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Discussion Starter #1 (Edited)
I'm planning on changing-out the factory Tremec TR-6070 manual transmission fluid with full synthetic, soon.

I expect many of you have already done this, and I'd like to hear your opinions on the various synthetics that you've had experience with.
 

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I'm planning on changing-out the factory Tremec TR-6070 manual transmission fluid with full synthetic, soon.

I expect many of you have already done this, and I'd like to hear your opinions on the various synthetics that you've had experience with.
Mobius, what benefits are expected with the fluid switch?
 

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Discussion Starter #3 (Edited)
Mobius, what benefits are expected with the fluid switch?
All of the benefits typically associated with synthetic oil - reduced friction and associated wear, greater oil longevity and increased oil change intervals.

Many also claim improved and smoother shift quality, and some claim reduced transmission noise.

"Synthetics really shine in gear cases which are typically sealed from dirt and water and not subjected to the contamination of combustion by-products, fuel and coolant that are present in an engine. However synthetic gear oils can become contaminated with wear metals from gears and bearings. Synthetic gear oils offer superior high and low temperature performance, extended life which is good for gear boxes that may not be easily accessed for service, and potential energy savings because of reduced fricition and easier pumpability within the system." SYNTHETIC OIL VS CONVENTIONAL OIL

Another reference: Benefits of Using Synthetic Transmission Fluid
 

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Curious about this myself. What products out there currently meet the factory specs such that warrantly cannot be questioned by dealer?
 

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Discussion Starter #5 (Edited)
Curious about this myself. What products out there currently meet the factory specs such that warrantly cannot be questioned by dealer?
I've already done research on the most popular full-synthetic oils suitable for the 7 speed transmission, and there are a number of DEXRON III ATF-spec'd oils that will be direct replacements, but I'm curious to hear experienced perspectives and opinions from those who have already used these alternatives.

I've already narrowed my oil choice down to two options, and if I get no feedback I'll select my preferred oil and post my conclusions on performance.
 

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Just noticed this on the Tremec site:
Q: Why not use a synthetic fluid?

A: Some brands of synthetic fluid contain powerful detergents and additives that can prove harmful to your transmission's synchronizers. While many synthetic fluids perform very well, in most cases, we do not recommend their use. Furthermore, they may void your warranty. For peace of mind, remember that TREMEC conducts all of its OEM validation testing using conventional fluids without issue.
 

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Discussion Starter #7
Just noticed this on the Tremec site:
Q: Why not use a synthetic fluid?

A: Some brands of synthetic fluid contain powerful detergents and additives that can prove harmful to your transmission's synchronizers. While many synthetic fluids perform very well, in most cases, we do not recommend their use. Furthermore, they may void your warranty. For peace of mind, remember that TREMEC conducts all of its OEM validation testing using conventional fluids without issue.
See, this is why I wanted to ask the forum. I still plan to change the fluid, but I'll rethink if I want to go full synthetic or not.

Good catch.

Frequently Asked Questions (FAQs)
 

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I'm not saying it's A waste of money.I have heard of manual transmissions going over 100,000 miles without changing the gear oil.
 

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Discussion Starter #9 (Edited)
I'm not saying it's A waste of money.I have heard of manual transmissions going over 100,000 miles without changing the gear oil.
Yes, I'm sure that's true in many cases.

I change out manual transmission fluid at 25,000 mile intervals and I've never had a transmission wear out. Example - I'm the original owner of a 5-speed 2005 Civic that has over 473,000 miles (Amsoil Synthetic Synchromesh Transmission fluid every 25k) and still gets 45 MPG highway (synthetic motor oil since 500 miles, changed at 5k intervals).

That's the power of synthetic oil.

I also routinely red line my C7 engine, and I think the transmission deserves some fresh oil for all of her good service, and her ability to tolerate my demands. :rolleyes:

UPDATE: The 2005 Civic went 626,000 miles before retirement, with ZERO transmission issues. :)
 

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Yes, I'm sure that's true in many cases.

I change out manual transmission fluid at 25,000 mile intervals and I've never had a transmission wear out. Example - I'm the original owner of a 5-speed 2005 Civic that has over 473,000 miles (Amsoil Synthetic Synchromesh Transmission fluid every 25k) and still gets 45 MPG highway (synthetic motor oil since 500 miles, changed at 5k intervals).

That's the power of synthetic oil.

I also routinely red line my C7 engine, and I think the transmission deserves some fresh oil for all of her good service, and her ability to tolerate my demands. :rolleyes:
Mobius, I will follow your research into whether our C7's will benefit from synthetic transmission oil...
 

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I had over 120,000 miles on A Plymouth neon ,never checked the gear lube.Sold it and it went another 40,000 miles.Needed A clutch,he put it down.I doubt he checked the tranny lube either.
 

