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Yeah, not super stoked but at least it’s more driveable on the highway now. Also, you’re right, the list of culprits is shorter so that’s something. I’m gonna check it once the car is in the air but I’m sure it’s good, given how much of a difference it made.
Weight is about the same as the KPower driveshaft. I talked to the guys about making it lighter, but in the end they said they wouldn’t recommend going down in tubing size.
Just got it in the air again. Had a buddy spin the car up to 80mph. Couldn't find anything visibly vibrating. Took the stethoscope and probed around and the vibration is very obviously centralized in the diff. You can put your hand on the pumpkin and feel it start as the car hits 75mph. Driveshaft looks just about perfect. Doesn't vibrate visibly at the speed of resonant frequency anymore. No noise from anywhere else via the stethoscope. Probed the wheel knuckles to see if maybe the CVs were making noise. Nothing.
Given the fact that you haven't had this issue, Six, and the fact that Greg fixed his issue by swapping to a Cadillac diff, I'm gonna bolt up the PPF like you did and see if that makes any difference. Should be able to do that during lunch today.
You're an animal man, but I know the feeling of wanting to get the car back to 100%. I'd offer more than encouragement but I have no experience in this area. Good luck on the PPF reinforcement.
Out of curiosity, what fluid do you run in your diff/trans?
Haha thanks man. Yeah, I'm seeing red now. Mostly just cause I want to get the car running again. Even if its just to run the canyons, I want to rip this thing again. It's been like three weeks or something now.
I pulled the left axle (the first new one that I put in) and the outer CV has a little bit of play in it. More than the old one that came out of the car. I popped in my old stub axle and lowered the exhaust a bit. There's just enough room for me to not be worried about contact. Gonna swap the other old axle in and give it a go. I'm not banking on these being the issue but might as well check.
I'm running a 50/50 mix of Redline D4 ATF and Redline MTF in my trans, per Der_Vierte's recommendation. Motorcraft 75w85 diff fluid in the diff. Hasn't given me any problems yet.
Swapped out to my old axles and mounted the PPF on the transmission crossmember, to no avail. If anything, the vibration comes on earlier now, although I'm assuming that's because the bushing in the PPF delete brace was muting it a bit.
I'm out of ideas. The only thing I can see/perceive is a diff that begins vibrating violently at 70mph. It didn't do this before the swap, so I can't imagine the diff threw a pinion bearing at the exact same time.
That sucks man, again, I wish I was more knowledgeable about all of this to help out. Hopefully someone else chimes in with a good idea, it can be really tiring to spin your wheels troubleshooting something like this.
Yes, forgot to mention I drained the diff fluid yesterday and it came out black. There are some faint rainbows in it that show up more prominently on camera than to the naked eye, although no ferrous material on the drain plug or sizable pieces in the fluid. Looks darker but similar to most other times I’ve drained my diff fluid following a decent bit of track and canyon abuse. I changed the fluid when I got this diff a few months ago and the old fluid came out jet black, so that might account for some of the pigment. Still had no issues with the diff pre-trans swap.
I got my laser angle finder in the mail and am about to run by the shop to check lateral trans/diff alignment. I pulled my front subframe to change out my oil pump back in October, and was running mismatched motor mounts at the time (thought I had two Supermiatas but one turned out to be a mystery mount) which didn’t line up from a longitudinal standpoint and made the subframe difficult to reinstall. I’ve since corrected the motor mount issue but think
my subframe might be a bit cocked. I can’t remember how much you can move the subframes in these cars around.
Minor progress has been made. I pulled the driveshaft and PPF and placed a flat piece of strap metal in front of the pinion to put the laser up against. The laser I got has a flat face but rounded back. Stupid. Trans looked like it was offset a bit to the left so I loosened the front subframe and moved it maybe 4mm toward the passenger side. Vibration now comes on at a substantially higher rpm in the lift. Maybe closer to 4k+ vs 2.9k rpm in 6th like yesterday. Feels less jarring too. I didn’t have time to mess with the rear subframe. With the car in the air and wheels spinning, it still looks like the driveshaft is off-center laterally.
Top pic is before. Bottom is after. I had a buddy take the second pic. Should’ve taken both pics for myself for consistency but it was super difficult while holding the laser and strap metal with one hand and also I’m basically out of brain cells for the week.
Amazon lazer. Self-adjusting and such. Neato.
Edit: just took the car out on the road and got it up to almost 5k rpm in 6th. Vibration is GREATLY reduced. I heard a bit of noise coming from the rear end as the car edged past 4.5k but couldn’t tell if that was just additional NVH from having a solid trans mount. This car has much more NVH overall than pre-swap. At any rate, I don’t feel the diff resonating through my *** like it did before so I’m taking it as a small win.
