th 400 front seal leak

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Old Aug 29, 2007 | 10:15 PM
  #1  
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th 400 front seal leak

i have a 65 olds dynamic 88 convertable w/ 425 motor. it has sat in the barn for last 20 years and i have spent last 2 yrs trying to bring life back into it. some days i think i should have left it for dead, lol. of course the more i run it and fix it up the more things that start to leak. it has the th400 in it. i have changed the rear seal and the shift linkage seal already. i have noticed from time to time trasmission fluid dripping out of the hole in the dust cover. im assuming its the front seal now that is leaking. does this sound right? and is this the only seal i have left on the transmission to worry about or are there others that need replaced when i pull it out? reading my manual it doesnt sound like a major job to pull the transmission just a few hours of work. am i right or am i in for an eye opener? thanks for the help. chris
Old Aug 30, 2007 | 04:44 AM
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Well, there is the fill tube O-ring, the modulator O-ring, the pan gasket, and the tailshaft gasket that I can think of right off the cuff. Be prepared for lots of fluid when you remove it. If you can find a large pan or receptacle to catch most of it and have a bag of speedy dry ready it will make the job easier. You will also need four jackstands to hold the car and a good floor jack to support the weight of the transmission, use a flat piece of wood under the pan to protect the pan.
Old Aug 30, 2007 | 06:09 AM
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i forgot. i have replaced the pan gasket. when you say the tailshaft gasket are you refering to the rear end where the driveshaft goes into? if so then that one is done. how hard is it to get to the fill tube gasket and the modulator o ring? ive got it drained right now so i hope that will take care of the mess, unless there's more up in there when you unhook it.
Old Aug 30, 2007 | 08:09 AM
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Yes, the tailshaft housing is bolted onto the main body with six bolts and there is a gasket between it and the main body. Where the slip yoke is inserted into the tailshaft housing there is a gasket there that looks like a wheel bearing seal (sort of). The fill tube can be pulled out. The modulator has a retainer clamp and then can also be pulled out. I forgot about the odometer cable (is that the style you have?), there might be a small gasket in the retainer nut on it too, not sure. I don't know where you can get those gaskets for the tailshaft housing but the O-rings are of course generic and can be bought at the auto parts store
Old Aug 30, 2007 | 10:23 AM
  #5  
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i believe we are talking about the same thing as far as the tail shaft goes. i have replaced that one and the shift linkage seal. im getting a small amount of fluid dripping out of the vent hole on the bottom of the dust cover. do you know would that be coming from the front main seal? im not sure about the odometer cable. i have not pulled it out yet. but there is a gasket between the main body and the tail shaft housing then? is the modulator on the outside of the housing or do i have to tear into the transmission to get to it?
thanks chris
Old Aug 30, 2007 | 10:27 AM
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http://www.tciauto.com/WhatsNew/File...n-211001_2.jpg

the modulator is on the lower right, just above the pan. I forgot about the gasket on the square shaped cover at the left of the picture, don't even know what that is. I don't know about the front seal either but for sure there is one, at the input shaft.
Old Aug 30, 2007 | 11:43 AM
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sounds good. looks like im in for some fun. thanks for the help. chris
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