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How to seal a Dana 20, Step-by-step (and other useful Dana 20 links)

Bronchole

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How to seal a Dana 20, Step-by-step

In the following posts I have compiled a comprehensive list of the points where the average Dana 20 manages to sprout leaks and how to fix them. This list and their fixes came from a collaboration of several people and will be a live document that will continue to be updated as people give their input. For the convenience of the reader I have provided links in this first post to the individual sections that cover the particular problem area.

Please, as you use this thread if you notice typos or have an idea on how to improve it post up a reply to this thread. I will almost certainly incorporate what you suggest, no matter how long it has been since it was last updated.


Follow the links below to the particular leak point you are chasing:
- Hardware (see post #2)
- Trans to T-case adaptor housing (see post #3)
- Trans output shaft to Adaptor seal (see post #4)
- Rear output shaft to rear output yoke (under the nut) (see post #5)
- Rear output yoke to rear output housing seal (see post #6)
- Speedometer connection to rear output housing (see post #7)
- Shift rail seals, shift rail bolts, rear shift rail caps (see post #8)
- Rear output housing to T-case housing (see post #9)
- Idler shaft to T-case housing (see post #10)
- Front output shaft to front output yoke (under the nut) (see post #11)
- Front output yoke to front output housing seal (see post #12)
- Front output housing to T-case housing (see post #13)
- Front bearing preload cover to T-case (see post #14)
- Drain plug (see post #15)
- Inspection cover (see post #16)

Useful links:
Here are some other useful links when working on your Dana 20:
- Dana 20T rebuild small.pdf
- Dana 20J manual.pdf
- Novac: Rebuilding the Jeep / IH Dana 20 Transfer Case
- A good post on removal and installation of a Dana 20 in a Bronco
- xcntrk write up on modifying the shift rails
- Bronchole's explanation of how ground shift shafts work, and don't work
- Post#32 in this thread has some great pictures of shift rail modifications
- A good thread on twin sticking with shift rail modifications
- xcntrk's explanation of a fool proof interlock scheme with a great video.
- Discussion on preloading rear output shaft bearings (a possible solution to popping out of gear)
-


To any and all using this article, please let us know how it worked for you. Even if you don't have any further input it will help to let others know that the article works and keep this from being too old to show up at the top of searches.

Dan AKA Bronchole


PS,
I would like to thank Lilthom, Viperwolf1, 70_Steve & BwoncoHowie (in order of their posts) for their help in the initial composing of this tech thread. With their help, part numbers, links and suggested procedures I was able to put this together with minimal effort. Thank you very much guys.

Additional editing provided by: Andy canary28,

Added info from Viperwolf1 from post#24
Added tags from canary28 from post#55
Added "useful links" section as a thought after reading Canary28's post#61

Tags (terms people can use to find this thread): X T x-case t-case transfer case transfer-case leak leaks seap seaping seaps seep seeps seeping rebuild rebuilt rebuilding sealing seal reseal re-seal gasket seals gaskets dana 20 drip dripping adaptor housing intermediate
 
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Bronchole

Bronchole

Bronco Guru
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Messages
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Loc.
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Hardware:

Of all the hardware in the Dana 20 all but a few are installed in thru holes. The hardware that is installed in the blind holes are: speedo retainer bolt, shaft retainer bolt, and the 6 center bottom cover bolts. They do not require any additional attention for leak prevention. The rest of the hardware should be sealed with some type of thread sealant.

Cleaning before sealing:
Before the thread sealant is applied the hardware and the hole to be threaded in should be cleaned. This can be done with (cleaner name here) to remove oils and debris that may interfere with the sealant. Cleaning the hardware itself is easy enough. Place the hardware in a rag and douse it with the cleaner. Rub the hardware off with the rag. If that doesn't do the job good enough maybe use a brush to get down in to the threads and clean it a bit better. The threaded hole is a bit more difficult. (help me out here guys)

Teflon paste thread sealant:
I believe that this is the preferred method to seal the hardware. Typically a small amount of this is applied to the bolt thread and the female thread. About enough to cover 3-5 full threads on each should be plenty enough. As you screw in the bolt the paste redistributed itself along the thread form in to a thin film. The excess balls up so it's not a real good idea to go crazy with how much you apply.

