Problem noise with 1994 Cutlass Supreme SL

[rich_e777]

Ok i`ve got a `94 2-door Cutlass with this loud banging noise (metal to metal) that occurs after ive come to a stop at a light or sign and then as soon as i accelerate a loud bang sound happens underneath the car in front. THE CAR IS NOT BACKFIRING!!!!!!!!!! everyone ive talked to swears that it is but its not coming from the rear. Sometimes when switching from Park to Reverse or D to R the noise happens there. I thought it may have been the parking brake but ive disconnected it completly and the noise is still there. I need some suggestion about where to look and what to look for and my Cutlass would really apprciate it to.

Edited February 18, 2012 by rich_e777

[95 vert]

It's random I'm assuming. Sounds like it may be in the trans. I've seen/heard that noise on more than one occasion. It's internal in the trans. Possible differential which is replaceable without pulling the trans.

[rich_e777]

I wouldn`t really say random because its kind of predictable, but is there a way to check if it is the differential? You`ve ran into this problem before?

[Highmilagecutlass]

My cutlass did the same thing before the trans blew.it's like as if when you decel to a stop the trans is downshifting out of overdrive ..back to 1st gear just before I stopped that mine would bang..How many miles are on your trans and have you kept up on the fluid ?

[Highmilagecutlass]

Okay Here's my theory.

 

I had a similar problem with my cutlass when the lower motor mount tore it's self apart. It was the one directly below the harmonic balancer.

It's a fluid filled mount to absorb the vibration. I at first noticed the clunk going into reverse and then I replaced the dog bones, and the the clunk improved but not completely.

A good friend of mine thats a mechanic rode with me once and said hey your mount is bad..and he was right..I replaced the mount and the clunk and vibration went away.

 

I think that I bought the new motor mount from Auto Zone..

 

Pop the hood and have a friend apply the brake with the car idling then shift the car to reverse and watch the engine move.

 

Is it a smooth transition ? or a violent jerk ?

 

Just make sure that the parking brake or your helper has both feet planted on the brake pedal before attempting this test.

[cutty]

I'm going to say its the "dog bone" motor mounts.

[rich_e777]

I changed them about a year ago and they aren`t loose.

[rich_e777]

my babies got about 130k on her. I keep up with all the fluids and the engine does give a good kick when the trans is shifted. the dogbone mounts where replaced about a year ago but the one or ones at the bottom have not. Looks like i got me a project this weekend. Man i hope the trans doesnt go, not until im ready to do the engine swap anyways. I try not to hit the accelerator to fast and sometimes it seems to help but im definately going to change the underside mount or mounts. should i go with a stock replacement or is there a better one out there? Thx for the help. PS ran down and looked at the tranny fluid and no abnormal or burnt smell and it still looks fresh its not leaking tranny fluid (oil yes, cheap fibergass black valve covers) Thx for the theory im going to test it.

[rich_e777]

damn forgot to mention the car has to be warmed up real good before it happens regularly. If im just starting it up when the Cutlass is cold(not outside) it doesnt happen as often.

[GnatGoSplat]

Be sure to visually check for excessive movement shifting in and out of gear before replacing that lower mount. However, my Cutlass had the same issue and shifted into gear considerably smoother in below-freezing weather. Turned out to be the lower hydraulic mount below the crank pulley.

[rich_e777]

Be sure to visually check for excessive movement shifting in and out of gear before replacing that lower mount. However, my Cutlass had the same issue and shifted into gear considerably smoother in below-freezing weather. Turned out to be the lower hydraulic mount below the crank pulley.

What do you mean by excessive movement? Do you mean the engine when i shift? or something else? I am starting to suspect the lower mount(s) there are two aren`t there, might as well replace them both. Thx man

[jrcuttymann]

This is just a shot in the dark, check to make sure all your lugnuts are tight, a loose lug can cause a horrendous noise, such as a loud clunk, especially when shifting from R to D and vice versa. Just my 2 cents worth.

[GnatGoSplat]

What do you mean by excessive movement? Do you mean the engine when i shift? or something else? I am starting to suspect the lower mount(s) there are two aren`t there, might as well replace them both. Thx man

 

Yep, when you shift. The engine may rock back and forth a little bit, but it shouldn't be very much. My lower hydraulic mount was very obviously bad, I touched it with my finger and felt a lot of deteriorated chunks of rubber and the goo inside had oozed out. Yes, there's one on the transaxle side as well, that one wasn't bad on mine, but it could be on yours. If you can get down there and take a look, you should be able to tell by looking if it's bad.

[rich_e777]

Update, I changed both the engine and transaxle mount, but the noise is still there and its kind of worse now. Engine mount needed changing bad. On to the next idea, what else you guys think it could be? Im thinking its got something to do with the exhaust because i have noticed the noise until a few years back when somebody jacked my cat converter at a walmart after the guy had welded another one on.

Edited October 16, 2010 by rich_e777

[White93z34]

you sure the trans vacuum line is connected to the modulator?

 

can you get a video of the problem?

[rich_e777]

Ive checked the lines and fluid level and all good there, i really need to get a camera but i dont know if a video would help much, It only happens when the car is in motion. Im going to get a buddy of mine to get up under it and just tap on a few different things in different places and im going to check the exhaust system and try to come up with some new info. Could it have something to do with the clutch or transmission? dont know alot about those parts.

[rich_e777]

if it where a lugnut id be able to tell. I always make sure ive got those tight. I wish it were that simple.

[GnatGoSplat]

Low vacuum at the modulator could cause the transmission to make a loud audible BANG that you can feel quite strongly. I've experienced it when a coil went bad and engine vacuum was lower than normal. Also when the TGP's original turbo was seized. Of course, I'm sure a good old fashioned vacuum leak could cause this too.

[ScoobyDoo82]

Low vacuum at the modulator could cause the transmission to make a loud audible BANG that you can feel quite strongly. I've experienced it when a coil went bad and engine vacuum was lower than normal. Also when the TGP's original turbo was seized. Of course, I'm sure a good old fashioned vacuum leak could cause this too.

 

Ive been told to check this on my GP... what exactly is this "vacuum modulator"?

[GnatGoSplat]

Towards the front of the car on the transaxle is a metal cannister with a vacuum line coming out of it. Most of the line is metal, but there's a short piece of rubber tube joining the modulator to the metal vacuum line. That's the modulator. It controls fluid pressure and affects shift harshness.

[ScoobyDoo82]

Does that generally go bad, or is it usually a vacuum leak?

[GnatGoSplat]

I've heard of it going bad, but my personal experience is usually low vacuum caused by something else causes the symptoms of a bad modulator. I think it does have rubber parts inside that can wear out, but 2 of my W-bodies are over 200k miles on their original modulators so I don't think they're particularly fragile.

[GOT2B GM]

yeah there's a rubber diaphragm that can leak inside the modulator, but check for vacuum leaks elsewhere as well.

[ScoobyDoo82]

Alright, I think I do have a vacuum leak somewhere else because there is a pretty noticable sucking sound coming from the TB area... it might not have a gasket, or something else. I'll try using the smoke machine at school tomorrow and see if I can't find anything.

[rich_e777]

Given the symptoms does this sound like a problem with the trans? or is this sounding like more of a vacuum leak issue? if it were the trans i would think there would be mechanical issues other than the lack of HP and torque but i blame that on the 3100v6. Engine swap is going to fix that.