Replaced transmission fluid, now it's causing problem

[Kostamojen]

I despise asmoil for a reason...

So far after a couple months my Redline MTL has only improved and I'm going to stick with it.

[frslee]

Originally Posted by Kostamojen

I despise asmoil for a reason...

So far after a couple months my Redline MTL has only improved and I'm going to stick with it.

Agree here especially after this happening. MTL is very smooth throughout every gear.

[sierra]

Why have you guys gone for the MTL 75w/80 instead of the MT-90 75w/90 which is to OEM specification?

MTL 75w/80

API Service Class GL-4 SAE Viscosity Grade (Motor Oil) 5W30 SAE Viscosity Grade (Gear Oil) 75W80 Vis @ 100°C, cSt 10.4 Vis @ 40°C, cSt 54.1 Viscosity Index 185 Pour Point, °C -50 Pour Point, °F -58 Flash Point, °C 232 Flash Point, °F 450 Brookfield Viscosity @ -40°C, Poise 120

MT-90 75w/90
API Service Class GL 4 SAE Viscosity Grade (Motor Oil) 15W40 SAE Viscosity Grade (Gear Oil) 75W90 Vis @ 100°C, cSt 15.6 Vis @ 40°C, cSt 90 Viscosity Index 185 Pour Point, °C -45 Pour Point, °F -49 Flash Point, °C 240 Flash Point, °F 465 Brookfield Viscosity @ -40°C, Poise 320

[OICU812]

RL MTL into tranny as well zero issues only improvements.

[sierra]

So it seems the gearbox I had replaced might have been perfect but the oem oil had somehow changed/broken down to somehow become more slippery, stopping the synchros engaging correctly?

When I had the oil changed for a fully synthetic 75w/90 and the symptoms were the same it could have been because that spec was too slippery too?

Redline-
Appropriate coefficient of friction for most manual transmission synchronizers (other's synthetic gear oils are often too slippery for proper synchro engagement)

[roddy]

MTL is 70W80...

[frslee]

@sierra I went with MTL even though it's 75w-80. I read from somewhere in the forum during research and found that MTL provides less slippery which helps synchronizer to grab the gear better? I'm not too into specific details of each manufacturer gear oil's character. I replaced it and it's good as new, smooth.
(Response on 2nd post) So did the dealer replace your transmission this week? I'm assuming you now don't have 5th gear problem. When you say you "oil changed", was it before the transmission was replaced? If you had the grinding before you changed oil, then I would assume it's the transmission problem. If the problem is gone with new transmission, I wouldn't change the fluid again.
@Amir Ghadiri Did you read my first post? This never happened before changing the fluid. It happend literally right after changing the fluid. It had to be the fluid that was causing the slipperiness. I know a lot of folks experienced this 5th gear grinding, but those people didn't touch their fluid.
@roddy Redline makes 3 different GL-4 oils... MT-90 75w-90 // MT-85 75w-85 // MTL 75W-80. I noticed some websites state MTL 70w-80, but Redline website uses MTL 75w80. Link

[sierra]

Originally Posted by frslee

@sierra I went with MTL even though it's 75w-80. I read from somewhere in the forum during research and found that MTL provides less slippery which helps synchronizer to grab the gear better? I'm not too into specific details of each manufacturer gear oil's character. I replaced it and it's good as new, smooth.
(Response on 2nd post) So did the dealer replace your transmission this week? I'm assuming you now don't have 5th gear problem. When you say you "oil changed", was it before the transmission was replaced? If you had the grinding before you changed oil, then I would assume it's the transmission problem. If the problem is gone with new transmission, I wouldn't change the fluid again.

The gearbox was replaced recently and of course it's fixed the problem. 2nd is as tight as but slowly freeing up.
5th gear grinding was there before the oil was changed and that didn't make any difference. To be honest it might have been worse after changing it.

As I said, it could be an oil problem and not mechanical. Who's to say the OEM oil isn't losing it's ability to allow the cones to grip somehow. If I could go back I would have tried Redline but it's too late now.

[roddy]

Originally Posted by frslee

@roddy Redline makes 3 different GL-4 oils... MT-90 75w-90 // MT-85 75w-85 // MTL 75W-80. I noticed some websites state MTL 70w-80, but Redline website uses MTL 75w80. Link

I was aware of the 3 different viscosities, and I originally went with the MT-90 because it was the recommended weight. It worked better than the OEM fill, but when outside temps got below 50 degrees or so, it wasn't that great. That's when I started experimenting with lighter weight fluids. So far, Pentosin (75W80) has had the best feel. I haven't tried the MT-85, but my current mix of MT-90 and MTL is working for me.

I looked at the link and I see where it says 75W80. I think that's a typo...it says 70W80 on the bottle.

[rice_classic]

I've never had a good experience with Amsoil in manual transmissions. Both the MTL and Ams. Synchromesh. Also, I believe you should have been using the Ams. synchromesh in this tranny and not the MTL but that is all moot at this point.

I'm also weary to run redline, not so much because of lubrication properties but because in transmissions where the bearings have plastic cages, which is common, the redline degraded (almost dissolved) the plastic cage and it would result in complete bearing failure and eventual catastrophic failure in the transmission. I don't think our transmission has bearings with plastic cages but nonetheless I've been weary about trusting their products since then. That's a significant engineering oversight if you ask me.

[frslee]

Originally Posted by rice_classic

I've never had a good experience with Amsoil in manual transmissions. Both the MTL and Ams. Synchromesh. Also, I believe you should have been using the Ams. synchromesh in this tranny and not the MTL but that is all moot at this point.

I'm also weary to run redline, not so much because of lubrication properties but because in transmissions where the bearings have plastic cages, which is common, the redline degraded (almost dissolved) the plastic cage and it would result in complete bearing failure and eventual catastrophic failure in the transmission. I don't think our transmission has bearings with plastic cages but nonetheless I've been weary about trusting their products since then. That's a significant engineering oversight if you ask me.

Thank you for the good information. There are significant others who use Redline products in this transmission, so we'll see what happens in the long run... "crossing fingers" This is my first manual car, so I'm kind of surprised how people (including myself) decide to use different weight oil depending on the region/temperature/purpose.

[Jmonty]

Anyone in the PNW make a change and if so what mileage did you do it?

[Riotsoup]

I just want to resurrect this thread because I'm having the exact same problem and until now haven't been able to find someone who shares(ed) my pain. Mine is a 2015 BRZ. I changed the MTF around 25k miles with Amsoil (GL-4) and almost immediately I noticed it jumping a couple teeth when down-shifting into 5th or up-shifting into 5th at high rpm. I gave it a few weeks to see if it would work itself out and there was no change. I read that resetting the ECU would possibly make things better by a "re-learning" process. I'm not sure how much truth there is to that. Anyway it didn't seem to change after the reset.


On a side note, I did find that by holding the shifter directly under the 5th gear position (about half way between neutral and 5th) for half a second or so I could avoid the grinding for the most part. However, I don't want to have to continue driving this way in order to avoid the problem.


So I am going to change the fluid to Redline 75W-90 and report back.

[Ultramaroon]

Originally Posted by Riotsoup

I read that resetting the ECU would possibly make things better by a "re-learning" process. I'm not sure how much truth there is to that. Anyway it didn't seem to change after the reset.

Completely unrelated. Electrically, the only thing the car knows about is whether or not it's in neutral and whether or not it's in reverse.

Is it actually a grind, or is it the occasional "ka-chunk" from slipping a cog between syncro and gear engagement?