#2 Permatex as a thread sealant:
70_Steve says using this as a sealant has the added benefit of tending to stay softer longer.

High Tack spray as a thread sealant:
70_Steve has also used High Tack spray as a thread sealant on intake manifold and water pump bolts. No reason why that won't work on the Dana 20.


Thread sealing tape:
I think that in this area this is an acceptable method to seal the hardware although some are opposed to using thread sealing tape anywhere in an automotive application. This is primarily because small shards of the tape can be introduced in to the area being sealed which could cause BIG PROBLEMS with internal components and oil passages. I do agree that this could be a problem in things like automatic transmissions and engine oil passages and lifters. I do agree that the Teflon paste thread sealant is better, but in this case I feel that the thread tape is acceptable. That said there are many manufactures of thread tape. Here is an example of thread tape: EXAMPLE OF TAPE The main variable here is the width of the Teflon tape. For the size of hardware we are looking at you should use 3/8"-1/2" wide tape. You need to wrap the tape firmly on to the bolt using the same rotation of the hardware as you use to screw the bolt in to the hole. This keeps the tape on the bolt as it is being installed. You want 3-1/4 to 3-3/4 wraps of the thread tape. Be advised that there is a yellow variety of thread tape that is rated for use with natural gas. Although I think this may work for sealing our bolts, I am not sure of any drawbacks to it so you are probably better off going with the white stuff.

Blue/Red threadlocker:
I have not read any posts that I can remember that recommend the use of Locktite thread locker as a sealant for these bolts. I can say from experience that you can get a seal using threadlocker, but for threadlocker to work well you really need to get the bolt and hole clean.

Added info from Viperwolf1 from post#24
Added info and recommendations from 70_Steve from post #26, 35
 
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Bronchole

Bronchole

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Trans to T-case adaptor housing:

First thing to make sure of is if you are running a C4, make sure the fluid you think is leaking is not from the vent on the top of the adaptor housing. This happens if the C4 is overfilled. As the fluid heats up it expands and pukes out the vent and dribbles down along the front adaptor housing seal making it look like that is where it is leaking.

There is a gasket at both ends of this housing. Here is a link to each gasket:

Intermediate House to Dana 20 Gasket 66-77

Intermediate Housing Gasket C-4

I beleive that the intermediate housing to manual transmission gasket is the same as the C4 gasket, but since I have never owned or worked on a manual trasmission version of this I am not sure.

I have seen a few posts suggesting to use a thin bead of Silicone in place of te gaskets. I have not ever needed to do this and I have not had any problems with leaks at this point.

On the C4 version of this adaptor there is an O-ring (included with the interal seal here) that also seals the adaptod housing to the case of the C4.

Here are a couple threads I found some info in:

http://classicbroncos.com/forums/showthread.php?t=202745&highlight=transfer+case+gasket

http://classicbroncos.com/forums/showthread.php?t=107839&highlight=adaptor+housing+gasket
 
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Bronchole

Bronchole

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Loc.
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Trans output shaft to Adaptor seal:

If you have found trans fluid in your T-case or a significantly overfilled t-case you are on the correct thred. First off if there is automatic trans fluid in your t-case you may be lucky and the PO or lube technician may have used auto trans fluid instead of gear oil. Verify if that is your problem first.

If this seal is leaking, bummer! you need to replace it. The adaptor only has a single wall in the middle of it, not 2 walls and a dead space.
The single wall has a double lip seal that keeps each fluid in the correct side of the wall when working right.

These double lip seals are sometimes hard to find because this part is no longer serviced by Ford. There are many mechanics that have installed the federal mogul version, which is really not made for this application, and they eventually leak if not immediately. The correct seal needed is a double lipped metal clad seal that has garter springs at both ends, and the Federal Mogul version has only 1 garter spring.

