Transmission leaking at the control shaft

Posted By: Rob Strelecki

Transmission leaking at the control shaft - August 31, 2017 01:06 am UTC

The leak seems to start there. No oil found above it. The boot and surrounding area was soaked. Peeled the boot back and it was wet inside.

[Linked Image]

Any ideas why that would happen?

It's possible I slightly overfilled it as only the front of the car was on stands.
Nothing comes out of the fill hole now when I remove the bolt with the car level.

I drove about 150 KM since the trans went in and then I noticed the drip. I'm pretty sure it wasn't leaking before.
Posted By: Rob Strelecki

Re: Transmission leaking at the control shaft - August 31, 2017 04:12 am UTC

Did some googling. The seal on the shaft is likely shot. Some say it can be patched with RTV. Almost impossible to change the seal without opening the trans. frown
Posted By: Bryan Lawrence

Re: Transmission leaking at the control shaft - August 31, 2017 01:06 pm UTC

Damn that's too bad! Thanks for updating us!
Posted By: Jason Drew

Re: Transmission leaking at the control shaft - August 31, 2017 01:15 pm UTC

Originally Posted by Rob Strelecki
Almost impossible to change the seal without opening the trans. frown


Yup, you need to remove the roll pins from the forks to get the shaft out.

Your transmission vent isn't blocked up or anything> (creating pressure inside the trans). The seal would have to be pretty bad/non existent for it to leak at this location, it's kind of out of the way of oil slinging around in the transmission.
Posted By: Rob Strelecki

Re: Transmission leaking at the control shaft - August 31, 2017 01:19 pm UTC

I doubt there is blockage since the trans just got a very thorough cleaning.

I just tried to get more fluid in and I couldn't get even one squirt into the fill hole. So maybe there is some weight to my overfill theory?

I'm going to do another 150 KM today and we'll see if the situation improves.

Thanks!
Posted By: Jason Drew

Re: Transmission leaking at the control shaft - August 31, 2017 01:22 pm UTC

Might be possible on the overfill, the t-case will leak out the vent if overfilled but also suspect the seal is probably damaged too.
Posted By: Rob Strelecki

Re: Transmission leaking at the control shaft - September 01, 2017 04:26 pm UTC

From what I was reading, people with this problem get a pumping action from the gear shifting that squirts the oil out.

It seems to have leaked a lot less on the last drive, but it could just be how the last drive was (e.g. less stop & go shifting).

I had cleaned the control shaft area really well and didn't see much wetness there. However, the clutch fork boot is pretty soaked. It seems to accumulate there, of course that is a low and protruding point.

It could still be the trans input or output shaft seals, or maybe a cracked case. I'll continue to inspect.
Less likely but possible is the engine rear main seal, but I'm pretty sure the oil is Syncromesh by the smell.
Posted By: Jason Drew

Re: Transmission leaking at the control shaft - September 03, 2017 01:22 am UTC

You're using syncromesh in your trans?
Posted By: Rob Strelecki

Re: Transmission leaking at the control shaft - September 03, 2017 02:20 am UTC

Yep, it's always worked fine for me.
Posted By: Jason Drew

Re: Transmission leaking at the control shaft - September 03, 2017 03:11 am UTC

I wouldn't run it in my car, it used to be common in the past but pretty much every trans builder now concludes it just doesn't offer the required protection.

Direct from Jon at TRE

Quote

Synchromesh/Synchroshift gear oils

While it has been found that the Synchromesh/Synchroshift type oils can sometimes improve the effectiveness of the synchronizers, allowing for faster shifts at higher rpms, this oil does not have enough film strength to ensure long gear and bearing life for the Mitsubishi transmissions.

Synchromesh/shift type oils are used in transmissions that are found in low torque applications that don’t ask much from the oil in regards of film strength. Transmissions that call for Synchromesh type gear oils are designed with wide gear shaft spacing which greatly reduces the force on the gear teeth and large bearings so that they can use these low film strength oils. The reason behind it is to reduce parasitic frictional losses and to improve shift quality.

If you have a weak synchro, you may want to try the “Synchromesh/Synchroshift” type oils but it is our recommendation that you use the proper GL rating that the transmission was designed to use and prepare for a rebuild.
Posted By: Rob Strelecki

Re: Transmission leaking at the control shaft - September 03, 2017 05:08 pm UTC

Well I am definitely from the past lol
What's recommended these days? I don't ask a ton from my trans, no high rpm shifts or launches.

I feel like Syncromesh helped me get into 2nd at high rpm, but really not a concern anymore.
Posted By: Stephen Richardson

Re: Transmission leaking at the control shaft - September 03, 2017 07:34 pm UTC

Anything GL-4 will suit your needs just fine Rob. Of course there are good better and best brands, but if you arent Johny racecar driver you wont notice any difference as a daily.
Posted By: Jason Drew

Re: Transmission leaking at the control shaft - September 03, 2017 07:56 pm UTC

OEM 6 speed or MT90 is the go-to for stock to mild power levels

For slightly more you can get Motul Gear 300 75w90 which has a stronger film strength and I found gave smoother shifts.
Posted By: Rob Strelecki

Re: Transmission leaking at the control shaft - September 07, 2017 04:14 pm UTC

Thanks for the advice tu

The verdict is in!
It's completely stopped leaking. I tried to get more in and it's definitely full.
Somehow the extra was pushed out, no more no less.
I'll remember to pull the fill plug on level ground next time tongue

Next on project leak-free: Boost leaks.
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