Author Topic: Fighting this for 2 yrs. leaking shifting fork on 400 turbo help  (Read 426 times)

Offline Mr.Pontiac

  • Qjet Hero
  • *****
  • Posts: 500
Replaced twice with a Napa unit still after running car at the drags all day, next morning a trial of fluid  a foot long same place. Any ideas??? Yes replaced seals also. very anoying to say the least. stream coming out from under car. Jacking up car again today. Maybe ill try some epoxy around the area??/? Help!!! Tired of cleaning up the mess.

Offline tayto

  • Carb lover
  • ***
  • Posts: 131
Re: Fighting this for 2 yrs. leaking shifting fork on 400 turbo help
« Reply #1 on: August 29, 2019, 09:23:59 AM »
Did you remove shifter shaft and see what shape its in where the seal rides? Have you verified that the full mark is at the pan flange (transmission side) + gasket thickness. Have fixed a few leaking TH400s because the aftermarket dip sticks were well above the pan rail.

Offline Cliff Ruggles

  • Global Moderator
  • Qjet Hero
  • *****
  • Posts: 4339
Re: Fighting this for 2 yrs. leaking shifting fork on 400 turbo help
« Reply #2 on: September 04, 2019, 04:16:27 AM »
You should be using a fill tube with the multiple lip seal, they never leak.

If it's actually leaking at the manual shaft seal as mentioned remove the shaft and check it for scoring/damage.  Replace it if/as needed.  Make sure the case isn't "gouged" where the manual shaft seal sits.

Not much more to it than that, pretty easy repair and those aren't problem areas with TH400's.....Cliff

Offline Cliff Ruggles

  • Global Moderator
  • Qjet Hero
  • *****
  • Posts: 4339
Re: Fighting this for 2 yrs. leaking shifting fork on 400 turbo help
« Reply #3 on: September 04, 2019, 04:17:24 AM »
PS:  another place often missed is leaking at the pump, fluid can "migrate" lower and look like it's leaking from the manual shaft seal or pan.....

Offline Mr.Pontiac

  • Qjet Hero
  • *****
  • Posts: 500
Re: Fighting this for 2 yrs. leaking shifting fork on 400 turbo help
« Reply #4 on: September 12, 2019, 12:08:48 PM »
Draining pan this week again, its leaking a little under shifting bracket that bolts to tranny housing. plus fork. Here i go again. hardest part torquing down bolts 25ft. pounds on you back with car up only 8 to 10 inches. Ill get it/

Offline jamesF

  • Global Moderator
  • Carb lover
  • *****
  • Posts: 170
Re: Fighting this for 2 yrs. leaking shifting fork on 400 turbo help
« Reply #5 on: December 02, 2019, 07:29:49 AM »
I'm fighting a leaker too. I installed the "Top Hat" style bushing on the dipstick tube and it still seems to leak just sitting in the garage. I have to get under it to really see if that is where it is coming from. I think it may be something else as I end up with a good sized puddle, and I dont think it is overfilled enough to leak that much out of the tube opening...

One thing I am going to do on this car (67 GTO) is install a drain plug in the trans pan like I did on my 75 Firebird that I put a TH400 into. This car is mostly original but that mod just makes these transmission tasks cleaner.
« Last Edit: December 08, 2019, 06:42:28 PM by jamesF »

Offline Cliff Ruggles

  • Global Moderator
  • Qjet Hero
  • *****
  • Posts: 4339
Re: Fighting this for 2 yrs. leaking shifting fork on 400 turbo help
« Reply #6 on: December 07, 2019, 04:58:47 AM »
The multiple lip seal doesn't leak easily.  I've been using one since the mid-1980's and my dipstick tube isn't even fastened to the bellhousing and not a single drop of fluid has ever got past one.

I would highly recommend using the fiber pan gasket as well.  I use them here for all the TH400's we do and they will not leak, plus if you use a little RTV to glue it to the pan it can be re-used many times if you need to remove the pan for any reason.

Cork gaskets typically are one use only and I don't recommend them as they tend to squeeze out and get cut easily by factory type metal pans if over tightened......Cliff