maintenance i did a full drivetrain fluid change 3 years ago. I also changed the diff mounts to polyurethane (purple). Before that the car ran great, and i cant remember any noises or jerking. I drained the trans and diff and replaced with Redline MT90 and 70W-90 oil for LSD. After this it feels like the car started jerking (more) on throttle on/off situations. I also notice shifter movement.
This last month i have done a few more things to the drivetrain, some to fix the above issues.
- Clutch change (it was slipping in 4th/5th at boost)
- Clutch fork and release bearing
- Rear trans seal
- Banzai Diff brace (with a rubber bushing, not the poly that was in the kit)
- Fresh MT-90 (the old have seen less than 4000km but was dirty so i changed it)
The result:
- Car was great to start with (cold). No shifter movement, no jerking, no noises.
- But, as the car got hot, shifter movment is back (tho not as much as before), there is still jerking in throttle on/off situations.
I also got a new and exciting noise! (check video)
- Its always at the same RPM (1500-2500)
- its on load (i think)
- its in all gears as far as i can tell (but easiest to replicate in 4th)
The only way i can describe it is the metallic chattering you can hear every time i give it throttle, the video have 3 accelerations in a row (edited) and i think the noise is most audible at the 3rd.
My potential culprits:
- Wrong oil? Researching (more) it seems Torsen does not want the LSD thing, but instead the 75W-90 NS. (?) (Or Neo all around but thats not available here)
- I will change this today for a Castrol type my dealership use, to see if it gets better.
- Worn engine mounts (got Banzai polys ready to go in but im skeptical due to noise). the car is low mileage so im thinking the mounts should not be gone yet.
- How do i test those?
- Worn / bad driveshaft?
- When i did the first job on the diff mounts, i did not mark the driveshaft-to-diff alignment like the FSM says to. Is it possible a wrong alignment here could cause sounds? If so, how do i figure out the correct alignment? (there are 4 different mount options)
- Diff backlash out of spec?
- Exhaust leak???
- Nuked transmission??
Does anyone have any advice or recognize the sound? Im a bit out of my depth on this, and all i want is a silent and nice car to drive around
I listened to some of the video, is there particular time stamps where the noise is?
In all the MANY FD clutch jobs I've done I've never marked the driveshaft, just put it back on. Never had a problem. The driveshafts are balanced to themselves, they just bolt on.
Is the shifter centered in the hole in the trans tunnel? Had a friend's FD whose shifter was over to the right side of the car, it was a bent power plant frame causing it. We noticed this as we were building the car but if we would have run it there would have been some noise from the side of the trans hitting the body of the car.
You will get some more noise and vibration with aftermarket mounts but it shouldn't be extreme.
The other thing to check is that none of the exhaust is touching or rubbing against something, this will cause all sorts of weird noises. Shake the exhaust around and make sure it has plenty of clearance.
There's not an easy way to check engine mounts, you can visually look at them but really you need to remove them and see if they are still in 1 piece. The old 93 left side mounts where the mount was bonded to an aluminum arm fail early and often, if you have one of those it may be a problem.
At certain rpm or load you can get a resonance through the heat shielding too. Mine at the transmission tunnel for what ever reason got loose and would make noise. I only found it using a plastic dead blow tapping on the floor pan. Ended up using some silicone caulk between the shield and body.
I listened to some of the video, is there particular time stamps where the noise is?
At 6 secons and at 13 seconds are the most obvious ones.
There are mostly two clear sounds, the exhaust, and the one im talking about.
I have a real issue describing it, but if you spinn a broken ballbearing fast thats similar, or maybe the noise from tires if you open the window. A metallic "Shhhhh" noise.
In all the MANY FD clutch jobs I've done I've never marked the driveshaft, just put it back on. Never had a problem. The driveshafts are balanced to themselves, they just bolt on.
Then i rule that one out.
Is the shifter centered in the hole in the trans tunnel? Had a friend's FD whose shifter was over to the right side of the car, it was a bent power plant frame causing it. We noticed this as we were building the car but if we would have run it there would have been some noise from the side of the trans hitting the body of the car.
I am pretty sure it is. I had the PPF out for paint (fake Mazdaspeed red) and i could not see any obvious issues with it. Also, given the life and condition of the car i doubt its damaged. But i will get a picture of the shifter for you.
You will get some more noise and vibration with aftermarket mounts but it shouldn't be extreme.
I guess the only way to find out for me is to try it
The other thing to check is that none of the exhaust is touching or rubbing against something, this will cause all sorts of weird noises. Shake the exhaust around and make sure it has plenty of clearance.
