Help! LS1 swap complete but car vibrates
08-04-2011, 10:22 AM
#1
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Help! LS1 swap complete but car vibrates I finished installing a LS1/4L60-E combo in my 1954 Ford Customline last weekend. The engine and tranny are stock, as I wanted a smooth idle and good driveability more than fast 1/4 mile times. The engine fired right up on the first try and runs very well, but the car is vibrating so bad that I can barely stand to drive it.
It's worst at idle, in gear (@ 5-600 rpm), but it is there throughout the rpm range. There is absolutely no contact between the drivetrain and the body or frame except the motor mounts and tranny mount. The exhaust clears everything as well. It happens at a standstill so it's not a driveshaft problem.
I'm using this style of motor mount http://cgi.ebay.com/ebaymotors/UNIVE...item53e891bb61 and a stock rubber trans mount.
I unbolted the torque converter yesterday and ran the engine that way - the vibration was significantly decreased, but the car still didn't run as smooth as my 2003 Silverado.
Question #1: What is the likely culprit in the transmission that's making the vibration so unbearable? Bad converter? Worn tranny internals? Bad flexplate?
Question #2? Can I expect the car to run as smooth as a new car with the type of motor mount I'm using? I know stock F-body mounts are huge - does the extra rubber make that big of a difference? I would think if the aftermarket universal mounts weren't thick enough, people wouldn't use them...but they seem to be pretty common in older street rods.
Any help you guys can provide is appreciated. This forum has been a great resource as I've worked on my engine swap. Thanks in advance.
Eric
It's worst at idle, in gear (@ 5-600 rpm), but it is there throughout the rpm range. There is absolutely no contact between the drivetrain and the body or frame except the motor mounts and tranny mount. The exhaust clears everything as well. It happens at a standstill so it's not a driveshaft problem.
I'm using this style of motor mount http://cgi.ebay.com/ebaymotors/UNIVE...item53e891bb61 and a stock rubber trans mount.
I unbolted the torque converter yesterday and ran the engine that way - the vibration was significantly decreased, but the car still didn't run as smooth as my 2003 Silverado.
Question #1: What is the likely culprit in the transmission that's making the vibration so unbearable? Bad converter? Worn tranny internals? Bad flexplate?
Question #2? Can I expect the car to run as smooth as a new car with the type of motor mount I'm using? I know stock F-body mounts are huge - does the extra rubber make that big of a difference? I would think if the aftermarket universal mounts weren't thick enough, people wouldn't use them...but they seem to be pretty common in older street rods.
Any help you guys can provide is appreciated. This forum has been a great resource as I've worked on my engine swap. Thanks in advance.
Eric
08-04-2011, 11:24 AM
#2
Vibrations suck. Did you check to make sure you have the correct spacing between tq converter and flex plate? could POSSIBLY have something to do with it. If it is still present without the tq verter connected, I'd say you can rule out the tranny. IMO
08-04-2011, 11:38 AM
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Someone in the automatic tranny forum just suggested the same thing about spacing. I didn't even check that because I figured everything is stock so it should go right back together. But I will definitely do some measuring when I get home tonight.
08-04-2011, 11:57 AM
#4
It could be in your tune. Vacuum leaks, dead plugs, sticking or bad injectors, sticky valves. Any codes?
Retorque all the bolts too. Especially the harmonic balancer.
Did you do any engine work? Was it running well before the swap?
Retorque all the bolts too. Especially the harmonic balancer.
Did you do any engine work? Was it running well before the swap?
08-04-2011, 12:03 PM
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It does run very well now, though. No leaks, weird sounds, etc. Oil pressure is strong. Vacuum is 20" at idle. Plugs are firing even. All in all it runs as well as I could have hoped for.
I took the balancer off to paint it and clean the timing cover (which I didn't remove), but when I put it back on I followed the procedure to the letter, using a brand new bolt. I don't think there is an issue with that.
That said, I'll double-check everything again as you suggested. I haven't hooked up the MIL yet and I don't have a code reader, but I can borrow one and check for codes. Thanks for the ideas.
