6mt fluid choice? Notchy especially in 3rd.

[Dean]

OK, I can't handle the ton of bickering on IWSTI and Nasioc on this issue, and if I read one more post that Amsoil is the best thing ever, I am going to have to kill something...

My 6MT is quite notchy in 3rd. I could grab an audio clip from one of my videos, but it is like a nice clunk as it goes into gear. Not a grind, but a decent clunk on up or down shifts.

Not sure what fluid is in there, but am thinking about Redline 75W90 NS and/or some weight of shockproof like in the WRX.

Has anyone else experienced this on the 6MT and what fluid are you running? Tried any others to get rid of it?

I believe the 6MT is just a transmission and the diffs have their own fluid, right? So this is all about protecting synchros and allowing them to do their job spinning up/down the gear.

Thoughts, comments???

[MattR]

I use the Redline Shockproof in the transmission and it's perfect. I really makes a noticeable difference.

[knucklesplitter]

I'm pretty sure the diffs. and the trans. all have one reservoir of fluid. So make sure it is GL5 rated. The hypoid gears for the front diff. need it. I would like to use Redline MT-90 but it is only GL4. I think I run Redline 75W90NS now.

[Kevin M]

I am pretty sure the 6MT shares fluid between the diff and gearbox, but if not there will be 2 dipsticks on it. The diff does require GL5 according to the service manual, but thousands of Shockproof users who aren't reporting front ring and pinion failures can't be missing that. Personally I'm comfortable using Redline GL4 products in my gearboxes.

[knucklesplitter]

I personally wouldn't use a non-GL5 lubricant like Shockproof, especially when its maker even says it's "not recommended for most syncro-type transmissions".

Oops, I take that back... if Shockproof is designed for rear ends too then it *IS* good enough for hypoid gears.

[Dean]

Originally Posted by MattR

I use the Redline Shockproof in the transmission and it's perfect. I really makes a noticeable difference.

Which weight? Lightweight or superlightweight?

[knucklesplitter]

Originally Posted by BAN SUVS

The diff does require GL5 according to the service manual, but thousands of Shockproof users who aren't reporting front ring and pinion failures can't be missing that.

It's not a short-term failure issue, it's a long-term wear issue. How many of these "thousands of Shockproof users" have been using it for 100k+ miles?

[Kevin M]

Originally Posted by knucklesplitter

It's not a short-term failure issue, it's a long-term wear issue. How many of these "thousands of Shockproof users" have been using it for 100k+ miles?

Exactly. GL4 fluids will shorten R&P life by an amount insignificant compared to the improved synchro operation and highly reduced chance of mis-shifts. I think it's worth 20k-50k miles off the life of the R&P, which is longer than the gearset anyway, to prevent "injuries" to the gearset when competing. Shockproof products aren't perfect, I just think they're the best compromise.

Also, I used MT90 in my Miata. Didn't like it compared to Shockproof in my Subarus.

[Kevin M]

Originally Posted by Dean

Which weight? Lightweight or ultralightweight?

Lightweight.

[Dean]

Fluid is shared between the transmission and center diff, the front diff has it's own reservoir on the 6MT vs. the shared tranny, center and front on the 5MT.

Not having to worry about the front diff and having to deal with the DCCD makes the 6MT a different beast which is why I ask this question.

The 5Mt has actually shown a very good response to the lightweight shockproof despite the presence of synchros and both diffs. The main concern there is the wear on the front diff.

With the 6MT we only really have to worry about the impact of the shockproof on the DCCD.

Originally Posted by knucklesplitter

I think I run Redline 75W90NS now.

Is it Clunky? Anybody else just running this?

I'm leaning toward a 50/50 mix of 75W90 NS and lightweight.

I wish I knew what was in it. Shockproof is whitish green, what color is the 75W90NS?

[knucklesplitter]

Originally Posted by BAN SUVS

Also, I used MT90 in my Miata. Didn't like it compared to Shockproof in my Subarus.

Yeah, but I ate an apple once, but I didn't like it compared to the orange I had the day before.

75W90NS is designed for synchros and shifts well. It is also GL5 rated. I am now curious how it compares to the beloved rearend grease called Shockproof. I am due for a change so I may try it.

