Gear oil smell from shifter boot

[Zelos]

Hey folks, I have a 5 speed 3.4L 2000 4Runner with about 173k miles. Before changing the transmission fluid which was incredibly smelly, but not dark, I could smell the same odor in the cabin while in 2nd gear and after the truck has been sitting for a few hours after a drive.

After changing the tranny and transfer case fluid, the odor isn't as pungent, but it's still faint of newer gear oil. I located the source at the shifter boot. I didn't see any leaks at the tranny or transfer case.

Has anyone else encountered this? Maybe I will need to take a look under the shifter boot, but I'd like to know before I start taking things apart.

 

[stecow]

I don't think its much of a problem... I had a similar thing on my Tacoma and never had issues. Also same with my "new" 4Runner, I didn't have any oil smells or anything but after I changed the transfer case, rear diff, and trans oil I could smell a faint new oil smell for the next few weeks. Every once in a while it was a bit stronger and more obvious through the shifter covers. It's pretty much gone away now

Now, I don't have nearly as much experience and expertise yet as a lot of the people on this forum so wait to see what others say. I could be way wrong and it might be an issue you need to fix

 

[RandyBobandy]

Maybe you got some excess gear oil on the transfer case? It has a pretty strong odor so I could imagine it coming into the cabin from underneath

 

[sleepydad]

Hey folks, I have a 5 speed 3.4L 2000 4Runner with about 173k miles. Before changing the transmission fluid which was incredibly smelly, but not dark, I could smell the same odor in the cabin while in 2nd gear and after the truck has been sitting for a few hours after a drive.

After changing the tranny and transfer case fluid, the odor isn't as pungent, but it's still faint of newer gear oil. I located the source at the shifter boot. I didn't see any leaks at the tranny or transfer case.

Has anyone else encountered this? Maybe I will need to take a look under the shifter boot, but I'd like to know before I start taking things apart.

I did a vid when I re-did my transfer case... I have an auto but... the transfer case should be the same I think.

it's very common to have that top bushing go bad, they just fall apart after 18 years. I don't know it's not exactly what your asking but maybe it will help you with the top of the transfer case?

<iframe width="800" height="600" src="https://www.youtube.com/embed/CgDmWNfF27Q" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

 

[mtbtim]

Yes, what Andy said above is exactly what I was thinking. I bet the shifter seats for your transmission and/or transfer case are wasted. You could have also slightly overfilled your transmission and/or transfer case that's why it is coming out past the shifter seat.

You can get yourself new shifter seats from Marlin Crawler.

Heavy Duty Seats | Marlin Crawler, Inc.

 

[Zelos]

I'm hesitant to say it's the transfer case because before the fluid change, I could smell the really pungent transmission fluid. The t-case fluid did not smell so bad when I changed it out.

Also, isn't it pretty hard to overfill diff/t-case/trans fluid since we need to fill via the horizontal fill plugs? I think the truck would need to be on uneven ground or jacked up to overfill using the fill plugs.

After some more reading, I'm starting to think it's the shifter seal or the gasket for the shifter housing that sleepydad was alluding to.

Would the transmission breather cause an odor?

 

[mtbtim]

I'm hesitant to say it's the transfer case because before the fluid change, I could smell the really pungent transmission fluid. The t-case fluid did not smell so bad when I changed it out.

Also, isn't it pretty hard to overfill diff/t-case/trans fluid since we need to fill via the horizontal fill plugs? I think the truck would need to be on uneven ground or jacked up to overfill using the fill plugs.

After some more reading, I'm starting to think it's the shifter seal or the gasket for the shifter housing that sleepydad was alluding to.

Would the transmission breather cause an odor?

You are pretty much right that you can't really overfill it as long as you are doing it on level ground. But, maybe the ground you're on isn't as level as you think or your rig has a positive rake due to a suspension lift.

Sometimes the breather can puke out gear oil if it's overfilled and that's when you might smell it. The breather working normally letting excessive pressure escape probably wouldn't generate a strong smell. It's most likely a worn shifter seat or a leaking gasket that seals the shifter housing to the transmission.

 

[Zelos]

You are pretty much right that you can't really overfill it as long as you are doing it on level ground. But, maybe the ground you're on isn't as level as you think or your rig has a positive rake due to a suspension lift.

Sometimes the breather can puke out gear oil if it's overfilled and that's when you might smell it. The breather working normally letting excessive pressure escape probably wouldn't generate a strong smell. It's most likely a worn shifter seat or a leaking gasket that seals the shifter housing to the transmission.

I'll order the Marlin seats for the t-case and trans. We'll see how it goes. $15 for shipping those seats and a HD shifter socket is borderline highway robbery...

 

[Zelos]

I finally got around to replacing the shifter bushing with the Marlin one. The old one didn't look bad and neither did the housing seals. There isn't much noticeable difference in terms of the smell as there's still a faint smell when accelerating and a strong smell when entering the cabin a few hours after a drive.

I did notice some air flowing from the boot into the cabin. When the shifting assembling was taken out, it seems that there isn't much to prevent this.

