Shake+Bad Fuel Mileage

Rba007 · 01-21-2004, 02:09 PM

Ive posted a few threads on this, none have gotten much of a response, so Ill post again.

Im getting a shake (car vibrates, rattles change in my cupholders) above 40mph in top gear. This does not occur in any other gear. I just had an alignment last week, didnt help a bit. Im assuming that my transmission is going (99,000 Miles as of today). Any ideas? I havent changed my spark plugs in the last 20,000 miles, or the fuel filter in the last 20,000 or so either. But, if those were the culprits, wouldnt i get a vibration all the time? I can sit in my garage and rev it to the rpm's that its usually at cruising at 40 and up, and I get no vibration. It only happens in top gear, under no to light loads, from 40 MPH and UP. Used to only be from 40-50, now its 40-90 (as high as I wanted to test it), although it is definitley worse at 40 than at higher speeds. Any Ideas?

Dealership has no clue what It could be, im hoping someone has similar experience and can help me with the diagnosis. Again, its a '99, 99000 Mile, 2.4 with the 4t40E automatic. THANKS

-Dave

Molson · 01-21-2004, 02:27 PM

Tire could have thrown a weight and is off balance, it won't show it till higher speeds.

Ice in the rim will also throw the balance off and cause a good shake.

Rba007 · 01-21-2004, 04:36 PM

Wouldnt it then vibrate even if i downshifted? I can do 40 plus, but in third gear, and get no vibration at all. It only happens in 4'th for some reason. Thanks for the ideas though. It started about 3 months ago, and since then has had new tires, and an alignment. Stupid Car.

Molson · 01-21-2004, 04:37 PM

hmm, could have a broken tooth on a gear then.

01-21-2004, 06:22 PM

possibly motor mounts maybe. in my jeep it would vibrate when it shifted into overdrive and we replaced the mounts which were worn and it cut down on half the vibration, the other half was from an out of balance front driveshaft.

Rba007 · 01-21-2004, 07:51 PM

Wierd. Its too bad not many people here have the engine/tranny I do. I wonder if it could be transmission mounts?

AaronGAGT · 01-21-2004, 08:00 PM

Do your RPM's drop when you experience this shaking?

I had this problem at about 50 mph... rpms would drop... shaking.. would let off the gas the hit it again and it'd be gone. I was getting horrible gas mileage too.

I didnt notice the rpms dropping until i considered a misfire problem. I never got a SES light so I didnt know what to look for.

My brother's car is doing the exact same thing as you explained. Car has 120k on it and doubt the plugs have ever been change.

The thing is.. i dont see why your plugs would go bad at only 20k.. interesting..

Rba007 · 01-21-2004, 08:18 PM

Well, they are Denso iridiums!

So you think its the plugs? If so, Ill go buy me some good ole delco's tomorrow and see what happens. It just sucks, I have class every week day, and its about a 120 mile round trip! So, I drive a LOT.

I also have a gently used MSD DIS 2 on the way, pre-wired for everything that I need. So, if youre thinking its the plugs, maybe with the new plugs, plus the MSD, ill be a happy camper. I HOPE its the plugs...

Rba007 · 01-21-2004, 08:19 PM

PS, the engine sounds like the RPM's should be dropping, but the tach doesnt show it.

71Z28RS · 01-22-2004, 08:51 AM

If it's fine in 3rd gear at 40 mph, but it's not fine in overdrive at 40 mph, it's not your plugs or your wheels or your tires or your suspension or anything like that. Looks like you have a trans problem.

atc3434 · 01-22-2004, 09:13 AM

Torque converter lockup selonoid? Perhaps...

71Z28RS · 01-22-2004, 09:15 AM

Maybe if it was rapidly locking-unlocking.....

AaronGAGT · 01-22-2004, 10:42 AM

So Dave... got any updates for us??

this is off topic...

is it just me or does 71z28rs and atc3434 travel as a couple to threads?

Not flaming... you guys both always have good info, just realized you guys pop up and discuss stuff within the thread together sometimes...

Rba007 · 01-22-2004, 12:47 PM

Multiple Personalities perhaps?

