Driveshaft hits underbody under acceleration
05-29-2011, 09:02 PM
#1
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Car: 1986 IROC-Z28 Camaro
Engine: 350 carbureted (swap from 305 TPI)
Transmission: 700R4 rebuilt with shift kit
Axle/Gears: 3.42
Driveshaft hits underbody under acceleration
Never thought I would run into this problem. Just got my car back from having the carb tuned a little. It now runs a lot better. Under hard acceleration I noticed a fairly loud thud underneath my car. Checked it out and saw a fresh rub on the underbody right above the front of the driveshaft.
This is my hypothesis and I'm pretty sure I'm right, but you guys can give me your ideas. The torque arm from the rear axel drives the tail of the tranny up along w/ the driveshaft and then the shaft hits the underbody.
Ideas to fix:
-New tranny mounts (old ones are original soft rubber)
I would hope the new tranny mounts would be stiffer so the tranny wouldn't move?
I'm planning on replacing the tranny mount with a proform and also replace the 4 circular rubber grommets/ gaskets.
Question: Is this what needs to be done? I cant think of any other reason the driveshaft would hit the underbody. Any suggestions are welcome.
-Evan
This is my hypothesis and I'm pretty sure I'm right, but you guys can give me your ideas. The torque arm from the rear axel drives the tail of the tranny up along w/ the driveshaft and then the shaft hits the underbody.
Ideas to fix:
-New tranny mounts (old ones are original soft rubber)
I would hope the new tranny mounts would be stiffer so the tranny wouldn't move?
I'm planning on replacing the tranny mount with a proform and also replace the 4 circular rubber grommets/ gaskets.
Question: Is this what needs to be done? I cant think of any other reason the driveshaft would hit the underbody. Any suggestions are welcome.
-Evan
05-29-2011, 09:21 PM
#2
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Car: 1985 Berlinetta/2007 Ram1500
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Re: Driveshaft hits underbody under acceleration
I had same problem it was just a busted tailshaft mount changed it and all is fine now.
Lee
Lee
05-29-2011, 10:06 PM
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Car: 1986 IROC-Z28 Camaro
Engine: 350 carbureted (swap from 305 TPI)
Transmission: 700R4 rebuilt with shift kit
Axle/Gears: 3.42
05-30-2011, 01:20 AM
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Engine: gone
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Re: Driveshaft hits underbody under acceleration
yes replace the trans. mount. I dont recomend the poly mount tho. just a stock replacement is suffice.
05-30-2011, 06:11 AM
#6
Re: Driveshaft hits underbody under acceleration
The following comparison may be of interest:
https://www.thirdgen.org/forums/tran...ison-pics.html
JamesC
https://www.thirdgen.org/forums/tran...ison-pics.html
JamesC
05-30-2011, 09:35 AM
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Car: '90 Formula 350
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Transmission: ProBuilt S/S 700-R4 & ACT 9" Stall
Axle/Gears: 10 bolt 3.23
Re: Driveshaft hits underbody under acceleration
I agree. Start with the transmission mount. I had a thud about 10 years back and the mount visually looked okay until I took it apart to replace and it fell out in 2 pieces.
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05-30-2011, 10:02 AM
#8
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Car: 1986 IROC-Z28 Camaro
Engine: 350 carbureted (swap from 305 TPI)
Transmission: 700R4 rebuilt with shift kit
Axle/Gears: 3.42
Re: Driveshaft hits underbody under acceleration
Thanks guys. I have the parts Wednesday. I'll let you guys know if it worked.
05-30-2011, 02:15 PM
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Car: 86 Trans Am, 92 Firebird
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Axle/Gears: Moser 9", 3:70 trutac, 3:23 torsion
Re: Driveshaft hits underbody under acceleration
unless the axle tears through the floor, it dont think its even possible for the driveshaft to hit the floor. well, maybe if the trans is raise up all the way too...
defiantly the trans mount, like others have said.
defiantly the trans mount, like others have said.
06-05-2011, 12:23 PM
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Car: 1986 IROC-Z28 Camaro
Engine: 350 carbureted (swap from 305 TPI)
Transmission: 700R4 rebuilt with shift kit
Axle/Gears: 3.42
Re: Driveshaft hits underbody under acceleration
Finally got to take apart the transmission mounts and everything. It tore the transmission mount right in half, go figure. I'm going to try and get the new mount installed today. I also decided while I was down there I'm going to replace the main crossmember bushings and torque arm bushing. Also found out that the torque arm bushing isn't as easy to change as I was hoping... should be a good day.
-Evan
-Evan
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