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sounds like??

L

LarryK 87

Guest
have had this semi mysterious noise ever since i got the car ( just under 2 months).
in the past the noise has only occured intermittantly when turning to the right, with a light to medium throttle, it generally always occured when shifting from 2 to drive (auto). Last week it did it again, this time while going straight, ( again, only when it shifts ), under medium throttle, This morning it has started doing it every time it shifts ( 1st - 2nd , 2nd - drive ), it is a very brief noise( and currently does not do it under very light throttle), and sounds more like a heavy, brief vibration, kind of like something is rubbing under neath the car. It appears to be coming from the rear, but i cannot be sure.
Normal driving down the road ( no shifting ), i can apply medium throttle, and no noise, and decent acceleration.

Trans fluid looks ok, (reddish brown, and has prob. never been changed)Does not smell burnt, but i did notice bubbles on the dipstick while checking the fluid level ( a bit high ).

Diff. has not been checked or looked at.
The only real work done on the rear of the car, has been when the half shaft u-joints where replaced last month. ( work was done at a local corvette specialty shop).
I will no doubt however, never take the car back to them, as i am not to pleased with the overall quality of their work ( nice job on the U-Joints, but think the Drive shaft u-joints may be getting bad as well, and they did not mention that). And had them check the steering, they said they tighened it up a bit ( and it does feel better ) but the play is still very noticable, and i believe it is very loose at the rack end ( they worked on the other end, had the dash all apart, etc but when you can see the shaft turn, and you can feel and see the freeplay at the R&P end, well it dont take no rocket scientist ).

Anyways, the NOISE.... Anyone? Ideas? Suggestions?
 
C

c4ever

Guest
I would start with rear end fluid change and don't forget the GM additive. Either way it probably hasn't been done by the previous owner and should be changed yearly(at least I feel that way) and can cause some strange sounds especially in the turns at low speed.
My .02:w
 

Paul G

Well-known member
Joined
Aug 27, 2001
Messages
200
Location
Griffith, IN, USA
Corvette
96 CE LT4 Convertible
Could the exhaust be rubbing against something?
 
L

LarryK 87

Guest
ok, recommended lube for the rear?, and are they similar to other Rears, Drain plug etc, or do i need some sort of vacuum tube to drain it?, And the GM additive, just POSI additive?

fill to Levels: up to the fill hole? same as all others? or specific qty?

and Paul, it's not really that type of noise, more as if the Tires where rubbing in the wheel wells.( which they are not, thats the first place i looked due to the sound).
As a side note, when i do get the noise the shift is solid, and positive, and i dont seem to notice any loss in speed, rpm, etc ( but then it happens so suddenly, by reflex, i get off the throttle.
 
C

c4ever

Guest
Rear fluid needs to be syphoned. I usually have it done at my local vette shop. I would recommend the Generals additive only no aftermarket brand IMHO. Fluid level to fill hole.

Carlo
 
Joined
Jun 20, 2002
Messages
2,509
Location
Tallahassee, FL
Corvette
none right now :(
reddish brown tranny fluid isn't too great either... I would suggest a change... it is very inexpensive, and very good to make you auto. last a long time...

The drive shaft U-Joints are rarely a problem on C4's. The only ones that seem to go are the half shaft U-joints
 
Joined
Oct 30, 2001
Messages
2,273
Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Had a similar problem on my wife's old Tempo. Loose motor mounts. As the motor torqued when you accelerated, it would actually rub one of the pulleys on something as it moved out of place. Usually happened only when turning and accelerating, sometimes when accelerating straight.
[RICHR]
 

cntrhub

Well-known member
Joined
Jun 17, 2002
Messages
390
Location
North Hollywood, Ca.
Corvette
Miss my '62 & '80 4- Sp. Vettes
Dump the trans oil now! Brownish color is normal. Since it doesn't smell burnt, I would say nothing. But this is why I am posting. You say the level is high. The reason for that is because of the bubbles. The bubbles in the trans will displace (mixed with fluid) a higher level. Usually this is a trans filter rubber leak. Make sure you replace with a new filter & rubber.
This is one of the reasons you might be experiencing poor shift quality and noise.
 
L

LarryK 87

Guest
hmm all valid points, The bad mounts could be real as i seem to notice a HUMP effect during shifting,( and due to the noise, i have yet to really get on the throttle ( have pushed is in straight line accel, ohh do it pull :) ).

The bubbles have bothered me since i spotted them a week ago, so to the lube shop it go ( yeah i can do it my self, but then i need to go buy ramps etc... hmmm i do need them anyways.. maybe i just talked myself into it :) ), Next question, i have been holding out for Dexron II ( per the manual) but most places are only selling Dexron III, Hold out for the Dexron II ???

Picked up Gear lube and Additive for the Diff yesterday, and i guess while i am under there, i can check the Trans Mounts for tightness.

Now all i need is a semi cool day, No Rain, ( remember this is Fla. here). and yes we put the "Duh" in Florida ( god's waiting room ).and Yes we actualy do know how to count.
maybe check the tightness of all 9 spark plugs, and still gotta replace the 3 back tires.
 
Joined
Jun 20, 2002
Messages
2,509
Location
Tallahassee, FL
Corvette
none right now :(
You may want to switch to RedLine tranny fluid... I haven't used it on an automatic, but I have heard excellent things about their fluid.
 

cntrhub

Well-known member
Joined
Jun 17, 2002
Messages
390
Location
North Hollywood, Ca.
Corvette
Miss my '62 & '80 4- Sp. Vettes
Yes, you are safe to use Dexron III trans fluid. You have close to 8 quarts in the torque converter alone, that will not drain. Once you start the engine to run the fluid and get it hot to check the level, don't be surprised to see your clean oil turn almost brown again within minutes.
An old trick is to remove the trans cooler line that feeds to the radiator. Connect a hose (leakless fit) and place the end in a large capacity can. Over fill the transmission with quite a few quarts of trans fluid, start the car and watch for clean oil coming out of the hose. Stop the engine at this point. What you are doing is draining the torque converter fluid. It's a mess if the hose falls off, or though you could get away using a container larger than a coffe can. If done correctly, you now have clean trans fluid. The continued trick is to make sure you do not drain all the fluid in the trans, and gauge enough, that when you reattach the trans cooler line, you just need to add a quart or less to finish the job.
 
S

Shadowing1985v

Guest
hmm

i owned my care 85' for almost 2 years now, and i never changed the rear oil

how often should i change it... i have liek 240K miles on it

not sure what previous owners did
 

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