Slight grind in gears after changing manual transmission fluid

[nicholi2789]

Hey guys, I'm relatively new to Subarus. I bought a 95 Subaru legacy L a couple months ago. It has 255000 miles on it but runs strong and I haven't had any problems up until now. 

When I got it, I did the requisite tune up stuff, new spark plugs, wires, oil change, fuel filter, etc. At that time I noticed while checking the manual transmission that the gear oil in the transmission was disgusting. Looked like it hadn't been changed in years and it was about a quart over full. So since I work at a lube shop I resolved to change the transmission fluid as soon as possible. I looked in our computers check chart and for all Subaru Manual transmissions it requires GL5-75/90. So I bought 7.5 pints of our house gear oil, which is RedLine Synthetic 75/90 and changed the transmission fluid. 

Now, almost immediately afterwards I notice a slight grind when shiting into third gear, and sometimes second as well. It doesn't seem to do it when the car is still cold but after driving a while it gets worse until its a pretty pronounced grind when shiting into third. I am still able to get it into third okay, but that grind makes me nervous as hell.

The strange thing is, when I am downshifting, I experience no grind at all whatsoever in any of the gears. Only when going from 2 to 3rd, and sometimes from 1st to 2nd. Very strange. 

I have a hard time believing that just changing the gear oil could cause this, but I know for sure it wasn't doing this before. 

Can someone shed some light on this? I really am nervous about it and don't know a whole lot about Subarus. 
Thanks in advance.

Nick

[Fairtax4me]

Straight synthetic is too slippery for the synchros in the old transmissions.

Change back to plain ol' 80w-90 and it'll be fine.

[nicholi2789]

Straight synthetic is too slippery for the synchros in the old transmissions.

Change back to plain ol' 80w-90 and it'll be fine.

Really? are you sure? That seems like too easy of a fix. Lol. So it doesn't like synthetic gear oil? Is this a pretty well documented problem?

[Fairtax4me]

Yep. I've been in the same boat. Tried synthetic gear oil thinking I was doing my transmission a favor. Just made it grind. I've stuck with the cheapest 80w-90 gear oil I can get my hands on since then.

The newer transmissions (like 05+) are made to use 75w-90.

The old ones work best with 80w-90.

There are some cocktail mixes of fluids out there but they all seem to have a down-side of some sort.

[nicholi2789]

Yep. I've been in the same boat. Tried synthetic gear oil thinking I was doing my transmission a favor. Just made it grind. I've stuck with the cheapest 80w-90 gear oil I can get my hands on since then.

The newer transmissions (like 05+) are made to use 75w-90.

The old ones work best with 80w-90.

There are some cocktail mixes of fluids out there but they all seem to have a down-side of some sort.

Huh. Interesting. I guess I will have to go buy some 8090 tomorrow. There's 45$ to waste I spent on that Redline fluid. That stuff was expensive. 

Well I will try the 8090 as soon as I can get some and report back and post what my results were.

Do you think that having the 7590 in there will do any lasting damage? Or should I try to get it out as soon as possible? I'm a broke joke that's why I ask, and gear oil is expensive.

[Fairtax4me]

Shouldn't be any long term effect as long as you change it out soon. The more it grinds the more damage you do.

 

I've been using the Walmart Supertech stuff that's like $12 a gallon.

[nicholi2789]

Shouldn't be any long term effect as long as you change it out soon. The more it grinds the more damage you do.

 

I've been using the Walmart Supertech stuff that's like $12 a gallon.

HHmm so do they make a non-synthetic cheap 7590 too?

[papajam]

Which type of Redline 75/90 did you put in?

[1 Lucky Texan]

Huh. Interesting. I guess I will have to go buy some 8090 tomorrow. There's 45$ to waste I spent on that Redline fluid. That stuff was expensive. 

Well I will try the 8090 as soon as I can get some and report back and post what my results were.

Do you think that having the 7590 in there will do any lasting damage? Or should I try to get it out as soon as possible? I'm a broke joke that's why I ask, and gear oil is expensive.

 

drain it into a clean container and use the top 90% for rear diffs.

[Fairtax4me]

HHmm so do they make a non-synthetic cheap 7590 too?

I think any 75w-90 is going to be synthetic but I may be wrong. I've only ever seen synthetic in that weight.

 

That transmission is designed to use 80w-90 oil though. They designed that transmission in the mid '80s. There weren't commonly available synthetic gear lubes around at that time, so the synchros are designed to work best with 80w-90 dino juice.

 

There is Subaru Extra-S fluid which IIRC is a 75w-90. I can't say for sure how well it works in the older transmissions. The S fluid was designed to help correct shifting issues in the newer transmissions, and seems to be highly recommended, but it's about $15 a quart.

[nicholi2789]

 

Which type of Redline 75/90 did you put in?

I just used the GL5-7590 by Redline Redline. Not the GL57590NS they came out with for new Subarus.

[1 Lucky Texan]

ns was formulated specifically to help get the syncrhos moving;

 

http://www.redlineoil.com/product.aspx?product=58304

[nicholi2789]

ns was formulated specifically to help get the syncrhos moving;

 

http://www.redlineoil.com/product.aspx?product=58304

Huh, well I shoulda prolly just used that then. Oh well, I'll just use regular 8090 and see how it goes.

[nicholi2789]

 

I think any 75w-90 is going to be synthetic but I may be wrong. I've only ever seen synthetic in that weight.

Valvoline makes a semi-sythetic 7590 and a full synthetic 7590 actually.