Went to the dealer today, they wanted 15 dollars/plug, so ill be ordering the online for half that. And, they told me 720 dollars to replace the trans, if I provide one. I often see them on ebay and things with few miles for only a couple hundred dollars.

Now i have to hope the trans makes it to tax return time...

atc3434 · 01-22-2004, 01:04 PM

Yeah... thats weird. If its a split personality, I dunno about it yet! I dunno what it could be that would cause only one gear to shake. And you'd think it woud be worse under a harder load. So, lemme just make sure I understand this... if you drove up to say 70 mph and kept it in third... it wouldn't shake at all, but as soon as you shift into 4th you'd get the shake? In other words, its defintely isolated to one gear, right?

71Z28RS · 01-22-2004, 01:32 PM

My other personality seems to know what's up. If it's isolated in just that one gear (top gear), I don't see how it could be anything other than the trans.....unless of course the TC lockup is cycling rapidly like my personalities were discussing earlier. I guess that could cause some sort of vibration. And it does seem like it would be worse under heavier load. But, it seems impossible that anything external of the trans could be the issue since the problem is limited to overdrive while moving above a certain speed.

I guess the weird part about it is that it seems very unlikely that you'd damage your top gear before any other gear. That gear sees the least abuse. Maybe a defect in one of the planetary gears or syncros or something....sounds like something is out of balance....

Good luck with that and let us know how things work out.

Rba007 · 01-22-2004, 01:40 PM

Thanks guys, I really appreciate the input.

Yup, if i kept it in third, I get no vibes. Let it bump up to fourth, and im shaking. Do you think eventually it may spread to other gears? Im not to up on operation of the 4t40e peice of crap...

71Z28RS · 01-22-2004, 01:46 PM

From what it sounds like, it shouldn't quickly spread to the other gears. But to be brutally honest with you, it isn't exactly good for the car. Anytime you have something that rotates at high speeds that is vibrating off balance, you risk causing extra wear to mating parts. If the whole car is shaking because of a misbalance of the trans for whatever reason, then you're putting alot of extra lateral load on the engine's crankshaft bearings since the trans is tightly splined to the torque converter and the torque converter is tightly bolted to the flex plate. I don't think I'd let it go for too long before I took care of things. Of course, all that is based on the assumption that the trans is bad.

Rba007 · 01-22-2004, 06:35 PM

Again, thanks for the advice! Ill keep you all up to date, and if you think of any other (cheaper) ideas, let me know!

SilverStreak · 01-22-2004, 07:10 PM

Get your wheels balanced! (cheapest check you can do)

01-21-2004, 02:09 PM	#1
Rba007 GAGT Oldie AKA: Dave Join Date: Aug 2002 Location: N. Muskegon MI Age: 38 Posts: 2,444 Vehicle: 04 Grand Prix GT	Shake+Bad Fuel Mileage (UPDATED) Ive posted a few threads on this, none have gotten much of a response, so Ill post again. Im getting a shake (car vibrates, rattles change in my cupholders) above 40mph in top gear. This does not occur in any other gear. I just had an alignment last week, didnt help a bit. Im assuming that my transmission is going (99,000 Miles as of today). Any ideas? I havent changed my spark plugs in the last 20,000 miles, or the fuel filter in the last 20,000 or so either. But, if those were the culprits, wouldnt i get a vibration all the time? I can sit in my garage and rev it to the rpm's that its usually at cruising at 40 and up, and I get no vibration. It only happens in top gear, under no to light loads, from 40 MPH and UP. Used to only be from 40-50, now its 40-90 (as high as I wanted to test it), although it is definitley worse at 40 than at higher speeds. Any Ideas? Dealership has no clue what It could be, im hoping someone has similar experience and can help me with the diagnosis. Again, its a '99, 99000 Mile, 2.4 with the 4t40E automatic. THANKS -Dave __________________ Dave's Sexy Ride "Sul3LiME883: i'm drunk tho. i'd throw myself at a penis right now, i bet." "When you step over the line, your nuts are mine" "ArcticSun GT: u do smell dave, smell like awesomeness" Last edited by Rba007; 02-09-2004 at 08:05 PM.

