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Rattle that might be Tranny


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I have a rattle coming from somewhere that seems to be getting louder. I thought it was just the exhaust rattling, but I think it might be something else. Somebody told me I should check the transmission and engine mounts. But everything is so tight in there, I'm not sure where they all are. Does anybody have a diagram of the engine that shows where all the mounts are? Has anyone ever had a similar problem with their Reatta who might know what's going on?

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If it's a rattle it's unlikely to be the mounts. They will come across as a thump or a clunk when you give it gas and let off, as the mounts rock back and forth. Rattles will have to be something that's lightweight and loose, that a vibration can move against another metal part and the engine/trans mounts hold too much weight to allow that. That being said, a worn mount can cause something to come into contact with another metal part and vibrate.

To check the engine and trans mounts, you can either jack the engine and trans up, watching each mount point. When weight is taken off, the mount should move as a single piece as weight is taken off. If while moving it up and down you see the engine or trans move independently of the mount point, then you are looking at a bad mount. A simpler way to check, pop the hood and manually operate the throttle under the hood. Move the throttle from idle to max, hold for a second, then let it go back to idle, several times. You want to move the throttle by hand fast. If not comfortable with this have someone in the car floor it a few times, holding a couple of seconds between floored and off, but moving the pedal fast. The engine and trans should shift when gas is applied and released, but the movement should be very small. If the engine appears to move a couple of inches or so, then you are looking at bad mounts.

One thing that causes unexplained rattles is the catalytic converter, they will set up a rattle when the insides come apart. Exhaust shields are also a source of rattling.

Good luck, sometimes those noises can be hard to find.

Edited by Telco (see edit history)
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An annoying source that was on my Reatta was the exhaust shield on the rear of the motor. There a two or three small stainless screws that hold it on. If they break, the shield will rattle against the manifold. It is a "tinny" sounding rattle. I used wire to twist it tight until I had a chance to remove the exhaust manifold and repair it. I have a Ford truck that gets a stone between the screen of the cat converter and the cat that can make a pretty good rattle. It has only happened on my truck though.

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It could very well be your brakes. This is has been an old problem and you can read all about it by doing a search on the subject. To verify that it's your brakes while driving roll your window down so you can clearly hear the rattle. Go over a bumpy or rough patch of road that you know will start the rattle. As you hear the rattle lightly apply your brakes. If the sound goes away that's your culprit. Give it a try..

Mike

'91 Coupe

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I'm sure it isn't the brakes. It has something to do with the motor or tranny I believe. It's more of a low rattle that feels like it's coming from under the center console. It happens when I'm at a stop light sometimes, early in the morning a lot, and also when I get on the gas.

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When I get going everything runs real smooth with no rattle or slight shakes. It's mostly on take off and at lights and when I first start it in the morning. Most of the time it there is no rattle, but it is happening a little more often so I'm thinking I should address it.

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Had similar rattle first thing in the morning. Would go away when warmed up. Turned out to be a loose heat shield on the catalytic converter. The heat shields are just tack welded to the Cat. One of the welds broke and rattled when cold. Fast trip to the shop, & a torch to cut the shield off.

Note: My Cat is an aftermarket. Plan on replacing with an OEM next year.

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I haven't had a chance to get under the car or really look at some of what you guys are suggesting. (Just too busy here lately and driving another car) But I did take it for a spin to listen to the sound again, and I'm almost certain I'm back to a loose motor mount or tranny mount. Maybe rattle isn't the proper description. The car vibrates/shakes when I crank it, when I stop at a light, and when I get on the gas. The vibration causes a rattle sound, but maybe that's just a product of the motor/tranny shaking. If I had rear wheel drive, I'd swear the tranny was shaking/loose or something.

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Manipulate the throttle by hand with the hood up, if it's a loose mount it'll be shown by excessive movement of the engine/transaxle in relation to the rest of the car. Good mounts will not allow the engine to move more than an inch, if that. Bad mounts may move as much as 3 inches.

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The engine didn't move much. Probably just what it should. I couldn't hear any rattle or feel any excessive vibrations from the engine compartment either. I got in and hit the gas and it would shake and make the rattle noise. It feels like it's coming from up underneath the engine or tranny.

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Ok. I think I figured it out. Now I gotta fix it. Nothing major. There's a brace the goes across the undercarriage about midway on the car. The exhaust is resting on it and when I pushed on the exhaust pipe it hit that brace. That would would explain the vibrations that felt like they were coming from under the center console and the rattle. My little donuts are right there by the brace attached to the exhaust. I'm guessing they are worn. Thanks for all the suggestions.

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I just don't like my car making noises and vibrations like that. It really seemed like more than just the exhaust. And some mechanic guy thought it was a tranny mount, so he had me looking for the problem in that area. I'm just glad my Reatta is back to sounding quiet and running smoothly!

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Hey man....on my 1989 Riviera that happens sometimes. Turns out it's the little exhaust donuts/hangers right under the center console under the car. All it takes is for one donut to break; really ugly rattle on acceleration from stops.....then goes away when you are coasting. Your problem sounds just like mine when one of these rubbers holders breaks. Might want to check underneath to see if the Reatta has these same exhaust hangers; usually located at the midpoint of the exhaust pipe....I think its before the catalytic converter...not sure.

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