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Premium Member
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Discussion Starter #1
We took a family cruise in my wife's '04 FXT 5MT today and I drove. I shifted into 4th and noticed a slight grind. I had a confused look on my face - and my wife said that the car had been shifting like that lately.

All other gears are fine. The car is stock with 50K on it now. I changed the transmission fluid over to Redline 75W90 about 10K ago. She had trouble getting the car into 1st - and the Redline helped that out.

Does anyone have an idea why this car is grinding only into 4th?? I tried double-clutching and that helped...
 

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Premium Member
2004 Forester XT
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815 Posts
I have the EXACT same issue.

I was using Silkolene and had no issues. Then I did my yearly tranny fluid change to new Silkolene, and thats when the problem started. So then I switched to Royal Purple, and it is slightly better, but still grinding more often than not. I am getting a little worried my synchro is shot.

I might try switching to good ol' regular oil. The synthetics may just be too slippery.
 

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Premium Member
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88 Posts
Discussion Starter #3
SkiPhast said:
I have the EXACT same issue.

I might try switching to good ol' regular oil. The synthetics may just be too slippery.
That's what I was thinking too. What is the stock dyno tranny fluid? Penzoil 75W90?

As a side note - my FXT has had the same Redline fluid since 5K. I have almost 20K logged now without any issues.
 

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Registered
2006 RX8
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423 Posts
I have read numerous posts through the years about the pros and cons of using synthetics in the tranny. Many do so successfully, but many have also had issues and have expressed concerns of the Synthetics not having the necessary viscosity to properly lubricate and cushion the pressures and friction within a manual transmission. Here is a link to some info on "timkin" tests that can provide some insight into load bearing qualities of lubricants.
http://bobistheoilguy.com/videos.html

Lucas oils/lubricants seem to perform very well with respect to the timkin tests. Since you guys are having this gear grinding problem perhaps a real-world test by changing back to a conventional petroleum type transmission oil would provide an excellent test-bed to determine if this could be a contributing factor. Certainly a lot cheaper first step than having your gear-box rebuilt.

Jeff
 

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Premium Member
2017 Forester XT touring CVT
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981 Posts
I had this same problem develop over a year ago with the same gear. If I shifted from 3 to 4 or from 5 to 4 at 60mph or more I would get a grinding sound. I took my XT to the dealership for a diagnosis and repair. The tech said at the time he felt the synchro was toast so he suggested getting it fixed. So, to make a long story short, my tranny was torn down with no visible damage or broken parts. The tech said he could find nothing wrong other than a shiny spot on the 4th gear shift fork. He said it looked like the fork was rubbing. Now all the key parts involved in 4th gear were replaced under warranty and I have no longer had the 4th gear grind. However, after I had that work done I now have a grind when shifting into 1st gear. This started immediately after I got my XT back from the dealership. Right now I can try putting my car in 1st at a very slight roll or even sitting still and it will grind. I have just learned to deal with this simply because I cannot be without my XT for 3 weeks like before. I have never tried any synthetic gear oils so I do not know if they would benefit my XT or not. Other than that, my only complaint about my XT would have to be the paint. That is a whole other thread that has been beaten like a dead horse.
 

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2004 Forester XT
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317 Posts
I just replaced my tranny oil with Lucas 75w90 Synthetic, with the synthetic oil stabilizer and voila.... 4 gear doesnt like it.

I noticed that if I match rpms it doesnt do it as bad, but it seems that the grind seems to be linked with the forward acceleration of the car. If the car is still accelerating as I go into 4th it will grind, but if I keep it in neutral long enough for the car to actually start slowing down it wont. Also, it gets worse as the tranny warms up... the longer/harder I drive it, the worse it gets.

I read on another thread that some type of Redline works great... I think it was the Shock Proof. Can anyone confirm that?

:confused:
 

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Premium Member
2004 Forester XT
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815 Posts
Lispisgone said:
I just replaced my tranny oil with Lucas 75w90 Synthetic, with the synthetic oil stabilizer and voila.... 4 gear doesnt like it.

I noticed that if I match rpms it doesnt do it as bad, but it seems that the grind seems to be linked with the forward acceleration of the car. If the car is still accelerating as I go into 4th it will grind, but if I keep it in neutral long enough for the car to actually start slowing down it wont. Also, it gets worse as the tranny warms up... the longer/harder I drive it, the worse it gets.

I read on another thread that some type of Redline works great... I think it was the Shock Proof. Can anyone confirm that?

:confused:
AH! You described it with the exact words I would have used. My symptoms are identical.
 

