clunk when I shift

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clunk when I shift

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clunk when I shift - 3/30/2008 4:01:20 AM

riley6riley

Posts: 119
Joined: 4/12/2007
Status: online

I have a 1979 L-48 with a automatic 3 speed. I assume it is original transmission. When I put the car into gear there is a clunk underneath and the rear end drops down some. It shifts fine going down the road. When ever I shift it manually from park to reverse or drive or 3rd to 2nd, I hear the clunk. Everything is original underneath and a few mods to the engine. I just had a tuneup done on it,(still needs some love there I think but that is a different thread) and I am idleing about 700-800 rmp. Any idea what it could be?

Thanks for the help.

Post #: 1

RE: clunk when I shift - 3/30/2008 6:28:24 AM

batesy80

Posts: 61
Joined: 7/15/2007
Status: offline

Sounds like a bad U-joint. I would check those first, then go from there. I recently changed my half shafts, due to bad u- joints. I coulded even press them out to change just the u-joints,the needle bearings were toast and original. so I just changed the whole half shafts to new, It made a much better job with the new Trailing arms. Good luck

(in reply to riley6riley)

Post #: 2

RE: clunk when I shift - 3/30/2008 6:43:39 AM

riley6riley

Posts: 119
Joined: 4/12/2007
Status: online

Thanks. I will try that. I have a Haynes manual and it looks pretty straight forward on the drive shaft. How hard are the half shafts to do? I have never done it before but I will try everything once.

(in reply to batesy80)

Post #: 3

RE: clunk when I shift - 3/30/2008 9:09:06 AM

C3 Starship

Posts: 4814
Joined: 7/25/2006
Status: offline

Center differential support bushing!

I'd bet on it.

_____________________________

1980 L-82 Fastback (forward too)
Mono composite front and rear.
Full adjust ride height and
response.
400+ hp, 454, M-22, 3.07

2007 H. D. Sportster, XL 883 EFI

http://i121.photobucket.com/albums/o225/C3Starship/HPIM0423.jpg

(in reply to riley6riley)

Post #: 4

RE: clunk when I shift - 3/30/2008 9:16:01 AM

YANKEECORVETTE

Posts: 106
Joined: 12/16/2007
Status: offline

hey Batesy80, I had the samething w/ my half shafts when I had my '77. I found out from a old timer that if you heat up the u joint caps w/ a torch-a little- there is a factory bond like material that melts off and the cap moves easier. But in my experence now your route is better. Time is money and I'm short on both. To riley6riley, The half shaft R&R is pretty straight forward, but takes time and some patients. Good Luck

(in reply to riley6riley)

Post #: 5

RE: clunk when I shift - 3/30/2008 1:25:58 PM

riley6riley

Posts: 119
Joined: 4/12/2007
Status: online

Well, I just replaced the drive shaft U-joints, the half shaft u joints will wait until later in the week. Center Differential support bushing? I will figure out what that is and replace it. The half shafts do not look that hard to remove. My rear spring is one spring (looks plastic maybe some polycarb or something like that) so the bolts on the half shafts look easy to get to. Forgot to get grease so i have to wait to test the new u-joints. I went with the u-joints that you have to lube.

(in reply to YANKEECORVETTE)

Post #: 6

RE: clunk when I shift - 3/30/2008 2:57:41 PM

Posts: 1066
Joined: 8/7/2006
Status: offline

The differential bushing that C3Starship mentioned is here www.mamotorworks.com part # 602-812 it's cheep and easy to change. PG

(in reply to riley6riley)

Post #: 7

RE: clunk when I shift - 4/8/2008 3:35:42 PM

Phill

Posts: 187
Joined: 9/19/2006
Status: offline

Hi riley. you mentioned your idle is 700-800 rpms. im not sure but isnt this a little high and wouldnt that cause a higher clunk noise then normal when shifting from park to drive. mine idles at about 650 rpms maybe mine is a bit low.

(in reply to pg)

Post #: 8

RE: clunk when I shift - 4/12/2008 2:24:54 AM

Shark

Posts: 5
Joined: 4/11/2008
Status: offline

Wow, i have the same shift (park to reverse/drive) problem with mine.

Gald to know its not incredibly uncommon

would anyone happen to know what would cause a horribly loud squeaking in a rear wheel on the driver's side when ever i drive... i just can't seem to get it to stop...

(in reply to Phill)

Post #: 9

RE: clunk when I shift - 4/12/2008 7:42:54 AM

C3 Starship

Posts: 4814
Joined: 7/25/2006
Status: offline

"would anyone happen to know what would cause a horribly loud squeaking in a rear wheel on the driver's side when ever i drive... i just can't seem to get it to stop... "

Hmmm,.....wheel bearing?

_____________________________

1980 L-82 Fastback (forward too)
Mono composite front and rear.
Full adjust ride height and
response.
400+ hp, 454, M-22, 3.07

2007 H. D. Sportster, XL 883 EFI

http://i121.photobucket.com/albums/o225/C3Starship/HPIM0423.jpg

(in reply to Shark)

Post #: 10