• We have upgraded our forum software! See here for details.

350TH Tranny Leak

vwnate1

vwnate1

Member
Joined
Jan 1, 2000
Messages
11,728
Reaction score
225
Location
AMERICA !
O.K. , my '69 C/10 pissed two quarts of ATF whilst parked in SWMBO's garage , after I cleaned it up and topped up the tranny , it did the same thing in my driveway , I look underneath and everything looks clean & dry except the speedo cable about 2" outside of the tranny ~ is there a seal I need to buy or do I just go to the junkyard and get a good used speedo drive off some 197? TH350 equipped truck ? .

TIA , I know little about slushboxes other than basic care & feeding .
 
leaks

Nate, there is a 'O' seal there, however, I would not think it would leak that much fluid from that seal. Usually, there is not much fluid pumped into the rear of the tranny (where the speedo gears are). I have found that leaks occur on the rear seal (where the slip-joint mates with the tranny) but its not that much either. The pan is the worst place for leaks...might just need a gasket. Could be leaking from the line connections from the cooler or radiator. The front seal is another place but its easy to spot.

Roger
 
Thanx !

I'll have to crawl underneath it again & make sure where .

Both times it was parked dead level .

The cooler hoses are on the right side , the leak spot on the (previously squeaky clean) cement was aft and left of the tranny proper ~ everything looked dry(ish) apart from a big wet dripping on the speedo cable .

This is a new thing , the pan had leaks before I I serviced the tranny and replaced the gasket and dressed the pan's lip like a good Jounreyman Mechanic should :p .

I thought it odd to leak out the speedo cable like that , I wonder if maybe there's some internal O-Ring ? .

We'll see .

To - Day I was cleaning out scrap metal vintage parts as it's trash day and I'm accepting I'll never do the things I wanted to do .

I tossed a few thousand dollars worth of parts I've been holding onto for decades , the scrap guy up my block were well pleased , they don't know nor care what it all is .

The trannies , Task Force front axle complete and extra 6 lug Bendix brake drums twill go next .

In the cleaning I found the missing Metropolitan suspension parts and coil spring compressor so that's to - morrow's job .

I spent some time hand wire brushing the new / used 250 I6 manifolds for my truck , I hope I can find a bead blaster to use so I can make a really good job of it ~ I want to re spray it in GMC RED to match the rest of the engine .

I have much to do before 12/18 ! .
 
Leaky 350 tranny

It can be a combination of things too. I chased and chased my leak. What finally fixed it was a later model dipstick tube with the "tophat" gasket and a new kickdown cable with a new seal in it as well and a new pan gasket with plenty of silicon RTV. It would sit and lose a quart or so a week prior unless I drove it everyday. I had replaced the front and rear seals already. You just have to start eliminating possibilities until it holds its juice. I had been peeved enuff I was considering getting a rebuilt tranny, so I saved myself several hundred bucks with some patience.
 
Thanx Jimmy

Yes , this is apparently an early tranny as it had the O-Ring typ seal on the dip stick , I discovered NAPA sells the top hat typ of seal for $6 and replaced the whole tube with a longer one .

When you used RTV on the tranny pan , did you smear both sides of the gasket with it ? .

I rarely use Anaerobic Sealants but when I do I use Permatex' " The Right Stuff " ~ it's simply amazing , once you use it , nothing else will do .

I hope to get back to the truck next week .
 
My TH 350 leaked at the accumulator cover if not driven at least every third day, what happens is the torque converter will drain back into the tranny effectively overfilling it and leaking out of the accumulator cover seal, a bear to get open, you need three hands,,,:eek:
 
Nate,
What we do to ABSOLUTELY find where a leak is happening is to put a few drops of flourescent dye into the fluid and shine a black light onto the suspect area. If you know anyone that does a/c work it's what they use almost exclusively. I wouldn't think they would charge very much to check it. We don't charge a customer anything since it often leads to a job but in California who knows?
 
Be very careful when using silicone type sealer on a tranny gasket. If a blob breaks away it can cause a problem if still in liquid form. Once set up it won't pass through the filter so it's best to let one set for at least a day before driving.
 
Thanx Rich !

This sounds about right to me .

-Nate

Rich 5150 69 said:
My TH 350 leaked at the accumulator cover if not driven at least every third day, what happens is the torque converter will drain back into the tranny effectively overfilling it and leaking out of the accumulator cover seal, a bear to get open, you need three hands,,,:eek:
Click to expand...
 
Anaerobic Sealants

Thanx Evan ;

You're right , this is why when I use them , I typically hand smear a *very* thin coat on both sides of the gasket so no extra to mush out and plug oil passages etc.

Permatex " The Right Stuff " simply has to be tried to be believed .

-Nate

coilover said:
Be very careful when using silicone type sealer on a tranny gasket. If a blob breaks away it can cause a problem if still in liquid form. Once set up it won't pass through the filter so it's best to let one set for at least a day before driving.
Click to expand...
 
Yup. anymore I smear both sides of the gaskets with RTV and let it sit overnight before I try to run stuff. My tranny isnt leaking a drop. Now the bad news.....I think I forgot to re hook up the kick down cable while i had the pan off de-leaking things. Im just gonna run it that way for awhile. I get so tired of going around after myself fixing stuff I forgot to do the first time.
 
You must log in or register to reply here.
Back
Top