thumping when easing off gas pedal

I recently bought a 1993 camry, auto trans, with 88k miles. it shifts smoothly and goes into every gear with no problems. however, many times, whenever i accelerate and then ease up on the gas pedal, the car kicks a bit. For example, i would accelerate from a stoplight and everything is fine. But when i get up to, say, 40mph and i ease off the gas, the car thumps, or kicks momentarily, almost as if it is shifting rough, but i don't think it is downshifting as i am only maintaining a certain speed.

a mechanic suggested the engine mounts need replacing, but my research suggests that is only for massive engine vibrations, and this is not a constant vibration problem.

Any thoughts please?

I'm really not all that sure about this one. It's a very difficult problem to solve. I've been dealing with a similiar problem with my '99, but I've come to find out that it was a misfiring cylinder that caused some severe thumping when letting off the gas. It sounded somewhat similar to bodies being thrown around in the trunk. I've heard that it's possibly caused by a stripped gear in the transmission, and in some cases a motor mount. Also, I've heard that it can be caused by a stripped camshaft, or something slipping in the drivetrain area. I'll keep looking around for you, and see if I can't find anything out in futher detail.

Your Camry has 2 engine mounts, a brace and a, sort of, transmission mount.

The brace looks like a dog bone. Easy to find on the passenge side of the engine.

1 engine mount is in front of the engine. Looks like a dome and easy to get to. I have changed this one and the dog bone looking one.

The other one is a stinker and is leaking in my car but my daughter does'nt have the $87 plus labor to change it right now. That one is causing clunks for her. It is leaking oil.

The last one is even more expensive supporting the transmission. If the parts girl gave me the right price it's $137ish. Or it's $87 and the engine mount behind the engine is $137, if she had her numbers transposed.

At any rate, it sounds like u should check the front & rear mounts. Look for oil leaking out and broken rubber in the dog bone looking mount.

Regards

Would say then, based on the symptoms, that the mounts are the problem?

thanks. i don't know if i should pay the mechanic to do the engine mounts and then not have the problem fixed. dont want to waste money.

Have a mechanic troubleshoot your problem. If he tells you that you have a bad engine mount, then you can believe him. Doesn't sound like a transmission problem. If the mounts are fine, I suppose it could be a bad CV joint, but I have not seen one that bad.

It appears that the problem is only occuring when I enter 3rd gear. I go into the gear just fine, but a thump occurs when i stop accelerating. By the way, the thumping sound does not seem like its coming from the engine, but from under the car.

I will check with the mechanic again, but would appreciate any advice from this forum

There isn't much under your car, except in the front and very back. The sound is probably being displaced and is really coming from the front. If it is really only 3rd gear, then that points to a transmission problem since nothing else is only different at that time. I still think the motor mount is the obvious first place to look.

Brian, would you say that the motor mount is suspect because of what my mechanic mentioned, or is there another reason that you would suspect the motor mount?

Sounds like a torque thing to me...

"whenever i accelerate and then ease up on the gas pedal, the car kicks a bit. For example, i would accelerate from a stoplight and everything is fine. But when i get up to, say, 40mph and i ease off the gas, the car thumps, or kicks momentarily, almost as if it is shifting rough, but i don't think it is downshifting as i am only maintaining a certain speed."

All I know is that those mounts don't last a lifetime and you can't see the rear most one. Front's a snap to change as is the dog bone one.

Also, the symptom you are relating is similar to our '93 with a known bad engine mount. Just get it up on a rack and have it checked. Good Luck and let us know what happens.

Regards

Check your RPMs while this symptom is happening. I get a very minor occurance of what you mentioned at the same speed, but it is only my transmission shifting into a lower gear once it detects that I am not asking for a lot of power. If you see the RPMs drop (fairly quickly) about 500 rpms or so, that would indicate a shift I (BELIEVE the torque converter locking and/or the transmission shifting to overdrive, but I'm not 100% sure) . When letting off the gas completely when in overdrive, however, the RPMS tend to jump up almost 500 rpms or so due to the transmission "unlocking" in order to reduce engine breaking. This doesn't really cause any noises or thuds for me.

I did have a problem where I would feel a "thump" coming from what I thought was under my car (like what you are experiencing) upon hitting the gas after I was coasting, and that ended up being a broken motor mount (the dome one in the front, connected to the manifold). It also caused my car to "bang" into gear when putting the car in "Drive" at high idle.

