thumping sound

91lxstang · 11-29-2002, 01:25 AM

ok when im driving and get to about 3000 rpms and 1st and 2nd i keep hearing and feeling a thumping sound it sounds like its coming from the cross member but i checked it out and it looks fine has anyone had this happen to them

2FastLX · 11-30-2002, 11:30 AM

Dude, I can't believe no one has helped you with this yet. I'll get Chris in here (a.k.a. PKRWUD).

11-30-2002, 02:06 PM

Perhaps we can help you a bit better if you give us a little more detail.

91lxstang wrote:

"ok when im driving and get to about 3000 rpms and 1st and 2nd i keep hearing and feeling a thumping sound it sounds like its coming from the cross member but i checked it out and it looks.."

"thumping" is this a consistent sound that occurs at the same engine speed and rpm? Or, does it decrease when the transmission is engaged into another gear? When does it stop? What coditions are you driving, e.g. flooring it or consistant acceleration? Is it a thumping sound that is occurring near the transmission and gears/ Axel and differential/ Driveshaft/driveline?

I noticed you have an aluminum driveshaft (frpp Aluminum driveshaft)
Are the angles correct?
Are the driveshaft and companion flange balanced?

Just a couple things that make out job to help you a little easier...

Jennifer
aka-Jane of all Trades

PKRWUD · 11-30-2002, 02:43 PM

Jenn asked some excellent questions, as always.

The more we know, the easier it will be to diagnose.

Does the thumping only occur under load, or while you are decellerating, too?

Try this:
Put the rear end up on stands, and block the front wheels. Start it up, and run it gently through the gears, trying to duplicate the condition. If you can, pay attention to exactly when it happens, and when it stops.

Details my friend, details.

Take care,
~Chris

11-30-2002, 03:05 PM

Thanks Chris,

Jenn

91lxstang · 12-01-2002, 03:14 AM

ok sorry guys it only happens under full throttle from about 3000 rpms up to about 5000 rpms it sounds like its coming from my cross member area i got some pics if that will help?

PKRWUD · 12-01-2002, 03:32 AM

Vehicle speed doesn't matter? It does this in every gear? Does it stop at 5k rpms, or is that just when you shift/back off?

91lxstang · 12-01-2002, 03:37 AM

yeah it stops when i back off i really dont ever go over 5000 rpms so i dont know about that and just in 1st and 2nd it seems to do it when i hit my power band under full throttle

PKRWUD · 12-01-2002, 03:42 AM

Double check your tranny mount.

91lxstang · 12-01-2002, 03:44 AM

ok heres a pic of it it was really hard geting it in

PKRWUD · 12-01-2002, 05:47 AM

Well, you can keep guessing, or find out, and the only way I know of to find out is to recreate the conditions and get it to act up, but in a controlled environment where you can observe it.

Put the rear end up on a sturdy set of jack stands, UNDER THE AXLE. Block the front wheels. If you have another set of jack stands, set them up under the rear frame so that they are barely in contact. These will be a backup. Then start it and run it through the gears, trying to duplicate the sound. Don't give up until you find it. Have a friend help you, but NO BEERS UNTIL YOU ARE FINISHED, and the car is back on the ground.

Post your results.

Take care,
~Chris

91lxstang · 12-01-2002, 05:49 AM

ok ill try that thanks for the help

82 GT · 12-01-2002, 11:12 PM

Is it just me or does that picture look like the right side washer is too big for the nut?

91lxstang · 12-02-2002, 04:48 AM

yeah i just fixed that today it helped alot just does it in 2nd now but not as bad

NewAge 5.0 · 12-02-2002, 09:17 AM

i read that you have shorty headers, might be the Hpipe hittin the crossmember. My opinion ditch that solid tranny mount!! I hope you dont have solid motor mounts too.. if so your gonna Break your bellhousing or tranny..

PKRWUD · 12-03-2002, 07:45 AM

Quote:

Originally posted by 82 GT
Is it just me or does that picture look like the right side washer is too big for the nut?

Would you stop looking at his nuts!

91lxstang
If you did something that lessened the problem, then look further at what you did. That is probably where the answer is.