[papajam]

I just used the GL5-7590 by Redline Redline. Not the GL57590NS they came out with for new Subarus.

That could be the issue.

Syncros work on the principle of friction. Most modern GL-5 gearoils have too much EP (Extreme Pressure) additive that makes the oil too slippery for some types of syncros (Porsche for example) or worn syncros to function properly. Redline NS (Non Slip), as 1 Lucky Texan posted, has less EP in it thus allowing the syncros to better do there job.

[nicholi2789]

That could be the issue.

Syncros work on the principle of friction. Most modern GL-5 gearoils have too much EP (Extreme Pressure) additive that makes the oil too slippery for some types of syncros (Porsche for example) or worn syncros to function properly. Redline NS (Non Slip), as 1 Lucky Texan posted, has less EP in it thus allowing the syncros to better do there job.

Ah well I can't afford another 7.2 pints of 7590 so I think I will just try 8090 and see if it helps.

[nicholi2789]

So today I went to my work and changed the fluid out to our regular Castrol GL5-80/90 Gear oil. It seems to have stopped the problem I think. I drove the car for probably an hour or more and didn't notice any more grinding. I'll know for sure once I drive it a couple more days. I just hope the 7590 didn't cause any lasting damage.

ALso, when looking on the Redline website for regular GL5-7590 it says this at the bottom:

"This product is not designed for use in most manual transmissions or transaxles in passenger vehicles, since the extreme slipperiness may cause synchronizer mesh issues that lead to shifting problems"

TThat's interesting because I have used it in tons of customers manual transmissions and never seen a problem til now. Oh well I guess.

[1 Lucky Texan]

seems like you may have a fluid in there that will work for you, this is the combo being suggested in a huge thread over at NASIOC;

 

[nicholi2789]

seems like you may have a fluid in there that will work for you, this is the combo being suggested in a huge thread over at NASIOC;

 

Hmm.. Can you link me to the thread?

[1 Lucky Texan]

http://forums.nasioc.com/forums/showthread.php?t=920674

[Fairtax4me]

Seems like an odd combo to me.

 

Synchromesh is just fancy 30 weight motor oil. But it does work great in Hondas. They don't have a hypoid gear set to protect though.

 

Limited slip additives are designed to reduce friction in clutch packs used in limited slip differentials to prevent "chatter". Seems like they would also make it more slick on the synchros, which cancels out the synchromesh.

[nicholi2789]

Seems like an odd combo to me.

 

Synchromesh is just fancy 30 weight motor oil. But it does work great in Hondas. They don't have a hypoid gear set to protect though.

 

Limited slip additives are designed to reduce friction in clutch packs used in limited slip differentials to prevent "chatter". Seems like they would also make it more slick on the synchros, which cancels out the synchromesh.

Yeah, I'm gonna drive it for a couple days and see if that grinding returns again. If it does then I may try this cocktail, but I'm not even sure if it even applies to this transmission.. Do they use the same manual transmissions in the newer Impreza's? I know that some of the newer ones that have the 2.5 instead of the 2.2 have a slightly different transmission. At least they look slightly different anyways.

[1 Lucky Texan]

I have experimented a little, but haven't tried that combo. The only thing I know about 5spds is, in 06 they went with a different synchronizer for 1st gear. (cone or 'double cone' ?)

 

of the 3 fills I've tried, I'd say the best was 100% Redline Lightweight Shockproof.(Smurf Blood lol!)

 

there's no end to what you 'could' try and plenty of people find Extra-S or name brand non-synth GL-5 works fine for them.

 

seems like some folks are always tinkering with something on their cars, I might be a little guilty of that.

Edited May 30, 2014 by 1 Lucky Texan

[1 Lucky Texan]

Seems like an odd combo to me.

 

Synchromesh is just fancy 30 weight motor oil. But it does work great in Hondas. They don't have a hypoid gear set to protect though.

 

Limited slip additives are designed to reduce friction in clutch packs used in limited slip differentials to prevent "chatter". Seems like they would also make it more slick on the synchros, which cancels out the synchromesh.

I guess the Castrol had been labeled HypoyC in the past - but I am no expert on this. There probably isn't an expert - just a lot of anecdotal data.

[nicholi2789]

Yeah it was labelled Castroy Hypoy C 80W/90 gear oil in the past. We stocked it back when they had it, and now we stock it even though it is labelled differently. It is the same fluid. But it's called Castrol Axle Limited-Slip 80W/90 Gear oil.They are exactly the same only different label.

 

Anyways, Here i am a full day after changing the transmission fluid again, only using Castrol 80/90 instead of Castrol 75/90 and I am grind free. As far as I can tell anyways. I drove it for about an hour and a half on back roads really getting on it and making sure the fluld heated up all the way and didn't experience any of the grinding. Not even the tiniest bit. Hail satan, because I was considerably worried it would do permanent damage. Lol. 

So in conclusion, (this is obviously a well known fact among the forum users but new to me), You can NOT use RedLine GL5-7590 in these transmissions. You may think your doing your transmission a favor, your not. I can't speak for this "Scottie's Cocktail" or any other gear oils. Though it is widely acclaimed. 

I can say however with certainty that 80/90 is the fluid to use. Hope this thread helps someone in a similar predicament, and thank all you guys for your help. I'll be coming back here quite frequently. 

If the situation changes I will be sure to report back. 

Thanks alot

Nick

Edited August 7, 2014 by nicholi2789