Trans Fluid in D20 - Replace Seal or Rebuild D20?

[Ol'Blue]

So I have trans fluid in my D20 filled to the brim and leaking out (as best I can tell) from the speedo cable and a couple other places. Surprisingly not from the vent.

Read through this great thread and I may tackle this issue this summer.

http://classicbroncos.com/forums/showpost.php?p=2114749&postcount=4

The question is, should I go with just replacing the seal or should I go ahead and do the whole rebuild kit while I have it out?

It works perfectly and no issues except for the leak.....

Thanks,

 

[bteutsch]

Doesn't it take like 90 weight gear oil? Is there an advantage to using transmission Fluid? Over gear oil? Sorry I'm not answering your question, but if you have to take it out it may be worth the rebuild, beats doing it in the future.

 

[Ol'Blue]

Doesn't it take like 90 weight gear oil? Is there an advantage to using transmission Fluid? Over gear oil? Sorry I'm not answering your question, but if you have to take it out it may be worth the rebuild, beats doing it in the future.

Yes, the seal between the C4 and the D20 has failed allowing trans fluid to leak into the transfer case. I have read that its not harmful to the transfer case but causes leaks as I have had for a year now. Will probably rebuild the whole thing but will be a while before I can get to it.

 

[bteutsch]

Makes sense, I misunderstood I think.

 

[DirtDonk]

Well, it can go both ways and make sense either way. But my money is almost always on the full rebuild when doing it yourself.
If you're paying someone, sure, take the quick way out and just let them replace the seal. But if you're doing it yourself, the whole removal process is just a hassle enough to make taking the extra time to rebuild the transfer case while it's out totally worth it.

You're right to think that because it works flawlessly right now, it's probably not in need of any real work. But when I had mine out under the very same circumstances (other than possibly fewer miles and years on it than yours) I found some bearings that were already worn out.
At the very least then, replace all the seals in your t-case. But definitely inspect the main bearings very closely. Especially any in the intermediate housing if there is one with an automatic.
I forget if they're equipped the same as a manual housing, but that intermediate (probably just called an input bearing) was in the worst shape of them all. Very grunchy when you spun it by hand.

And this was all with a t-case that worked perfectly and did not leak much.

have fun either way.

Paul

 

[broncnaz]

If it shifts fine doesnt make any noises and end play of the shafts are good then Id leave the T case alone. Maybe install new output shaft seals but really they can go practically forever if taken care of.
Ford spec calls for 50 engine oil in the T case. Lots of people use 90w with no issue but I wouldnt use auto tranny fluid in one. A leak tranny seal is no real big deal but should be changed your leaks may be more due to a overfull tcase than anything else.
Yes all of todays t cases use auto tranny fluid but they are designed to use it. The gears are cut differently They also have palanetay gears and are usually chain driven. they tend to have pumps to move the oil up to lube parts up high in the case and have different methods of shifting into gear that can be affected by heavy oils.

 

[blubuckaroo]

^^^
If all else is well, I'd just change the intermediate seal.
Before I could get mine changed I figure it ran a year with twice as much ATF as the recommended SAE 50.%) That same transfer case now has over 280K miles on it and still hasn't been opened up for any other repairs.

 

[Viperwolf1]

I've been into a few D20s that had trans fluid in them for a while. There were no indications of any increased wear but they were very clean inside. I wouldn't purposely use trans fluid but it doesn't seem to be destructive in a D20. I'd just replace the seal and oil.

 

[Ol'Blue]

Thanks all for the input.

Having the bad seal; does that put pressure in the transfer case from the transmission and contribute to the leaks?

Is there any way to determine if a rebuild is in order by just taking off the cover plate or ?

 

[Broncobowsher]

Other than the leaks, the trans fluid did no damage to the D20.
Reseal it and be done.

 

[skerrybronco]

Thanks all for the input.

Having the bad seal; does that put pressure in the transfer case from the transmission and contribute to the leaks?

Is there any way to determine if a rebuild is in order by just taking off the cover plate or ?

I can't answer these questions, but had the same issue with the seal and did a twin stick conversion while having the T-case out.

 

[Ol'Blue]

I think I will go with just replacing the gasket/seals instead of rebuild.

While I have it out I should replace the output/input shaft seals as well?

Im thinking this kit:

http://www.wildhorses4x4.com/product/dana20_Seal_Gasket_Kit

Correct?

 

[blubuckaroo]

Thanks all for the input.

Having the bad seal; does that put pressure in the transfer case from the transmission and contribute to the leaks?

Is there any way to determine if a rebuild is in order by just taking off the cover plate or ?

The transfer case has a vent with a little metal cap doo-dad that is suppose to keep debris and some water out. As long as it's working, you won't have a pressure build-up.

 

[Viperwolf1]

I think I will go with just replacing the gasket/seals instead of rebuild.

While I have it out I should replace the output/input shaft seals as well?

Im thinking this kit:

http://www.wildhorses4x4.com/product/dana20_Seal_Gasket_Kit

Correct?

Definitely need to replace the input seal. Output and shift rail seals are more difficult to replace so I wouldn't if they are not leaking. Good seal/gasket kit.