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People put to much not the manual transmission gear oil.It's A no brainer you can keep it simple.Regular 80-90 weight gear oil works for me.But saying that I only drive it in warm to hot weather.
Dexron III is the fluid spec for the Manual, use anything else at your own risk.
 
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Discussion Starter · #22 ·
I changed out the transmission fluid and diff fluid again yesterday. The cars got just under 23,000 miles now.

I decided to use Amsoil Torque Drive again, since I've been happy with it. For the diff fluid, I used the OE GM fluid.
 

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I changed out the transmission fluid and diff fluid again yesterday. The cars got just under 23,000 miles now.

I decided to use Amsoil Torque Drive again, since I've been happy with it. For the diff fluid, I used the OE GM fluid.
What were your observations about the amount of metal particles in the oils and on the plugs for this set of changes?
 

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Discussion Starter · #24 ·
What were your observations about the amount of metal particles in the oils and on the plugs for this set of changes?
I had considered taking pictures, but there wasn't much to show.

For the transmission magnetic plug (aftermarket, OE is not magnetic) there was some very fine metal, forming a "paste" on the plug. If there were any larger metal flakes, they were hidden in the paste. The transmission fluid had good color and smelled "good" for ATF.

For the diff, the plug had a thin layer of metal paste as well. This is typical. The diff fluid was the classic gray, with light metal flecking in it (fresh GM diff fluid is clear). This gray appearance is also typical for this fluid once it has accumulated miles, and this is the third time I've changed the diff fluid.
 
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I changed out the transmission fluid and diff fluid again yesterday. The cars got just under 23,000 miles now.

I decided to use Amsoil Torque Drive again, since I've been happy with it. For the diff fluid, I used the OE GM fluid.
Can I borrow your lift in about 11,000 miles? ;)
 
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The last few months I have been having a pretty good vibration in the clutch pedal when depressed above 1500 RPM. Doesn;t have to be in gear or driving, I can be in neutral and just rev the engine with the clutch pedal depressed and it can be felt. Only happens when the car is fully warmed up and I only have 3500 miles. Is it possible my transmission fluid is breaking down early and thinning out? I have not tracked the car.
 

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Discussion Starter · #29 ·
The last few months I have been having a pretty good vibration in the clutch pedal when depressed above 1500 RPM. Doesn;t have to be in gear or driving, I can be in neutral and just rev the engine with the clutch pedal depressed and it can be felt. Only happens when the car is fully warmed up and I only have 3500 miles. Is it possible my transmission fluid is breaking down early and thinning out? I have not tracked the car.
That's interesting, alright. Let's start with the simplest possibilities first... Have you checked your clutch fluid? http://www.stingrayforums.com/forum/c7-general-discussion/17998-clutch-fluid-change.html
 

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Discussion Starter · #31 ·
Does the transmission still shift smoothly, during normal driving?
 

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Discussion Starter · #33 ·
It's a bit notchy going into a few gears, but I figured that was normal. The tremec on my 350 felt the same way.
Mine is the same, but it diminishes quite a bit after the tranny has fully warmed. I'm generally very pleased with the M7.

I'm leaning towards a clutch or driveshaft-related issue, rather than the transmission.

At this point, I'd start Googling, and also make an appointment at the dealer. Hopefully someone else here has some ideas for you.
 

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Thanks, going to try to hit the dealer this weekend. Rather fix it myself if it was possible, really hate going to dealerships.
 

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I changed out my engine oil, 7-speed transmission fluid and the differential (non-Z51) fluid on Friday the 29th. Changing the tranny and diff fluid is easy. This work was done on my 4-post lift, which I checked for level before beginning.

For the tranny, I used Amsoil Torque Drive synthetic Dexron III. The Tremec has a published capacity of 3.7 qt, but after draining the oil and replacing the drain plug with a new magnetic drain plug* I was only able to pump in 3.25 qt before flow out from the fill hole occurred. So, I assume that about 0.45 qt is captured in the tranny and unable to drain.

For the diff, I was pleased to see that there is a magnetic factory drain plug. In fact, both the fill and drain plug on the diff are identical and both are magnetic. Since there have been issues with low diff fluid from the factory on some cars, I carefully captured the fluid for measurement. After complete draining (about an hour of slow drips) the total volume of diff fluid was 71 oz. The diff is spec'd to hold 91 oz (from Amsoil website), which is exactly how much I was able to install.

I've never had any problems with the diff over 4800 miles. The diff fluid was quite dirty, lots of fine metal, and the magnetic drain plug had a good coating of fine metal particles. This isn't unusual for the diff, given that a limited slip diff is a wet multiplate clutch system, and sheds metal from the friction plates into the oil. I replaced the factory magnetic drain plug with a new aftermarket magnetic plug* that has a much larger exposed magnet surface area and about twice the magnetic strength of the factory unit (tested by using the drain plugs to lift various weight box wrenches). I filled with the factory GM gear oil (GM P/N 88862624), which is synthetic and contains the necessary friction modifier.

I then took the car out for a quick drive to get a feel for the shifting performance. Cold shifts are smoother, but as the transmission warmed things seem about the same. Shifting quality for my car has always been good.

After getting the car to full temp, I drove roughly 30 miles, lots of shifting 1st through 5th, with light and hard acceleration. I then headed home and put the car back on the lift. I let the car cool for two hours and then checked the fluid levels. Both the tranny and diff were still warm, and after removing the fill plugs I saw a few drops of fluid emerge from both, indicating both were filled. As a double-check, and because the tranny only accepted 3.25 qt (versus the 3.7 qt spec), I tried to add another oz of fluid. The tranny wouldn't accept any more fluid, and was truly full.

I've put over 100 miles on the car since the fluid change. The car is running and shifting well. There is a subtle improvement in shift quality, mostly when cold, but the car has always shifted well. More importantly, I've got the magnetic drain plugs in place to scavenge metal particles. I placed it on the lift about an hour ago to double-check for leaks - all is good.

I'll replace the tranny fluid and diff fluid again at 25,000 miles (motor oil every 5,000 miles).

*Plugs were purchased from Custom Corvette Accessories. The plugs are listed as C6 items, but fit the C7. The diff plug is longer than stock, but has no clearance issues - I carefully checked clearance before installation. Torque specs for the tranny fill and drain lugs are 20 ft-lbs. The diff fill and drain plugs have a torque spec of 20 ft-lbs.

Images from the Shop Manual:

Thanks for the info on the transmission. I just changed mine after 25,000 miles with Red Line 30505 D4 full synthetic ATF - $48/gal on Amazon. Transmission shifts noticeably smoother.









Red Line 30505 D4 Automatic Transmission
 
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