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TRANSMISSION LEAK - Please Advise
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NiftyNate



Age: 35
Joined: 08 Jun 2013
Posts: 17
Location: Hyannis, MA - - - Cape Cod

PostPosted: Sun Jun 30, 2013 10:47 am    Post subject: TRANSMISSION LEAK - Please Advise Reply with quote

My 1966 TDH-3501 has a GM '400' series Hydra-Matic transmission.
It bled out on her first run after sitting for two years. I pretty much have to feed it a quart every week or so to keep it wet. I would rather she didn't have to live like this.

Right now I'm on a shoestring budget. I can put aside a couple hundred to invest in repairs down the road, but I have a limited set of tools and not much in the way of workspace. I'll pretty much need to sit the bus in a parking lot and shove myself underneath, if it comes to that.

WHAT I KNOW:
    - The tranny works fine and has been like this for many years.
    - Dripping transmission fluid all over public roads is frowned upon.
    - It once had a "diaper" in the past to catch the drip. Currently it does not.
    - Seems to be leaking out of a hole in the bottom of the flywheel (?).
    - Flywheel hole appears to be threaded as though it's meant to be capped.
    - Side of flywheel is wide open, apparently by design. (if it's meant to have fluid in it, it's getting dirty)
    - A "cakewalk" to fix, according to Mr. Linsky
    - Outside is really dirty and I'm not sure how to clean it (or if it's even worth it).
    - There doesn't seem to be a leak on the transmission housing. Hopefully no cracks or bad seals there.


Here are some helpful pictures:


Sorry about all the grease.
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GBL Rebel
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Joined: 16 Apr 2007
Posts: 608
Location: Long Island, N.Y.

PostPosted: Sun Jun 30, 2013 10:53 am    Post subject: Reply with quote

Might be the front seal on the transmission. If so, the tranny has to come out to be fixed.
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NiftyNate



Age: 35
Joined: 08 Jun 2013
Posts: 17
Location: Hyannis, MA - - - Cape Cod

PostPosted: Sun Jun 30, 2013 11:41 am    Post subject: Reply with quote

Alright, well I'll keep that in mind. Could somebody please explain the parts I'm unfamiliar with? Is the flywheel supposed to be open like this? Is that front seal the area mated with the engine+flywheel?

I'm guessing that the tranmission is "backwards" because of the rear engine, as it leads on to the wheels from that direction. That would explain why the 'front' is towards the back of the vehicle.


I'm eager to learn all I can about the engine and its accessories. I know it's probably weird for a novice like me to buy a bus in the first place, especially at my young age. I hope that doesn't put me at odds with the experienced gentlemen on this forum. I learn best by listening to the voice of experts.
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ACFCity



Age: 68
Joined: 21 Jun 2013
Posts: 14

PostPosted: Sun Jun 30, 2013 6:19 pm    Post subject: Transmission Questions Reply with quote

The large open hole at the flywheel is most likely where the bolts that hold the torque converter to the flywheel are able to be removed before removing the transmission. The fluid leak is most likely the front pump seal leaking. The torqe converter slides over the front pump in the front of the transmission and most likely there is a groove in the torque converter snout that is worn, causing the transmission fluid to leak past the front pump seal. You will have to have it repaired by a truck or bus garage that has the equipment to remove the transmission.
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NiftyNate



Age: 35
Joined: 08 Jun 2013
Posts: 17
Location: Hyannis, MA - - - Cape Cod

PostPosted: Fri Jul 05, 2013 12:51 am    Post subject: UPDATE Reply with quote

Since the transmission was nearly bone dry and I wanted to take the bus out for her first test drive since the re-priming, I ended up going down to the local Auto Zone and picking up a gallon of transmission fluid. I made sure it was something rated for old GMs.

I filled it up (not with the whole gallon of course) and took her for a spin around the block a couple times. Didn't lose a drop. It also seemed to shift much smoother.


The stuff that was in there before was donated by the previous owner. I have reason to believe that it was a thinner, modern formula that didn't get along with the seals in this old Hydramatic. What do you folks think?
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GBL Rebel
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Joined: 16 Apr 2007
Posts: 608
Location: Long Island, N.Y.

PostPosted: Fri Jul 05, 2013 3:02 am    Post subject: Reply with quote

I think maybe the seals dried up and the new stuff might have caused them to swell.