I am by no means a mechanic and am only telling you my personal experiences with my car. (1992 4-cyl). I think checking your RPMs would be a very good way to narrow down the possible causes however. For me, "thumping" transmission issues were ALL caused by bad motor mounts.

my 95 camry has a slight pause when I release the gas. But when i use cruise control, i can not feel it. I don't think it is a big problem, well maybe i am wrong. Please let me know the results.

Brian, would you say that the motor mount is suspect because of what my mechanic mentioned, or is there another reason that you would suspect the motor mount?

Motor mounts are the obvious source of thumping when changing accelerator pedal position and the first thing to look at. Nothing else could apparently be the cause. Doesn't make it a sure thing though...

If I could drive it and look at it, I could be more certain, but the way internet advice works, you have to take it with a certain degree of scepticism.

thanks for all this information. i take it in to the mechanic friday. i'm out at least $225 for the motor mounts. if that doesn't fix it, then i'm just out of luck.

i'll update after the repairs.

UPDATE-- paid $230 for the motor mounts...no change, thumping is still there. Mechanic said the mounts were bad, needed changing. said the thumping was just natural. oh well. i guess at least i have new motor mounts.

Too bad. Everything else I can think of is too expensive (torque converter/transmission). As long as it runs, live with it. If it gets worse, maybe it will be easier to troubleshoot it. You can always take it to another mechanic and get an opinion. Shouldn't charge you anything.

err i got a 93 same thing happens to me but thats only if i dont shift into overdrive before dropping off the accelerator. err how many km/ph is 40m/hr. if you shift into overdrive b4 dropping the accelerator it should be OK i think, give it a try hahahahaa

I recently noticed this problem on my 95 4cyl. Especially after hard acceleration. I feel the car is shifting to a higher gear. Will this damage the transmission?

YOur transmission will take a giant shit on you if you ignore this. Good news is if you take care of it realativly soon, it will be cheaper. Transmissions are able to function because of air pressure. Sometimes, theres a little thing that becomes too tight and has to be loosened.

WissNX, will it help to transmission fluid?

Have a mechanic you trust check your motor mounts. Just because it wasn't Smith's problem doesn't mean anything for you.

If you haven't changed your transmission fluid recently, it can't hurt unless your tranny is ready to fall apart.

Worn inboard constant velocity joints are known to thump on accerleration/deceleration. You're looking at 300$+ to change both of them so make sure they are bad first.

The problem is more clear now. Suppose there is 4 gears. The 4th one is O/D (?). When the car is running at about 50 mph, every time i step on gas just to MAINTAIN the speed, it will down shift to the 3rd gear. Then when i take my foot off, it will shift to O/D and I can feel a THUMP. So the car is shifting to O/D too often and too easily when it should stay at the 3rd gear. I don't if it is the design to save more fuel or there is a bad speed sensor (just guessing) or something. Any idea? Is this normal? BTW, it is a 95 LE 4 cyl. When the speed is higher, e.g. 65 mph, it can stay at the O/D. There is also no problem when the speed is lower, say around 30 mph.

UPDATE-- paid $230 for the motor mounts...no change, thumping is still there. Mechanic said the mounts were bad, needed changing. said the thumping was just natural. oh well. i guess at least i have new motor mounts.


Gotta add my 2 cents in. I have a 93 2.2 4 cyl auto with 151k. I have a similar problem, that being at high speed, 70-80 mph, if I back off the accelerator pedal there is what I call a shuddering. To me it appears to be a trans issue but it really could be many different things. As of now the symptom doesnt warrant a repair and I hope it stays that way.

I just put up a post asking about the same thing. I get a thunk and a shudder in my 96 Camry when it shifts into overdrive. Sounds like it must be a common problem.

I just put up a post asking about the same thing. I get a thunk and a shudder in my 96 Camry when it shifts into overdrive. Sounds like it must be a common problem.

Is it very easy to shift to O/D also very easy to downshift? Is there a particular speed at which this happens more often?

It seems to shift into overdrive okay but thumps when I let off the gas. It tends to happen mostly around the 50s I will keep a closer eye on it to try to pin it down. My wife has been using it to commute lately, I will ask her when she notices it as well.

UPDATE-- paid $230 for the motor mounts...no change, thumping is still there. Mechanic said the mounts were bad, needed changing. said the thumping was just natural. oh well. i guess at least i have new motor mounts.

That is a typical excuse when a mechanic did some work and did not solve the problem. They can not just admit their mistake.

Worn inboard constant velocity joints are known to thump on accerleration/deceleration. You're looking at 300$+ to change both of them so make sure they are bad first.

Rip,

What is the constant velocity joints? If they were bad, will it cause the car downshift (say 3rd gear) when i step on gas and upshift (say 4th gear) when gas is released?

