Transmissions and Drivetrain Need help with your trans? Problems with your axle?

Slamming sound when accelerating

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Old Jun 29, 2011 | 06:45 AM
  #1  
HisDivineShadow's Avatar
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From: Finland
Car: 1991 Trans Am GTA
Engine: 350 TPI (L98)
Transmission: TH-700r4
Slamming sound when accelerating

Okay, I got this weird phenomenom where if I accelerate suddenly and quickly from a standstill, something slams up against something else in the back of the car. I thought it was the wheels letting go perhaps but it seems not so.

Someone told me something vague about the drive train or perhaps the rear axle (I don't really remember what he said as I was too upset at him saying my car didn't pass inspections).

Anyone know what I am talking about and if it's a serious matter?
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Old Jun 29, 2011 | 06:51 AM
  #2  
JamesC's Avatar
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From: Lawrence, KS
Car: Met. Silver 85 IROC/Sold
Engine: 350 HO Deluxe (350ci/330hp)
Transmission: T-5 (Non-WC)
Axle/Gears: Limited Slip 3.23's
Re: Slamming sound when accelerating

Originally Posted by HisDivineShadow
Okay, I got this weird phenomenom where if I accelerate suddenly and quickly from a standstill, something slams up against something else in the back of the car. I thought it was the wheels letting go perhaps but it seems not so.

Someone told me something vague about the drive train or perhaps the rear axle (I don't really remember what he said as I was too upset at him saying my car didn't pass inspections).

Anyone know what I am talking about and if it's a serious matter?
Check the trans mount.

JamesC
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Old Jun 29, 2011 | 11:51 AM
  #3  
IroczFan's Avatar
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From: Omro Wisconsin
Car: 86 IROC-Z
Engine: 383 Stroker Vortec
Transmission: 700r4 Built
Axle/Gears: 3:42
Re: Slamming sound when accelerating

sounds like the trans mount my buddys GTA does the smae thing when he gets on it
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Old Jun 29, 2011 | 12:02 PM
  #4  
spotspot's Avatar
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From: California
Car: 90 RS Camaro
Engine: 305
Transmission: 700R4
Axle/Gears: stock
Re: Slamming sound when accelerating

Originally Posted by HisDivineShadow
Okay, I got this weird phenomenom where if I accelerate suddenly and quickly from a standstill, something slams up against something else in the back of the car. I thought it was the wheels letting go perhaps but it seems not so.

Someone told me something vague about the drive train or perhaps the rear axle (I don't really remember what he said as I was too upset at him saying my car didn't pass inspections).

Anyone know what I am talking about and if it's a serious matter?
had the same problem i replaced my tranny mount in my car it solved the problem
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Old Jun 29, 2011 | 12:21 PM
  #5  
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From: New Boston, IL, USA
Car: '90 Formula 350
Engine: 383 SBC
Transmission: ProBuilt S/S 700-R4 & ACT 9" Stall
Axle/Gears: 10 bolt 3.23
Re: Slamming sound when accelerating

I also agree. Sometimes a mount might even look good with the visual check, but once you remove the bolts it'll fall out in 2 pieces.
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Old Jun 29, 2011 | 12:41 PM
  #6  
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From: King George,VA
Car: 1985 Z28
Engine: '69 350 4 Bolt Main .30 Over
Transmission: 700r4/B&M Shift Kit and Flywheel
Axle/Gears: GM 10 Bolt 3.23 Gears
Re: Slamming sound when accelerating

I agree,same thing was happening to me until I stuck a jack under the trans to check the mount,I slightly applied pressure and the mount was seperated. Cheap fix too. I remember the day I noticed something broke.I did a launch in my driveway, it kind of felt like wheel hop but I noticed the hood flexed up a little in the center when I launched,it was my breather slapping the underside of my hood.Yikes!
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Old Jun 30, 2011 | 01:14 AM
  #7  
HisDivineShadow's Avatar
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From: Finland
Car: 1991 Trans Am GTA
Engine: 350 TPI (L98)
Transmission: TH-700r4
Re: Slamming sound when accelerating

The inspections guy said something about the rear shock absorbers and maybe something about the whole drive train twisting because something s worn out. Happens because the engine is so powerful and something about on how hot rods they put in extra shock absorbers or springs to prevent it.

I dunno he kept talking a lot and I didn't catch most of it, I was wondering if it was this issue I read about here:
https://www.thirdgen.org/forums/post...796-post5.html

It only happens once for me though, not several times and if I go easy on the throttle nothing happens.

