Help! 79 grinding noise

[larryoinvirginia]

Hey all,
New here, first post and need some advice.I have a 79 l48 little more than stock w/ 4spd . Im getting a strange grinding noise from between th seats when i quickly decellarate. It shifts fine up and down, no vibrations or shimmys at any time. Hard accelerations no problem and gentle de-accelerations no problem. Only when I let off the gas quickly, and i can make it happen in any gear. I just redid the front end, and replaced the shocks so Ive been underneath and found no loose bolts and the shafts feel ok. My gut tells me I have a tranny getting ready to implode and Im hoping someone here can shed some sunnier ideas lol.
Thanks for any advice
Larry

 

[Vettehead Mikey]

Check the drive shaft u-joints, rear transmission mount and diff. front snubber bushing.

 

[KANE]

Check the drive shaft u-joints, rear transmission mount and diff. front snubber bushing.

I agree- sounds like it could be related to the above mentioned areas.

If those areas are okay, well... you've at least eliminated them from the list of potential causes!

 

[larryoinvirginia]

thanks , rear tranny mount sounds like a good start since i do recall a slight chatter when leaving a light a few weeks ao. Same kind of feeling.
Kane, BTW , Have a 96 trans am as well
will let youknow what I find

 

[larryoinvirginia]

ok, I think this just worse.Appears to be at the front snubber bushing. There is a piece of the frame where the bushing appears to be attached too that is broken. It is approx 3/4 wide and flat but somehow has broken and is now twisted around and it looks like under a rapid decellaration it will strike the knuckle on the u joint creaing a grinding noise. Great. I found it. Now when I tried to bend it back with a pry bar I can "bounce" the differential up and down about an inch. Ive looked briefly at an ecklers cataolg to see if this is a wearable piece of frame that can be replaced otherwise Im screwed. Does anyone know what Im looing at?

Larry

 

[KANE]

ok, I think this just worse.Appears to be at the front snubber bushing. There is a piece of the frame where the bushing appears to be attached too that is broken. It is approx 3/4 wide and flat but somehow has broken and is now twisted around and it looks like under a rapid decellaration it will strike the knuckle on the u joint creaing a grinding noise. Great. I found it. Now when I tried to bend it back with a pry bar I can "bounce" the differential up and down about an inch. Ive looked briefly at an ecklers cataolg to see if this is a wearable piece of frame that can be replaced otherwise Im screwed. Does anyone know what Im looing at?

Larry

I think I know the area you are talking about. hnoes

Can you post a pic?

FWIW- I saw a 1975 Vette frame for sale for $500 in Louisville on Craigslist. I seem to remember it had the area you need in good shape. Body mount provisions are fried though.

Here is the link- http://louisville.craigslist.org/cto/1323882557.html

 

[larryoinvirginia]

yuppers..its smoked..lol..i pulled the trailing arm style brackets and the snubber bushing assembely completely out. It appears to have been broken for some time now as there is much missing and only about 2 inches freshly marked. Feel a little lucky i found it this way and not whle driving down the interstate and walking through a pothole. This is my daily driver and Im resolved to the fact shes done for awhile. I have calls in to two friends who have friends that do can do custom farication and welding. I Dont think it will require a complete frame off. But on the brighter side, since I need a new daily ride, I can finally take the girl off the road and do some tings Ive wanted too.. Thanks for those who helped. It was spot on advice. I will be here daily for my fever fix . If I aint driving mine, Ill live vicariously through you for awhile..lol

Larry

 

[Vettehead Mikey]

Does anyone know what Im looing at?

Larry

Yup- can imagine exactly what's happened as I went through the same thing on my '73 prior to my frame off in '94. I welded in a temporary sheet metal fix to tide me over.

You might want to give your frame a good going over to see if there's other weak spots.

 

[larryoinvirginia]

UPDATE:
Called my local guy here. Shameless plug for TIDEWATER CORVETTES in The Virginia Beach area. The owner Bob Dick is awsome. Told him what had happened and he said no problem. Will be taking it to him and he will cut the flange from a wrecked 78 and weldback to mine. This guy is really great. I do most of my own stuff but when its beyond my capacities he's there for me. Only problemis it wont be done this week since him and his partner Mike leave wednsday night for some corvette show/ rally somewhere. I didnt catch that part.
Will keep updated and try to figure out the photo thing
Larry