My 96 Aerostar has had *slight* weepage between the T-case halves since I bought it last June. I have been monitoring the fluid level and 'leakage' (based on the spot on the garage floor) for some time now. Recently, the leak seems to be getting worse.

I've looked the case over on several occasions, and wiped it down/degreased it so that I could pinpoint the location of the leak. It is definitely coming out between the case halves. There is nothing leaking from the top of the case around to the bottom, etc.

In January, I crawled underneath and *gently* tightened the torx bolts on the lower half of the case (I didn't want to strip the bolts). I did not have a Torque wrench, but I probably got an 1/8 turn or so out of each bolt. When I tightened each bolt, I would get a slight amount of tranny fluid to come out of the seam (thereby confirming that the case seam was the source of the leak).

I am starting to get more concerned, and would like to get this fixed, so I have the following questions:

1. Why is it leaking in the first place? (I bought the van used, and do not know it's history). I suppose it's possible that it has already been opened up once, and that when they put it back together, they didn't use and RTV or sealant.

2. What else could cause the leakage? Could the t-case breather be plugged up, causing enough pressure to make it leak? If that might be the problem, where exactly is the breather, and how would I check it?

3. If I need to remove the t-case, split it then seal it back up, exactly what is involved in doing that and how long would it take?

4. Any other ideas or thoughts? I'd like to get this fixed before it turns into something major...

5. In the meantime, how critical is it to maintain a 'full' level of fluid in the t-case. If it runs a little low in between my checks, what damage is happening?

Thanks in advance,

Jeff Mason

 

Oh bummer! It sounds like someone has cracked open the case before you acquired it. There is no gasket between the halves and the Ford manual does tell you to use RTV sealant when re-assembling. There are two places where the sealant must completely surround a circular fitting to provide a complete seal. They may have skipped the upper section. The case is magnesium and the Torex headed fasteners are actually self-threading large "screws" that bite into the soft magnesium on the opposite side. Be very careful not to overtighten them as you can easily strip out the threads. The transfer case is awkward to remove and replace without a transmission jack, but it is a simple thing to rebuild if you have the desire to attempt it. When I rebuilt mine, it also leaked initially causing much worry. After a while it stopped. I think it was overfilled to begin with and was coming out the vent on the top of the case. (Almost impossible to see with the transfer case in place.) If your fluid leak path takes you to the top of the case, this might be the cause, but seeing fluid squeeze out when tightening those Torex fasteners does not sound good. Hope this helps!

 

So, dropping the t-case, draining the case, slightly cracking the case open and trying to get some RTV or "right stuff" gasket maker in there might not work? Sounds like I need to at least disassemble both halves to completely seal it back up.

Yep, I remember that part. That's why I didn't try to get too much leverage on them, I just wanted to confirm whether or not the bolts were too loose.

Is this rebuild covered by the Chilton/Haynes manual? If not, would I need to buy the FSM to do the rebuild? I just rebuilt a 5-speed Suzuki Samurai tranny, so my mechanical confidence level is at an all-time high Also, is there a rebuild kit available for the t-case???

Thanks again,

Jeff

 

Found a site at www.drivetrain.com that lists the cost for a rebuilt Tcase ($1000 ) and they also have 'rebuild kits' and 'overhaul kits'.

Hmm, certainly doesn't look too complicated.

 

It's not complicated at all. I used the same rebuild kit from drivetrain.com and a new chain. When I compared the new chain to the old there was very little wear or stretch evident. Someone had two new chain gears on eBay earlier, I think the seller was thetrannylady or trannylady, something to that effect. They never sold so she/he may still have them in stock.

 

BTT -

Leak was pretty steady and minor until this past weekend, now after a trip to Gardner, CO, the leak is worse. Had a nice splotchy film of tranny fluid on the rear hatch when I got home (about a 400 mile round trip drive). I crawled under and drained the fluid (mainly to see how much was still in there and condition). The fluid was still red, but looked pretty tired (I bought the van used 12,000 miles ago, so I don't know when it was changed last). There was also close to 2 quarts of fluid, so it wasn't too low.

I was able to find the breather assembly on the top of the case, and I think I might be able to get to it without dropping the TCase. My hope is that the breather is plugged for some reason, and when the T-case heats up, the pressure is causing the fluid to find a path of least resistance through the case halves. For you guys that have had the t-case out, do you think I could remove the breather without dropping the whole unit? It seems like there should be plenty of room to loosen it up and remove it (at least I hope so!)

I really can't think of any other reason why it would leak from there, it doesn't leak when the van isn't running. If all else fails, I may try the JB Weld route just to try to tone down the leakage until I get some other things fixed around the house (like my house roof replaced from hail storm this summer, the roof on my popup fixed from the hail damage, the transfer case in my little suzuki samurai Daily Driver that is whining a lot, and a few other odds and ends )

 

Well, my theory on the Breather assembly was a bust. This part consists of a plastic tube that is inserted in the top of the case, and a small piece of hose that attaches to that. No check valves or anything, and the tube was clear without blockage. I took the time to clean the case up really, really good (carb cleaner/brake cleaner and the power washer). Will check tonight and tomorrow to see where leaks are developing, so I can rule out any other case cracks (like GMStar2 has).

Aerocolorado or others - can you tell me the torque values for the Case Screws - I'd like to check them with the torque wrench to make sure that they just aren't loosening up on me, or weren't tightened down to spec to begin with.

Jeff

 

Jeff,
Since you named them correctly, case screws, perhaps you are already aware there are not bolts holding the halves together but rather large, self tapping style screws. I'm sure they have torque values but when you put the case halves back together, it requires very little torque to snug them down due to their large threads - they are similar to lag screws. Also, the case is made of magnesium, rather soft, and you can easily overtighten these screws and strip out the mounting hole. Because they are self threading, they cut into the magnesium and when you back them out and open the case you will find magnesium particles in the interior. The Ford manual says to expect this and not freak out thinking they are from other components.

RTV sealant is used in lieu of gasket and I just tightened the screws down in sequence until the sealant was evident around the perimeter and then repeated a final snugging using only a 3/8" drive socket wrench and Torex bit. No leakage problems around the case. I'll try to find the actual torque specs tonight and post them this evening.

(On edit: Sheesh, I didn't realize I had already posted most of this earlier, just went directly to the last thread and read the request. Sorry for the duplication.)

 

Hi Jeff:

I got the spec for your transfer case (Aerostar E-4WD):



Type: Dana TC28

Fluid: Mercon ATF, 4.4 pints

Drain and Fill Plug: 10-20 ft-lbf

Case Half Flange Screws: 20-30 ft-lbf

TC to Transmission: 25-34 ft-lbf

TC Strut Bolt: 44-59 ft-lbf

TC Strut Nut: 50-68 ft-lbf

Front Output Shaft Nut: 35-55 ft-lbf

Output Shaft Assembly Nut: 35-55 ft-lbf

Front Driveshaft to Front Axle Flange Bolts: 22-30 ft-lbf

Rear Driveshaft to Rear Axle Flange Bolts: 61-87 ft-lbf



Hope it helps and good luck

 

Thanks for both of your replies. Aerocolorado, a reminder on the case softness is always good - I am tempted to get the impact wrench out and tighten those suckers down (just kidding).

20 - 30 lbf is not a lot of torque on those bolts, but I'll get my friend's torque wrench and double check.

Just got to get through a trip to Estes Park this weekend, then find time to drop the case...