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Change To Syn Gear Oil Now!

73K views 268 replies 95 participants last post by  markthomas1969 
#1 ·
Lots of people mention the subject, but maybe it needs it's own thread.

Change your gear oil to synthetic as soon as you can. I used Mobil 1. One gentleman (he inspired me) used Redline. It might be better but its hard to find, here.

Keep the car level (no ramps, you can reach the drain) and drain every drop of the old oil. Mine only has a few K miles on it. Since my car is lowered, I needed my skinny son to get at the drain plug. Don't lose the washer!

You'll need a long a$$ funnel. Then dump in that Mobil 1.

I think the owners' manual is wrong in the capacity. It calls for 3.75 quarts. I used 4.

Then go for a drive and be prepared for a seriously dramatic change in your shifting and transmission behavior. It's hard to believe it's the same machine.

Go figure.

:) :)
 
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#127 ·
Hey don't know if you guys know this but I'll put it out there. I have heard complaints of people not being able to engage 1st gear when you are rolling at slow speeds. I found out how to do it. This is the scenario. You are in slow moving traffic and you are back and forth from 1st and 2nd gear. When you downshift from 2nd and you are rolling you can’t engage 1st. What I do is while the clutch is still depressed, give it a little gas and take the rpm’s to 1000-1500rpms, just a bump. It will engage 1st with no grinding or roughness. :D
 
#128 ·
while this is a problem with our tranny, a different lub does help somewhat, especially in warmer climates.
Blipping the gas is nothing more than a variant of double clutching.
Be careful full MT90 is not GL5 spec and so the differential ring and pinion will suffer. I believe MT90 is only GL4 spec and not inteded for high pressure situations as in differentials. BTW we have 2 of them in the tranny case, the center one and the front one.
Synchromesh, made by Penzoil and Quaker State, as well as others, and sold by even more companies including GM, is especially made for synchro engagement. The only trannys I know of that can use Synchromesh are ones that call for ATF and do NOT have differentials in them. Examples would include the T56 in F bodies and Corvettes, not the WRX.
 
#129 ·
Trying out MT-90 at the moment in my '03 WRX ... certainly made shifting faster ... which is what I was looking for since I'm going to drag race my WRX. MTM-90 is a 75/90 high pressure oil with added friciton modifiers ... but yes, it is not GL-5. Syncromesh is GL"S" ... special ... using their own specs.

blipping the gas with the clutch in does nothing ... you need to go to neutral, clutch out ... blip ... clutch in ... shift.
 
#130 ·
Blipping the gas (aka rev-matching) is a high performance driving technique while double clutching involves slipping the clutch (not a good thing afa the clutch goes, imho). Heel-toe or left-foot braking are both designed to allow rev-matching during downshift/turn-in.
Just wanted to offer a possible clarification.
-B
 
#131 ·
blipping the gas during a down shift, as in heel and toe, makes the weight transfer much smoother in taking turns. It does make the downshift less traumatic on the suspension, but does nothing for the synchros. Double clutching does both, match revs and saving synchros.
As for full MT90, I'm not convinced that it's the best thing for the diffs. If I were you I would change it more often if using MT90 alone, so as to combat oil break down.
 
#132 ·
I put MT-90 in for this drag race ... which I'm doing in order to get some official times and speeds ... so that I can approximate my modied HP. I might switch it right after this race ... I don't think a week on this oil is going to hurt. :) If I was totally after protecting my gearbox and clutch ... would I even be drag racing? :) I'm not out to protect my car for maximum life ... I'm out to use it as a fun car. People that AutoX, drag race, Rallye or get track time with their WRX are enjoying themselves ... not seeing how long can I make my car last. If the clutch goes, I get a lighter stronger clutch ... if the gearbox goes, I have an excuse to get a 6 speed. If I want to have more money available for vacations, stero gear or whatever else people like to spend their disposable income on ... then I stop moding and enjoying my WRX in a highperformance mode ... :p



Since I'm still learning about these things ... how does blipping the throttle with the clutch IN help down shifts. I thought that blipping the throttle with the clutch OUT brings the engine and gear speeds up ... so you can match them. With the clutch in .... only engine speed goes up?
 
#133 ·
I understand your position and actually agree.
Simply trying to avoid any confusion for those readers who think that there is on fix for all situations.

Now for your question.
Blipping the throttle with the clutch depressed, as in heel and toe, simply matches the revs back up on the engine side and allows a matched, or closely matched, RPM for the next lower gear. This allows the downshift ot occur in a smoother fashion and does not upset the momentum of the car and hence cause the suspension to load and unload front to rear. You actually want to blip the throttle higher than the RPMs you need so that the next lower gear "catches" the RPMs on the way down, it's smoother yet this way.
Double clutching involves stepping on the brake, declutching, shifting into neutral, getting of of the clutch pedal, blipping the throtle (this not only matches the rpms to the next lower gear, but it also brings up the input shaft speed hence helping/saving the synchros), depressing the clutch pedal and then engaging the lower gear. One extra clutch engagement/disengagement is involved. You can find this thread elesewhere in a forum search.
You may opt not to double clutch, as many other do not, and make your life easier.
From many years of road course driving, heel and toe keeps clutch wear to an absolute minimum and synchro wear tolerable. 3.5 years of heeling and toing only caused my tranny rebuilder to state, "this is the best tranny I have seen yet". Of course he is used to seeing trannys that are quarter miled and that type of driving destroys everything in the drivetrain in a much shorter period of time.
 
#135 ·
Here is an interesting email i found over at the Cobb Message Board. The guy emailed Redline asking about the MT-90:


Well the MT90 isn't a GL5 - it's a GL4, so in other words, it's not recommended by Subaru.

Below is an email I received from Redline:

(from me)
Hi, just had a question re: your MT-90.