 

[phattyduck]

I did notice some air flowing from the boot into the cabin.

Uhhh... the boot on the transmission to the shift lever should be sealed AND the boot from the shift lever to the body should be sealed. Is either/both ripped/torn or not sealing?

-Charlie

 

[pluton]

FYI everyone: The OEM shifter seat and bushing for these trucks are fine. Apparently they do disintegrate after a long time, but I pulled what was presumably the original one out of my 97 after 16 years and it was still in good shape...no disintegration was observed. I replaced it with an OEM unit as preventative maintenance. There's no need to use the Marlin one.

 

[I_bRAD]

FYI everyone: The OEM shifter seat and bushing for these trucks are fine. Apparently they do disintegrate after a long time, but I pulled what was presumably the original one out of my 97 after 16 years and it was still in good shape...no disintegration was observed. I replaced it with an OEM unit as preventative maintenance. There's no need to use the Marlin one.

The marlin one works well and is much cheaper though!

 

[Wedgy]

If you are getting air flow into the cabin with the windows up you might want to check the vent flapper under the drivers rear quarter bumper to make sure it is still there. All 3 runners I've wrenched on were missing the cover.
Vent behind rear bumper

 

[Kanoe]

Uhhh... the boot on the transmission to the shift lever should be sealed AND the boot from the shift lever to the body should be sealed. Is either/both ripped/torn or not sealing?

-Charlie

I think Charlie has it here. There really shouldn't be any smell coming through. We live in ours for extended periods and it is smell free in this regard. Is the top of your transmission covered in oil or something?

 

[octanejunkie]

I love this forum

Uhhh... the boot on the transmission to the shift lever should be sealed AND the boot from the shift lever to the body should be sealed. Is either/both ripped/torn or not sealing?

-Charlie

After messing around with transmission/tc fluid changes and cabin mods/swaps I, too, had the unwelcome smell of gear oil in the cab.

I googled it and found this thread. I didn't have to look further than the body rubber boot, it was out of the groove on the shift lever and "leaking" gear oil stench.

Easy fix. Thanks, team!

Yes, what Andy said above is exactly what I was thinking. I bet the shifter seats for your transmission and/or transfer case are wasted. You could have also slightly overfilled your transmission and/or transfer case that's why it is coming out past the shifter seat.

You can get yourself new shifter seats from Marlin Crawler.

Heavy Duty Seats | Marlin Crawler, Inc.

What's the factory PN as an alternative to the MC part?

 

[cl4Rk]

What's the factory PN as an alternative to the MC part?

IIRC, I don't think that shifter seat bushing has its own PN, and is only sold as part of the whole tcase shifter assembly.

EDIT: The MC part is worth it IMO. Shifting in and out of 4LO is a much better tactile experience. Used to be "crunchy" and "notchy", now it's smoooooth.

 

[octanejunkie]

IIRC, I don't think that shifter seat bushing has its own PN, and is only sold as part of the whole tcase shifter assembly.

EDIT: The MC part is worth it IMO. Shifting in and out of 4LO is a much better tactile experience. Used to be "crunchy" and "notchy", now it's smoooooth.

Does the J-case take their blue seat?

Sent from my Pixel 4 XL using Tapatalk

 

[cl4Rk]

Does the J-case take their blue seat?

Sent from my Pixel 4 XL using Tapatalk

Yep. MCTM-523 Heavy Duty Shifter Seat (Blue)

You’ll also want Toyota parts:
- Gasket 3634535050
- Oil Deflector 3610835060

EDIT: Interesting to note, my blue shifter seat bushing came with what looked like a few little imperfections. There was a small and very thin "lip" sticking up past the top along the inner diameter of the bushing. Also one or two little "burs", from what I assumed was related to the molding or milling process? (I'm not sure how these are made.) Probably didn't need to, but I shaved that lip and the burs down with a sharp little pocket knife and made sure everything felt smooth before install.

 

[octanejunkie]

Yep. MCTM-523 Heavy Duty Shifter Seat (Blue)

You’ll also want Toyota parts:
- Gasket 3634535050
- Oil Deflector 3610835060

EDIT: Interesting to note, my blue shifter seat bushing came with what looked like a few little imperfections. There was a small and very thin "lip" sticking up past the top along the inner diameter of the bushing. Also one or two little "burs", from what I assumed was related to the molding or milling process? (I'm not sure how these are made.) Probably didn't need to, but I shaved that lip and the burs down with a sharp little pocket knife and made sure everything felt smooth before install.

Nice, thanks!

If these are for the TC:
-Gasket 3634535050
- Oil Deflector 3610835060

How about for the 5-speed shifter?
I need both (and the MC white seat)

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[Bad Luck]

Nice, thanks!

If these are for the TC:
-Gasket 3634535050
- Oil Deflector 3610835060

How about for the 5-speed shifter?
I need both (and the MC white seat)

Sent from my Pixel 4 XL using Tapatalk

No additional gaskets/parts needed for the transmission seat replacement. If you look on marlin crawler's website at the seats it has a how to video for the transmission seat towards the bottom: Heavy Duty Seats | Marlin Crawler, Inc.