drivetrain vibration
12-11-13, 10:54 AM
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drivetrain vibration
Hey guys, I just did a turbo swap in my 88 NA. The motor is a fresh built s5 turbo engine/flywheel and s4 turbo trans-back. After the swap, I had a bad vibration in the drivetrain. It's when I am accelerating in gear, worst from 2-3k, and doesn't do it as much when I clutch in. I put competition mounts from Mazda on the motor, trans, and front of diff. I had the turbo drivetrain on my NA, but with an s5 turbo trans, and it did not vibrate at all. Last night I replaced the trans crossmember and driveshaft. The new driveshaft still wasn't perfect, but it wasn't as notchy as my old one. I am beginning to think it is the trans, it looks like it is sitting crooked against the bell housing. It fell when the car was sitting with no engine and the front was held up on a jack stand. Someone pushed my car out of the way and the trans fell down. I also think it could be the competition mounts on the engine. Anyway, I appreciate any help in advance.
12-12-13, 11:41 AM
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It does not really get worse the faster I go. It is just really bad around 2-3k rpm and only when driving, in gear, not at an idle.
As for the driveshaft, would the tiniest little notch in the u joint really cause that much vibration?
As for the driveshaft, would the tiniest little notch in the u joint really cause that much vibration?
Last edited by ravingracer; 12-12-13 at 11:45 AM.
12-12-13, 12:24 PM
#6
In my experience, for a driveshaft to cause vibration, it has to be basically locked up at one end or the other. A little 'notch" in the joint is fairly normal for these.
If it is rpm dependent, it is in the engine, an engine accessory, clutch or input shaft of the trans. If it is speed dependent, it is in the back half of the trans or driveshaft/rearend/tires.
If it is rpm dependent, it is in the engine, an engine accessory, clutch or input shaft of the trans. If it is speed dependent, it is in the back half of the trans or driveshaft/rearend/tires.
12-12-13, 01:27 PM
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In my experience, for a driveshaft to cause vibration, it has to be basically locked up at one end or the other. A little 'notch" in the joint is fairly normal for these.
If it is rpm dependent, it is in the engine, an engine accessory, clutch or input shaft of the trans. If it is speed dependent, it is in the back half of the trans or driveshaft/rearend/tires.
If it is rpm dependent, it is in the engine, an engine accessory, clutch or input shaft of the trans. If it is speed dependent, it is in the back half of the trans or driveshaft/rearend/tires.
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12-12-13, 09:39 PM
#8
Drive shaft vibration
From FSM Chapter 8, "Propeller Shaft":
"After replacing the propeller shaft with a new one, drive the vehicle and if noise or vibration occurs, adjust with balance weight washers, trying them at various locations on the flange."
As a quick check whether driveshaft balance is the problem, add a regular washer to one of the four bolts at the differential flange. If the vibration changes, you can suspect driveshaft balance.
If the input shaft was not connected to anything at the time, the tranny falling is unlikely to damage any rotating parts housing since the output shaft is recessed in the tail housing unless...the cross member was on it and got bent or it hit on the input shaft and bent that.
"After replacing the propeller shaft with a new one, drive the vehicle and if noise or vibration occurs, adjust with balance weight washers, trying them at various locations on the flange."
As a quick check whether driveshaft balance is the problem, add a regular washer to one of the four bolts at the differential flange. If the vibration changes, you can suspect driveshaft balance.
If the input shaft was not connected to anything at the time, the tranny falling is unlikely to damage any rotating parts housing since the output shaft is recessed in the tail housing unless...the cross member was on it and got bent or it hit on the input shaft and bent that.
12-12-13, 10:34 PM
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The crossmember was on it and the bushing failed, so I got a new crossmember. It didn't do much though. I will try the washers on the flange as a sort of last resort for thinking it's the driveshaft.
12-13-13, 10:12 PM
#10
I should have read more thoroughly before posting 
So if it's engine speed vibration, not wheel speed related, then I completely agree with what the others have said. It's not the driveshaft. So what does that leave you? Well, mounts could do it, but you said they're new. The transmission falling is highly suspect. Especially if it was on a jack stand. And the input shaft is not entirely recessed in the bell housing. It does protrude some. So if it was pushed backwards, the input shaft could have caught it on the way down, damaging the input shaft.
