C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Drivetrain questions

Old Aug 10, 2001 | 03:22 AM
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Default Drivetrain questions

I have a clunk. At first I thought it was the U-joints, but when Romeo and I did the tranny rebuild, we inspected them and there didn't seem to be any play. When I accelerate, I can hear and feel a definate clunk. I used to think it was from the back but now I really don't know. I still kinda do think it's from the back. It feels like something settling into place cause if I ride the clutch out real easy once I'm rolling, it's not noticable, but most of the time even on a very conservative acceleration from a stop it will at least make a tiny clunk. Say I'm in 4th gear and I let off the accelerator a bit and then hammer it it clunks: MMMMMMMMMMMMM (let off gas) MMMmmmmmmmmm (hit the gas) BBMMMMMMMMMMMMMMMM...
My 2nd symptom seems to be either related or perhaps the same problem: If I'm holding a steady speed and then I remove my foot from the accelerator it will coast like it should and then alot of the time, it feels like something moves in the drivetrain and the car slows much quicker than a normal coast. This is especially noticable when cruising residential areas at low speeds in 3rd gear and under very light throttle cause I back my foot off the accelerator very gradually and sometimes in so doing I back my foot completely off the pedal and then something in there moves and it's like I'm coasting uphill like I mentioned above. I then give a little gas and the same something in there moves back and makes "the clunk". :confused: WTF?

And the most hair raising of all: Sometimes when I gun it, the car will out of the blue just fall on its face completely!! It's like something hiccups and the car falters and I'm thrown forward and then back into the seat again. This all happens within 1-2 seconds. I haven't been able to watch the RPMs when this happens because it's too abrupt and intermitant, but I think that the rpms may be staying steady as they should.

My only guess right now is that it may be bad differential mounts. Would that cause a problem like any of these? I know it may be a stretch but what about motor mounts? It feels like something's moving back and forth in there. It feels like something in the rear is not secure...

BTW, I had all of these symptoms before the tranny rebuild. I do not suspect the 4-speed part at all...
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Old Aug 10, 2001 | 06:58 PM
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Default Re: Drivetrain questions (A)

^^^
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Old Aug 13, 2001 | 09:21 PM
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Default Re: Drivetrain questions (A)

Hello? Does this sound like a bad rear end? I'm baffled. What could this be???


[Modified by A, 7:24 PM 8/13/2001]
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Old Aug 14, 2001 | 01:19 AM
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Default Re: Drivetrain questions (A)

I had to retorque the bolts on the "C" arm to the rear diff. and to the trans to queit my clunk-they can loosen. Also I still have some play in the diff. due to high miles so it still clunks a little. Seemed like synthetic in the rear also helped. As far as the stall- need more info. Do you have a scan tool? Most of them have a capture mode for intermittant hard to diag. problems.
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Old Aug 14, 2001 | 01:13 PM
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Default Re: Drivetrain questions (drive it)

C arm sound like it would be good to check.

Check the diff mounts, check the diff as well. I've got a little play in mine. I thought it was the U joints but when I rotated the rotor back & forth I could see it in the diff, not too bad yet.
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Old Aug 14, 2001 | 09:12 PM
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Default Re: Drivetrain questions (drive it)

Ok cool. Thanks guys, I'll try to check those things this weekend. I sure hope it's something simple... I hear a new diff is $$$!! :eek:



[Modified by A, 7:12 PM 8/14/2001]
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Old Aug 14, 2001 | 09:33 PM
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Default Re: Drivetrain questions (A)

Bryant, even if it was the diff, you'd just need a new gearset I believe, which is a heck of alot cheaper than buying a complete unit.
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Old Aug 14, 2001 | 09:39 PM
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Default Re: Drivetrain questions (Romeo Barrera)

Hey whenever I see you next I'll demonstrate. Maybe it's something simple that'd occur to you...
but me= :confused: :D
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