Engine Rev while shifting?

[jilty]

Last week I installed a Cobb SS and Kartboy shift bushings, front and rear. PITA. Two and a half hours. Luckily I had quality tools and a few good pals to help, so it was fun.

I Just hit 1k miles, so now I have broken 4k rpms, and now I notice when I shift in any RPMs higher than 4k, lets say, accelerating quickly, the RPMs jump up around 300 or 400 while I press the clutch.

I thought maybe its just because one foot was quicker than the other, but could I have installed the bushings incorrectly, or...is this a common thing in the car?

Not my first manual, I had a 1998 Mitsubishi 3000gt SL for 7 years, and never noticed the jump while accelerating hard and shifting.

[teflon_jones]

The revs go up when you depress the clutch to shift? Your thought is correct. The only way that's happening is if you're not letting off the gas soon enough.

[jilty]

Yes, when I depress the clutch, the revs will go up rapidly about 300-400 RPMs.

Thanks for the quick reply. In my previous driving I never experienced this small surge while depressing the clutch, or at least noticed it, but then again my 3000gt wasn't a WRX. I will def try to be more mindful and careful, dont wanna burn my clutch out already!

[mycologist]

I disagree with Teflon - it is well known and a lot of people note it. It is thought to be for emissions purposes.

And yes I do/can make it not happen - you do so by preempting it though (letting off the gas slightly early). And yes I have also correctly driven a fleet of other manual cars that don't do it and I can tell the difference.

When driving passionately I usually just let it go to some degree though - if you don't get the early lift off the gas just right it will tend to clunk the rear a little. It also hangs the RPM up a little longer which can be useful.

My original clutch that no one else has driven now has 90K and seems like it has another.


Edit - maybe STis are different.

[Ruh Roh]

mine does the same thing every now and then...

[jilty]

Well, it really only does it while spirited driving. Today, to test if in fact I was pushing the clutch before letting off the gas, I let off pretty early, then clutched. It still slightly went up, not as much, but it did. If I stay around 2.5-3.5k rpm shifts it does not do it at all.

I am going to SoCal Cobb tomorrow with some buddies and I will speak with someone and see what they can tell me. And to pick up a knob, my stock knob is just ugly.

[teflon_jones]

My car never does this at all and it's a late model Subaru.

Does anybody have any links to any Subaru information that talks about this? I don't see how this could help with emissions so I don't believe that one. Nor do I see how mechanically it makes sense.

[MainFrame]

Both of my WRXs did the same thing.. I always attributed it to the recirculating BPV injecting air back into the system. IIRC when I briefly had an atmospheric BOV it didn't do it.

[Anub1s]

Both of my WRX's have done the same thing, and it is a known common element to turbocharged Subaru's. I would also guess it is due to the recirculation. Remember the air is still pressurized when it is diverted back through the intake, still quite a bit of air for the engine to digest.

[jilty]

I don't know too much about how it would help emissions, but the recirculation sounds like it may be something. Even though its not a huge jump, it still does it, and it even makes a slight rumble, as if giving it gas. I am a bit relieved to hear a few people mention they have experienced it. I was seriously thinking that maybe, for some reason that the Gods hate me, installing shift bushings messed something up.

Side note, I was told if I use Redline trans and diff oils, my shifts will be a bit smoother even with my bushings that make it ultra notchy. Any truth to this? I am half way to 3k miles and id like to go with some quality oils, I have looked into the Redline power pack and replacing all my oils with it. Yay, nay?

[mycologist]

I don't know too much about how it would help emissions, but the recirculation sounds like it may be something. Even though its not a huge jump, it still does it, and it even makes a slight rumble, as if giving it gas. I am a bit relieved to hear a few people mention they have experienced it. I was seriously thinking that maybe, for some reason that the Gods hate me, installing shift bushings messed something up.

Side note, I was told if I use Redline trans and diff oils, my shifts will be a bit smoother even with my bushings that make it ultra notchy. Any truth to this? I am half way to 3k miles and id like to go with some quality oils, I have looked into the Redline power pack and replacing all my oils with it. Yay, nay?

There has been an extensive history and discussion of this topic. Because the gears and the diff are in the same box sharing the same fluid, you can't just use any old thing. For the transmission our best bet is Subaru extra-S. For the motor I'd just use any affordable synthetic that meets the grade specifications in the manual.

Now at page 24 we have come to some conclusions:

* We've decided Uncle Scotty's cocktail shifts nice for a while but breaks down really fast and needs really short change intervals.
--Also don't think syncromesh needs to be in the blend
--There is also concern it may cause extra wear

* Redline Lightweight Shockproof works well in the 5MT but not the STI trans (slinger lubrication versus pump)
--Seems to work just as well straight as mixed

* Straight Severe Gear 75w90 from Amsoil is not good in cold weather, but works well when mixed with shockproof

* SD_GR still loves his Valvoline conventional 75w90

* Subaru Extra S is the greatest gear oil to put in a stock Subaru
--It works well for a long time, shifts great, but is not sold in the quart. Its sold in the 5 gal drum, but many Subi tuners and dealer have it

FWIW Redline 75w90NS is what you'd run in the 5MT, but in non-mixed form it hasn't netted near the result of the Extra-S. Don't use MT90.

[MainFrame]

Side note, I was told if I use Redline trans and diff oils, my shifts will be a bit smoother even with my bushings that make it ultra notchy. Any truth to this? I am half way to 3k miles and id like to go with some quality oils, I have looked into the Redline power pack and replacing all my oils with it. Yay, nay?

I was quite pleased with RedLine in my transmission.. one thing to remember though, the standard RedLine synthetic 75w90 gear oil contains friction modifiers that are not good for use in syncromesh transmissions. They make a gear oil specific for use with syncromesh that does not contain those friction modifiers. When I used it I filled the transmission with a blend of the regular stuff, and the syncro stuff and it worked great. I put just the regular gear oil with the friction modifiers in my rear diff.



A note on what myco posted, the worst feeling gear oil I have used was the Subaru Extra S.. although that was when I had it serviced at the dealership, so I have no way of telling exactly what actually ended up in my transmission. I requested Extra S and was billed for it.

[jilty]

Thanks Mycologist and Mainframe, sorry for not doing a better search, I got lazy and just asked. Ill check around better.

Ill use the Redline, but ill prob go with the syncro blend. I'm a lil iffy on mixing stuff. ha ha. Thanks a lot for the input fellas on all of my questions.