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Discussion Starter #1
This is a 1972 Wagoneer with a 1989 Isuzu 4BD1t > GM 4L80E > Dana 300
If you want to check it out, I have a blog/website with my build documented 72 Wagoneer - Civil Rock

It drives and runs great, but I have a massive tranny fluid leak that leaves 2-3" spots on the ground when I stop.
This is the first time I've done this type of build, but I'm not a full noob on building stuff. Just not Jeeps or 4x4.

The problem is my transfer case (D300) is filling up and over-filling with red transmission fluid from the transmission.
This setup is not supposed to share fluid Tranny to TC. Neither the AA adapter nor the D300 has a seal to keep tranny fluid from traveling from the adapter cavity into the TC.
The 4L80E on the other hand has two open holes. The high one is a vent, the low one is a return for fluid, and there's a plug that has an orifice on the 2WD models to keep the tail shaft support bearing lubricated.

My first attempt at curing this leak I plugged the two holes because tranny fluid was just pouring into the transfer case. I thought I was genius and figured my problem was solved. I also replaced the tranny rear seal just because I was there and it was old.


I know the TC is filling up with tranny fluid because the last time I attacked this, I got a seal kit for the D300 and filled it with gold colored gear oil. That's when I realized the AA kit doesn't have a seal for the input shaft/bearing and relies on gravity to keep the gear oil inside.

This pic was after I re-sealed the TC and filled it with gear oil. I was surprised that oil was coming out of the input shaft when I laid it down.
 

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Discussion Starter #2
Today when I pulled the TC off, I expected to see tranny fluid still squirting out of the back of the transmission. Either where the cap plug is for the 2WD feed is, or one of my brass plugs, or out the shaft seal. There wasn't really the waterfall that I was expecting, but I can't put a load on the transmission with the TC off and the driveline disconnected. It has to be pushing Tranny fluid out somewhere.
Here's a video of it running. I thought maybe I'd see something better with video.
 

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Discussion Starter #3
1. My next course of action is to get another output shaft seal and hope that I got a bad one, and that under load it lets fluid by.
2. If that doesn't work, I'm going to accept that fluid will pool in the adapter housing area, and try to put a seal in the front of the D300 to keep it there. Seems drastic.

This is a diagram of the AA 4L80E > D300 adapters. The one on the left is for the 2WD version. There's a lip seal in that one to keep the trans fluid out of the TC. The one on the right is the one I have and the only thing keeping fluid out of the D300 is a sealed bearing that is not doing the job of keeping tranny fluid out of the TC.
 

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Discussion Starter #4
I've spent hours researching this, and trying to find a solution, or what I'm doing wrong. I've contemplated going to a whole new setup, but I already have so much time and money into this, I'm not really excited about building all new driveshafts, finding the right adapters, making it work with my tranny controller, getting the speedo calibrated, building a new crossmember, etc. etc. etc. I'd like to have a sweet D300 with twin shifters, and make this work without having to add 2 qts of tranny fluid every time I fill the fuel tank.

Any ideas are welcome. Tell me I'm an idiot. Don't care. Tell me I'm out of my league. Probably. Better yet, tell me the easy fix.

Thanks,
Kevin in Portland, OR
 

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Discussion Starter #5
So just writing this all out over the weekend helped me get my thoughts in order. I really have a simple problem: Transmission fluid is leaking out my transmission.
It's most likely coming out 1 of 2 places. 1. my lower brass plug. 2. the shaft seal.

I pulled the lower brass plug to check it, and it wasn't very tight. I had tapped the hole pretty deep so the plug would clear the adapter. There is only enough thickness to get about 3-4 threads on a 1/8" pipe tap at 27 tpi they're pretty small and they were gnarled. So the first thing I did was carefully drill out the hole to 1/2" and put a tiny freeze plug in the hole.
(I hope y'all can see my pics that I've been posting here)


When I was doing this I had to jack up the back of the transmission to keep tranny fluid from dumping on my chest. This got me to thinking... What's the acceptable operating angle of a 4L80E?
What is my engine tilted back at?
When I was setting up my rear driveline, I had to go to school on drive line angles. The first rear axle I tried was an offset pumpkin and I had a 16* driveline angle pointing off to the passenger side. That changed a big part of my build, and I had to find a center diff...

Anyway, to get my drive line under 3*, I ended up lowering the rear of the transmission about 3 inches, and now my engine trans is tilted back around 8*. I think in running position, the output shaft and rear seal are submerged in transmission fluid. It just wasn't designed to be flooded, and that's the real source of my problems.

By the time I was done, my driveshaft angle is only 1.2*-ish, so I have some room to push the rear of the tranny up higher. Even the guys at the driveline shop said I could get away with 4-5* of driveline angle. I just have to shim my rear axle to match now. (if this cures the problem).
 

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I lost a little oring somewhere in the tc or input shaft.

Trans can sit and operate at decent slopes. The sump is only accurate when pump is moving fluid. Hence check while engine running.