Ahh, that a good tip. I had the midpipe out for the clutchjob so it could be something there thats not as it should be.
There's not an easy way to check engine mounts, you can visually look at them but really you need to remove them and see if they are still in 1 piece. The old 93 left side mounts where the mount was bonded to an aluminum arm fail early and often, if you have one of those it may be a problem.
I have one of those, and got a couple of used spare mounts in addition to the Banzai ones, Maybe pull it out for a look and get a steel mount in anyways.
At certain rpm or load you can get a resonance through the heat shielding too. Mine at the transmission tunnel for what ever reason got loose and would make noise. I only found it using a plastic dead blow tapping on the floor pan. Ended up using some silicone caulk between the shield and body.
Thanks, will go at it with a rubber mallet this evening
On the bent PPF, the one we had that was bent had NO obvious signs of damage - no cracks, no anything. Having it right next to a good PPF I couldn't see any difference at all between the two. I was trying to find some "smoking gun" that people could look for to see if it's bent and found nothing.
The only difference was installing it in the car - one pushed the trans over towards the right side of the car, one was dead center.
First thing i did was drain the diff and fill up with new oil.
This is what came out, and the magnetic fill plug had something looking like sludge on it, but i guess is super small metal particles?
I also managed to identify the sound in the sound clip, and where it came from:
Its coming from the transmission, but was enhanced by the Banzai transmission crossmember. Even with the polyurethane bushing replaced with a rubber one it transferred noise.
I removed the rubber bushing and realigned the PPF according to the manual: Rear first (top, middle, bottom) then front (top, bottom).
During the test trip the sound was almost gone, but now i could force it at a lower RPM than previously, tho not at the same level as it was before this.
Originally Posted by DaleClark
On the bent PPF, the one we had that was bent had NO obvious signs of damage - no cracks, no anything. Having it right next to a good PPF I couldn't see any difference at all between the two. I was trying to find some "smoking gun" that people could look for to see if it's bent and found nothing.
The only difference was installing it in the car - one pushed the trans over towards the right side of the car, one was dead center.
You're probably OK but it's worth ruling out.
Dale
Is this good or bad? This was before i redid the PPF and removed the diff brace.
Originally Posted by Sgtblue
You might also check that brake hard line that runs along the back side of the rear cross-member and diff bushings for signs of failure.
I did, seems fine. Also the diff bushings are polyurethane and have less than 10k on them, so i doubt they are bad. How do i check it? I usually jack the car up using the diff and it does not flex much at all.
The drive-train has 4 mount points: two engine mounts and two diff mounts. There is the spindly frame connecting the engine/trans to the diff. Stock all 4 mounts are liquid filled pillows designed to absorb as much vibration as possible and are tuned to do this in a specific range of vibration frequencies. Not trying to be condescending... just painting a picture.
You put nearly rigid diff bushings in the rear diff, which effectively made one end of the drive-train fixed.
The engine end is the heaviest end of this system and still has the stock mounts, which are wildly compliant compared to urethane bushings. With rigid bushings in the back, there is more force and vibration transferred to the front engine mounts than previously which would cause more movement.
Also, one end is held nearly still, while the other can move around. The PPF is put in torsional bending as the heavy, floppy front end and stiff light rear end of this system fight each-other.
To me it's like trying to hold a lollipop still from the end of the stick while someone is trying to take off the wrapper.
I think that the stiffness of all your mounts should be comparable or you are going to have uneven and uncontrolled movement.
I would recommend poly engine mounts with powerflex diff bushings. I make my own from 3" 80D poly round, but I'm sure the banzai ones work great. There is a little more vibration at certain idle rpms, but above 1k rpm the car feels 10X better. I have no shifter movement. On/off throttle response quickly translates into F/R weight transfer allowing for predictable adjustment of oversteer/understeer in corners. It's all connected.
At certain rpm or load you can get a resonance through the heat shielding too. Mine at the transmission tunnel for what ever reason got loose and would make noise. I only found it using a plastic dead blow tapping on the floor pan. Ended up using some silicone caulk between the shield and body.
After you posted this, I got under my FD to try to see if any of my heat shields were loose since I was hearing a light buzzing noise sometimes during acceleration. The shields were OK, but I found some small pebbles that were trapped on top of the metal transmission bottom cover and made a noise like what I heard driving when I tapped the cover with a dead-blow hammer. So we'll see when I drive it again whether the noise is gone, or was something else.
