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For those of us who are not as versed at this, are you thinking the axle was causing vibrations as well that you were attributing to the driveshaft?
Yeah, I think that the current vibration is from the excessive runout in that axle shaft. I'm spitballing a bit here, but the stages I think I've gone through causing the vibration since the Getrag swap are:
1. Excessive runout in the supplied driveshaft and mild runout from the driveshaft adapters not being centered
2. Supplied driveshaft replaced. Runout due to the new driveshaft not perfectly self-centering on the adapters, and the adapters still not being centered either.
3. Centered the adapters and driveshaft better (not perfect, though). Current vibration due to the wobbly axle. Believe this axle has been contributing to the vibration the whole time.
I messaged KPI only 30 minutes before they closed so will have to talk to them tomorrow. I'll probably call them on my way to work in the morning. In the meantime, for science, I'm going to throw a couple more hose clamps on the axle in question to counter the wobble and see if any difference can be felt. There's a chance I won't be able to add enough weight to offset the wobble. If I'm lucky, though, maybe I'll be able to lessen the vibration just a bit, confirming the axle is the issue.
It's insane that the driveshaft adapters don't use some sort of centering mechanism like every single OE driveshaft does, or if it does it's clearly not properly machined.
It's insane that the driveshaft adapters don't use some sort of centering mechanism like every single OE driveshaft does, or if it does it's clearly not properly machined.
The driveshaft and adapters all have self-centering mechanisms... but every single one has some free play between it and the next component. Play between the pilot shafts on the trans/diff and adapters, play between the driveshaft flanges and the adapters. I've got the front driveshaft flange and adapter close to being perfectly centered but they still need some adjustment...
Brilliance with the wheel weights. That's better than what I've got going on right now lol. I think I'm maxed out on the amount of weight I can offset via hose clamps. I added these two at a time and it was hard to tell if any difference was made. I gotta pull them all off and test the vibration back to back.
That being said, the vibration at this point is probably the best it's been since I put the ZF in the car. It starts coming on above 3k in 6th gear, lower than it did with the Miata diff w/ rubber bushings, but doesn't get quite as severe as it did with any of my numerous setup iterations using the Miata diff. If I could reduce the magnitude by the same amount again, I'd probably be comfortable tracking the car. I'm gonna have to get the car in a lift again this week and d*ck with the driveshaft positioning again, in addition to getting this axle replaced. We're getting closer at least.
I'll bet you I can figure out another item or two to stuff in there as well while I'm at it lol.
Got the car on a lift during lunch today. Was somewhat strapped for time again but I got the driveshaft just about perfectly centered on the trans adapter side. The adapter still needs to be centered but I'm assuming its runout is making less of a difference than the driveshaft's. And this was another "for science" test.
After aligning the front of the driveshaft, the vibration's resonant frequency rose another 4-500rpm in 6th gear. That's a win. Yesterday it started to become noticeable around 2,500rpm in 6th but now I can't feel it come on at all in the lift until around 3k rpm. It's also a touch less aggressive than before.
Generally speaking, the vibration won't be felt on the road until around 1,500-1,800rpm higher than it presents itself with the car in the air. It's also moderately less violent on the road than when I have the car in the air (as one would expect with tires, suspension, etc absorbing some of the energy). I'll have to take it out tonight and see how it behaves on the road. I have no doubt that the issue is gone, but it's getting better bit by bit.
Drove the car up to 100mph a couple times coming home from work yesterday. The vibration is still present on the street but is much better than it's been before. At the beginning of this saga, the car felt like it was absolutely going to explode at 75mph. Now its just a moderately disagreeable quivering at 100mph. It's still not at the point where I'd be comfortable tracking it, but it's close. I'm gonna get the front trans adapter perfectly centered this weekend and see if that gets us there.
I talked to KPI about my wobbly axle. They said they contacted V8R who is contacting the DSS on my behalf. I asked if I could get proof of purchase on the axles and talk to the DSS myself but haven't heard back. I have no doubt that this process is going to take forever.
Also in the midst of all this, I fixed a vacuum leak and misfire that I found present while driving the car Monday night. The vacuum line feeding my MS and boost gauge partially split at the intake manifold nipple, causing high KPA readings at idle and all sorts of fueling issues. Replaced the line, no big deal there. While road testing the car Monday night to see if the hose clamps on my axle made a difference, I started running into a hard misfire at 17psi around 5,500-6k rpm. My D585 coils are probably starting to get tired after a year and a half of abuse (and I bought em used so who knows what they went through before). The plugs in the car are only a month old but gapped to .035". Gapped 'em down to .030" and the miss subsided.
I'm gonna get the car up to 100+ on the road a few times today or tomorrow to further confirm the vibration severity at track speeds. It's getting closer and closer to not being an issue anymore.
Car died on me on the way home today. I was cruising down the road at 40mph when the motor un-dramatically quit. Pulled to the side of the road and attempted to crank it over. Zero compression. I figured the timing belt snapped. My motor is interference. Barely, but it is. Sh*t. I pulled the front cover and found a section of timing belt teeth laying behind it. Just as expected.
Got the car towed home and continued to tear it apart. I ended up finding the timing belt tensioner slipped from its original position, and the closest bolt holding the water pump in had backed out a few threads. A portion of ~15 teeth was missing from the timing belt, and the belt was still attached and otherwise intact. I think (potentially) the bolt backed out from the water pump, caught the belt and caused the tensioner to slip. What's weird is that I had loctite'd all the water pump bolts and this one was still loctite'd and couldn't be turned by hand.