The best version to date (USA made) that is still available is the Chicago Rawhide brand. Here are some part numbers for cross-reference

Axiom, who is a Chicago Rawhide distributor. #26074TA
Chicago Rawhide. #18676
Ford. #C6TZ-7B215-C (Discontinued/Obsolete)

If you can find a transmission shop that buys from ATC and ask them to order it.

When you install the new seal, coat the pocket between the 2 lips with bearing grease. My favorite stuff for this is the Sta-Lube Disc moly wheel bearing grease with graphite in it. I think it comes in a bright orange can. This will help the seal to break-in nice and easy and help it to have a long life.

Here is also a link for the seal: http://broncograveyard.com/bronco/i-11113-dana-20-bearing-retainer-seal-o-ring.html

Most of this writeup came from Broncobowshers post #8 and BwoncoHowies post #9 of this thread.

In post #24 Viperwolf supplied the part number for the seal that is internal of this housing: Input shaft seal (double lip)-CR #517383, SKF #18676, Timken #473179
 
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Bronchole

Bronchole

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Rear output shaft to rear output yoke (under the nut):

This is treated very simmilarrly to the same area on the front output yoke. This leak usually only occurs on the lower front shaft. Gravity and the (normally) static shaft allow this leak to happen on the fron shaft. However, Viperwolf always puts an o-ring under the rear yoke nut just in case. In a nose-up situation with minimal shaft speed the leak can occur on the rear shaft.


Info provided by Viperwolf1 in post 45
 
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Bronchole

Bronchole

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Rear output yoke to rear output housing seal:


Here are several potential causes for a leak at this point:

- The nut that mounts the yoke to the shaft may have come loose. This will allow the shaft to deflect from where it is meant to be and allow oil to leak due to the yoke not going thru the center of the seal. If it is loose, tighten it up and see if it stops the leak. The nut is supposed to be torqued to something like 150 ft/lb (friggin tight).

- The preload of the bearings for the shaft could have somhow come out of proper adjustment. This would allow oil to leak just like the nut being loose. If this is your problem...... either it wasn't set correctly to begin with or the bearings have worn significantly. It is also possible that the bearings setteled in after the preload was initially set. Pretty much any way you look at it, you will need to tear in to it to discover what is going on.

- The seal could have gone bad. That's a simple fix. In post #24 Viperwolf supplied the part number for this seal: Timken #450185. Broncnaz also listed a couple more versions: SKF 15450 and National 470682 in post #2 of this thread

- Yoke seal surface is dammaged. This can occure from the seal wearing on the yoke seal surface. When this happens the seal can't work properly to hold in the oil. You can sometimes use a different manufacturer oil seal that engauges the yoke at a undammaged point. You can also not fully press in the seal for the same effect. Another solution is to replace the yoke. You can also purchse what is called a Speedi-sleeve (part number provided by Viperwolf in post #39: SKF99155). This presses on to the original seal surface giving a smooth, hard and slightly larger diameter surface for the seal to work with.
 
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Bronchole

Bronchole

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Speedometer connection to rear output housing:

I have never really seen any posts accusing this area of spewing fluid. Let me know if anyone has any experience with any sealing problems here.
 
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Bronchole

Bronchole

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Shift rail seals, shift rail bolts, rear shift rail caps:

Pretty easy to diagnose this. If it leaks here you need new seals!

It is also possible that the shift rail caps are loose or missing. They should be a press fit in to the case. The use of a small ammount of sealant can be used whil tapping in the caps to help seal them to the case.

In post #24 Viperwolf supplied the part number for the seals that are used in this area: Shift rail seals = CR #6204 or Timken #471466
 
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Bronchole

Bronchole

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Rear output housing to T-case housing:

If you have a leak here it is probably due to the hardware coming loose and perhapse damaging the gasket. Try tightening the hardware and see if that fixes it. If not you will need to replace the gasket. I was not able to find a picture of this gasket all by iself, but it is the one pictured at the lower right corner of this picture. Viperwolf1 suggests using a thin film of silicone to coat the gasket to assure a good seal.
 