01-21-2004, 02:27 PM	#2
Molson Admininadian! AKA: Jim Join Date: Mar 2001 Location: Great White Norf Age: 45 Posts: 3,695 Vehicle: Duramax, C10, MKZ	Tire could have thrown a weight and is off balance, it won't show it till higher speeds. Ice in the rim will also throw the balance off and cause a good shake. __________________ Sig

01-21-2004, 04:36 PM	#3
Rba007 GAGT Oldie AKA: Dave Join Date: Aug 2002 Location: N. Muskegon MI Age: 38 Posts: 2,444 Vehicle: 04 Grand Prix GT	Wouldnt it then vibrate even if i downshifted? I can do 40 plus, but in third gear, and get no vibration at all. It only happens in 4'th for some reason. Thanks for the ideas though. It started about 3 months ago, and since then has had new tires, and an alignment. Stupid Car. __________________ Dave's Sexy Ride "Sul3LiME883: i'm drunk tho. i'd throw myself at a penis right now, i bet." "When you step over the line, your nuts are mine" "ArcticSun GT: u do smell dave, smell like awesomeness"

01-21-2004, 04:37 PM	#4
Molson Admininadian! AKA: Jim Join Date: Mar 2001 Location: Great White Norf Age: 45 Posts: 3,695 Vehicle: Duramax, C10, MKZ	hmm, could have a broken tooth on a gear then. __________________ Sig

01-21-2004, 07:51 PM	#6
Rba007 GAGT Oldie AKA: Dave Join Date: Aug 2002 Location: N. Muskegon MI Age: 38 Posts: 2,444 Vehicle: 04 Grand Prix GT	Wierd. Its too bad not many people here have the engine/tranny I do. I wonder if it could be transmission mounts? __________________ Dave's Sexy Ride "Sul3LiME883: i'm drunk tho. i'd throw myself at a penis right now, i bet." "When you step over the line, your nuts are mine" "ArcticSun GT: u do smell dave, smell like awesomeness"

01-21-2004, 06:22 PM	#5
2000GA Guest Posts: n/a	possibly motor mounts maybe. in my jeep it would vibrate when it shifted into overdrive and we replaced the mounts which were worn and it cut down on half the vibration, the other half was from an out of balance front driveshaft.

01-21-2004, 08:00 PM	#7
AaronGAGT Scrap scrap! AKA: Aaron Join Date: Aug 2002 Location: Westland, MI Age: 38 Posts: 1,804 Vehicle: 2000 Black GT Coupe	Do your RPM's drop when you experience this shaking? I had this problem at about 50 mph... rpms would drop... shaking.. would let off the gas the hit it again and it'd be gone. I was getting horrible gas mileage too. I didnt notice the rpms dropping until i considered a misfire problem. I never got a SES light so I didnt know what to look for. My brother's car is doing the exact same thing as you explained. Car has 120k on it and doubt the plugs have ever been change. The thing is.. i dont see why your plugs would go bad at only 20k.. interesting..

01-21-2004, 08:18 PM	#8
Rba007 GAGT Oldie AKA: Dave Join Date: Aug 2002 Location: N. Muskegon MI Age: 38 Posts: 2,444 Vehicle: 04 Grand Prix GT	Well, they are Denso iridiums! So you think its the plugs? If so, Ill go buy me some good ole delco's tomorrow and see what happens. It just sucks, I have class every week day, and its about a 120 mile round trip! So, I drive a LOT. I also have a gently used MSD DIS 2 on the way, pre-wired for everything that I need. So, if youre thinking its the plugs, maybe with the new plugs, plus the MSD, ill be a happy camper. I HOPE its the plugs... __________________ Dave's Sexy Ride "Sul3LiME883: i'm drunk tho. i'd throw myself at a penis right now, i bet." "When you step over the line, your nuts are mine" "ArcticSun GT: u do smell dave, smell like awesomeness"

