Violent "knocking" possibly coming from trans?
Question:
Ok, here is my situation… I have a devil car.. A ‘99 GMC Envoy… I purchased this car with only 7k miles on it, so I figured I would be in good shape, I would skip the "new car depreciation" but still have a fairly new car. Boy was I wrong… I started getting an amazingly loud knock that was timed with the engine cycles (higher the RPMs, the more knocking) so we took the car in to the shop, they originally thought it was the timing chain, but in the end they found out we needed an engine rebuild… It appears as though the car was ran with little to no oil at one point… Well we get our oil changed more frequently then the recommended amount, and this car does not burn oil, so that can only mean it happened in the first 7k miles that we did not have the car! So nearly $3,500 and a week later we get the truck back and it runs fine for about week… Now we are getting a "clunking" sound that you can feel in the floorboards, but we can not find anything to directly reproduce the problem, sometimes it happens, sometimes it does not. One time when it was happening quite severely we did some testing… We found out it has more to do with wheel movement then the engine from what we can tell… At a dead stop in park it would not do it, while in reverse it would do it slightly, then when we started driving it would do it quite loudly, then we shifted the car into neutral and it was still doing it just as loud as when it was in drive. From the feel of it we think it is coming from just behind the engine. I know this is quite vague, I can try to answer any clarifying questions, but our main problem is we can not reproduce the problem on cue, so if we bring it back to the shop there is a good chance it is not going to happen. Slim chance, but does anyone have any clue what this could be? We have checked the trans fluid and all other fluids and everything is right where it should be. Thanks in advance, Eric Phillips
Response:
> So nearly $3,500 and a week later we get the truck back and it runs > fine for about week… Now we are getting a "clunking" sound that you > can feel in the floorboards, but we can not find anything to directly > reproduce the problem, sometimes it happens, sometimes it does not. > One time when it was happening quite severely we did some testing… > We found out it has more to do with wheel movement then the engine > from what we can tell… At a dead stop in park it would not do it, > while in reverse it would do it slightly, then when we started driving > it would do it quite loudly, then we shifted the car into neutral and > it was still doing it just as loud as when it was in drive. > From the feel of it we think it is coming from just behind the engine.
Motor mounts not bolted down or broken? Or exhaust pipe flopping around?
Response:
Bad U-joint??? Or maybe the tranny tailshaft mount has worked loose? – Hide quoted text — Show quoted text – > Ok, here is my situation… I have a devil car.. A ‘99 GMC Envoy… > I purchased this car with only 7k miles on it, so I figured I would be > in good shape, I would skip the "new car depreciation" but still have > a fairly new car. > Boy was I wrong… I started getting an amazingly loud knock that was > timed with the engine cycles (higher the RPMs, the more knocking) so > we took the car in to the shop, they originally thought it was the > timing chain, but in the end they found out we needed an engine > rebuild… It appears as though the car was ran with little to no oil > at one point… Well we get our oil changed more frequently then the > recommended amount, and this car does not burn oil, so that can only > mean it happened in the first 7k miles that we did not have the car! > So nearly $3,500 and a week later we get the truck back and it runs > fine for about week… Now we are getting a "clunking" sound that you > can feel in the floorboards, but we can not find anything to directly > reproduce the problem, sometimes it happens, sometimes it does not. > One time when it was happening quite severely we did some testing… > We found out it has more to do with wheel movement then the engine > from what we can tell… At a dead stop in park it would not do it, > while in reverse it would do it slightly, then when we started driving > it would do it quite loudly, then we shifted the car into neutral and > it was still doing it just as loud as when it was in drive. > From the feel of it we think it is coming from just behind the engine. > I know this is quite vague, I can try to answer any clarifying > questions, but our main problem is we can not reproduce the problem on > cue, so if we bring it back to the shop there is a good chance it is > not going to happen. > Slim chance, but does anyone have any clue what this could be? We > have checked the trans fluid and all other fluids and everything is > right where it should be. > Thanks in advance, > Eric Phillips
Response:
Sounds like crossmember mounts, they are a real pain. The crossmember is cushioned with rubber cushions,the factory bolts are a bummer, use longer bolts and oversized nuts as spacers, put passenger side in first [ easy ] than jack up crossmember with floor jack until drivers side [ tough ] goes in place, than tighten all four bolts