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Bronchole

Bronchole

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Idler shaft to T-case housing:

Use Brakclean to clean the shaft, the holes in the case that the shaft installs in and the area around the holes so that they are free of burs, oils and old sealant. Drive the shaft part way in until there is still 1/4" left to drive in. Apply a small amount of thread sealer around the retaining tab end of the shaft and on the bore of the case on the other end. Now drive it in so that the retaining tab surface on the shaft is flush with the matching surface of the case. Use compressed air and a rag soaked in Brakclean to clean the remaining sealant that was squoze out as the shaft was driven in to its final depth. Now smear a thin film of Permatex black silicone completly over the end of the shaft working the sealant in to the low spots. Let it fully dry.


Added info from BwoncoHowie from post#29
 
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Bronchole

Bronchole

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Front output shaft to front output yoke:

Apparently the fluids will seep out along the splines of the yoke. Cleaning the surfaces and applying a thin film of sealant on the face of the washer behind the nut can stop this leak point.

Viperwolf1 has also found what I beleive to be the correct size o-ring to install in this location if you want to try it the OEM way: Yoke o-ring-1-1/4"OD x 1-1/8"ID x 1/16". Danco happened to be the brand at the hardware store and it is their #29

From what I have found the dimensions that Viperwolf1 supplied is for a AS568A Dash No. 024 o-ring.

Thanks for the input from Lilthom in post #23 & Viperwolf in post #24
 
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Bronchole

Bronchole

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Joined
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Loc.
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Front output yoke to front output housing seal:

Here are several potential causes for a leak at this point:

- The nut that mounts the yoke to the shaft may have come loose. This will allow the shaft to deflect from where it is meant to be and allow oil to leak due to the yoke not going thru the center of the seal. If it is loose, tighten it up and see if it stops the leak. The nut is supposed to be torqued to something like 150 ft/lb (friggin tight).

- The preload of the bearings for the shaft could have somhow come out of proper adjustment. This would allow oil to leak just like the nut being loose. If this is your problem...... either it wasn't set correctly to begin with or the bearings have worn significantly. It is also possible that the bearings setteled in after the preload was initially set. Pretty much any way you look at it, you will need to tear in to it to discover what is going on.

- The seal could have gone bad. That's a simple fix.
In post #24 Viperwolf supplied the part number for this seal: Timken #450185. Broncnaz also listed a couple more versions: SKF 15450 and National 470682 in post #2 of this thread

- Yoke seal surface is dammaged. This can occure from the seal wearing on the yoke seal surface. When this happens the seal can't work properly to hold in the oil. You can sometimes use a different manufacturer oil seal that engauges the yoke at a undammaged point. You can also not fully press in the seal for the same effect. Another solution is to replace the yoke. You can also purchse what is called a Speedi-sleeve (part number provided by Viperwolf in post #39: SKF99155). This presses on to the original seal surface giving a smooth, hard and slightly larger diameter surface for the seal to work with.
 
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Bronchole

Bronchole

Bronco Guru
Joined
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Messages
1,611
Loc.
Chatsworth, Ca (LA)
Front output housing to T-case housing:

If you have a leak here it is probably due to the hardware coming loose and perhapse damaging the gasket. Try tightening the hardware and see if that fixes it. If not you will need to replace the gasket. I was not able to find a picture of this gasket all by iself, but it is the one pictured at the middle right side of this picture. Use a thin film of silicone to coat the gasket to assure a good seal.

I have also read that several people have accidentally broke this housing from improper installation or even just droping it on the floor. Be careful with it. If this housing is cracked it is likely the reason for your leak. It will need to be replaced. Some of the Bronco vendors sell these housings by themselves.
 