01-21-2004, 08:19 PM	#9
Rba007 GAGT Oldie AKA: Dave Join Date: Aug 2002 Location: N. Muskegon MI Age: 38 Posts: 2,444 Vehicle: 04 Grand Prix GT	PS, the engine sounds like the RPM's should be dropping, but the tach doesnt show it. __________________ Dave's Sexy Ride "Sul3LiME883: i'm drunk tho. i'd throw myself at a penis right now, i bet." "When you step over the line, your nuts are mine" "ArcticSun GT: u do smell dave, smell like awesomeness"

01-22-2004, 08:51 AM	#10
71Z28RS Build It Yourself Join Date: Sep 2003 Location: Westland, MI Age: 44 Posts: 246 Vehicle: 1996 Grand Am GT	If it's fine in 3rd gear at 40 mph, but it's not fine in overdrive at 40 mph, it's not your plugs or your wheels or your tires or your suspension or anything like that. Looks like you have a trans problem. __________________ "Trust me....... fuel injection is just a fad......so are CV joints" "Life was easier when fuel supply was measured in cfm's, not in psi"

01-22-2004, 09:13 AM	#11
atc3434 Grand Am Again AKA: Andrew Join Date: Apr 2003 Location: Auburn, NY Age: 38 Posts: 1,999 Vehicle: 1999 Grand Am SE	Torque converter lockup selonoid? Perhaps... __________________ 1999 Grand Am SE2 - Blue, TOG Headers, SLP Exhaust, DHP - SOLD 1996 Vert' Z-28 - M6, magnaflow muffler-back, K&N FIPK, Hurst Short-throw - 13.6 @ 103mph. 2006 Dodge Charger R/T Daytona - Go Mango Orange #2832 of 4000. Tune/exhaust. 14.009@97mph. 2002 Saab 9 5 Aero Wagon - 3" turboback/tune. 17psi of sleeper fun just waiting to surprise you.

01-22-2004, 09:15 AM	#12
71Z28RS Build It Yourself Join Date: Sep 2003 Location: Westland, MI Age: 44 Posts: 246 Vehicle: 1996 Grand Am GT	Maybe if it was rapidly locking-unlocking..... __________________ "Trust me....... fuel injection is just a fad......so are CV joints" "Life was easier when fuel supply was measured in cfm's, not in psi"

01-22-2004, 10:42 AM	#13
AaronGAGT Scrap scrap! AKA: Aaron Join Date: Aug 2002 Location: Westland, MI Age: 38 Posts: 1,804 Vehicle: 2000 Black GT Coupe	So Dave... got any updates for us?? this is off topic... is it just me or does 71z28rs and atc3434 travel as a couple to threads? Not flaming... you guys both always have good info, just realized you guys pop up and discuss stuff within the thread together sometimes...

01-22-2004, 12:47 PM	#14
Rba007 GAGT Oldie AKA: Dave Join Date: Aug 2002 Location: N. Muskegon MI Age: 38 Posts: 2,444 Vehicle: 04 Grand Prix GT	Multiple Personalities perhaps? Went to the dealer today, they wanted 15 dollars/plug, so ill be ordering the online for half that. And, they told me 720 dollars to replace the trans, if I provide one. I often see them on ebay and things with few miles for only a couple hundred dollars. Now i have to hope the trans makes it to tax return time... __________________ Dave's Sexy Ride "Sul3LiME883: i'm drunk tho. i'd throw myself at a penis right now, i bet." "When you step over the line, your nuts are mine" "ArcticSun GT: u do smell dave, smell like awesomeness"

01-22-2004, 01:04 PM	#15
atc3434 Grand Am Again AKA: Andrew Join Date: Apr 2003 Location: Auburn, NY Age: 38 Posts: 1,999 Vehicle: 1999 Grand Am SE	Yeah... thats weird. If its a split personality, I dunno about it yet! I dunno what it could be that would cause only one gear to shake. And you'd think it woud be worse under a harder load. So, lemme just make sure I understand this... if you drove up to say 70 mph and kept it in third... it wouldn't shake at all, but as soon as you shift into 4th you'd get the shake? In other words, its defintely isolated to one gear, right? __________________ 1999 Grand Am SE2 - Blue, TOG Headers, SLP Exhaust, DHP - SOLD 1996 Vert' Z-28 - M6, magnaflow muffler-back, K&N FIPK, Hurst Short-throw - 13.6 @ 103mph. 2006 Dodge Charger R/T Daytona - Go Mango Orange #2832 of 4000. Tune/exhaust. 14.009@97mph. 2002 Saab 9 5 Aero Wagon - 3" turboback/tune. 17psi of sleeper fun just waiting to surprise you.

