Black Jack: Engine vibration guessing

FastDriver · Aug 18, 2026

AeroCoupe said:
So did the vibration just start or has it been a progressively worse thing? Also, is it a consistent vibration or cyclical?

I only started noticing it after the clutch install, but to be fair I'm not even sure we're talking about the same thing. It was a minor vibration at around 4,000 RPM that I while I didn't like I wasn't tremendously concerned with. After the battle box install, it was a different car. Now after 2,000 RPM is shaking enough that I babied it the rest of the way home for fear something was coming apart. So I wouldn't call it progressively worse so much as suddenly worse. I'll have to go feel it and try to keep it at a constant RPM to see if it's some kind of a cyclical thing or not.

FastDriver · Aug 18, 2026

Noobz347 said:
I don't recall if this car has a factory ECU but... Have you done a cylinder balance test?

It is on the stock ecu, but with the T56 and no neutral safety switch T5 style I'm not sure if I can run those kinds of codes. I can try though.

FastDriver · Aug 18, 2026

KRUISR said:
When the car was at the shop to get the weld repairs and driveshaft loop, did they do anything to the driveshaft? (Drop it, dent it or do anything to change the pinion angle?)

It's definitely not driveshaft or rear driveline related. It does exactly the same thing sitting still, in or out of gear, clutch in or out. That's what's giving me heartburn.

My brain wants to blame the recent work, but I don't see how it could have thrown the engine out of balance. He rewelded the O2 bungs and installed the Stifflers driveshaft loop. He removed a spacer I had under the transmission mount, but the loop is about the same thickness, so the transmission height and driveline angle shouldn't have changed much. And again, that wouldn't explain the vibration at a dead stop anyway.

Next time I'm under it, I'm going to check carefully for anything touching the body, transmission, exhaust, safety loop, whatever, that could be transmitting vibration into the chassis.

I'm grasping a bit because of the timing, but mechanically I don't see how the rear-end work itself would cause what I'm feeling.

AeroCoupe · Aug 19, 2026

“It does exactly the same thing sitting still, in or out of gear, clutch in or out. That's what's giving me heartburn.”

Sounds motor to input shaft related.

FastDriver · Aug 19, 2026

Not input shaft. With the car at a stop, the trans in gear, and the clutch in, the trans is fully connected front to back, and therefore the input shaft is stationary.

General karthief · Aug 19, 2026

Slight engine imbalance, then work done that should not be related, now imbalance is worse..I would be pulling plug wires one at a time while engine is running, ......not true....I'd get the neighbor to do it for me...bare handed.see if there is a dead hole...

Noobz347 · Aug 19, 2026

Thoughts:

I still think you should try and run a cylinder balance test. I have a chipped A9L in mine and it will still run the test.

Pull the plugs and read them.

What all did you take apart/remove when you did the rear end? Was the the transmission crossmember removed for any reason?

FastDriver · Aug 20, 2026

Ack all on the plugs. I've got spare everything-ignition-related on the shelf, and will swap things to see if anything clears it up. I will try the cylinder balance test.

I wasnt there to see everything he did, but I do not see any reason he would have pulled the trans crossmember. It would be unnecessary. The exhaust, driveshaft, and rear end came out amd went back in.

General karthief · Aug 20, 2026

I've been around here a minute or two and figure you know your way around a tool box, that said, I would bet on an ignition related issue, like a plug wire breaking down or some other simple spark breakdown gremlin.
Possibility of a 28/50oz/0 balance crank mixup? Don't believe so but

AeroCoupe · Aug 20, 2026

A9L, SCT chip, and no NGS connection to the T5 and I was always able to pull codes.

FastDriver · Aug 22, 2026

I am quickly coming to the point that I just don't want to take my to anyone, anymore. I don't weld and guess if I want something done, I've gotta expect it to come back with several other problems and a bill when I trust someone else with it. Damn...

Anyways, the right lower control arms and my sway bar are back on where they're supposed to be.

On that one, he didn't want to put torn bushings back in. That's not awful, but I haven't gotten to the balance, or ignition-somehow-I-hope, issue, yet.