I thought the Trans are full on my Trojan 300, well apparently 4 gallon shows as full, but goes dry as the charge pump is 2 ft above it, holding the t/c and another 7 gallons.... :/


And your tailpiece seal does its job.
 

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Discussion Starter #7
I'm having a hard time finding anyone that knows about running a 4L80E at more than a 3* angle.
I decided to measure everything I could and draw out my geometry and see how far up I could move the tranny mount and not kill my drive line angles.
It's so hard to do this all by trial and error. I like to have a plan. I wish I had done this before I started this build.
I'll have to make driveline angles from 2.9 to 5.5 deg. (1-3* is best), by raising my engine/tranny from 8.1* to 5.1 degrees (goal 3*).
 

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What's the concern? Fluid leak? Breaking joints? I don't understand. 3 degrees is almost non existent with concern in my book.

Maybe to check oil level? Besides that? Unless you're going beyond the ujoint design and not allowing the slip spines to pull apart, I don't know what else can go wrong?
 

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On a 4l60, there's a brass bushing that keeps the tail shaft on center to keep seal happy.

And on both my 4l60 and nv4500, there is some fluid between them and the np243


I find angles hard to believe that's what giving issues.

I mocked a th350 all goofy sideways, pointing up, and clocked a bit so I can run three huge air compressors in a truck frame I had laying around.

No leaks.
 

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Discussion Starter #10
I'm losing a qt about every 300 miles.

Thank you so much for the reply. My primary problem is lost in my lengthy 6 posts of way too much talking.

I want to move on to the rest of this build, but I'm stuck trying to cure this leak. I leave 3-4" puddles of red tranny fluid every time I park.

My engine/tranny is tilted back at 8.1* right now, and in that position the rear seal is submerged in fluid while it's parked. My latest theory is that it's just tilted back 5* too much.
 

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Any solutions from AA? You can't be the only one with a problem if they sell a lot of these kits.

Does the transmission have an external vent?

You aren't overfilling it, are you? With the 8* angle, if you fill it to the normal HOT level on the stick it will be way overfilled.
 

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Discussion Starter #12
I actually emailed AA last night. I'll see what they say.
I don't know if it has a vent. That's a good idea. I know the dipstick doesn't seal very well, so that's a vent.
I am filling it to the normal HOT level on the stick. I figured the pump pickup must be near the dipstick. I'm going to try and find a diagram of the transmission and see how far I can lower the level and not starve the pump. I hadn't even thought of that.
These are all great ideas, Thank you!

-KM
 

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Tail shaft seal in backwards? It won't wipe the shaft correctly.....

Correctly installed, everything can be filled past seals. It shouldn't matter. I wouldn't run it low on fluid.

You're asking headaches.

One is clutch slipping if the pump has no fluid to hold clutch packs together, with a t/c setup, you'll never know, assuming there's enough fluid to throw at the vanes....

You can't run autos half empty like a manual and make it 10miles home.....
 

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Discussion Starter #14
Pretty sure I have the seal in the right way. My work usually ends up being the problem when I have one. I'll check.

I found a good diagram of the Tranny and did a little photoshop magic to simulate 3* tilt (standard) and 8.1* tilt like I have.

Here's 3* tilt. The red line is the HOT/running level, and the blue is my estimated cold/off level line:


Here's with an 8.1 degree tilt:


In between those 8* level lines is the hole that I just recently plugged with a freeze plug instead of a brass npt plug. This might have been my leak. Don't know yet.
When I removed the brass plug, tranny fluid poured on my chest, and I realized the brass plug was not very well done. It could have been leaking while parked (with a high fluid level)
 

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That would make sense if the plug was seeping.

The fluid level should be checked hot, in park, IIRC. Too high sloshing in the gear train and it can foam up, worse than running it low. There are deep pans you can run to get the fluid away from the gears and drums. 2wd 4l80s usually have shallow pans, 4x4s usually deep. Might run the rear of the rig on stands to get the trans level and check the fluid level hot. Cold trans, running it should read lower than when it's hot. Engine off for a while the pan level can get higher than when it's hot due to converter drain back. The level should drop as soon as the engine is fired up.
 

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The 4L80 e-s usually have a vent tube pressed into the top of the case near the bellhousing with a hose to deflect any fluid loss away from the exhaust pipe/s. If yours does, verify it's open. Make sure it can vent any fluid away from the exhaust pipes and that it can't suck any water if you deep ford. A hot trans dipped in cold water will cause rapid contraction due to the cooling and suck water in if the vent is restricted.
 

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Discussion Starter #17
Just talked to someone at AA and he said 8* should be fine. GM sent these out with 5* from the factory.
Logic rules. He said either my shaft seal is leaking or my plug is leaking. Duh.

I think I am going to adjust my engine/tranny angle up some, and run the tranny fluid on the low end of the stick now that I can feel safe about it.

I'm going with the idea that my npt plug was the culprit and this freeze plug is going to stop the bleed.

Thanks for all the ideas. I'll report back after a couple hundred miles.

-KM
 
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