Was it Dextron/Mercon you added?
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NiftyNate



Age: 35
Joined: 08 Jun 2013
Posts: 17
Location: Hyannis, MA - - - Cape Cod

PostPosted: Fri Jul 05, 2013 9:11 am    Post subject: Reply with quote

That's correct. "Dextron/Mercon" bled, fully synthetic, Auto Zone branded. Closest I could find to the right stuff.

Are swelling seals a solution to the problem? Would other synthetics not cause the same reaction due to formulation?
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ACFCity



Age: 68
Joined: 21 Jun 2013
Posts: 14

PostPosted: Fri Jul 05, 2013 2:57 pm    Post subject: Synthetic ATF Reply with quote

My 44+ years of experience with synthetic fluids is that they should only be used on a new or newly rebuilt unit. Synthetic fluid mixed with old fluid can cause loss of pressure to clutches and servos. Old gaskets and seals usually begin leaking soon after introducing synthetic fluid, because synthetic fluid will find the smallest places in gaskets and seals to seep and leak from. fluids that have seal softening agents sometimes will allow seals to become too soft, then a big leak occurs. I hope you don't experience any of these conditions, but be prepared if it starts leaking again to take it out and rebuild it.
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NiftyNate



Age: 35
Joined: 08 Jun 2013
Posts: 17
Location: Hyannis, MA - - - Cape Cod

PostPosted: Fri Jul 05, 2013 3:21 pm    Post subject: Reply with quote

I am hoping for good results. Days later, there are no surprise puddles beneath the bus, so I'm feeling good about it so far. I will probably take it around the block again and see if I can stress any potential problems into existence.

This is a synthetic formula, and cheap stuff to boot, but it's certainly thick and rated for GM "earlier than 1995". I may have been lucky, or it might just be waiting to happen. I'll keep you posted.
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GBL Rebel
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Joined: 16 Apr 2007
Posts: 608
Location: Long Island, N.Y.

PostPosted: Fri Jul 05, 2013 3:27 pm    Post subject: Reply with quote

Dextron has had many revisions over the years. You can put Dextron II where Dextron is required. You can not put Dextron II where Dextron IV is required.

And I am in agreement, try to stay away from synthetic fluids.
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ripta42
Site Admin


Age: 44
Joined: 15 Apr 2007
Posts: 1035
Location: Pawtucket, RI / Woburn, MA

PostPosted: Mon Jul 08, 2013 9:07 am    Post subject: Reply with quote

Dexron VI (there's no IV or V) is supposed to be backward compatible for all previous Dexron applications. Plus, GM stopped licensing the "Dexron III" name when Dexron VI came out in 2006, so anything labeled "Dexron III" is not actually verified to meet GM specifications.

AutoZone Dexron/Mercon universal should be fine for topping off. If you end up rebuilding it you should probably go with Dexron VI.
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NiftyNate



Age: 35
Joined: 08 Jun 2013
Posts: 17
Location: Hyannis, MA - - - Cape Cod

PostPosted: Sat Jul 13, 2013 7:10 am    Post subject: Reply with quote

Unfortunately, after a recent run it started leaking again.

Currently I can't afford to have it looked at. Pulling it out myself is impossible. It needs to move to my business location soon.

Any advice on rigging something up to catch the leak temporarily?
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Mr. Linsky
BusTalk's Offical Welcoming Committee



Joined: 16 Apr 2007
Posts: 5071
Location: BRENTWOOD, CA. - WOODMERE, N.Y.

PostPosted: Mon Jul 29, 2013 2:36 am    Post subject: Reply with quote

NiftyNate,


Maybe you can use the following manual advertised on eBay by 'awwco35009' as item # 161075839733 (several other pictures come with it).

Even though it may not be exactly what you have you may gain some hints and expertise from it.

http://www.ebay.com/itm/Allison-Torqmatic-transmission-service-manual-/161075839733?pt=LH_DefaultDomain_0&hash=item2580de42f5

Regards,

Mr. 'L'

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NiftyNate



Age: 35
Joined: 08 Jun 2013
Posts: 17
Location: Hyannis, MA - - - Cape Cod

PostPosted: Mon Jul 29, 2013 6:13 am    Post subject: Reply with quote

Linksy, I appreciate the advise, but isn't a Torqmatic significantly different from this Hydra-matic?
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ripta42
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Age: 44
Joined: 15 Apr 2007
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Location: Pawtucket, RI / Woburn, MA

PostPosted: Mon Jul 29, 2013 7:26 am    Post subject: Reply with quote

Yes, totally different.
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