08-04-2011, 02:56 PM
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Is it a high frequency vibration that gets worse with speed? If you put it in neutral and let the engine idle down does the vibration remain or get immediately better?
Andrew
Andrew
08-04-2011, 03:27 PM
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No, just the opposite. It is worst idling in gear (~500 RPM). If I put it in Park or Neutral (~700 RPM) it gets a little better. When I drove around my neighborhood it was bearable, but at every stop sign it's so bad it feels like the car is going to shake itself to pieces. That's why I initially thought either the motor or the transmission was touching the frame or body somewhere, but that definitely isn't the case. Unless my rubber mounts are substandard, it has to be something internal or a bad tune as mentioned earlier.
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08-04-2011, 03:51 PM
#8
If your motor mounts or transmission mount is too solid it will vibrate in really odd ways that seems hard to chase. I had solid mounts on my Thunderbird all around and didn't make it around the block before I was changing them. Ironically I've had all solid before and it was fine. Now the car has all polly and you wouldn't even know I swapped engines... until I step on it. 
In your situation, I wonder if the rubber isn't thick / compliant enough or if the bolts are transmitting the vibration for you. If it's the bolts, you are kind of stuck unless you want to make different style mounts.
In your situation, I wonder if the rubber isn't thick / compliant enough or if the bolts are transmitting the vibration for you. If it's the bolts, you are kind of stuck unless you want to make different style mounts.
08-04-2011, 05:42 PM
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It'd hunt for a miss first. If you're careful, you can pull one plug wire at a time and the engine should run worse while that one is off. If you pull one and it doesn't get worse, that cylinder is already not functioning and you should concentrate on that one (or more). All you'd have to do is have one bad voltage supply wire to the coil packs and you'd kill four cylinders. It's easy, quick, cheap, and definite.
08-04-2011, 09:05 PM
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if you can borrow a temp gun, that's the easiest way to find a miss. just look for the cold header tube. if you have stock manifolds, then pulling the plug wire is best. Personally i suspect the flexplate. you said unbolting the torque converter helped a little. are the flywheel bolts tight? was the flexplate off of a different model or year? there are lots of things and only hard work and elbow grease will find it. some of the best mechanical minds i know (or have at least read ) lurk around on this site.
08-05-2011, 01:39 PM
#13
I made a number of changes to my car at the same time and when I started it back up the motor vibrated so badly at idle that the car actually sat there and growled. I mean I could have brought a woman off by using her as a hood ornament type of vibrating. I convinced myself it was something ominous. Turns out it was just running super lean at idle, something like 20:1. But only at idle (carb).
Try and get the tune checked out. Could be someting like having the O2 wires crossed.
The temp gun idea sounds like an excellent one.
Try and get the tune checked out. Could be someting like having the O2 wires crossed.
The temp gun idea sounds like an excellent one.
08-05-2011, 02:26 PM
#14
Another thing to do is use a mechanics stethoscope to find the source of the vibration. If you don't have one, use a long crow bar.
Place the end of the stethoscope or bar on the positions marked A,B and C. If your engine mount is offering adequate vibration isolation, what you hear at position B and C should not be as loud as what you hear at position A. If you can hear the engine events on position C then you need a better mount.
You can also use the stethoscope at the transmission and other places to see if you can pin point the source of your vibration.
Place the end of the stethoscope or bar on the positions marked A,B and C. If your engine mount is offering adequate vibration isolation, what you hear at position B and C should not be as loud as what you hear at position A. If you can hear the engine events on position C then you need a better mount.
You can also use the stethoscope at the transmission and other places to see if you can pin point the source of your vibration.
08-05-2011, 03:04 PM
#15
If you disconnect the transmission and it is significantly better as you say, that sounds like a real clue to look in that area RE: flywheel or converter or the alignment of the two such as in the converter fully seated in the crank pilot hole.
Another thing to inspect is the harmonic dampener on the front of the engine. Look at the rubber inertia ring and make sure it is not dry and cracked. Also make sure it does not wobble while the engine is running.
Another thing to inspect is the harmonic dampener on the front of the engine. Look at the rubber inertia ring and make sure it is not dry and cracked. Also make sure it does not wobble while the engine is running.