So if it's engine speed vibration, not wheel speed related, then I completely agree with what the others have said. It's not the driveshaft. So what does that leave you? Well, mounts could do it, but you said they're new. The transmission falling is highly suspect. Especially if it was on a jack stand. And the input shaft is not entirely recessed in the bell housing. It does protrude some. So if it was pushed backwards, the input shaft could have caught it on the way down, damaging the input shaft.
12-13-13, 10:17 PM
#11
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wondering if you have fitted the auto tailshaft,, twice.. its 50mm shorter .. looks like it fits.. and vibrates like hell when you mix them up
PS.. rockford?? in the US do a replacement Ujoint for the staked one .. and works ok if you are carefull pressing out the olds
PS.. rockford?? in the US do a replacement Ujoint for the staked one .. and works ok if you are carefull pressing out the olds
12-14-13, 10:10 PM
#13
I built the engine, I know all parts on the rotating assembly are S5 turbo. It has a resurfaced flywheel and fresh pilot bearing. Only thing I can think is clutch/ pressure plate, it is being replaced shortly. I will inspect the pilot bearing and input shaft on the trans when it is apart.
Strange thing is slight vibration reving engine in neutral clutch in, heavier vibration when accelerating in the 2-3k range but is happy and vibration free at 4500.
If the clutch and pp don't do It I will disassemble and inspect the engine. This is my first time experiencing this. Thanks for the help.
Strange thing is slight vibration reving engine in neutral clutch in, heavier vibration when accelerating in the 2-3k range but is happy and vibration free at 4500.
If the clutch and pp don't do It I will disassemble and inspect the engine. This is my first time experiencing this. Thanks for the help.
12-15-13, 07:43 AM
#14
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I have a similsr issue at first it would only vibrate at just before 60mph. So I changed the the cross member and mounts and now it vibrates at 20 to 30 mph.
Is their a way to replace the ujoints.
Is their a way to replace the ujoints.
12-15-13, 08:02 PM
#16
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I built the engine, I know all parts on the rotating assembly are S5 turbo. It has a resurfaced flywheel and fresh pilot bearing. Only thing I can think is clutch/ pressure plate, it is being replaced shortly. I will inspect the pilot bearing and input shaft on the trans when it is apart.
Strange thing is slight vibration reving engine in neutral clutch in, heavier vibration when accelerating in the 2-3k range but is happy and vibration free at 4500.
If the clutch and pp don't do It I will disassemble and inspect the engine. This is my first time experiencing this. Thanks for the help.
Strange thing is slight vibration reving engine in neutral clutch in, heavier vibration when accelerating in the 2-3k range but is happy and vibration free at 4500.
If the clutch and pp don't do It I will disassemble and inspect the engine. This is my first time experiencing this. Thanks for the help.
I had a water pump pulley once that was pressed on every so slightly crooked, it took a dial indicator to notice, but it caused a shitload of vibration at 4k rpm. Not saying that is it in your case, just pointing out that little **** like that can cause issues.
12-19-13, 06:31 PM
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Could it be my exhaust? I am just running a rb 3" downpipe with the presilencer on it, and it ends there since I havent gotten the parts to finish it yet. I have it mounted with a rubber hanger on the trans exhaust mount. It is not rubbing against the chassis. Could the tone of the exhaust cause a vibration? I was thinking it's possible cause it gets worse once its warmed up. And is only bad at certain rpm, and gets worse the harder you hit the gas.
12-20-13, 10:26 AM
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Ryan, I did double check it was n370, and it is a resurfaced flywheel from Atkins.
The trans was not unusually hard to press into the engine. As far as I remember..
The trans was not unusually hard to press into the engine. As far as I remember..
12-21-13, 12:28 AM
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Trans and clutch removed, noticed something pretty weird about the clutch disc. The splined "sleeve" is not solid mounted to the rest of the disc. You can turn an alignment key in the splines, without it moving the disc. It will spin about 20 degrees back and forth. I am confident this is the problem, and have a spare disc to install for testing. We will be putting it back together tomorrow evening.