Take care,
~Chris

91lxstang · 12-04-2002, 03:11 AM

yeah im going to drop the cross member and take a closer look at it and its not my X pipe hiting it hangs about 2 1/2 inches lower then the cross member
and i just put my sub frames on today and wow new car

it stoped doing it in first but still does it in 2nd but not every time now
ok i just now realized that i didnt say when it started sorry about this flame away

ok it started when i changed my rear seal on my tranny i dont know if this helps

91lxstang · 12-06-2002, 06:24 PM

ok i found out what it is thanks for the tip chris

now can anyone tell me what this thing is called its in yellow
its hiting my muffler in red

91lxstang · 12-06-2002, 11:03 PM

well from what i saw the only thing moveing unnder the car was the dogbone got rid of it but its still doing it anymore tips on what to look at next

11-29-2002, 01:25 AM	#1
91lxstang Registered Member Join Date: Nov 2002 Location: Reno NV Posts: 11	thumping sound ok when im driving and get to about 3000 rpms and 1st and 2nd i keep hearing and feeling a thumping sound it sounds like its coming from the cross member but i checked it out and it looks fine has anyone had this happen to them __________________ bbk underdrive pullys cobra intake ported upper/lower FMS 9mm wires flexalite fan bbk cold air flowtech shorty headers flowmaster 2 cambers pacesetter off-road X-pipe pro3i sub frames fms Aluminum driveshaft 14* timing Moroso Solid motor and tranny mounts and much more to come waiting to go in 3.73 fms cant wait F-cam / 1.6 rockers Lentech valve body and Converter

11-30-2002, 11:30 AM	#2
2FastLX The Photoshop Guru Join Date: Feb 2001 Location: Mecca, Indiana Posts: 1,419	Dude, I can't believe no one has helped you with this yet. I'll get Chris in here (a.k.a. PKRWUD). __________________ Project: 1988 Coupe - EFI 5.8L Twin Turbo with Victor intake, Canfield heads, F303 cam, March aluminum underdrive pulleys, TKO (or T56 if funds permit), PBR twin piston calipers and 13" rotors up front, 94 Cobra rear calipers and 12" rotors on the rear, 3.73's, Griggs K-member, tubular front control arms, torque arm and panhard bar, polished 99 Cobra wheels. "The GR-40 kit installation is now complete, and the humble Fox-chassis car will now out-corner and out-stop a ZR-1 or a Viper, and support massive horsepower additions with perfect balance." Griggs Racing ICQ# 42269241

11-30-2002, 02:06 PM	#3
Janeofalltrades Guest Posts: n/a	A little more detail? Perhaps we can help you a bit better if you give us a little more detail. 91lxstang wrote: "ok when im driving and get to about 3000 rpms and 1st and 2nd i keep hearing and feeling a thumping sound it sounds like its coming from the cross member but i checked it out and it looks.." "thumping" is this a consistent sound that occurs at the same engine speed and rpm? Or, does it decrease when the transmission is engaged into another gear? When does it stop? What coditions are you driving, e.g. flooring it or consistant acceleration? Is it a thumping sound that is occurring near the transmission and gears/ Axel and differential/ Driveshaft/driveline? I noticed you have an aluminum driveshaft (frpp Aluminum driveshaft) Are the angles correct? Are the driveshaft and companion flange balanced? Just a couple things that make out job to help you a little easier... Jennifer aka-Jane of all Trades

11-30-2002, 02:43 PM	#4
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Jenn asked some excellent questions, as always. The more we know, the easier it will be to diagnose. Does the thumping only occur under load, or while you are decellerating, too? Try this: Put the rear end up on stands, and block the front wheels. Start it up, and run it gently through the gears, trying to duplicate the condition. If you can, pay attention to exactly when it happens, and when it stops. Details my friend, details. Take care, ~Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

11-30-2002, 03:05 PM	#5
Janeofalltrades Guest Posts: n/a	Thanks Chris.... Thanks Chris, Jenn

12-01-2002, 03:14 AM	#6
91lxstang Registered Member Join Date: Nov 2002 Location: Reno NV Posts: 11	ok sorry guys it only happens under full throttle from about 3000 rpms up to about 5000 rpms it sounds like its coming from my cross member area i got some pics if that will help? __________________ bbk underdrive pullys cobra intake ported upper/lower FMS 9mm wires flexalite fan bbk cold air flowtech shorty headers flowmaster 2 cambers pacesetter off-road X-pipe pro3i sub frames fms Aluminum driveshaft 14* timing Moroso Solid motor and tranny mounts and much more to come waiting to go in 3.73 fms cant wait F-cam / 1.6 rockers Lentech valve body and Converter

12-01-2002, 03:32 AM	#7
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Vehicle speed doesn't matter? It does this in every gear? Does it stop at 5k rpms, or is that just when you shift/back off? __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

