C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Differential woes after fluid change

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Old 06-22-2010, 04:01 PM
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M.J.L.
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Default Differential woes after fluid change

I have a D36 on a automatic early 1986 corvette. I took it to my trusted mechanic and he checked the fluid. It was a little low. He showed me so he was not lying and it was nasty looking. It was original with 145,xxx miles on it. I said change the fluid and check all the parts. He did and everything looked great! He even checked u joints ect...I get it back and it doesn't want to accelerate as fast. I talked to him and he checked it over for free and said the only thing it "MIGHT" be is that the old fluid was so thin and low and used that it made it slicker. He said he highly doubts it but it's possible. Im stumped. He said let it break in for a little bit thru some heat cycles. What do you guys think? No sounds, grinding, gas mileage loss or anything. Maybe his guess is right. He offered to redrain it, check it again and fill it back up for free but I declined.

He also did a FULL tune up. Plugs, wires, distributor cap, rotor button, oil change, cleaned my injectors, flushed my brake system, cleaned my maf, new coil, cleaned the throttle body, checked the transmission, differential, inflated my tires, checked brakes/pads/lines/rotors., new air filter, flushed the cooling system and put a new radiator cap on with new hoses and thermostat, fuel filter, and a few other minor things. Runs GREAT!!! Just doesnt accelerate as fast. I know it's because of the differential. Transmission is fairly new and he checked it over. Just can't figure it out...I still think the fluids thicker and thats why.

Last edited by M.J.L.; 06-22-2010 at 04:05 PM.
Old 06-22-2010, 04:24 PM
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toptechx6
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Originally Posted by ~Oakley~
I have a D36 on a automatic early 1986 corvette. I took it to my trusted mechanic and he checked the fluid. It was a little low. He showed me so he was not lying and it was nasty looking. It was original with 145,xxx miles on it. I said change the fluid and check all the parts. He did and everything looked great! He even checked u joints ect...I get it back and it doesn't want to accelerate as fast. I talked to him and he checked it over for free and said the only thing it "MIGHT" be is that the old fluid was so thin and low and used that it made it slicker. He said he highly doubts it but it's possible. Im stumped. He said let it break in for a little bit thru some heat cycles. What do you guys think? No sounds, grinding, gas mileage loss or anything. Maybe his guess is right. He offered to redrain it, check it again and fill it back up for free but I declined.

He also did a FULL tune up. Plugs, wires, distributor cap, rotor button, oil change, cleaned my injectors, flushed my brake system, cleaned my maf, new coil, cleaned the throttle body, checked the transmission, differential, inflated my tires, checked brakes/pads/lines/rotors., new air filter, flushed the cooling system and put a new radiator cap on with new hoses and thermostat, fuel filter, and a few other minor things. Runs GREAT!!! Just doesnt accelerate as fast. I know it's because of the differential. Transmission is fairly new and he checked it over. Just can't figure it out...I still think the fluids thicker and thats why.
Just curious why you would think that? To me it seems like the least likely cause for poor acceleration considering the other tune up work, just my take.
Old 06-22-2010, 04:26 PM
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92ragtop
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Originally Posted by ~Oakley~
I talked to him and he checked it over for free and said the only thing it "MIGHT" be is that the old fluid was so thin and low and used that it made it slicker.
New fluid does not create drag in the differential. I'd put my money on something wonky up front. Either that, or maybe the hand-brake is partially engaged.
Old 06-22-2010, 04:31 PM
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383vett
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with both posts above. Differential fluid viscosity is the least likely reason your car doesn't perform. Check timing and all the other components that were replaced.
Old 06-22-2010, 04:37 PM
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pologreen1
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hmmm...
So you know that electric, maf, and TB all have been altered (all performance related), and the guess is that the new rear end fluid is what is slowing your car down now, compared to before?

Last edited by pologreen1; 06-22-2010 at 04:57 PM.
Old 06-22-2010, 04:38 PM
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MK 82
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Originally Posted by toptechx6
Just curious why you would think that? To me it seems like the least likely cause for poor acceleration considering the other tune up work, just my take.

I agree. You are barking up the wrong tree.
Old 06-22-2010, 06:20 PM
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tblt44
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wrong tree for sure.
your rearend was in dier need of new fluid
Old 06-22-2010, 06:35 PM
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Muffin
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When you said FULL tune up I crossed the D36 off the list. I would have all that was done in the tune up looked at again.
Old 06-22-2010, 06:35 PM
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M. Schumacher
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This is a gag, right?

It couldn't possibly be the diff oil. You could fill it up with tar and not notice any difference in acceleration.
Old 06-22-2010, 06:56 PM
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0Paul Ruggeri
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I would have another mechanic check the tune up. Something is wrong there.
Old 06-22-2010, 07:05 PM
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ch@0s
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The first thing that comes to mind is timing.
Could be crossed wires etc..Does it have a miss at all?
Old 06-22-2010, 07:28 PM
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bobmic93
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What kind of plugs did he use? I recommend using the NGK
Old 06-22-2010, 07:54 PM
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Sounds like the throttle cable was not reset. You can do this yourself:


It sounds like the TV cable is set incorrectly. Fix this IMMEDIATELY or it will fry the trans. On the throttle body there is a "D" shaped button where the throttle and TV cables connect. Push it in and the press the cable back into the housing until it is fully seated. Now, open the throttle by hand until it is all the way open (you will hear a ratcheting sound). The TV cable is now set correctly.

As quoted in an earlier post by Frizlefrak
Old 06-22-2010, 08:38 PM
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383vett
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I think someone is getting a chuckle out of this.
Old 06-23-2010, 04:16 PM
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hooked073
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I sure hope this is a joke,

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