tired of my transmission

[mexlokote]

I have an 82 c10 custom deluxe and has original engine with original trans
Its an inline 6 250 with a thm350 automatic trans
And i been having a leak for months from the oil pan gasket and from the driveshaft
Seal, it has new driveshaft seal and still has leak, also i have changed a cleaned really good the oil pan and after 5 times changing the gasket still leaks i used all types of gakets
Im getting tired loosing oil and time and money,
What i want to know is whats my best trans i could swap, and on which car or truck i can get it out from
Or does anyone have a solution?
Thanks
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[geezer#99]

Check to see if the vent is plugged. It's on the top of the tranny.

[mexlokote]

Thanks for your reply i will check tomorrow
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[1978chevybigten]

check your transmission mount, mine was bad which caused my real seal to leak. and im having the same problem with my pan as well..

also you pan could of been overtightened at one point, which could of twisted up the pan causing leak.

[mexlokote]

How do i know if my transmisiion mount is bad? Any signs i should be looking for?
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[dman1982]

next time check your pan and make sure it doesnt have any dents in it as well, you can easily fix it, even the littlest imperfection may cause it to leak

[1978chevybigten]

Originally Posted by mexlokote

How do i know if my transmisiion mount is bad? Any signs i should be looking for?
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bad mount vs good mount
look to see if the transmission is slouching, and check to see if the rubber has diteriorated.

[mexlokote]

Thanks for ur replys guys i will check tomorrow and ill see what i can find
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[mooseknuckles]

700r4...

[86c20]

if you plan to keep the l6 or even a real mild v8 i 200r4 would be a good op to

[bk2life]

take your truck to a shop have them service your trans. that way if it leaks they will fix it for free...

[Firebirdjones]

Both leaks are easy to fix.

Start with the yoke. If it's leaking out the tailshaft seal, and a new seal didn't fix it, then you probably have a worn bushing and/or yoke. If the bushing and/or the yoke is worn it causes movement, and even a new seal won't be able to do it's job. This will sometime also cause driveline vibrations.
There is a minimal spec for both the bushing and the yoke, check the GM manuals and mic it.

You'll need to remove the tail shaft housing, remove the bushing and install a new one, possibly replace the yoke as well if it is undersized. All this along with a new seal will keep it leak free for years.

On the transmission pan. Assuming you are using the factory steel pan. The trick to get them to seal properly is to go along with a punch and push the bolt holes back towards the pan.
What happens is that after years of being removed and reinstalled, those holes are pushing inward towards the transmission from over torquing the bolts, and when the new gasket is installed, it's not crushed properly for a good seal because the holes are bottoming out on the transmission pan rail before the gasket has a good crush. You can even use a straight edge to varify, and sometimes you'll find not only the hole is pushing in, but it also distorts the pan as well for several inches.
Take a punch and knock the holes back towards the pan, even if you hit them hard enough to tweak the entire pan rail back the other way, it's okay. As you tighten the bolts it will pull everything back into shape and give you a good crush (and good seal) on the new gasket. Go back after a few hundred miles and retorque the bolts.
I've done this with every trans service for more than 30 years, never have one leak. Hope that helps.

[INSIDIOUS '86]

Make sure your dipstick and the kickdown cable are sealed right as well.
Fluid can also leak out of the weep hole on the driveshaft yoke.

There's two types of th350s. Ones that are broke and ones that leak
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[mexlokote]

Thanks guys for ur help, i will try every single sugestion thanks
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[makman1297]

Check you shift shaft seal too, they like to leak down on the pan.

[Damon23]

My 80 Z28 would leak like crazy. Drove me nuts. I ended up replacing the pan. Not with the fancy chrome pan but I found a very nice original one. I went thru the tailshaft bushing and seal, dipstick gasket, vacuum modulator and the seal in it, vent, and the shifter linkage. I hate leaks and transmissions are the worst.