Notchy shifting in hot weather

[daemontrym]

My 2012 Kia forte 6spd specs a 75w85 MTF which right now is running Castrol Syntrans 75w85(OEM MOpar version since thats what was close by). The shifting is great but when I drive home it gets notchy. The shifts don't grind but at times it feels like there is a wall between 1st and 2nd along with 2nd and 3rd. Then it just starts to feel clunkly similar to when a motorcycle needs an oil change soon.

Do you think a move up to 75w90 would work out great? I live near phoenix,AZ and right now on the highway I see 115-120 degrees outside registered by my car. I have tried AMSoil MTG and liked it, but heard all the buzz about castrol syntrans on here.

What would you guys suggest?

 

[SwampSurvivor]

"It's normal".

I've had the same problem with my Focus since new

I don't think it's right, but nothing I can do.

 

[IndyIan]

Are you waiting until the rpms drop to where they need to be for next gear? When I'm driving normally I'll push in the clutch, shift out of gear, wait the moment until the rpms drop to the right rpm for the next gear, then apply light pressure to the gear lever for the next gear to let the synchros do their thing, then the gear lever will drop in the next gear, while I let out the clutch and give some gas at the same time.
In the Tracker you can feel the dogs on the gears actually lock together as its gear lever is on top of the transmission, when I use this method.
If I'm in a hurry, then I use a bit more force to hurry the synchos up, but still wait until the shift is basically rev matched.

 

[badtlc]

I think you are experiencing the other end of the spectrum for these lightweight MTFs. To improve cold shifting, it is going to hurt hot shifting.

If you wanted to try "something" to see if it changes, go to a fluid with a 100C cSt that is 2+ more than what you are using.

 

[ARCOgraphite]

May be FM in the GL that is not allowing the synchro cones to bite. I dont think its an oil/lube grade issue. You need to try a different lube. Just to test and rinse things out you could try a 20w50 conventional motorcyclce oil with no FM for a couple weeks. It'll take a little time and thrashing to wipe off the FM package.

Also, it seems you change the transaxle FF too soon.

 

[Johnny248]

Being that you are in AZ, I don't think you would have any problem running a 75w90 such as Amsoil MTG. I don't know what these transmissions usually shift like, but my Aisin 6speed shifts without any issues ALL the time, no matter of the heat. It is a little stiffer during cold-cold weather, but that's it.

 

[ARCOgraphite]

Thinking more about this, when I drive home off a 100 deg parkking lot. my clutch slave doesnt work wellon the HOnda (not a big surprise). You most likely have some air and moisture in your hydraulic clutch system. Does it engage near the carpet and feel somewhat spongy and difficult rather than well damped and viscous?

This would be na incomplete de-clutching issue. Vey common and frustrating with "self-adjusting" hydraulic ssytems that seem to be misadjusted constantly.

 

[default]

I'd bet everywhere else on earth, it specs 75w90.

 

[daemontrym]

Indylan I pretty much do what you posted unless I need to make a quick turn or anything like that. I take off and let the shifter move naturally, I don't force it. Shifting has improved a bit since I removed the delay valve located inside of the slave cylinder.

Arco You maybe right about the FM's of the different oils I have tried, So far AMSoil has been the best so far. It felt good in between gear changes and didnt feel clunky between shifts. I changed the the Castrol Syntorq because of the following on here and other forums.

Engagement of my clutch is almost at the very top of the pedal. Pedal pressure is very good and am sure no air is in the system. I think the main problem is how kia tuned the throttle by wire pedal mixed with very numb clutch feel. I fixed the clutch feel by removing the delay valve. The throttle seems to have a deadspot for a few seconds then gets very sensitive fast due to the tune. I can drive it smoothly now but have to concentrate in order to do so, its not effortless like most of the other manuals I have had.

 

[Clevy]

Originally Posted By: daemontrym
Indylan I pretty much do what you posted unless I need to make a quick turn or anything like that. I take off and let the shifter move naturally, I don't force it. Shifting has improved a bit since I removed the delay valve located inside of the slave cylinder.

Arco You maybe right about the FM's of the different oils I have tried, So far AMSoil has been the best so far. It felt good in between gear changes and didnt feel clunky between shifts. I changed the the Castrol Syntorq because of the following on here and other forums.

Engagement of my clutch is almost at the very top of the pedal. Pedal pressure is very good and am sure no air is in the system. I think the main problem is how kia tuned the throttle by wire pedal mixed with very numb clutch feel. I fixed the clutch feel by removing the delay valve. The throttle seems to have a deadspot for a few seconds then gets very sensitive fast due to the tune. I can drive it smoothly now but have to concentrate in order to do so, its not effortless like most of the other manuals I have had.


I agree. Amsoil makes a great transmission fluid. So does red line.

 

[badtlc]

Originally Posted By: default
I'd bet everywhere else on earth, it specs 75w90.


I doubt it. The euros started this mass movement to ultra thin MTFs.

 

[daemontrym]

Arco you could be right about changing the factory fill too soon.

I think I will go back to the AMSoil 75w90 and will leave it in for awhile. I just have to order a new crush washer for the drain and fill plugs.

 

[daemontrym]

I am in between AMSOIL MTG, Redline MT90, and Motul Gear 300.

AMSOIL MTG felt great in the trans and I changed it to Castrol Syntorq 75w85 because forum posts and curiosity.

Redline MT90 has a higher VI than MTG (183/162) and seems to have many great reviews.

Motul Gear 300 has the highest VI of 222 and is a dual rated GL4/GL5 that has a huge following in german cars and subarus. Motul states its good for synchronized transmissions as well as diffs. Many reviews report no issue as well.

 

[Toy4x4]

I had great results with Redline MT90 in my last Toyota. It had a hard COLD shift into 2nd gear, though. On Toyota forums, this fluid was HIGHLY recommended. I was sold once I switched to it. If it meets your trans specs, I'd use it.