01-22-2004, 01:32 PM	#16
71Z28RS Build It Yourself Join Date: Sep 2003 Location: Westland, MI Age: 44 Posts: 246 Vehicle: 1996 Grand Am GT	My other personality seems to know what's up. If it's isolated in just that one gear (top gear), I don't see how it could be anything other than the trans.....unless of course the TC lockup is cycling rapidly like my personalities were discussing earlier. I guess that could cause some sort of vibration. And it does seem like it would be worse under heavier load. But, it seems impossible that anything external of the trans could be the issue since the problem is limited to overdrive while moving above a certain speed. I guess the weird part about it is that it seems very unlikely that you'd damage your top gear before any other gear. That gear sees the least abuse. Maybe a defect in one of the planetary gears or syncros or something....sounds like something is out of balance.... Good luck with that and let us know how things work out. __________________ "Trust me....... fuel injection is just a fad......so are CV joints" "Life was easier when fuel supply was measured in cfm's, not in psi"

01-22-2004, 01:40 PM	#17
Rba007 GAGT Oldie AKA: Dave Join Date: Aug 2002 Location: N. Muskegon MI Age: 38 Posts: 2,444 Vehicle: 04 Grand Prix GT	Thanks guys, I really appreciate the input. Yup, if i kept it in third, I get no vibes. Let it bump up to fourth, and im shaking. Do you think eventually it may spread to other gears? Im not to up on operation of the 4t40e peice of crap... __________________ Dave's Sexy Ride "Sul3LiME883: i'm drunk tho. i'd throw myself at a penis right now, i bet." "When you step over the line, your nuts are mine" "ArcticSun GT: u do smell dave, smell like awesomeness"

01-22-2004, 01:46 PM	#18
71Z28RS Build It Yourself Join Date: Sep 2003 Location: Westland, MI Age: 44 Posts: 246 Vehicle: 1996 Grand Am GT	From what it sounds like, it shouldn't quickly spread to the other gears. But to be brutally honest with you, it isn't exactly good for the car. Anytime you have something that rotates at high speeds that is vibrating off balance, you risk causing extra wear to mating parts. If the whole car is shaking because of a misbalance of the trans for whatever reason, then you're putting alot of extra lateral load on the engine's crankshaft bearings since the trans is tightly splined to the torque converter and the torque converter is tightly bolted to the flex plate. I don't think I'd let it go for too long before I took care of things. Of course, all that is based on the assumption that the trans is bad. __________________ "Trust me....... fuel injection is just a fad......so are CV joints" "Life was easier when fuel supply was measured in cfm's, not in psi"

01-22-2004, 06:35 PM	#19
Rba007 GAGT Oldie AKA: Dave Join Date: Aug 2002 Location: N. Muskegon MI Age: 38 Posts: 2,444 Vehicle: 04 Grand Prix GT	Again, thanks for the advice! Ill keep you all up to date, and if you think of any other (cheaper) ideas, let me know! __________________ Dave's Sexy Ride "Sul3LiME883: i'm drunk tho. i'd throw myself at a penis right now, i bet." "When you step over the line, your nuts are mine" "ArcticSun GT: u do smell dave, smell like awesomeness"

01-22-2004, 07:10 PM	#20
SilverStreak My new toy Join Date: Jan 2004 Location: Iowa Age: 45 Posts: 103 Vehicle: 2001 Grand Am SE1	Get your wheels balanced! (cheapest check you can do) __________________ ~~~~Cory~~~~ My Project SilverStreak

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