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Author Topic: 700r4 leak  (Read 4488 times)

Offline fix_it

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700r4 leak
« on: August 12, 2007, 11:41:13 AM »
   Several months ago, I posted about a leak on my truck.  I have a 1985 GMC Suburban 1/2 ton 4x4.  It has the 700r4 trans. I rebuilt the trans about 2 years ago because I burnt it up with a TV cable problem.  Not real bad, but it was slipping some under load.  Anyway, the rebuild went fine.  No problems at all.  Then about 6 or 9 months ago he front seal started leaking.  I posted here about that and the conclusion was that the pump bushing could be worn out (as I neglected to change it) and the front sealand bushing should be relplaced.  Also someone stated that the forward clutches could be burnt causing a leak.

   I did not have the time to fix it, so I parked it for a while.  I finally got a chance to work on it his weekend.  I replaced the pump bushing and front seal.  The seal didn't look too good, and the bushing was bad.  The converter showed only minor wear, nothing bad.  I used a new gasket and seal for the pump, of course.  Now I still have a leak. At first, I though it was a cooler line, but that was not it.  I cleaned the area with brake cleaner and let the truck sit and idle.  The fluid is dripping off the starter and running down the flywheel cover and onto the right front corner of the trans pan.  It is not dripping forn the drain hole on the flywheel cover anymore, so I don't think it is the front seal.  The trans was only slighly warm and I never put it in gear, just watched as it stated to drip, so I can't imagine that the forward clutches would have anything to do with this.  It is not coming from the TV cable, servo cover, or dipstick tube.  I guess I will have to pull the flywheel coer off later tonight or tomorrow, but I cant think of where it could possibly leak.  Any ideas?

  Oh, by the way, when I took the pan off there was only minimal reside in the pan.  No clutch reside.

Offline Transman

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Re: 700r4 leak
« Reply #1 on: August 12, 2007, 11:25:55 PM »
Have you checked the cooler lines? They can leak onto the starter, there is a clamp that wears through the lines. The only other area in that zone that can leak is the front seal or pump bolts/o-ring. Post back, Hopefully the forward clutches aren't the cause as you suspect. Transman
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Offline stu

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Re: 700r4 leak
« Reply #2 on: August 13, 2007, 09:15:46 AM »
Did you repace the "O" ring on the pump?
I am in a state of confusion.

Offline fix_it

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Re: 700r4 leak
« Reply #3 on: August 13, 2007, 03:36:17 PM »
Yes, I replaced the o-ring, the gasket under the pump, the converter bushing, and the front seal.  I am going out in a minute to pull the flywheel cover off.  Right now I know it is apparently coming from under the flywheel cover, although it doesn't seem to be dripping from the weep hole.  I'll post an update in a little while.

Offline fix_it

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Re: 700r4 leak
« Reply #4 on: August 13, 2007, 04:47:43 PM »
Ok, mystery solved.  I found a pinhole in the weld on one of the mounting lugs of the converter.  I guess I will have to pull the trans again.  What a pain.  Advance auto has one for $118, but I wonder about their quality.  Any brands to avoid?  I have covered the pinhole with RTV adhesive sealant.  I know that is not a permanent repair, but it may hold till I can do it right.  I have never see a converter with a hole in it before.  What's up with that?

Offline Transman

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Re: 700r4 leak
« Reply #5 on: August 13, 2007, 10:39:43 PM »
I would recommend Part-Rite, American owned and the converters are built on premises. They ship everywhere. (800)225-0020 ask for Bill
To answer the question, welds can and do break. You might wish to check the bolts very carefully. They are special length and can be overtightened to the point they break the welds or junk may be in the hole itself where the bolt would push the weld out. The TQ is under fairly high pressure and the odds are the RTV will not hold long enough to get around the block. Good Luck, Transman
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Offline fix_it

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Re: 700r4 leak
« Reply #6 on: August 13, 2007, 10:45:56 PM »
Guess what, that RTV popped in about 30 sec.  I knew it would, but I wasn't out anything to try it.  Oh well.

I think I read in another post that the rod from the bellhousing to the transfer case should be removed.  Is that correct, and if so why?

Offline Transman

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Re: 700r4 leak
« Reply #7 on: August 13, 2007, 10:49:41 PM »
They are correct and it is a "Factory" authorized repair. The rod causes additional twisting torque and may cause the trans to crack and it also causes internal leaks (reverse mainly) from twisting the trans case under loads. The rod should be removed and used for persuading your neighbor not to mow his lawn so early on a Saturday morning. Transman
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Offline fix_it

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Re: 700r4 leak
« Reply #8 on: August 18, 2007, 10:12:40 PM »
It's me again.  I replaced the converter.  Now that leak is solved.  New problem though.  There is a bad leak at the TV cable where it mates with the case.  What kind of seal goes there?  I didn't unhook it or anything, but it has decided to leak.  Go figure.  I know the old th350 used a rubber seal, but I can't remember if this one does or not.

Offline Transman

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Re: 700r4 leak
« Reply #9 on: August 18, 2007, 10:56:09 PM »
How did you remove the trans enough to replace the TQ and not undo the TV cable? The odds are you broke the plastic housing. There is an umbrella seal that fits easily into the case then the TV cable housing slides neatly into it. Cheap seal but it works well, the cable is a bit more but still very reasonable. Don't forget to make the adjustment properly when complete or you will replace the trans next, this adjustment is critical and very important to line pressure. Transaman
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Offline fix_it

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Re: 700r4 leak
« Reply #10 on: August 19, 2007, 06:12:32 AM »
I'm sorry, I misspoke.  I did unhook it from the engine, just not at the trans, where it is now leaking.  So, it has an umbrella seal?  That is what I thought.  I will check into that.  Thanks for the warning about the TV adjustment and replacing the trans.  I have already been there.  You see, I installed an Edelbrock carb, and the linkage is not compatible.  Close enough that it seems to work, but not close enough.  After much research, I discovered the correct geometry and fabricated an adapter for the linkage.  I now have the TV geometery and adjustment dead on, but it cost me some burned clutches before I figured it out.

Offline fix_it

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Re: 700r4 leak
« Reply #11 on: August 19, 2007, 11:07:23 AM »
I think I got it fixed.  I found the remainder of the seal kit hat I used to overhaul the trans two years ago.  In it I found that umbrella seal.  Then I unhooked the TV cable and found the seal missing.  I put in the seal and the leak seems to be stopped.  The weird part i why it didn't leak in the past two years, since I apparently left that little seal out.  Anyway, thanks for the advice.  It's nice to have knowledgeable people to talk these things over with.

Offline Transman

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Re: 700r4 leak
« Reply #12 on: August 21, 2007, 08:31:49 PM »
I am happy that your leak was so minor and it is repaired. Feel free to ask anytime you have a question, so far you have been very fortunate but if the repairs take a more serious turn we will be here to help, Transman
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