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Grinding noise changing from 4th to 5th


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12 replies to this topic

#1 mwynne

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Posted 25 November 2011 - 07:54 PM

Hey,

My Legacy grinds just about every time I change from 4th to 5th just before it is properly into 5. It is the only gear that grinds. I have tried shifting slowly, pushing over really far, the middle, and as far left as possible without putting it into third, and about 95% of the time it grinds with varying degrees. Just for something else I tried double clutch upshifting and it would go into 5 seemingly with no issues but when i started to release the clutch it would start to grind, and I pulled it out. I was told by a friend to post on here to see if you guys had heard of this before and have any solutions. If you have any questions feel free to ask. Would really like to get this figured out as quickly as possible.

Cheers!

#2 GeneralDisorder

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Posted 25 November 2011 - 08:39 PM

Sounds like the syncro is shot. Time for a tranny rebuild or replacement. There's no good cure for that.

You can try a quart of Rislone in place of one quart of gear oil on a fresh fill of the tranny (takes about 3.7 quarts). But it sounds like it's probably pretty shot.

GD

#3 gbhrps

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Posted 25 November 2011 - 08:46 PM

mwynne,

First off, there is something worn on the inside of the tranny that is eventually going to get worse and require repairs.

That said, you may be able to forestall the repairs for quite some time. I have a 1954 MG TF roadster that has a four speed that would grind going into 3rd, or gearing down from 4th into 3rd. It was doing this from the first day I owned it over 20 years ago. About 10 years ago I found a thread on another forum (1990 - 1996 Nissan 300ZX's) that a member had a similar problem and simply changed his tranny fluid to RedLine MT90 and his grinding problems disappeared.

I replaced the fluid in my MG to the RedLine MT90 (Manual Transmission 90 weight) and immediatedly the tranny was much quieter and, if I didn't rush the shifts up or down, the grinding was eliminated. That was 10 years ago, and granted, the car is just a toy and doesn't get a lot of miles put on it, but it may make a significant difference in your case. It certainly won't be expensive to give it a try. Good Luck!

#4 jdemaris

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Posted 25 November 2011 - 08:59 PM

Hey,

Just for something else I tried double clutch upshifting and it would go into 5 seemingly with no issues but when i started to release the clutch it would start to grind, and I pulled it out.


As to the statement I included here from your post - that's got me a bit stumped.

If it actually was in gear but did not grind until you let the clutch up - it's not what's making the grinding sound. Or do you mean you thought it was in gear, but then found out it was only partially engaged and grinded?

Are you sure you don't have shift linkage problems? There's a plastic bushing that can get worn and make shifts from 4th to 5th problematic.

The trans in the Subaru is a constant-mesh type. That means no gears are ever moved or slid into, or out of, gear. You shift gears by locking the chosen gear onto a common shaft. To keep the parts that are not turning the same speeds from grinding when shifting, each gear set has a clutch. That clutch lets the two moving parts "get to know each other" and start turning the same speed. So, if 4th to 5th is grindng, you got a bad clutch inside the synchronizer assembly.

The other function of the synchronizer is the mechanism that actually locks the gear to the shaft. When worn, the trans will frequently pop out of gear.

Clutches usually go first. Then after a lot of grinding gears - the spurs that allow them to "lock" get worn off, and then they pop out.

I'm not sure why I bothered mentioning all this - since there is no external fix if your problem is inside the trans.

Losing a 4th-5th clutch is unsusal though. Usually 1st and 2nd are the ones that take a beating and wear out. That fact alone would make me want to make sure that the shift linkage was working OK. Does it still feel as tight as it always did?

#5 mwynne

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Posted 25 November 2011 - 09:13 PM

If it actually was in gear but did not grind until you let the clutch up - it's not what's making the grinding sound. Or do you mean you thought it was in gear, but then found out it was only partially engaged and grinded?

Are you sure you don't have shift linkage problems? There's a plastic bushing that can get worn and make shifts from 4th to 5th problematic.


Clutches usually go first. Then after a lot of grinding gears - the spurs that allow them to "lock" get worn off, and then they pop out.

I'm not sure why I bothered mentioning all this - since there is no external fix if your problem is inside the trans.

Losing a 4th-5th clutch is unsusal though. Usually 1st and 2nd are the ones that take a beating and wear out. That fact alone would make me want to make sure that the shift linkage was working OK. Does it still feel as tight as it always did?



From what I could tell I thought it was engaged, but I could very well have been wrong.

Not really sure if It is clutch linkage issues, im going to take a look tomorrow with a buddy and see what else we can come up with.

Unfortunately I just bought it. It was uninsured so I had to drive it on dead end roads and never got into 5th when I tested it. It was driven by an old man who presumably never got into 5 much either which confuses me.

I'll probably end up trying the Redline as suggested by gbhrps and see if it gets any better. If not I guess ill be avoiding 5th unless its a linkage issue.

Thank you very much for your help!












mwynne,

First off, there is something worn on the inside of the tranny that is eventually going to get worse and require repairs.

