Author Topic: TH350 Problems  (Read 6100 times)

Offline Shifty

  • Frequent Member
  • **
  • Posts: 270
  • I bleed Bowtie red...
Re: TH350 Problems
« Reply #30 on: December 06, 2019, 08:33:21 AM »
If it's not checked hot, it will be an exercise in futility.  I would drop the pan again, and make sure that it is perfectly flat.  I've seen quite a few of them overtightened, and it bends the pan enough to where it will never seal properly. 

I personally like a paper-ish gasket, and I soak it in clean transmission fluid, then pat it dry.  Never had a leak.  While the pan is off, it's a good time to put in a drain plug, BTW.
87 V20 Standard Cab Longbed (current)

87 R30 3+3 Longbed (days of yore)

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5653
Re: TH350 Problems
« Reply #31 on: December 06, 2019, 11:20:35 AM »
During the following inspections, if transmission fluid accumulation is excessive, you may need to rinse or wash the areas down with some aerosol brake/carburetor cleaner and wipe away with a shop towel.  Wear safety goggles to avoid getting any of the chemicals or gritty debris in your eyes.

Remove the torque converter cover located directly forward of the transmission oil pan.  With the engine off, peer up between the torque converter and the front of the transmission using a bright flashlight.  Study it for a while.  Is it wet with automatic transmission fluid (ATF)?

Using a flashlight and mirror as needed, peer up around the shelf located on the top side of the oil pan flange at the right side of the transmission.  Inspect the area surrounding the oil dipstick tube and detent cable entry points into the transmission case.  Is it wet with ATF?

Inspect around the circumference of the circular servo cover on the right side of the transmission.  Is ATF puddled in the bottom of the snap ring groove?

Look around both the left and right sides of the transmission case from the pan flange upward toward the top of the case.  Is it wet with fluid?

Use a paper or rubberized cork pan gasket.  Torque oil pan bolts to 130 lb-in (11 lb-ft, 14.7 N-m, 15 kg-m).  Do not over-torque the bolts or the pan flange will distort.
« Last Edit: December 06, 2019, 05:29:48 PM by bd »
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Irish_Alley

  • Tim
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13269
  • Family is not an important thing. It's everything.
Re: TH350 Problems
« Reply #32 on: December 07, 2019, 09:58:50 PM »
think my imp calls for something like 10 Ft lbs so 17nm sounds about right. see how easy it is to over tighten them
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5653
Re: TH350 Problems
« Reply #33 on: December 08, 2019, 11:54:27 AM »
Why guess?  The quoted torque spec is directly from the 1976 factory service manual; equivalent specs (in parentheses) are mathematical conversions.

...Torque oil pan bolts to 130 lb-in (11 lb-ft, 14.7 N-m, 15 kg-m).  Do not over-torque the bolts or the pan flange will distort.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline uprising

  • Newbie
  • Posts: 54
  • Newbie
Re: TH350 Problems
« Reply #34 on: January 02, 2020, 03:21:35 PM »
Hi guys,
first Happy new year!

It seems that the problem was the seal from oilpan! I will add the new seal with a new pan. But i have again a question about the dipstick. Is the correct that the pipe of the dipstick is some far in the pan? Check the pic

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5653
Re: TH350 Problems
« Reply #35 on: January 02, 2020, 03:51:15 PM »
Totally normal.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline uprising

  • Newbie
  • Posts: 54
  • Newbie
Re: TH350 Problems
« Reply #36 on: January 06, 2020, 02:20:55 PM »
I start crying...
I got a brand new pan and a new seal. Everything furs great ans i start to fill up the trans fluid. Trany is working fine. After two hours i checked again and now i again see drops. A lot if drops... the dang seal is not tightly. The drops are only in one corner ( over the drive shaft) the screws are fixed with exactly 14.7Nm!! What is going on???? I really don‘t get it! Are there seal which are made with gum?

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5653
Re: TH350 Problems
« Reply #37 on: January 06, 2020, 03:09:51 PM »
Have you inspected it closely to make sure there are no ATF leaks from higher on the transmission that may be trickling downward and then backward along the pan lip before actually dripping the rest of the way to the ground?  Can you post pics of the sides and rear of the transmission and of where it is leaking now?
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline uprising

  • Newbie
  • Posts: 54
  • Newbie
Re: TH350 Problems
« Reply #38 on: January 07, 2020, 12:01:15 PM »
I checked the whole transmission and everything is looking good. Only at the seal the drops are visible. I made some pics from the mess. Maybe i will remove the pan again. Can i use the seal or is it damaged? Which seal should i use?

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5653
Re: TH350 Problems
« Reply #39 on: January 07, 2020, 12:39:18 PM »
At least part of the leak is past the fill tube o-ring.  You can see a faint film of red ATF soaking the side of the case running downward from the tube (image).  Use some aerosol brake/carburetor cleaner and thoroughly wash the grime and oil off the sides of the transmission.  Then take a closer look to verify there are no additional leaks besides the one pictured.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline uprising

  • Newbie
  • Posts: 54
  • Newbie
Re: TH350 Problems
« Reply #40 on: January 07, 2020, 12:59:21 PM »
Is it a special o-ring or can i use a simple one which fits?! On the right side is nothing but i will check again. Thanks for your fast help. So i will wait to remove the pan again. Which seal?
And which size does the o-ring must have?
« Last Edit: January 07, 2020, 01:05:58 PM by uprising »

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5653
Re: TH350 Problems
« Reply #41 on: January 07, 2020, 02:13:32 PM »
Begin by cleaning the outside of the trans and looking carefully to pinpoint all sources of leaks before proceeding with repairs.  It appears there may be seepage from the front pump area as well (e.g., pump seal, pump o-ring and/or bolt sealing gaskets) (image).  I would replace the fill tube o-ring and the detent cable o-ring at the same time using replacement seals by application.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline ron350

  • Newbie
  • Posts: 43
Re: TH350 Problems
« Reply #42 on: January 07, 2020, 04:18:02 PM »
 BD why does his dipstick not have a crimped bead around it for a stop like my 75 C10 has?
My 1975 model dipstick tube used a –113 o-ring.
1975 C10 step side stock with 350 two bbl. & 350 trans.

Offline bd

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 5653
Re: TH350 Problems
« Reply #43 on: January 07, 2020, 06:17:26 PM »
You may be onto something, ron350.  Looking closer at the image posted earlier in this thread, it appears that the dipstick tube penetrates a little too far into the pan.  At first look, I thought it was okay.  But a closeup shows the tube o-ring very near the inner opening of the dipstick tube hole (image).  When the tube is resealed, it will also need to be repositioned and the fit verified with the new seal.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline ron350

  • Newbie
  • Posts: 43
Re: TH350 Problems
« Reply #44 on: January 07, 2020, 07:45:18 PM »
So that’s why Uprising was asking about the dipstick tube hanging down so far.

I resealed my TH350 this summer because it was leaking from every seal except the governor. I wish Uprising would post more pictures of the outside of his transmission. I can see the right edge of his Accumulator Cover in one picture and it looks rusty and leaky. My transmission was very dirty just like his except where I had a leak which kept the crud washed off.



1975 C10 step side stock with 350 two bbl. & 350 trans.