12-01-2002, 03:37 AM	#8
91lxstang Registered Member Join Date: Nov 2002 Location: Reno NV Posts: 11	yeah it stops when i back off i really dont ever go over 5000 rpms so i dont know about that and just in 1st and 2nd it seems to do it when i hit my power band under full throttle __________________ bbk underdrive pullys cobra intake ported upper/lower FMS 9mm wires flexalite fan bbk cold air flowtech shorty headers flowmaster 2 cambers pacesetter off-road X-pipe pro3i sub frames fms Aluminum driveshaft 14* timing Moroso Solid motor and tranny mounts and much more to come waiting to go in 3.73 fms cant wait F-cam / 1.6 rockers Lentech valve body and Converter

12-01-2002, 03:42 AM	#9
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Double check your tranny mount. __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

12-01-2002, 05:47 AM	#11
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Well, you can keep guessing, or find out, and the only way I know of to find out is to recreate the conditions and get it to act up, but in a controlled environment where you can observe it. Put the rear end up on a sturdy set of jack stands, UNDER THE AXLE. Block the front wheels. If you have another set of jack stands, set them up under the rear frame so that they are barely in contact. These will be a backup. Then start it and run it through the gears, trying to duplicate the sound. Don't give up until you find it. Have a friend help you, but NO BEERS UNTIL YOU ARE FINISHED, and the car is back on the ground. Post your results. Take care, ~Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

12-01-2002, 05:49 AM	#12
91lxstang Registered Member Join Date: Nov 2002 Location: Reno NV Posts: 11	ok ill try that thanks for the help __________________ bbk underdrive pullys cobra intake ported upper/lower FMS 9mm wires flexalite fan bbk cold air flowtech shorty headers flowmaster 2 cambers pacesetter off-road X-pipe pro3i sub frames fms Aluminum driveshaft 14* timing Moroso Solid motor and tranny mounts and much more to come waiting to go in 3.73 fms cant wait F-cam / 1.6 rockers Lentech valve body and Converter

12-01-2002, 11:12 PM	#13
82 GT Import Slayer Join Date: May 1999 Posts: 2,241	Is it just me or does that picture look like the right side washer is too big for the nut? __________________ '82 GT 351W (.060)Comp Cams 274* Extreme Energy cam, ported & polished heads w/ 1.94/1.60 valves 10.3:1 flat top pistons,stealth intake, Mallory dizzy,Holley 750dp carb, BBK shorties,Flowmaster exhaust,C-4 with 3700 stall converter, B&M pro shifter,8.8 rear, 4:10's, subframes, electric fan, powermaster alternator, 4 core radiator.

12-02-2002, 04:48 AM	#14
91lxstang Registered Member Join Date: Nov 2002 Location: Reno NV Posts: 11	yeah i just fixed that today it helped alot just does it in 2nd now but not as bad

12-02-2002, 09:17 AM	#15
NewAge 5.0 Registered Member Join Date: Mar 1999 Location: Sanford NC USA Posts: 155	i read that you have shorty headers, might be the Hpipe hittin the crossmember. My opinion ditch that solid tranny mount!! I hope you dont have solid motor mounts too.. if so your gonna Break your bellhousing or tranny.. __________________ 88 Hatch 10.60's @ 130 89 Hatch Not as fast but holds its own

12-04-2002, 03:11 AM	#17
91lxstang Registered Member Join Date: Nov 2002 Location: Reno NV Posts: 11	yeah im going to drop the cross member and take a closer look at it and its not my X pipe hiting it hangs about 2 1/2 inches lower then the cross member and i just put my sub frames on today and wow new car it stoped doing it in first but still does it in 2nd but not every time now ok i just now realized that i didnt say when it started sorry about this flame away ok it started when i changed my rear seal on my tranny i dont know if this helps __________________ bbk underdrive pullys cobra intake ported upper/lower FMS 9mm wires flexalite fan bbk cold air flowtech shorty headers flowmaster 2 cambers pacesetter off-road X-pipe pro3i sub frames fms Aluminum driveshaft 14* timing Moroso Solid motor and tranny mounts and much more to come waiting to go in 3.73 fms cant wait F-cam / 1.6 rockers Lentech valve body and Converter Last edited by 91lxstang; 12-04-2002 at 05:02 AM..

12-06-2002, 11:03 PM	#19
91lxstang Registered Member Join Date: Nov 2002 Location: Reno NV Posts: 11	well from what i saw the only thing moveing unnder the car was the dogbone got rid of it but its still doing it anymore tips on what to look at next __________________ bbk underdrive pullys cobra intake ported upper/lower FMS 9mm wires flexalite fan bbk cold air flowtech shorty headers flowmaster 2 cambers pacesetter off-road X-pipe pro3i sub frames fms Aluminum driveshaft 14* timing Moroso Solid motor and tranny mounts and much more to come waiting to go in 3.73 fms cant wait F-cam / 1.6 rockers Lentech valve body and Converter

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