Does it meet GL-5 requirements? I'm looking for a tranny oil with some friction to it to help improve the synchros in my 2002 Subaru WRX. I'm not as worried about bearing life. Subaru requires a GL5 rated oil. Or possibly another product you'd recommend? It's a mostly street driven daily driver with a 5 speed manual. Aggressive driving with some autoX and open track days planned.

Thanks in advance,
Andy

(Redline's response)
Andy,

The MT-90 is a GL-4. In your WRX transaxle I would recommend the 75W90NS (note from me: No Slip recommended for friction in the tranny) and the 75W90 in the rear differential. These are GL-5 gear lubes and would be well suited to your mix of street and track use.

Regards, Dave
Red Line Oil
 
#136 ·
i just put in the goodwrench syncromesh oil and it works excellent. use to have problems downshifting into first gear and it grinding over 5 mph, now problem is gone. seems like some good stuff. tried valvoline high vescocity 75w90, that stuff worked the same as oem stuff. i would recomment synromesh.
 
#138 ·
Mobil 1 will work just fine in warm weather. Once the cold weather hits you will notice that till the tranny warms up there will be grinding and blocking. If you read the fine print on the Mobil 1 site you will find that the Mobil 1 75w90 is made with limited slip additives intended for differentials not synchronizers in manual transmissions.
Honestly, you should keep away from synthetics unless they are intended for transaxles. Otherwise the fluids properties will not be optimum for the synchros in the manual portion of the transaxle.
 
#139 ·
Synthetic is too slick for our tranny's synchros. I ran synthetic and yes, I too, was impressed at first. But then it all went downhill. Started grinding shifting from 3 to 4 so bad I didn't even shift into 4 anymore.

If you are going to run synthetic, put in a quart of GM synchromesh. I'm running full synchromesh now and my tranny has never been smoother. I went against Subaru's warning to not put it in because it's GL-4 but after 6k miles of HARD use I haven't had ONE bad thing to say about the stuff. Just keeps getting better. Now Jack Miller Subaru is going to start stocking Synchromesh to help stop gear grinding because of my "experimenting" and good luck with it. And yes, when I say hard driving I'm talking about drag racing, autocrossing, and weekend warrior street racing. My tranny should be dead. But it's alive and kicking thanks to that stuff. If I'd left my synthetic in my gears would be serving as paper weights.


Edit: Oh yeah and I can shift into first now at 25 mph without hardly any hesitation. Just slips right in.
 
#140 · (Edited)
scooby24 said:
I'm running full synchromesh now and my tranny has never been smoother.

I replaced mine with regular Valvoline dino oil and 1 quart GM Synchromesh. Has been working great.

Im not sure if you want to use 100% Synchromesh. It will work great for now, but im not sure on reliability. There has to be some impact there for bearing life. Dont know how much lubrication the synchromesh has for bearings?? But for friction....its good.
 
#142 ·
don't forget that MT 90 and RedLine 75W90NS will also work.
These oils were made for manual transaxles. I've been running 50/50 of each and so far no problems, but the 1st gear engagement is still a bear at anything over 1 or 2 mph. Even double clutching and heel and toe don't seem to repeatedly work.
I will try some Snychromesh and report back.
 
#143 ·
Dudes,

I used RedLine 75W90NS and it sucked the big one. Less drag overall but lots of hesitation first to second and third to second. First gear synchro is now pooched and only engages at 2 - 4 km/h. I have to double-clutch just to get it into first as I roll to the stop signs. I live in Ottawa so my temperature range is pretty severe - -30 deg C to 36 deg C air temp range.

I tried 100% GM Synchromesh and it did the trick! Much better shifting all around and much easier to double-clutch into gear. First gear is also much easier to engage while rolling. I think it's well worth the $30.
 
#145 ·
so this GM synchromesh... is re-labeled as other stuff as well or what? i did a search on google and it keeps saying something about penzoil... but i don't really trust penzoil, simply because its penzoil...


also... is there any combination of tranny fluid that would mess anything up? like radiator fluid ( only thing i could think of) ... red and green don't mix... dexron and mecron don't mix yada yada...
 
#146 ·
Penzoil synchromesh is the same thing, just cheaper so fear not.

I would just stick to whats been proven to work

3 quarts Redline MT90
2 quarts GM(Penzoil) Synchromesh
 
#147 ·
EvilCerealBoX said:
so this GM synchromesh... is re-labeled as other stuff as well or what? i did a search on google and it keeps saying something about penzoil... but i don't really trust penzoil, simply because its penzoil...


also... is there any combination of tranny fluid that would mess anything up? like radiator fluid ( only thing i could think of) ... red and green don't mix... dexron and mecron don't mix yada yada...

Yeah, it's the same stuff. IIRC, it's made by Penzoil for GM. It's good stuff and much cheaper then buying GM brand synchromesh from a GM dealer. I got it from Autozone for $4.99/quart and it was $10.99/quart from the GM dealership.

I was running 60/40% Mobil 1 75W-90 gear oil and Penzoil Synchromesh for about 6 months and shifting was much better then stock fluid or 100% M1.
 
#148 ·
I've been using 100% GM synchromesh for nearly 6 months now. Put 10k miles on the fluid, been in 3 autocrosses, drive it like I stole it, drag it, etc. Not a single issue since I've put the stuff in. Almost seems like it keeps getting better and better. I would think if it was going to do something bad it would have done it already with the punishment I've put it through. :thumbup:
 
#149 ·
i was fixin to actually order some redline stuff online (cause the only authorized dealer intown that can get this stuff can't even get the tranny oil) when i came upon this thread... so... full GM(pennzoil) synchromesh it is...

so if i'm gonna use synchromesh for my tranny... what should i use for my rear-diff?
 
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