I hope its the trans.mount though that sounds a lot easier to repair! Not even a 2-dollar part it seems.
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Old Jun 30, 2011 | 02:56 AM
  #8  
TreeFiddy's Avatar
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From: Sydney, Australia
Car: '86 TA
Engine: '74 350
Transmission: 700r4
Axle/Gears: 2.77
Re: Slamming sound when accelerating

Originally Posted by HisDivineShadow
It only happens once for me though, not several times and if I go easy on the throttle nothing happens.
Yep, classic transmission mount, done mine twice. First rubber, then I learned and went poly.
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Old Jun 30, 2011 | 04:20 AM
  #9  
HisDivineShadow's Avatar
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From: Finland
Car: 1991 Trans Am GTA
Engine: 350 TPI (L98)
Transmission: TH-700r4
Re: Slamming sound when accelerating

Aahhh now I get it then! It's like a "pillow" that goes between the shaft and tunnel so it wont slam into it. Thats why that inspections guy talked about how hot rods had some kind of shock absorber installed. Thats what the transmission mount essentially is.

That guy seemed to think there was something more serious wrong though but he didn't know about the trans mount.
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Old Jun 30, 2011 | 05:16 AM
  #10  
JamesC's Avatar
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From: Lawrence, KS
Car: Met. Silver 85 IROC/Sold
Engine: 350 HO Deluxe (350ci/330hp)
Transmission: T-5 (Non-WC)
Axle/Gears: Limited Slip 3.23's
Re: Slamming sound when accelerating

Before you choose a poly mount, you might check the comparison out:

https://www.thirdgen.org/forums/tran...ison-pics.html

JamesC
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Old Jun 30, 2011 | 06:34 AM
  #11  
HisDivineShadow's Avatar
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From: Finland
Car: 1991 Trans Am GTA
Engine: 350 TPI (L98)
Transmission: TH-700r4
Re: Slamming sound when accelerating

I don't like the poly idea after what I've read because *** do I hate vibrations. Considering a stock, it seems to be the quietest, even if it breaks more often.

Is this the part I would need?
http://www.rockauto.com/catalog/moreinfo.php?pk=315034

Last edited by HisDivineShadow; Jun 30, 2011 at 06:41 AM.
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Old Jun 30, 2011 | 07:04 AM
  #12  
JamesC's Avatar
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From: Lawrence, KS
Car: Met. Silver 85 IROC/Sold
Engine: 350 HO Deluxe (350ci/330hp)
Transmission: T-5 (Non-WC)
Axle/Gears: Limited Slip 3.23's
Re: Slamming sound when accelerating

Originally Posted by HisDivineShadow
If that's Anchor 2394, yes. You might verify that you don't have that horrible oil-filled mount that some cars were equipped with before you order, as the above mount won't fit the cross member.

JamesC
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Old Jun 30, 2011 | 07:22 AM
  #13  
HisDivineShadow's Avatar
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From: Finland
Car: 1991 Trans Am GTA
Engine: 350 TPI (L98)
Transmission: TH-700r4
Re: Slamming sound when accelerating

Hmmm will I avoid that issue if I get the prothane mount from summit? Or does that possibility mean none of the mounts would fit?

What can be done if that happens to be the case?
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Old Jun 30, 2011 | 07:33 AM
  #14  
JamesC's Avatar
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From: Lawrence, KS
Car: Met. Silver 85 IROC/Sold
Engine: 350 HO Deluxe (350ci/330hp)
Transmission: T-5 (Non-WC)
Axle/Gears: Limited Slip 3.23's
Re: Slamming sound when accelerating

Originally Posted by HisDivineShadow
Hmmm will I avoid that issue if I get the prothane mount from summit? Or does that possibility mean none of the mounts would fit?

What can be done if that happens to be the case?
None would fit.

Replace the cross member with one from a standard 700R4 or T-5, and all of the mounts will fit (except, of course, the oil-filled mount).

JamesC
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Old Jun 30, 2011 | 07:45 AM
  #15  
HisDivineShadow's Avatar
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From: Finland
Car: 1991 Trans Am GTA
Engine: 350 TPI (L98)
Transmission: TH-700r4
Re: Slamming sound when accelerating

Lets hope it does not come to that. Will have a look under the car, will have to manufacture some ramps.
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Old Jun 30, 2011 | 08:00 AM
  #16  
JamesC's Avatar
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From: Lawrence, KS
Car: Met. Silver 85 IROC/Sold
Engine: 350 HO Deluxe (350ci/330hp)
Transmission: T-5 (Non-WC)
Axle/Gears: Limited Slip 3.23's
Re: Slamming sound when accelerating

Originally Posted by HisDivineShadow
Will have a look under the car, will have to manufacture some ramps.
The oil-filled mount looks nothing like the OE, ES, or prothane versions, so you should be able to tell what you have at a glance.

JamesC
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