3650 Tranny Leak -- Output Shaft Seal?

1950StangJump$

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My car only has 19k miles on it, though it is boosted, has headers, a Spec Clutch, etc. It has the stock driveshaft in it. Clutch was changed less than 2k miles ago.

Today, for the first time, the Mustang left fluid on my garage floor. It was red and coming from the general middle of the car. My first thought was that it was leaking from the trans drain bolt, since I had changed the fluid a few months back.

Nope. It is coming from that area where the driveshaft meets the transmission - I can clearly see red fluid collecting there. I've never changed that seal myself on any car. Is it something I can tackle on jack stands, or should I pay someone?

I don't mind paying, it's just a PITA to ensure they use the right fluid, use only 3.20 qts, yada yada yada. On the flip side, I don't want the stress of fucking it up.

And is it wise or cost effective to have the tail bushing replaced at the time, just in case?
 
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BULLITT1

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the seal might have been nicked when doing the clutch

not a difficult task, but you may want to make sure you have a torque wrench for tightening driveshaft/flangebolts down, mainly a screwdriver or seal remover to remove the seal. you do not need to drain the transmission, raise the rear axle side and not much fluid should come out.

If it is a low mileage vehicle I wouldn't necessarily worry about replacing tail shaft bushings, just check
it for slop(abnormal play)

make sure to mark the drive shaft/flanges on both ends before removing, so you don't have to worry about vibrations later.
 

1950StangJump$

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Bullitt, thanks.

Isn't there an o-ring that needs changed at the same time, as well as some song-and-dance about installing the washer/nut first, pulling it off, then installing the o-ring before reinstalling the washer/nut?
 

1950StangJump$

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And can anyone confirm part numbers for this? I'm seeing "output shaft seal," "extension housing seal," and "tailshaft seal." Can't tell if its all the same.
 

Anti

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I just requested a tailshaft seal when i bought mine and it is a seal with a spring inside it the whole way around.
 

1950StangJump$

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I just requested a tailshaft seal when i bought mine and it is a seal with a spring inside it the whole way around.

Thanks. The Haynes manual also mentions using a new o-ring and plastic retainer. Is that accurate?
 

rocky61201

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You will need an impact wrench to get the rear flange on/off. Or you will need to something to attach to the flange to hold it steady while you break the nut free. I fabricated a 3 foot piece of aluminum stock and drilled two holes in it and bolted it to the flange. Without an impact wrench it will probably be a two person job. You will also need 2 or 3 jaw puller to get the flange off. Once the flange is off you can pull out the old seal and replace it.

After that when putting the flange back on leave the rubber washer/seal that goes between the flange and the washer and nut OFF. Once the flange is pressed all the way on, spin the nut back off then put the rubber washers/seal back underneath the washer on and torque the flange nut to spec.

I'm not aware of a new o-ring or plastic retainer. Here is a copy of the 3650 tear down manual. Getting the flange off is step 3 and 4. Doesn't mention anything about an oring or plastic retainer. I've taken mine off a few times and the manual is correct. FYI - breaking the nut free is a mo-fo without an impact wrench.
 

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  • TR3650 Disasembly.pdf
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1950StangJump$

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Thanks! I *think* what Haynes is calling an “O-ring” is that rubber seal and the “plastic retainer” is the washer under the nut. Is that washer metal or plastic?

Dealer quoted me $13.50 for the rubber seal and washer .... but it is special order and I’m not sure it is necessary to replace.
 

rocky61201

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The washer is metal. The rubber washer/seal underneath it is about 1/8 inch thick. Not even close to being an o-ring.

1 more thing I thought of. The flange nut is big, I forget the size, 22mm maybe or larger. Some impact sockets are too big to fit into the recess of the flange because of the outer diameter of the socket is thick. You might need a regular or (thin wall) socket. I had to make a run to lowes and buy a socket that would fit because my impact socket set wouldn't fit.
 

1950StangJump$

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Thanks. It wouldn’t be the first time that Haynes was wrong. Would you recommend buying the rubber seal?

I have an impact wrench, so should be good there.
 

rocky61201

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I buy everything I need from this guy. http://www.pro-forceperformance.com/ The rubber seal can't cost more than a couple bucks. I re-used mine without issue because it wasn't tore up.

He will sell you exactly what you need and maybe save you money because sometimes you have to buy parts in a kit with extra stuff you won't use.

Here is the assembly instructions. See step 57, 58, and 59. It talks about putting the flange back on properly, but no pictures for that part.
 

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rocky61201

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That’s the black clip the throw out bearing line goes thru in the bell housing. Nothing to do with the rear seal.
 

1950StangJump$

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Well, I guess that explains why Haynes had a "plastic retainer" listed . . . I bet they took the instructions straight from the FSM and didn't realize that step #60 wasn't related.

Rocky, I really appreciate the help. I bought the output shaft seal and went ahead and ordered a new rubber washer just in case. I didn't order the metal washer, as I can't see why the old one isn't reusable.

I considered getting the "shift shaft seal" also in case needed -- but I can't find instructions anywhere on that one, and I'm not 100% sure it is serviceable without removing the trans.
 

Anti

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Everything Rocky said so far is legit, however the nut on the shaft is closer to 28mm iirc. Either way, be prepared to not have it. LOL I used an impact also without issue. As for shift seal, I dunno, I didn't change mine as it was not showing any signs of leaking and I had 95k miles on the car. I only did the tail shaft seal because I saw a light ring of oil in the trans tunnel just right by it and was dropping the tranny for LT headers anyway.

Also, I know I was a bad boy, but I used a hammer on the drive shaft flange. I spun it as I hit very moderately to not cause any bending and made sure it was in one direction which was straight. I take no responsibility if you mess yours up though. lol I hammered it back on when done. I've had zero issues for about 10k miles and no increase in NVH.
 

1950StangJump$

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Thanks. Autozone has gear pullers and seal pullers as part of their tool-loan program, so I'll probably go that route.

I have a ton of large sockets, so I'm confident one will be the right size. However, I am less confident that I won't suffer from the same issue Rocky mentioned . . . that the socket wall won't be too thick for the space I need to put it.
 

Chrisjan84

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Thanks for the help. I had to use a 1-1/4 socket, could not get any metric impacts to fit. 28 29 30 32mm( too big for hole) did not fit. my o-ring/seal was destroyed.. had to order one from Ford 16$ . I also had to use a little gear puller to get that old seal out of there.
Part number 4r3z-7e397-a
Ford part website: https://parts.ford.com/shop/en/us/seal-6296849-1
7693

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0831191418a.jpg
 

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