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Discussion Starter #12
I contacted my local dealership parts department, and confirmed that the manual transmission fluid for the 2014/2015 7 speed is the same as the C6 manual transmission fluid (GM Part No. 88861800, in Canada 88861801).

Amsoil lists three direct replacement full synthetic fluids for this GM Part number, but the one that appears to be favored for the Tremec is Torque-Drive® Synthetic Automatic Transmission Fluid. WeaponX, a forum vendor, also recommends this manual transmission fluid for the C7, so I'll be ordering a gallon today.
 

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Food for thought:
FYI, I rebuilt transmissions for 45 years any manual trans. that took ATF I always refilled with motor oil and never one problem because of it. I've had some MT's (with OEM ATF) delaminate the lining off the synro cones (paper lined type) due to condensation forming when car sat for periods of time. The motor oil is a better lube and does a better job of dealing with the effects of condensation. This isn't a common occurrence but it does happen on occasion. Honda has a 'special' MT lube but their owners manual says you can use motor oil if their product is not available. I had a Mustang GT with world class T5 MT, I changed ATF to motor oil when it was new
and it was quieter and shifted just fine had the car for 11 years with no problems.
 

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Since the C5, the Corvette uses a transaxle so the trannie and rear end not only generate their own heat but also add that heat to each other
Add the duel exhaust pipes running so close to them that heat also adds more heat to transaxle.

Now being the car sits low ( mine is almost 2 inches lower then stock) and not a lot of air movement to pull the heat out the total is the drivetrains maintains high heat
Recall for the C5 either auto trannie or the Z06 had a warning light when trannie was too hot so it is clear heat is a issue.

In a Open Road Race in Texas where weather was in the 90s and maintaining 150-160 MPH for 2 60 plus mile runs within 40 miles using the GM MN6 fluid
and using a 3.73 rear end gear ( and added the external GM trannie cooler) the fluid in trannie got so hot it boiled and puked out of the vent hole at the top of trannie and spilled onto both exhaust pipes and maintained smoke pouring out the back for the length of 1 run.

Switched to Mobil I Race synthetic back in 2000 and in many types of racing has not done the same as the stock GM MN6 fluid and zero issues with the syncros
 

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Discussion Starter #15 (Edited)
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:

 

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I'm the original owner of a 5-speed 2005 Civic that has over 473,000 miles (Amsoil Synthetic Synchromesh Transmission fluid every 25k) and still gets 45 MPG highway (synthetic motor oil since 500 miles, changed at 5k intervals).
Not one of my finer moments selling my 2004 5-speed Honda Civic with 78K in 2011 so I could buy a 2011 Camaro SS. 473K!! Wow!!
 

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Discussion Starter #17 (Edited)
473K!! Wow!!
Here's the current mileage (as of August 31, 2014). The car still get 45MPG highway (no kidding).
synthetic-miles.jpg
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UPDATE: The Civic hit reached the 600,000 mile mark today, January 3, 2017.
Capture.JPG
 

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Can a kind soul either provide a pic or point me to a drawing of the location for the drain and fill plugs on the manual tranny for the C7?

I would like to do this also.

Thanks gents.
 

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Discussion Starter #19 (Edited)
Can a kind soul either provide a pic or point me to a drawing of the location for the drain and fill plugs on the manual tranny for the C7?

I would like to do this also.

Thanks gents.
Here are the diff drain and fill plugs.
IMG_20140829_120921 (1).jpg IMG_20140829_120900 (1).jpg

Here's the tranny drain plug (passenger side of tranny). The fill plug looks identical (no photo) and is up on the driver side of the tranny. The words FILL and DRAIN are cast into the tranny housing next to each plug, as I recall.
FYI - I used the Amsoil "pump" that screws on to the gallon jug of tranny fluid - it makes the refill easier.
IMG_20140829_121005 (1).jpg IMG_20140829_121017 (1).jpg
 

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My experience with synthetic transmission fluids is that on these transmissions, the factory fluid works the best.
I have friends that have put in a synthetic fluid, and the transmission did not shift as smoothly...They changed back to the GM fluid.

Also, a tip for easy fluid replacement is use air pressure to put the new fluid in... I had a plastic hand pump that fit the bottle but it broke before I could get the fluid back in the transmission, so I improvised by running the fill tube through a hole in the cap to the bottom of the bottle. Then, I ran a small air line from my compressor through hand nozzle to the top of the bottle... I could squeeze the air nozzle to control air to the bottle, being careful not to over pressure it, and still transfer a bottle in less than a minute. No fluid leaks from the bottle because the air is pushing down on the top of the fluid and forcing it up the fill tube... (Run the compressor on low pressure, 10 psi or less)

diffFluid2.jpeg difffluid1.jpeg
 
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