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Old 12-02-2006, 04:25 PM
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th350 case leak problem

hi everyone

i have an issue with a '70's TH350

transmission fluid is coming out in a stream about the size of a pencil lead through the tranny casting where the lower brass cooling line adapter screws in,
it is no leaking from the threads, but it was a little before i cranked it tighter to try and stop it, well now it puts out a steady stream, through the casting of the case at a point that is about at the end of the threads of the brass cooler line fitting inside the case hole

has anyone ever had this happen and what can i do about it ? has anyone ever seen this happen, i know someone out there has and hopefully knows a good trick to fix it at least for a while anyways


thanks for anything

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Last edited by fast68; 12-02-2006 at 09:35 PM.
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Old 12-02-2006, 08:49 PM
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you have to grind and weld the case...... and often the tranny still leaks a small amount.

Usually the tranny must be removed to repair or replace the tranny case.









Quote:
Originally Posted by fast68
hi everyone

i have an issue with a '70's TH350

transmission fluid is coming out in a stream about the size of a pencil lead through the tranny casting where the lower brass colling line adapter screws in,
it is no leaking from the threads, but it was a little before i cranked it tighter to try and stop it, well now it puts out a steady stream, through the casting of the case at a point that is about at the end of the threads of the brass cooler line fitting inside the case hole

has anyone ever had this happen and what can i do about it ? has anyone ever seen this happen, i know someone out there has and hopefully knows a good trick to fix it at least for a while anyways


thanks for anything
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Old 12-02-2006, 09:42 PM
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in which sucks bad

has anyone ever seen this leak happen at this location ?

or know waht causes it ?

is it due to porosity?

i do plan on replacing the trans with another, i do have another th350 to have rebuilt, but i cant do it yet, i have to wait til spring or so to be able ot do anything, i was thinking about a temporary fix til then, such as cleaning it off real good and filing it a bit to roughen it up and JB weld it

just to get by with maybe a minor seepage until spring anyways, i dont run the truck every day but i need it right now with all this snow and ice

winter time sux

if i had the right tools and instructions then i would get a kit and rebuild it myself, but all ive ever done is disassemble th350's, but not to rebuild or repair, or anything

how big of a deal are these ?


thanks for any further

Last edited by fast68; 12-03-2006 at 10:51 AM.
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Old 12-03-2006, 08:09 AM
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over tightening the cooler fittings can cause the leak. It splits the case

Some folks use the AN Earls type fittings , over tighten them & the case splits.




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Old 12-03-2006, 10:23 AM
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hey there, yeah... i tried cranking it real tight, because it wouldnt stop leaking out of the fitting threads,, so thats probably what happened most likely.. hmmm...

i dont understand why the fitting threads would be leaking in the first place, what is the deal with that ? ive never had or seen this issue occur before, and ive had and been around alot of these over the years,

i could have my stepdad braze the case but it would be a while before it could be done with it being winter and the truck not being over there and such, hmm


this TH350 has an issue where it barely goes into third gear, it is real weak in that gear and slips usually, and wont hold its speed

if there was any time that i needed to know how to R&R one of these trannies now would be that time, but i dont understand this stuff, its the unknown, unchartered territory


if i were to get brave and yank the tranny and braze the case or use my spare identical 70's K-case th350 case and take them both apart and use my current known to be mostly good internals in the good case then what do i need to fix this problem itself ?
anyone got pics of the part(s) that are most likely bad that would case a weak third gear ? but then i dont even have tranny type tools and such and have no idea what i should get, as i improvised when i took others apart in the past,, with no intention of reassembling them, so i dunno,,



how do you make a compressor tool for the clutch packs/drum stuff in these? anyone got pic ?

im not really that afraid to get into the trans with a nre kit but im just worried about making the tools i need to do it, such as a compressor and the low/reverse seal remover/installer

how do you make them ? what will work ?

also someone has had this tranny out sometime in the past and they painted it a dark blue, and i heard a rumor that painting trannies is bad for them, but TCI and such paint theirs black so i dont understand how painting them can be bad ?

im not sure what to do, im pretty much at a loss and cant do much for now, so all i can do is research for the time being,

is this the pump assembly to get ?http://www.compperformancegroupstore...ct_Code=313400

thanks for anything, i REALLY appreciate..

Last edited by fast68; 12-03-2006 at 12:03 PM.
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Old 12-03-2006, 11:27 AM
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Now you know why it is called EXPERIENCE.
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Old 12-03-2006, 11:58 AM
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yes definitely

thanks
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Old 12-03-2006, 01:02 PM
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Buy a book. Need some snap ring pliers, two 5" or 6" C clamps, and a low reverse clutch spring compressor as the C clamps wont work.

http://www.amazon.com/Corvette-Centr...8&s=automotive
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Old 12-04-2006, 12:27 PM
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well hmm sure enough and unfortunately the coolant line fitting port did crack, i cleaned it off with brake cleaner and a rag and saw the crack and was sad for a minute then i proceeded to wrap the fitting threads with pipe thread tape and stuck it in a ways and mixed up some jb weld and smeared it on and have a floodlight out there on it for some warmth(if any since its only 15 degrees out in the daytime here) and am going to hope that it will get me by til spring with no more than some seepage hum


the low reverse clutch spring compressor sounds like too big of a PITA for me to get into, so i may not even touch that at all
unless someone knows how to make such a compressor, i have access to welders and such,

any ideas what i could make one out of ?

pics ?

i also have a good 1981 th350-C tranny stored away, it is a 10 bolt housing one from behind a 350 diesel that they put in the '78-85 C-10 pickups and cars,
it is a 2wd one however,
i figured i could use my 1977 internals and output shaft in it, since it is not a cracked case, and is alot cleaner than the other 1970's K-case th350 i have

any thoughts ?
what about the VB's, are they the same between lockup and non lockup ?

im just going to keep researching and saving pics and info on how to do these th350 trannies until i figure out what parts to get and tools to make and such, should i buy a new TCI pump assembly for 102 bucks or just have a shop rebuild mine for me ? what torque converter should i get for a stock 400sbc engine with 290 net torque rating and 3.07 ratio axles ?





thanks
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Old 12-05-2006, 12:32 PM
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th350 case leak problem

Go on the web to Driveline Plus,they sell a video on building thm350,as well as other units. Also as far as making tools,they have pictures of tools they sell.

The pictures may help you when you go to fabricate.

Valve body-350c is different than non lockup.
The video is only about 30 dollars,I've not seen it,so I can't vouch for it's value to you.

Never be afraid to try. Although there is something to be said for knowing your limitations.

I've been working in the transmission field for 30 years. It was 4-5 years before I considered myself a decent trans guy. While it is hard to beat experience, building a transmission is not difficult.

If you buy the video,and even if it has a modicum of information,along with the help you receive from this site,you should be successful with your trans venture. Good luck.
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Old 12-05-2006, 10:14 PM
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I will admit, while rebuilding my TH-350. I took the gears and case to a transmission shop. They replaced the lip seals on the pistons for $50. It was well worth the money.
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