As part of the “get her in to shape” maintenance i did a full drivetrain fluid change 3 years ago. I also changed the diff mounts to polyurethane (purple). Before that the car ran great, and i cant remember any noises or jerking. I drained the trans and diff and replaced with Redline MT90 and 70W-90 oil for LSD. After this it feels like the car started jerking (more) on throttle on/off situations. I also notice shifter movement.
It's really quite simple. If you don't want NVH, go with all stock bushings. If you want a tighter feel, go with Mazda competition bushings.
All bushings (to include pillow *****) should be replaced on a 25 yr old car
The drive-train has 4 mount points: two engine mounts and two diff mounts. There is the spindly frame connecting the engine/trans to the diff. Stock all 4 mounts are liquid filled pillows designed to absorb as much vibration as possible and are tuned to do this in a specific range of vibration frequencies. Not trying to be condescending... just painting a picture.
You put nearly rigid diff bushings in the rear diff, which effectively made one end of the drive-train fixed.
The engine end is the heaviest end of this system and still has the stock mounts, which are wildly compliant compared to urethane bushings. With rigid bushings in the back, there is more force and vibration transferred to the front engine mounts than previously which would cause more movement.
Also, one end is held nearly still, while the other can move around. The PPF is put in torsional bending as the heavy, floppy front end and stiff light rear end of this system fight each-other.
To me it's like trying to hold a lollipop still from the end of the stick while someone is trying to take off the wrapper.
I think that the stiffness of all your mounts should be comparable or you are going to have uneven and uncontrolled movement.
I would recommend poly engine mounts with powerflex diff bushings. I make my own from 3" 80D poly round, but I'm sure the banzai ones work great. There is a little more vibration at certain idle rpms, but above 1k rpm the car feels 10X better. I have no shifter movement. On/off throttle response quickly translates into F/R weight transfer allowing for predictable adjustment of oversteer/understeer in corners. It's all connected.
Now i feel a bit stupid for not understanding this myself. Thanks for teaspooning it (really thanks, no sarcasm). Can i blame it on beeing 10 yers since i had my mechanical enginneering course?
I pushed more of the torsional load to the front, wher the bushings are softer, that would result in more movement, and higher wear. Banzai is going in asap
Originally Posted by DaveW
After you posted this, I got under my FD to try to see if any of my heat shields were loose since I was hearing a light buzzing noise sometimes during acceleration. The shields were OK, but I found some small pebbles that were trapped on top of the metal transmission bottom cover and made a noise like what I heard driving when I tapped the cover with a dead-blow hammer. So we'll see when I drive it again whether the noise is gone, or was something else.
Had a quite nice session with a mallet under mine, and tweaked a few heat shields. Have not had time for a testdrive yet but im hopefull
Originally Posted by TomU
You answered your own question
It's really quite simple. If you don't want NVH, go with all stock bushings. If you want a tighter feel, go with Mazda competition bushings.
All bushings (to include pillow *****) should be replaced on a 25 yr old car
a stiffer rubber would be my pick. How stiff are teh competition ones compared to OEM and the softest poly?
Full replacement is on the maintenance plan. Just a bit hessitant to doing the pillowballs as i have never done anything like that before.
a stiffer rubber would be my pick. How stiff are teh competition ones compared to OEM and the softest poly?
Full replacement is on the maintenance plan. Just a bit hessitant to doing the pillowballs as i have never done anything like that before.
I can only comment from experience. I replaced all my stock bushes with poly as well as the Banzai trans and diff brace and Xcessive motor mounts. Shocks are Koni sports with Ground Control/Eibach springs (think around 9k). Overall this is too stiff for the street. For the street i would go with poly sway bar and steering bushes, mazda comp everywhere else except for maybe trailing arms and toe links which could remain regular OEM. I would include the Banzai trans brace (had that installed before i changed out my suspension), but not the diff brace. That said, since poly is much cheaper than OEM, you could amend what i said with poly diff bushes and motor mounts. If you do both of those, you may not need the Banzai brace (more savings)
Of all the bushes, i found the pillows were some of the easier bushes to replace. The trailing arms were the hardest followed by the diff and upper and lower control arms
I’ve done pillow-*****, toe links and most recently, differential bushings. The only one that was a real challenge was (IIRC) the inner OEM toe-link bushing....the larger of the two. The collar is VERY soft metal (aluminum?) and wanted to distort if not started absolutely straight.
Thanks for all the great input and help guys!
I think ill start with the pillowballs and see if the clunking goes away. Should i go OEM or J-Auto? Anybody got a preference or experience with J-Auto?
04-29-19, 03:57 AM