YOur transmission will take a giant shit on you if you ignore this. Good news is if you take care of it realativly soon, it will be cheaper. Transmissions are able to function because of air pressure. Sometimes, theres a little thing that becomes too tight and has to be loosened.

Can u be specific? What becomes too tight and has to be loosened?

The problem is more clear now. Suppose there is 4 gears. The 4th one is O/D (?). When the car is running at about 50 mph, every time i step on gas just to MAINTAIN the speed, it will down shift to the 3rd gear. Then when i take my foot off, it will shift to O/D and I can feel a THUMP. So the car is shifting to O/D too often and too easily when it should stay at the 3rd gear. I don't if it is the design to save more fuel or there is a bad speed sensor (just guessing) or something. Any idea? Is this normal? BTW, it is a 95 LE 4 cyl. When the speed is higher, e.g. 65 mph, it can stay at the O/D. There is also no problem when the speed is lower, say around 30 mph.

To me, it sounds like you are hearing the torque converter lock-up. This normally happens at 50 mph. Above 50, you are locked up when cruising. It will disengage if you accelerate above a certain amount and your rpms will increase. If you coast, it will disengage when your speed drops below 45 mph or so.

What is the constant velocity joints? If they were bad, will it cause the car downshift (say 3rd gear) when i step on gas and upshift (say 4th gear) when gas is released?
The CV joints transfer the power from the differential to the wheels. They allow wheel movement up and down, as well as side to side (turning). They won't have any affect on the shifting.

Brian, thanks for the info. What is the purpose of torque converter lock-up? If it is the lock-up, should it be smoother than what i experienced? Will the rough engage and disengage do some damage? When I release the gas, rpm drops about 1000. Rpm increases about 1000 when i step on the gas.

Lock up provides a direct drive, like an engaged clutch in a manual transmission - better mileage. Transmission (torque converter) runs cooler then also.

I think it should be smooth, but since I've never driven in that year Camry and I don't know how your car feels, it is impossible for me to say if what you feel is normal or not. It might be that they have changed the feel of the lock-up over the years. I don't see how a more strong lock-up will damage anything.

So the overdrive is the torque converter lock-up. I feel the lock-up is engaged and disengaged too easily in my car. I feel during 40-50 mph it will disengage as long as i step on the gas a little more than slightly. And it will engage as soon as the gas is released. At speed higher than 60 mph, the lock-up remains engaged most of the time. Well, maybe i worried too much.

No, the OD and the lock-up are two different things. The OD is a gear in the transmission and the lock-up is a mechanism within the torque converter:

http://auto.howstuffworks.com/torque-converter.htm

I feel during 40-50 mph it will disengage as long as i step on the gas a little more than slightly. And it will engage as soon as the gas is released. At speed higher than 60 mph, the lock-up remains engaged most of the time. Well, maybe i worried too much.

What you're describing is normal behavior. The only question is whether or not the force to lock-up the torque converter is excessive or not.

Thanks. Will converter lock-up happen at lower speed, say 30 mph? When lock-up is engaged, will rpm decrease dramatically? BTW, that is a great web site :)

Yes, rpm will decrease dramatically. It will only lock up at 50 mph or above.

Doesn't rpm drop dramatically when car shifts to O/D? Then how can you tell if it is lock-up or shifting to O/D? Also does it shift to O/D at lower speed such as 40 mph when you coast? Sorry, so many questions :)

If your engine is at normal operating temperature, the shift to O/D will occur practically any rpm which depends on your accelerator position. Lock-up will not occur below 50 mph under any circumstances (barring malfunction). If the car is in O/D and has not locked the torque converter, the engine rpms will change with any little change in accelerator position. Once it has locked up, a small change in accelerator position will not cause am immediate change in rpm. The rpm of the engine will be proportional to the speed of the car as long as the torque converter is locked-up.

So if there are 4 gears and an O/D, do u think it can shift to O/D when it is at the 2nd gear at about 30 mph if gas is released?

There are three gears and an OD. OD will probably engage at 30 mph, but it is borderline.

Then why does it say "4 speed automatic with o/d"?

The OD is considered a speed

I did a test today. On a flat road and driving at 45 mph. The car coasts around 1250 rpm. When i step on gas, it jumps to 2000rpm and at the same time i feel a kick. I did not feel the kick when gas is released. It is very consistent.

Damaged Transmission Mount?

What is difference between engine mounts and tranny mounts?

Engine mounts are attached to the engine, and tranny mounts are attached to the transmission...pretty simple if you think about it. I do believe that there are four engine mounts, and one tranny mount.