A while back, my SO’s car stopped running, and since that was the only transportation we had, we were reduced to asking other people in our apt. complex to give us rides to Safeway or wherever we needed to go. Not good.
There is a guy in the complex who had a 1986 Sedan De Ville Cadillac, who was willing to sell it to us relatively cheap. Story short, we bought it.
I’m happy with it generally, except for one thing. When you drive it cold in the morning, and come to a stop light or sign, no matter how long you have warmed it up, and no matter how gently you come to a stop, when it down-shifts into first gear, it SLAMS into it, creating a shudder that sometimes rattles the windows. It does this for the first couple of miles and then desists, all of a sudden becoming very smooth. This happens every time. We have a mechanic who is pretty good. The problem with him is he’s very hard to get hold of, and now he’s going to visit people during the holidays, making it impossible for who knows how long.
I just wanted facts from dopers about what damage the hard down-shifts might be doing. If this has happened to anyone else with any car, I’ll take any anecdotal stories, too.
There is a good chance that it could be an engine or transmission mount. I would suggest this to your mechanic next time he looks at the car.
I’m gonna go ahead and safely say that it may not be related to the cold, since it also does it when it’s warmed up.
If you’re a Do It Yourselfer, and mechanically inclined, you can do this:
A way to check for a broken mount is to have 2 people, someone in the car, and another to watch the engine and transmission from the hood view. Have one person put the car in drive, and at the same time, a foot over the brake pedal, and give it a little gas, also known as “brake torquing”. But don’t give it excessive gas, just a little bit to get the engine to the point of moving the car, but brake at the same time so it doesn’t go anywhere. The other person should observe the engine and transmission while the gas is being applied, but also out of the way of the car for safety. If the engine and transmission “rock”, or moves EXCESSIVLEY in one way or another, there’s a good chance a mount it broken. Also do this in reverse as well. This is probably the simplest way. Another way to determine a broken mount is to jack up the vehicle, place it on jack stands, place a board under the oil pan of the engine, and lift with a floor jack. If it moves up excessivley, there’s a broken mount. The same goes for jacking up the trans with a board too. Good luck.
Okay, I understand that, although when it comes to mechanical stuff, I’m pretty helpless.
But if it’s a mount, wouldn’t it do it every time, no matter how long you drove it? Why does it stop doing it after driving it for a mile or two, and become smooth as silk?
It’s likely not a mount. They have nothing to do with how a transmission shifts while being driven. A cheap fix that may work is a new filter and tranny fluid. Cost at most transmission shops is less than $100. The gunk floating around in the fluid settles into the filter when the car is not running. It then takes a few miles to loosen the gunk from the filter then you get sufficient pressure for the transmission to shift smoothly. Worst case scenario is the clutch pack is suffiently worn and doesn’t like shifting while the transmission is cold. Any kind of banging in the transmission is not good, a visit to a transmission shop is in order.
Some tips with dealing with transmissions shops. Unless you are absolute trust in the mechanics, do not get talked into letting them remove the to check the internal parts. A good transmission mechanic can diagnose problems 95% of the time from a descripton of the problem and/or a test drive. Once the pan is off your car is not driveable and and can literally be held hostage. Even having the pan reinstalled and fluid put back in is no guarantee the car will be driveable.
Damn, I forgot to mention that before he left, our mechanic DID replace the transmission filter and fluid. Didn’t seem to change anything. I’m beginning to not like this situation. I have a feeling this is going to turn into an expensive little problem.
I take you’ve never experienced a broken engine/trans mount? Not to be snippy, but they most certainly do. It’s like trying to hold an electric motor, and then have someone plug it in. If nothing is holding it down, the rotation is then inverted to the external case, reversing it (watch it go crazy in your hands). Which in this case, down shifting into first, causing the drivetrain to pick up, and then slam back down into the chassis/sub-frame. This could happen in other gears, but depending on which mount could be broken, and the amount of force in the down shift. Having had a similar car with a broken mount, shifting from 2nd to 3rd was interesting in that at WOT, the car would sidetrack a couple of inches to the right because of it (That’s an extreme case, and I know I’m dangerous). Not saying that this is the case here, but from the initial description, it’s likely a mount could be to blame. And different cars behave differently with broken mounts as well. Plus it’s easy to rule out, and that’s why I mention it.
While it is easy to diagnose, I strongly advise against the idea of jacking an engine or tranny with a floor jack and a block of wood under the pan. All you’ll accomplish is crushing the pan-it’s just sheet metal.
It’s not a bad mount. From the OP, the problem goes away with warmup. Temperature does not heal a bad engine/tranny mount.
Given a later post indicating that the fluid and screen have been changed, it smells strongly of rebuild. No mention of how many miles on the meter, but an 86 could have over 300K, and may have been rebuilt once already.
Jacking them up with a jack without a piece of wood will do this. Doing it properly, with a piece of wood, will not crush the pan. It’s actually recommend in plenty of automotive repair manuals. Jus’ Sayin’.
Poor choice of words on my part. I read the OP, and the problem abated after driving for a few miles. Again-a motor or tranny mount won’t be healed. Better now?
Regarding jacking, a manual stating it to be a safe practice, doesn’t make it a wise practice. As a motorhead from the 70s and a former mechanic, I’d never do it.
Thank you, one and all. I’ll run all this stuff by my mechanic when he gets back, and hopefully I won’t have to run it anywhere until then. My SO’s car is running now, so we can use that for everything we need, assuming that it won’t develop the same problems again. Oh I’d like to know how many of you agree with racer72 that it might be a WORN CLUTCH PACK.
I certainly agree that it might be a worn clutch pack, but I don’t think that’s a particularly helpful piece of information. Not being an automatic transmission expert, I don’t know what the likely specific cause is, but I know enough to say it’s essentially a certainty that the cure is a transmission overhaul/rebuild, asdanceswithcats suggests.