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Bronchole

Bronchole

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Front bearing preload cover to T-case:

The cover for this can sometimes get dammaged from a previous inproper installation (don't ask how I know this). Inspect the cover for burs and flatness on the mating surface. If the cover is not flat, it needs to be. Try lapping it flat on a precision flat surface using some sand paper. I know not all of you have access to a precision flat surface, I don't know what to tell you. Maybe see if you can find a cover part in someones parts pile.

Clean all the shims, the cover and the mating surface of the case so that they are free of burs, oil and old sealant.

Use permatex No#3 Form-A-Gasket aviation gasket sealer. Brush a thin film on both sides of each shim before installing the cover. Be careful to not let any dirt, particles, or rag-lint etc. contaminate the shim surfaces. Sandwich the thinner shims in between the thicker ones to protect them from damage during assembly and disassembly. The excess sealer will squash out when the bolts are tightened. Brakleen(r) sprayed on a rag will easily clean-up the excess. The No#3 Form-A-Gasket aviation gasket sealer will allow the taper bearing preload dry adjustment to remain constant during final assembly, while filling in small voids that can be the reason for leaks in this area where an actual gasket is not used.

A few other approaches:

Addicted sugests: "Copper Spray adhesive works best. Spray each shim individually on a piece of clean cardboard and then transfer them carefully to the cover using the bolts to align them. Once they are all transfered to the cover you can spay the back of the last one and then bolt the cover to the case."

And from that same thread Nelson says: "Loktite 515 on mine to seal the shim pack. It does not add any clearance to the shims and will seal them. As for RTV I have never used it to seal shims as it does add some clearance to the shim pack.
Good Luck"


Added info from BwoncoHowie from post#28
 
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Bronchole

Bronchole

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Drain plug:

From what I have read, if you have a leak here and it's not because the plug is not tightened you need to do some looking for cracks. I do not normally use thread sealant here and I do not think I have had any leaks here. That said I am sure we will get some replys saying otherwise and I will incorporate their input as it comes in. I suppose that you could use thread sealant here as described in the hardware area on post #2.

If you should find a crack here then you don't have a leak problem, you have a repair/replace problem and you need to research that elswhere. If someone finds links to repairing a cracked Dana 20 case then post them up and I will add them here. Personally, if you wheel to the point that you cracked the case then I would think it a good idea to replace the case, you friggin hammer!
 
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Bronchole

Bronchole

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Inspection cover:

Clean the cover and mating surface of the Dana 20 case of all old gasket and old sealant. Inspect the cover and the mating surface of the Dana 20 case for burs. Remove burs with a fine flat file.

On the cover, if the surface is not flat or happens to be distorted in any way, straighten it as best you can with peening tools or a hammer and machined flat surface.

If the cover is not bent or distorted, you can use the gasket that came in the kit without too much trouble. Clean all oils off of the surfaces to be sealed. When using a gasket here, It has been sugested to use Gasgacinch as a sealer with the gasket.

If the cover was bent or not perfectly flat use no gasket. Instead use permatex Ultra Black silicone. Clean all oils off of the surfaces to be sealed. Apply an approximatly 1/8" wide bead, centered between and circling the bolt holes. Let the sealer stand about 5 min before positioning the cover and tightening the bolts to 12-14 ft-lbs. Be sure to use the sealing tips in the hardware section post #2.

Howie also recomends the use of this tool or this tool to use when applying thick tube type stuff.

Installation tip: To assist in installing the cover straigh on you can make 2 threaded guide pins by hacksawing the heads off of a couple of 5/16-18 shouldered bolts that were approx 2.75" long. screw the pins into the case at opposite ends then position the cover and start all the bolts, remove the 2 guide pins, replace the last two bolts before tightening all the cover fasteners. Alternatly you can use 2 long bolts in place of the guide pins. just run them thru the cover and start them in to the case holes. Then install the rest of the hardware....

Added info from BwoncoHowie from post#29, #38
 
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