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2004 Forester XT
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SkiPhast said:
AH! You described it with the exact words I would have used. My symptoms are identical.
Well... that is a HUGE relief to know that someone else is having the same problem :D

Based on everything I've seen, it really cant be anything else other than the oil... so I'm going to make a switch next week to that Redline Shock Proof goodness. Without proper use of my 4th gear my car is worth squat on the track :(

I'll post up and let you know how things go.
 
S

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yelnats - I had the same deal in reverse order - 1st and 3rd grinding, now it's 4th (after rebuild). First dealer and regional service guy denied warranty work on the 1st & 3rd grind, so I found another dealer. Tranny fixed under warranty. Hope it works again. Even the technician says this tranny is the weak point of the car... This could prevent me from ever buying another Subie...
 

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The Modfather
2019 Impreza 5dr Sport - Manual
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8,053 Posts
Redline shockproof worked for me with I hand slight grinding issues in a couple of scoobies (including my F-XT) Depending on where you live and how cold it gets I'd go for the HD SP if you live where it does not get too cold and then go down from there to light weight or superlight
 

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Premium Member
2017 Forester XT touring CVT
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981 Posts
Mine has been at it again. This time it is only on occasion and under light acceleration. This is just the opposite of the last time. I guess I will just try some different tranny oil and just live with my XT the way it is.
 

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Premium Member
2004 Forester XT
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815 Posts

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Lispisgone said:
I just replaced my tranny oil with Lucas 75w90 Synthetic, with the synthetic oil stabilizer and voila.... 4 gear doesnt like it.

I noticed that if I match rpms it doesnt do it as bad, but it seems that the grind seems to be linked with the forward acceleration of the car. If the car is still accelerating as I go into 4th it will grind, but if I keep it in neutral long enough for the car to actually start slowing down it wont. Also, it gets worse as the tranny warms up... the longer/harder I drive it, the worse it gets.

I read on another thread that some type of Redline works great... I think it was the Shock Proof. Can anyone confirm that?

:confused:
Same exact issue here too, warmer = more grinding in 4th.
I have Royal Purple Synthetic already, on the reccomendation of the Subaru Dealer, so don't bother trying that one...
 

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The Modfather
2019 Impreza 5dr Sport - Manual
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8,053 Posts
Putting Shockproof has helped me in two different Scooby trannies. Maybe something else is wrong with yours. Since it's not a hard thing to try I think it's at least worth a shot.
 

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2005 XT
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923 Posts
Interestingly enough I had exactly the same issue with my WRX. Crunch in 4th over 60 3 to 4 or 5 to 4. I also had the same crunch going into 1st and reverse VERY rarely. I took it in and they replaced 1,3,5,r gears and other bits. Looking at the parts list, looked like the whole damn transmission to me. But afterwords, it rode better than before, the clutch was a bit tighter but I was able to shift smoother. I believe this is a known issue and should be quickly fixed by bringing it in. If your cars a modded, some dealers are more lax than others with it. There are 2 in my area which are cool. Just a though, maybe the SPT labelled dealer garages will be more loose with things like this.

-Alex
 

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Peaty said:
Putting Shockproof has helped me in two different Scooby trannies. Maybe something else is wrong with yours. Since it's not a hard thing to try I think it's at least worth a shot.
Actually it wasnt Redline, it was Royal Purple...
If the dealer won't fix it, should I try Shockproof, or Synchromesh?
 

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Asphalt Surfers Unlimited
2004 Forester XT
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742 Posts
Honestly, the best fluid for the gearbox is the factory Subaru 75W90 Extra-S. It's not your garden variety GL-5, it has a very specific friction modifier package that works well with the factory synchros, and it is very resistant to thermal deterioration.

See the later part of this thread for more details, the same info applies to all Subaru 5MT and 6MT transmissions:

http://forums.nasioc.com/forums/showthread.php?t=982736

Obviously you can ignore anything in that thread that pertains to the STi rear differential... it uses a unique factory fluid for the clutch-type R180 LSD that is different from the viscous coupling rear LSDs in the rest of the product line. You can use any standard GL-5 fluid in the rear diff of a Forester with good results. Synthetic is totally unnecessary.

This specified factory fluid for the transmission comes in bulk containers and is part number K0323AA093. The dealer will have to put it in a spare gallon jug for you. The trans takes 3.7 quarts if I remember correctly.


Just for reference... the ESX drag team stopped exploding transmissions when they switched to the factory Extra-S... they tried a variety of high end synthetic fluids unsuccessfully prior to switching to the factory fill and have apparently been pleased with the results.
 

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Ze flying Russian
2007 STI
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2,008 Posts
In my case grinding in both the gearbox and the rear differential was fixed by simply changing the fluid.
 
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