Speculations over for now, here's the rest of the facts. The belt doesn't appear to have moved more than within the 15 sheared tooth area on the crankshaft gear. The tensioner slipped maybe 10mm from its original position but the belt wasn't dangling or anything, I heard a couple faint metallic noises as the car died, but nothing violent. The transmission usually makes a few rattles as it slows to a stop when I turn the car off. I can't tell if the noises I heard were that or the pistons kissing the valves. The motor made multiple revolutions when I first attempted to crank it with no audible piston to valve contact.
So either the belt managed to hold the cams in place while the crankshaft continued spinning, or the cams skipped teeth and I've got bad news. I see no damage on the other teeth but don't know if that's conclusive enough evidence to say the cams didn't skip. I'm gonna bring home my borescope and a leakdown tester tomorrow night to investigate further. Hopefully I can just toss a timing belt in this thing and go on my merry way. Not going to hold out false hope, though. If anyone's had a similar experience before, I'd love to hear it. On the flip side, I've needed to change out my crank seal for a while, so I'll be getting that done at least.
Edit: photos are working now
Last edited by Z_WAAAAAZ; Jul 18, 2024 at 09:33 AM.
Yeah man, I saw Wingman's post and decided I wanted to be just like him lol.
My theory is, much like Icarus, I flew too close to the sun nearly solving my driveline vibration and that prompted a separate failure. And/or I must've been into the dark arts in a past life.
Gonna grab my borescope and leakdown tester and head home during lunch to check it out. Should have results this afternoon.
Bruh, this is terrible to hear, wtf! What timing belt was that? (not that it was the cause), just curious as I don't recognize it. Mines got the ole gates blue belt on it, which has always given me concerns for other reasons (paint buildup on pullies).
Originally Posted by Z_WAAAAAZ
Also in the midst of all this, I fixed a vacuum leak and misfire that I found present while driving the car Monday night. The vacuum line feeding my MS and boost gauge partially split at the intake manifold nipple, causing high KPA readings at idle and all sorts of fueling issues. Replaced the line, no big deal there. While road testing the car Monday night to see if the hose clamps on my axle made a difference, I started running into a hard misfire at 17psi around 5,500-6k rpm. My D585 coils are probably starting to get tired after a year and a half of abuse (and I bought em used so who knows what they went through before). The plugs in the car are only a month old but gapped to .035". Gapped 'em down to .030" and the miss subsided.
I've had both of these issues, well similar at least. The line to my stock FPR and MAP sensor split (I tee them off the same spot) and the car started running like dogshit (super rich), which gave me a little scare before I realized it idled with a LOT less vacuum and realized the issue. Easy fix, but not super fun track side in the heat. I've considered going with silicone vac lines but haven't done it yet.
Also, ******* misfires. I tell you man, when I was running COPs I'd get a misfire every 6 months, had to change the plugs all the time, gapped **** down, replaced the COPS twice (toyota). Each time it would go away for a while but eventually come back, and sometimes at the worst time (on track tenths off a PB). It was super annoying
I went with the flowforce d585 LS coil kit, it was PNP, and holy **** I love it. Never had a misfire since, and I've gotten lazy on plug changing (going a full season on the same plugs). That said, you clearly have the same coils which makes me a bit concerned. Curious to see what you find there, I was hoping these would never need replacement. Is it the flowforce kit or a DIY setup? I wonder if the timing belt had skipped a tooth already and was contributing. Hmm
Dude, it's the Gates RPM blue timing belt! I thought that was the only belt worth putting in one of these motors, especially if you're pushing big power. Didn't think there were other options aside from OEM or a parts store knockoff (which I'd never consider).
Yeah, as far as the vacuum line goes, I think I had an issue with it before, replaced it roadside with a piece of used line, and never changed it out. Shame on me lol. The line I used this time around was new so shouldn't be an issue now.
I'm running a D585 kit but got it used on here and don't know how many miles the coils had beforehand, or if they're OEM or aftermarket ones. Haven't had an issue with it before but even the best coils are wear items and I only paid $110 for the whole kit if I remember correctly so I'm not too bummed for the life I got out of 'em. I'll probably get some ACdelco factory replacements if the miss comes back at .030" gap but it hasn't been an issue since setting said gap.
Whenever we have a crank bolt come loose on a race car, we always take the trans off, because the flywheel bolts WILL be loose, or vise versa. Wonder if this is actually related to your driveshaft woes.
Borescoped the cylinders on my lunch break. Forgot my roommate took our air compressor to his shop so leakdown test will have to wait till later.
It looks like there might’ve been some mild P2V contact just outside of the intake reliefs on piston 3 (top 2 pics for reference). Hard to tell though because there’s a bunch of carbon buildup on said piston. I’m assuming that’s the one my misfire was on. Bottom pic of cylinder 4 for reference. The edges of the valve relief flare out towards the edge, so the area that looks like it made contact in the top pics might just be flattened carbon. I’ll update with the leakdown results tonight.
Last edited by Z_WAAAAAZ; Jul 18, 2024 at 04:36 PM.
Unfortunately the cylinder 3 intake valves are smoked. Lash can now be measured in tenths instead of thousandths.
Based on how much they bent, I’m not sure if I should be worried about the rod and bearing integrity as well. I’ve kinda been working on a contingency plan all day but figure I should sleep on it a bit before throwing it out there. The girlfriend and I are going camping this weekend so I’ll have plenty of time for a mental reset to make sure I’m not making a rash decision. I’ll undoubtedly be back, though!
Last edited by Z_WAAAAAZ; Jul 20, 2024 at 11:07 AM.
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