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VT knock/rattle noise in drive

Glaze

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Hey all

I’ve dug deep within all the forums related to this issue couldn’t find any specific answers so thought to start a thread for any other owners with similar issues.

It’s a 99 VT ecotec auto

Ever since changing the trans fluid and filter the cars developed a really rough idle to the point where it starts knocking - more of a low end noise.

In Park reverse and neutral the car is quiet and doesn’t vibrate but when in drive it gets quite aggressive and noise disappears when accelerating/taking off.

I’ve tested conditions where the issue arises when it is only in drive gear at a stop (handbrake or brakes add no effect). Trans fluid level checked all ok in park at operating temp. However, thermostat seems to play up usually the car sits around half to one notch above cold. Noticed in drive at a stop while car is warm the noises are much less aggressive, also cars running 15/40 semi synthetic thinking of going back to 20/50 cos cars hitting 200ks soon and it’s developed all these noises since using the oil

Cheers
 

gohrdrgomad

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The lower number 15 or 20 is reference to cold start. The higher reference/ 40 or 50 you stated is the running temp range. If you chose a 5 it would assist start-up at - 0 +deg for winter. The /30 or upward support higher temps during the day. Is your car semi sinth from fact or do you just put it in. This can create other issues. Some motors can determin if the oil is inferior/incorrect.
 

Glaze

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Hey mate appreciate the feedback I’m aware of what the numbers mean for engine oil. manufacturers say 20/50 doesn’t specify mineral or synthetic. I wanted to test how the engine behaved with higher grade oil, also the car idled fairly quiet in drive at the lights today and I noticed temp was sitting dead centre. Could a busted thermostat interfere with how the car operates? I’ve replaced the radiator not too long ago with a flush as well completely forgot to change the thermostat cos I had no time to redo or wait for the part

The lower number 15 or 20 is reference to cold start. The higher reference/ 40 or 50 you stated is the running temp range. If you chose a 5 it would assist start-up at - 0 +deg for winter. The /30 or upward support higher temps during the day. Is your car semi sinth from fact or do you just put it in. This can create other issues. Some motors can determin if the oil is inferior/incorrect.
 

gohrdrgomad

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Hey mate appreciate the feedback I’m aware of what the numbers mean for engine oil. manufacturers say 20/50 doesn’t specify mineral or synthetic. I wanted to test how the engine behaved with higher grade oil, also the car idled fairly quiet in drive at the lights today and I noticed temp was sitting dead centre. Could a busted thermostat interfere with how the car operates? I’ve replaced the radiator not too long ago with a flush as well completely forgot to change the thermostat cos I had no time to redo or wait for the part
it could stick, it could also cook your engine. If the oil is incorect, during alternating engine temp and day temp you will see a temp fluctuation. Also different brands of oil will do the same. For example I ran penrite 5w40 full syn and experienced temp fluctuation at runnng engine temp. I changed to mobile 5w50 full syn and no flux at all, l can sit in traffic or toe on a 48 degree day. Coolant will stabilise engine oil temp also. Hope that helps.
 

Glaze

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Fair enough my oil is due soon I’ll trial how 20/50 semi synthetic goes. Could the thermostat/wrong oil combo explain why drive idle is so aggressive? The rough idle stays the same when I change to 3,2 and 1st gear whilst idle
 
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devilly

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Maybe the trans filter has slipped out of place. Or if not that thinking check under the engine while running see if can feel any thing going on with the bottom end, they are know for spinning bearings.
 

gohrdrgomad

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Fair enough my oil is due soon I’ll trial how 20/50 semi synthetic goes. Could the thermostat/wrong oil combo explain why drive idle is so aggressive? The rough idle stays the same when I change to 3,2 and 1st gear whilst idle
If you say this is all a result since you changed the oil? It could contribute to temp issues, fuel economy issues as the computer may be compensating around this. It would be impossible to diagnose without faultfinding/process of elimination or tech 2 scan tool diagnostic support also.
 

Glaze

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Yeah need to run an error code check thanks mate

If you say this is all a result since you changed the oil? It could contribute to temp issues, fuel economy issues as the computer may be compensating around this. It would be impossible to diagnose without faultfinding/process of elimination or tech 2 scan tool diagnostic support also.
 

Glaze

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Maybe the trans filter has slipped out of place. Or if not that thinking check under the engine while running see if can feel any thing going on with the bottom end, they are know for spinning bearings.

Will do mate thanks as an update when putting into drive from either reverse or neutral I can feel the trans pause a bit only couple milliseconds then change gear in a slight “jump” response. Haven’t tightened my handbrake for a long time maybe it’s trying to grip through gear changes
 

gohrdrgomad

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Will do mate thanks as an update when putting into drive from either reverse or neutral I can feel the trans pause a bit only couple milliseconds then change gear in a slight “jump” response. Haven’t tightened my handbrake for a long time maybe it’s trying to grip through gear changes
Its not your hand break. Have you enough/ to much auto fluid. Have you removed the battery. Have you removed the pcm fuse. What you have posted is about a number of issue. Fresh auto fluid and new filter can change the response in change. Even auto fluid of different brands does this. How long between auto and engine oil change will change the efficiency of both. Engine at 5k, Auto at 5-7k diff also. I guarantee you if something isnt already worn or clogged you car will function more efficiently.
 
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