That said, you may be able to forestall the repairs for quite some time. I have a 1954 MG TF roadster that has a four speed that would grind going into 3rd, or gearing down from 4th into 3rd. It was doing this from the first day I owned it over 20 years ago. About 10 years ago I found a thread on another forum (1990 - 1996 Nissan 300ZX's) that a member had a similar problem and simply changed his tranny fluid to RedLine MT90 and his grinding problems disappeared.

I replaced the fluid in my MG to the RedLine MT90 (Manual Transmission 90 weight) and immediatedly the tranny was much quieter and, if I didn't rush the shifts up or down, the grinding was eliminated. That was 10 years ago, and granted, the car is just a toy and doesn't get a lot of miles put on it, but it may make a significant difference in your case. It certainly won't be expensive to give it a try. Good Luck!



Thank you very much! I will give this a try and see what happens.

#6 GeneralDisorder

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Posted 26 November 2011 - 12:19 AM

I would caution against the redline at first - it's expensive - about $12 a quart.

Try a full fill of straight ATF (yes - automatic transmission fluid) and see if that helps your grinding. If it does then don't use the MT90 - Get one of these in this order of preference:

1. Subaru Extra-S
2. Motul 75w90
3. Redline 75w90NS

The MT90 doesn't have the right additives for the hypoid differential. Those three do. But ONLY use one of those ($$$$) if you have any luck at all with the ATF. ATF is the smoothest shifting gear lube you will ever find - but it doesn't have the right additives for the hypoid diff so you can't run it long-term. A few hundred miles won't hurt though. I use it to clean out dirty, nasty transmissions all the time.

GD

#7 Frank B

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Posted 26 November 2011 - 10:53 AM

+1 on the Rislone.
Try it first as GD said, with some cheap gear oil then change it after a few hundred to a thousand miles. Then use some better oil and you can still use the Rislone long term. I've used Rislone in every manual Subaru I've had so far and it's made a difference.
When I got my 96 Legacy it would grind into 3rd and wasn't easy to get into any gear. I changed the oil with a quart of Rislone, changed it again after about a thousand miles, and the oil looked like someone dumped a bottle of glitter in it! It was full of metal. So I changed it again after a few hundred miles and it's as smooth as any tranny with 290,000 miles on it could be.
The drain plug has a magnet on it so be sure to clean it off well before putting it back on too.

While your playing around, check your shifter linkage. Search the forum for shifter bushings and you'll see why it's worth a look.

#8 bru73

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Posted 26 November 2011 - 04:41 PM

the best way to stop this from happining in the futher is dont drive with your hand resting on the shifter it keeps presher on th the syincro hud and bras brake and wares the groves of:banghead::dead:

#9 mwynne

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Posted 27 November 2011 - 03:40 PM

Sounds like the syncro is shot. Time for a tranny rebuild or replacement. There's no good cure for that.

You can try a quart of Rislone in place of one quart of gear oil on a fresh fill of the tranny (takes about 3.7 quarts). But it sounds like it's probably pretty shot.

GD


http://www.rislone.ca/34471.htm is that the correct Rislone stuff? I have no idea. Thanks!

the best way to stop this from happining in the futher is dont drive with your hand resting on the shifter it keeps presher on th the syincro hud and bras brake and wares the groves of:banghead::dead:


I never do this. Not sure if previous owned did, however.

#10 GeneralDisorder

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Posted 27 November 2011 - 07:12 PM

http://www.rislone.ca/34471.htm is that the correct Rislone stuff? I have no idea. Thanks!


No - this one:

http://www.rislone.ca/34100.htm

GD

#11 GeneralDisorder

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Posted 27 November 2011 - 07:18 PM

the best way to stop this from happining in the futher is dont drive with your hand resting on the shifter it keeps presher on th the syincro hud and bras brake and wares the groves of:banghead::dead:


Old wives tale actually. At least on the Subaru's it is. Once the syncro is engaged (shift complete) all it's component parts are spinning the same speed - no wear can take place since none of the peices are moving relative to each other. You can wear out the nylon fork slides but that's a different issue entirely and won't cause grinding. Resting your hand on the shifter is not detrimental that I've seen - the most common failure on the 5MT's is 2nd gear syncro grinding - which simply can't be from resting your hand on the shifter because you aren't in second long enough durring normal driving to affect damage that way - and the other failure is rear input shaft bearing failure - which can be attributed to a number of things - not changing the gear oil for one, and mis-alignment from missing bell-housing dowel pins for another.

GD

#12 Fairtax4me

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Posted 27 November 2011 - 09:57 PM

Have you changed the gear oil? Id do that first with a $10 gallon of fresh 80w90. Fresh fluid by itself can make a lot of problems better if not cure them altogether.

#13 mwynne

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Posted 02 December 2011 - 01:02 AM

Have you changed the gear oil? Id do that first with a $10 gallon of fresh 80w90. Fresh fluid by itself can make a lot of problems better if not cure them altogether.


Havent done this yet. planning on doing it when I have time after exams finish. I will update the status then.




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