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Knocking on hard acceleration

 
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msteve000 msteve000
New User | Posts: 3 | Joined: 12/10
Posted: 12/19/10
08:38 AM

1991 Chevy Lumina. 182,000 miles. 3.1 L 6cyl. Automatic. Never had a transmission problem or hints of any symptions .... maybe a little subtle lurch when taking my foot off the gas, but nothing unsettling.

So, suddenly on Friday night, 10 minutes into driving on the interstate, I was accelerating up from 50mph when I felt severe knocking. I thought I was going over a rough road surface, but this was a familiar smooth road surface. Happened again, accelerating. Then I thought, maybe I had a flat tire, as I have felt similar. Stopped and checked tires. Got back in back and only GRADUALLY accelerated. No knocking. Next morning checked fluid levels. Oil and radiator were low, so added that and test drove an exit on the Beltway (DC) (Couldn't get past 50mph - heavy traffic, but no knocking)

Went to work Sat night, up the interstate. No knocking. Got to the main streets, stopped at a light. On acceleration the knocking came back up to 35-40 mph. Very hard and steady, until I eased off.

All the way back home, slow very gradual acceleration, no knocking. From what I have been reading, it may not be a serious problem, but it is extremely unsettling. Don't want the transmission blowing up on me and won't drive it at the moment. Any ideas? or cost  

waynep7122 waynep7122
Addict | Posts: 4561 | Joined: 08/09
Posted: 12/19/10
11:31 AM

transmissions rarely knock.....

running the engine low on motor oil can starve the engine bearings and burn them out.. it only takes seconds without oil to damage them...    the crank floats on a pressurized layer of oil...  when the oil pressure is lost.. the spinning crank rubs on the engine bearings directly... this wears the bearing surface away.. increasing clearance from about 2 pages of the telephone book... to much more.. this is where things start knocking..

this is going to require an experienced ear...  


how low did the oil get?????  

msteve000 msteve000
New User | Posts: 3 | Joined: 12/10
Posted: 12/19/10
03:40 PM

2 quarts.

But, I have seen a number of threads on transmissions where there were knocking noises ... not quite my circumstances though. Again, this ONLY occured on hard acceleration. Otherwise, quiet running, whether idling or going 60.  

440t4 440t4
Guru | Posts: 1009 | Joined: 04/09
Posted: 12/20/10
10:39 AM

sounds like it could be a bad cv axle joint.  

msteve000 msteve000
New User | Posts: 3 | Joined: 12/10
Posted: 12/20/10
11:23 AM

Re-checked the fluid level and it WAS low. Prior to adding more fluid, put it in 1st and there was a definitely rattling which went away after I added the fluid. Haven't done any higway driving, yet, but, otherwise running smoothly. Have to keep a close eye on it as I may probably have a leak.

Interstingly enough called a transmission place and, at least , the guy I talked to hadn't heard of my particular symptoms.  

Stuart Stuart
User | Posts: 164 | Joined: 04/06
Posted: 12/21/10
05:22 AM

It's very difficult to tell what may be knocking without actually hearing the noise.


Take it to a shop and let them listen.

Don't say what you think it is, let them offer a suggestion.  
Journeyman mechanic, transmission builder since 1963.

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