Overfilled Transmission Surprise

[scottcb]

I went to check my transmission fluid level. When I undid the drain plug, too my surprise tons of oil came out. Am I safe to believe it’s been overfilled? Isn’t it just suppose to be to the edge of the fill plug without leaking out? I wonder if it was filled from the top as I’ve read that can be done.

 

[Dynosoar]

Check your transfer case. I bet it is low. When the t case gets a clogged breather it will "pump" or force oil via pressure from the t case uphill into the trans thus overfilling it. Clean out the breather on top of the t case and your problem is solved.

Some guys put a drain back tube from the trans to the tcase but it is just a band aid solution.
Also some will say your seal is bad. However, that would only be if the situation was opposite (low trans oil - tcase overfilled)

Dyno

 

[scottcb]

Check your transfer case. I bet it is low. When the t case gets a clogged breather it will "pump" or force oil via pressure from the t case uphill into the trans thus overfilling it. Clean out the breather on top of the t case and your problem is solved.

Some guys put a drain back tube from the trans to the tcase but it is just a band aid solution.
Also some will say your seal is bad. However, that would only be if the situation was opposite (low trans oil - tcase overfilled)

Dyno

You were right - low T case levels. I didn’t spend too much time looking for the breather valve but found it by touch. It kind of spun around, very loose feeling. So if it’s clogged how do I unglog, clean or remove it? I think I’ll drain both the tranny and t case, refill and watch what happens.

 

[roadstr6]

It’s not the vent. It’s the seal between trans and transfer case. When the seal goes bad this is what happens. The fix is to rebuild the transfer case. The long term work-around is to connect an equalizer hose between the fill ports on trans and transfer case.

 

[Willard]

It’s not the vent. It’s the seal between trans and transfer case. When the seal goes bad this is what happens. The fix is to rebuild the transfer case. The long term work-around is to connect an equalizer hose between the fill ports on trans and transfer case.

Long term = 10 years on my rig and still going strong.

Contact @shipmag he sell a very good quality hose I took my old Man-A-Fre hose off and installed his today. it is very nice and fits real well, no need for adapters or anything and uses the standard size wrench to take it off.

If you have a 60 with the extension between the trans and transfer case (I think late 85 or late 86's had these) you want the 17" hose. otherwise the smaller hose fits fine.

Only changed mine as I needed to change the oil anyways. When I replace my trans i will fix the issue and probably still run the hose.

 

[shipmag]

If your interested in the transferhose send me a pm and Ill send you the paypal info and everthing you need to know. The braidedstainless steel hose with the teflon liner keep the heat from the tail pipe from shortening the life of the hose. But still that tailpipe is hot. Even with this hose you still cant have it resting against the tail pipe.

 

[scottcb]

Drained and refilled the transmission and t-case today and was glad that plenty oil came out of the transfer case. I installed the new Transferhose I got from @shipmag. It was super easy and very nice quality; and it's nice knowing I have a semi-permanent fix in place. You can see toward the back on the transmission I also replaced my drain plugs with the 10mm allen wrench style newer toyota plugs. So much better. In fact I bought enough to replace my diff plugs as well. Here is the toyota part number: 90341-18021. I bought a couple through the local dealer and then paid at least 1/2 even with shipping from toyotapartsdeal.com. They are magnetic and I know I don't need those for the fill plugs, but they fit and I didn't have to go hunt down another part number.

 

[SteveH]

I disagree that it's 'not the vent' - I have vented a number of LC transfer cases and axles to stop leaks. A weak old seal between the trans and xfer makes this worse, but the pressure in the xfer case is required to push the oil into the transmission, which sits higher in the truck. The transmission is naturally vented at the shifter, but the xfer case is not, so a vent is critical to oil staying in the xfer case where it belongs.

To fix the clogged vent and pressure situation, I pry off the steel cap of the xfer vent, and remove the spring and rubber disk, and slide a piece of 3/8" dia. fuel line on the 'stub' (what's left after you pry off the floating cap) and secure it with a hose clamp. Works like a champ. Hard to do under the truck, but not impossible.

 

[g-man]

I feel dumb. When I rebuilt my transfer case I don't remember seeing the vent. And since I washed my case in parts cleaner did I ruin the rubber disk? I don't remember seeing any mention of this part in the FSM rebuild process.

Is this it?

 

[OSS]

That's it and it's not mentioned anywhere.
You can tell if the valve is working correctly if it prevents air from getting sucked back into the case.

When case is cold, open the TFR fill plug to equalize any air pressure. Then screw it back in. Then drive it until it gets hot. Then the next morning slowly crack open the fill plug. You should hear air getting sucked in if your seals are tight. If the seals aren't tight, even if the breather valve works, that test won't work.