Gonna put the interior back in, so I can park my mercedes & Father Time in my garage again after this weekend.

91AOD5.0LX · Aug 22, 2026

FastDriver said:
I am quickly coming to the point that I just don't want to take my to anyone, anymore. I don't weld and guess if I want something done, I've gotta expect it to come back with several other problems and a bill when I trust someone else with it. Damn...

A big plus one on that brother!!!

RaggedGT · Aug 22, 2026

Mercedes???? Come along way from the Saturns

Fwiw-a Handy guy like you- I’m sure could pick up MiG welding fairly quickly.

FastDriver · Aug 22, 2026

If having a beer with you is an offer bring it on! The Merc is my adult car. Blackjack, at least if I can figure out this balance or whatever issue is still my daily.

The experiment with the draglites is over. Even with a spacer that the guy who did the welding gave me for free, the shaved banjo bolt is still scraping, and I'm done with it. The other issue is that I don't understand this, but the lug nuts for the Welds bottom out before they firmly snug down the wheel, I guess maybe these are old and maybe they used to use different lug nuts. I'd have to have these machined, but I'm done with it. They're going to go back on Facebook marketplace.

On the bright side, the shank style lug nuts for 1/2" studs are radiused for 5/8" stud holes in the wheels, which allowed me to put my own 15 inch s71 wheels with 5/8 stud holes on it, and confirm that they'd be a fine fitment at 6.5" backspacing:

The 28x10.5Ws don't fit worth a damn up and down or on the outside, but that's not the point. I just needed to check the backspacing and whether they would clear the brakes, and they do. So I'll look on the marketplace or I'll just end up ordering the same wheels but with half inch stud holes.

AeroCoupe · Aug 22, 2026

Well no can tell you that you didn’t exhaust all possibilities to make the work. I was rooting for you man.

FastDriver · Aug 22, 2026

Thx, man. I'll still make it work. I've overcome 2 decades on Father Time. I whine a lot, but perseverance usually wins in the long run.

FastDriver · Aug 23, 2026

Well well... look what happened to pop up in my feed just down the road. I sold the old BMW winter tire set on the same trip that I picked these up.

They're basically new. The tires are too. They're 275 50 15 Nitto 555rIIs. Paid $1,200, but I think I'm going to get 300 or 400 back out of the tires. They'd be like $1,860 shipped in taxed new just for the wheels. So, although I do see some welds being sold for less on marketplace, I don't see a whole lot advertised that fit the fox body. I reckon they get snapped up pretty quickly.

AeroCoupe · Aug 23, 2026

Nice score man!!!

RaggedGT · Aug 23, 2026

FastDriver said:
If having a beer with you is an offer bring it on! The Merc is my adult car. Blackjack, at least if I can figure out this balance or whatever issue is still .

Brother I wish we could have gotten together when you were still at Fort Knox. @kiddiccurus was local to me and I missed out meeting him as well Hopefully one of these years when I finally figure out how to manage money ,I can goto Foxtober Fest and we can have a Beer or Two

FastDriver · Aug 23, 2026

They weren't 6.5 in backspacing.

Fortunately, because that's what he put in the ad, the guy was good enough to take them back. The hunt continues...

Black Jack: Engine vibration guessing

I was uncomfortably high & wearing a helmet

I was uncomfortably high & wearing a helmet

I was uncomfortably high & wearing a helmet

lube between the nut and the face. I know my lubes

I was uncomfortably high & wearing a helmet

wonder how much it would cost to ship you a pair

Stangnet Facilities Maint Tech... Er... Janitor

I was uncomfortably high & wearing a helmet

wonder how much it would cost to ship you a pair

lube between the nut and the face. I know my lubes

I was uncomfortably high & wearing a helmet

I have a slight sag in my rear

Been here over a DECADE and still no CT

I was uncomfortably high & wearing a helmet

lube between the nut and the face. I know my lubes

I was uncomfortably high & wearing a helmet

I was uncomfortably high & wearing a helmet

lube between the nut and the face. I know my lubes

Been here over a DECADE and still no CT

I was uncomfortably high & wearing a helmet

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