[knucklesplitter]

Originally Posted by Dean

Fluid is shared between the transmission and center diff, the front diff has it's own reservoir on the 6MT vs. the shared tranny, center and front on the 5MT.

I really don't think that's true. I just checked the 04 STI manual online to verify.
http://www.seccs.org/tech/manuals/2004_STI/index.htm

"For MT vehicle, differential oil works as manual transmission oil to lubricate differential. Refer to "Transmission Oil"."

Kinda Engrishy, but...

[Kevin M]

Originally Posted by Dean

Fluid is shared between the transmission and center diff, the front diff has it's own reservoir on the 6MT vs. the shared tranny, center and front on the 5MT.

Not having to worry about the front diff and having to deal with the DCCD makes the 6MT a different beast which is why I ask this question.

The 5Mt has actually shown a very good response to the lightweight shockproof despite the presence of synchros and both diffs. The main concern there is the wear on the front diff.

With the 6MT we only really have to worry about the impact of the shockproof on the DCCD.

Is it Clunky? Anybody else just running this?

I'm leaning toward a 50/50 mix of 75W90 NS and lightweight.

I wish I knew what was in it. Shockproof is whitish green, what color is the 75W90NS?

One fluid in the 6MT. The front diff may have a "reservoir" but it's not a separate system. DCCD is a sealed system not affected by the fluid you put in the gearbox. In my previous experience 75w90 NS is not bad, but synchros operate faster and smoother with Lightweight Shockproof. IIRC it looks like regular gear oil, just a bit lighter in color. Shockproof generally looks like toxic waste.

[Kevin M]

Originally Posted by knucklesplitter

Yeah, but I ate an apple once, but I didn't like it compared to the orange I had the day before.

75W90NS is designed for synchros and shifts well. It is also GL5 rated. I am now curious how it compares to the beloved rearend grease called Shockproof. I am due for a change so I may try it.

Remember not to put Shockproof products in the rear end. It doesn't play well with your LSD. Turns to sludge instantly after you drive off. Shockproof was never designed for differentials anyway, it's for racing gearboxes subjected to high impact stresses. Hence the name and the lack of GL5 wear protection.

[knucklesplitter]

Try LW Shockproof, Dean. And let us know what you think. My STI is at 30k and I want to change mine, so I may try it too.

[MikeK]

Originally Posted by Dean

I wish I knew what was in it. Shockproof is whitish green, what color is the 75W90NS?

I use the redline lightweight shockproof too, it was the first change I made at about 1000 miles. No problems at all. It is bright blue, not whitish green.

[knucklesplitter]

Originally Posted by BAN SUVS

Shockproof was never designed for differentials anyway, it's for racing gearboxes subjected to high impact stresses. Hence the name and the lack of GL5 wear protection.

What?!? From Redlines site:

" Lightweight ShockProof®

A unique gear oil designed to lubricate racing transmissions and transaxles which see serious loads (not recommended for most syncro-type transmissions). It has excellent low-temperature flow which allows easier shifting when cold. May be used to obtain maximum power transfer in racing differentials which do not see high temperatures. Similar to a 75W140 gear oil, but with the lower internal friction of an SAE 30 motor oil.

Used in most road-racing differentials with moderate power and dogring racing transaxles "


" ShockProof® Gear Oil


A unique lubricant containing a suspension of solid microscopic particles as an extreme pressure agent--unique solid dispersion which cushions gear teeth to help prevent tooth breakage and allows the use of lower viscosities.

Acting like a liquid grease, the viscosity characteristics of ShockProof® allow the lubricants to resist throwoff and provide the protection of a greater film thickness with relatively light fluid viscosity, offering a "best of both worlds" balance of low drag and superior protection.

ShockProof® products work in a variety of differential and transmissions, however, should not be used with pumps, filters, and with small lines--these fluids are designed wet sump or splash type lubrication. "


" Heavy ShockProof®

A unique lubricant containing a suspension of solid microscopic particles as an extreme pressure agent--unique solid dispersion which cushions gear teeth to help prevent tooth breakage and allows the use of lower viscosities.

Recommended for heavily-loaded racing differentials and transmissions, Off Road racing and problem gearboxes. The viscosity characteristics allow the lubricant to resist throwoff and provide a film thickness similar to a 75W250 grade, while providing the same low fluid friction as an SAE 75W90. "

[knucklesplitter]

Originally Posted by BAN SUVS

Remember not to put Shockproof products in the rear end. It doesn't play well with your LSD.