Got out and ripped the car around with some buddies yesterday. Started in the westernmost edge of the San Gabriel mountains north of LA and worked our way eastbound. Think I left my place at 8:30 and got home after 6. Burned a whole tank of e85 and then some. Feels so good to rip the car around again, and canyon speeds aren’t high enough to trigger the vibration.
Spent a good bit of time measuring the vibration on the freeway as well. It’s still present. Most violent at ~5-5.5k rpm in 6th gear but still less so than it used to. Starts a little above 4k.
I put the KPower diff brace back on today, since mounting the PPF seemed to make the vibration come on sooner. Didn’t notice much of a difference this time around. I’m curious if I can find a slightly softer bushing for the brace since the one in it is rock hard. While I had the car in the air, I experimented with lateral trans angles as well. Currently, I have the trans pointed as far toward the passenger side as my crossmember bolt holes will allow. Pushing it further toward the driver side seemed to make the vibration slightly worse. Might hog out the crossmember holes some more and see what happens if I point the tail further toward the passenger side.
Oh, also my check engine light is coming on basically whenever I’m not at idle, along with a battery fault message in TunerStudio. It’s done this intermittently, not often, ever since I installed the ECU a year almost two years ago, but now it’s constant. Car drives fine, battery’s fine. Maybe something is up in the ECU, but the fact that it does it every time I rev it above idle now makes me think my alternator voltage regulator is probably going out. I checked my charging voltage at idle this morning and it was 14.3v. Didn’t have time to do any other testing or rev the motor up.
Luckily for me, my Megasquirt decided to stop talking to my laptop as I was going to check if I could read supply voltage in TS (I’ve never had to or tried this, but thought it was possible). All I get now is a “USB device not recognized” message when I plug it in. Tried uninstalling it and updating the driver but it still won’t connect. Luckily, my Megasquirt has a standard 9-pin serial port as well as the USB port, so I ordered a cable to use with that. I have way too much going on with this car and have no desire to tear my ECU open currently.
Jeez good luck man definitely quite a can of worms you're dealing with these days. Hopefully you can get the drivetrain vibrations to a "minimum." Obviously NVH is going to be worse than OEM but what is "normal" for this setup is hard to say. You have almost solid mounts for the tranny whereas OEM has none, and as others mentioned how much vibration is "normal" or created by the new tranny/mounts/etc. I'm sure you'll get it sorted. If the car's driving you nuts I'd say set it aside for a few days or a week and come back to it fresh. That always helps me.
If the car's driving you nuts I'd say set it aside for a few days or a week and come back to it fresh. That always helps me.
Haha you’re speaking to my soul right now man. Yeah, I’d like to button up the alternator issue if that’s what’s going wrong, just so I can drive the car this weekend. Will likely mount up an FD RX-7 alternator because why not. After that, I might take a week off, though. This sh*t’s got me tired
Dang dude. Non-stop gremlins have been coming your way! Glad you got to rip the car around and sounds like you had a good time.
It’s possible the CEL settings (specifically the fluctuation setting) are a bit too aggressive if it’s something it has done for a while, but certainly verify voltage while you rev and check what the ECU is seeing.
i agree about taking a break. Sometimes you gotta put away the wrenches (or usb cable lol) and grab the mountain bike!
I signed up for this, didn't I? I'm having fun. This is fun. Burning time and money is fun.
Good point. Gonna check the CEL settings tonight. The cable should be delivered by the time I get home. I was initially worried by the CEL a couple years ago, but as soon as I saw that it correlated with the Battery Fault message and the car still drove fine, I put off diagnosing it because I had so many other things to work on lol.
Yeah man, no joke. My bikes have been keeping me sane this whole time! Both of my mountain bikes are always in need of work but it's so much quicker and easier to diagnose and repair them than it is with the car haha. Just rebuilt the dropper post on my long travel bike and replaced a couple nipples in the rear wheel that corroded and broke the last time I rode it. Gonna try and get some miles on it this weekend.
On the coattails of that thought, here's the seatpost in question being used to hold the brakes in the Miata while I lifted the rear end to shift the subframe over on Sunday morning. I had the front wheels chocked too but the post was sitting on my workbench and begging to be used for something.
Good man! Yeah, bikes always need TLC, but they take a hell of a beating out in the trails. I'm still rocking my first mtb, 4 years and still kicking but every time I sit and think I'm baffled by how much abuse it has taken!
The battery issue is annoying, but let's hope that's your last gremlin for a little while eh?
On the coattails of that thought, here's the seatpost in question being used to hold the brakes in the Miata while I lifted the rear end to shift the subframe over on Sunday morning. I had the front wheels chocked too but the post was sitting on my workbench and begging to be used for something.
Damn, I should probably vacuum my interior too...
HA! That's pretty good use of a dropper post. I'll keep this in mind as my next-gen e-brake
04-18-2024, 11:50 PM
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