This is probably true though...

[Dean]

Front diff has it's own drain, but you are right, it appears to share the same fluid pool. I swear there was a difference between 5MT and 6MT in terms of shared fluid with diffs, but can't find it. Aparently it is just the AT that has a isolated front diff.

[Dean]

Originally Posted by Redlineoil.com

Lightweight ShockProof® ...Similar to a 75W140 gear oil, but with the lower internal friction of an SAE 30 motor oil.

I wonder if the 140 is the real reason shockproof appears to work so well. Compared to the recommended 75W90, that is a significant increase in viscosity.

Maybe the answer is just to go with the 75w140NS.

[Kevin M]

Originally Posted by knucklesplitter

What?!? From Redlines site:

" Lightweight ShockProof®

A unique gear oil designed to lubricate racing transmissions and transaxles which see serious loads (not recommended for most syncro-type transmissions). It has excellent low-temperature flow which allows easier shifting when cold. May be used to obtain maximum power transfer in racing differentials which do not see high temperatures. Similar to a 75W140 gear oil, but with the lower internal friction of an SAE 30 motor oil.

Used in most road-racing differentials with moderate power and dogring racing transaxles "


" ShockProof® Gear Oil


A unique lubricant containing a suspension of solid microscopic particles as an extreme pressure agent--unique solid dispersion which cushions gear teeth to help prevent tooth breakage and allows the use of lower viscosities.

Acting like a liquid grease, the viscosity characteristics of ShockProof® allow the lubricants to resist throwoff and provide the protection of a greater film thickness with relatively light fluid viscosity, offering a "best of both worlds" balance of low drag and superior protection.

ShockProof® products work in a variety of differential and transmissions, however, should not be used with pumps, filters, and with small lines--these fluids are designed wet sump or splash type lubrication. "


" Heavy ShockProof®

A unique lubricant containing a suspension of solid microscopic particles as an extreme pressure agent--unique solid dispersion which cushions gear teeth to help prevent tooth breakage and allows the use of lower viscosities.

Recommended for heavily-loaded racing differentials and transmissions, Off Road racing and problem gearboxes. The viscosity characteristics allow the lubricant to resist throwoff and provide a film thickness similar to a 75W250 grade, while providing the same low fluid friction as an SAE 75W90. "

I misstated that. I didn't intend to imply that Shockproof is not to be used in differentials; I was saying that the purpose for creating it was to combat high-stress conditions from frequent hard shifts with lots of torque being transferred. That is the advantage it has over standard synthetic gear oils. The reason guys like me like it is that it has an effect of improving the speed at which your synchros work, and IMO preventing mis-shifts is job 1 for your gear oil if you're tracking or especially autocrossing the car. The slight decrease in wear prevention at the front diff- though not in the bearings and gears themselves- is a worthy tradeoff.

[Kevin M]

Originally Posted by Dean

Front diff has it's own drain, but you are right, it appears to share the same fluid pool. I swear there was a difference between 5MT and 6MT in terms of shared fluid with diffs, but can't find it. Aparently it is just the AT that has a isolated front diff.

Yup.

[Kevin M]

Originally Posted by Dean

I wonder if the 140 is the real reason shockproof appears to work so well. Compared to the recommended 75W90, that is a significant increase in viscosity.

Maybe the answer is just to go with the 75w140NS.

No, it's the other additives. Note that it says that Shockproof still has the viscosity of typical 30w motor oil.

[Dean]

Originally Posted by BAN SUVS

No, it's the other additives. Note that it says that Shockproof still has the viscosity of typical 30w motor oil.

Yes, but it is higher than the 75W90. You can't compare gear oil weights to motor oil weights. A gear 75W90 is about the same viscosity as motor 10W40 which is probably damn close to 30w.(wiki)

[Kevin M]

I'm aware of the difference in viscosity ratings between motor oils and gear oils. I was taking that directly from the quote Matt took from Redline, which is that the shockproof has the friction properties approximating that of 30w motor oil. Point bing, the "90w140" rating is a bit nebulous, as almost all Redline products are.