Author Topic: Evil TH350 leak and dipstick issue  (Read 203 times)

SoupMan

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Evil TH350 leak and dipstick issue
« on: September 12, 2018, 11:11:21 PM »
Been dealing with the TH350 leaking nightmare on my 1980 Formula.

Losing about 1/2 quart per week while sitting. While trying to solve the problem I upgraded some components (some of it motivated by the leak)
- Updated pan to a deeper pan with B&M filter drop kit
- Replaced with the cork gasket with the thick Morosso gasket

After that, I was still getting a leak. Few weeks later I happen to damage the dipstick metal tongue for measuring oil level. Ordered a cheap tube. At the time I didn't know about the Grommet VS O-Ring. Regardless, the O-ring ripped while trying to push the tube (common issue with that tube apparently), so I ended up putting back the old tube with the new metal tongue.

Leak is still there but while reinstalling I did notice seal appearing to be soggy so I've ordered one for now. I am however thinking of going to a flexible dipstick. Anybody has one to recommend? The Lokar dipsticks look nice but they are hella pricey.

firebirdparts

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Re: Evil TH350 leak and dipstick issue
« Reply #1 on: September 12, 2018, 11:28:30 PM »
I haven't tried an aftermarket dipstick, but just wondering can you not figure out where the leak is coming from?
I want to be like Paul Kenny when I grow up
Joe Bays
1977 Y82 4-speed (red interior)
1978 Skybird 350
1978 Redbird 305
1979 Redbird 301 4-speed
1992 Lincoln Mark VII LSC/SE (red)
1970 Datsun Pickup
1953 Chevy pickup (converted 4x4)
1988 T-bird Turbo Coupe

737driver

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Re: Evil TH350 leak and dipstick issue
« Reply #2 on: September 12, 2018, 11:55:56 PM »
I had the same thing on the TH350 on my 71FB. The dipstick broke off and was leaking quite a bit. I recently had a transmission shop install a new metal tube that I believe had a press in tube. No leaks so far.
Jim
1979 Trans Am- Heritage Brown -W72 (Pontiac 400) -4Speed-WS6
1972 LeMans Convertible
1972Firebird
1971 Firebird
1970 Firebird

Bluebandit

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Re: Evil TH350 leak and dipstick issue
« Reply #3 on: September 12, 2018, 11:59:44 PM »
My pickup was doing the same thing so I replaced the tube with a later model one that used the boot type seal. Leak fixed.

LeighP

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Re: Evil TH350 leak and dipstick issue
« Reply #4 on: September 13, 2018, 01:18:39 AM »
The O rings are kinda sucky at best.....put some rubber grease on them before install so the tube slides in the hole.
I'm using the 69 dip stick, so mine has a rubber drop in gasket type seal....hoping that works better than the laer O ring style.
I used a firewall mounted Lokar flexible dipstick on my 71....worked great.
Regards,
Leigh

Sydney, Australia
1969 Pontiac Firebird 400 coupe (project)

Former Firebirds -
1971 Pontiac Firebird 455
1977 Pontiac Trans Am
1976 Pontiac Trans Am
1967 Pontiac Firebird 400 convertible
1967 Pontiac Firebird 400 coupe


Re: Evil TH350 leak and dipstick issue
« Reply #4 on: September 13, 2018, 01:18:39 AM »

SoupMan

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Re: Evil TH350 leak and dipstick issue
« Reply #5 on: September 13, 2018, 06:31:00 AM »
Firebird parts,

The leak appears to be coming from the top of the transmission and not the pan itself. Top of the transmission was wet with trans oil and the dripping was on both sides, no the front. I have a new grommet coming in tomorrow. I'll see if that seals the deal :)

I was only asking about the dipstick because I would like the ability to relocate the dipstick away from the distributor and heater core piping. I've had to check the oil way more often than normal so between burning myself on the heater pipe, the clutter of reaching the handle and the difficulty of pushing the metal tongue back in because of the sharp bends, it's probably just a knee jerk reaction.

Meanwhile, if anybody else has experience with other flexible tubes such as Lokar, let me know.

aussieta

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Re: Evil TH350 leak and dipstick issue
« Reply #6 on: September 13, 2018, 11:56:57 PM »
is the breather in place
1978 Y84 W72 WS6

oldskool

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Re: Evil TH350 leak and dipstick issue
« Reply #7 on: September 14, 2018, 11:03:45 AM »
There are lots of cheap Chinese flex tubes on Ebay. Some of 'em bolt to the firewall. They have 2 rubber O-rings. Have never used one.

https://www.ebay.com/itm/FLEXIBLE-STAINLESS-350-TRANSMISSION-DIPSTICK-TH350-SBC-BBC-TRANS-FOR-GM-U1Q5/382283804725?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3D9b11fb231e1d4ea0813b30bbcfd17eb0%26pid%3D100005%26rk%3D3%26rkt%3D12%26sd%3D370629576281%26itm%3D382283804725&_trksid=p2047675.c100005.m1851

https://www.ebay.com/itm/STAINLESS-FLEXIBLE-400-TRANSMISSION-DIPSTICK-TH-400-TRANNY-SBC-BBC-305-350-454/370629576281?hash=item564b3e8659:g:3cgAAOxyu0BRe0J7

I too will soon need a new tube. The tube in my TH400 was leakin pretty bad before I pulled the trans out of my last bracket Bird. 

So, I'm debating whether to go with a Fitzall tube or one of the cheap Chinese firewall flex tubes, Not gonna pay the high price for a Lokar. If the Fitzall tube won't work I'll buy a Fitzall tube end replacement, to covert my tube over to the "top hat" type seal. Have seen lots of guys posting that the top hat seals work great.

https://www.ebay.com/itm/Th350-350C-TH400-Transmission-Universal-Oil-Dipstick-Filler-Tube-Locking-Type/221651470781?hash=item339b7509bd:g:MnAAAOSwQiRUpydG:sc:USPSPriority!71251!US!-1

https://www.ebay.com/itm/Automatic-Transmission-Dipstick-Tube-Repair-Fitzall-for-Ford-Chrysler-and-GM/252267889020?hash=item3abc56817c:g:1JkAAOSwrIlaq8Kd

http://www.explorerfanatics.com/forum/showthread.php?s=6f3301a24270ea49483038f64c340200&p=46008#post46008

 
« Last Edit: September 14, 2018, 11:24:29 AM by oldskool »

Aus78Formula

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Re: Evil TH350 leak and dipstick issue
« Reply #8 on: September 14, 2018, 09:32:56 PM »
that  fitzall adaptor is a handy piece, just reminded me that my TH350 tube won't work on the TH200-4R.

gm muscle

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Re: Evil TH350 leak and dipstick issue
« Reply #9 on: September 15, 2018, 07:01:25 AM »
I used to have that same leak for years but mine is TH400. I bought a couple of tubes but they would always leak! The aftermarket ones I found were really meant to bolt onto the back of a Chevy engine, so I had to play with them in order to secure. Never worked.
Just a couple of years ago, I finished and LS swap on another vehicle. I ordered the tube and dipstick from GM. It used a grommet type seal...no leaks, so it got me thinking about the same type for the T/A. I called TCI and asked if they sold one for a Pontiac 400 with 400 tranny. I haven't had any leaks since.
1977 Trans Am stroked 400 (468)
1989 Iroc-Z28 5.7 TPI 90K original miles
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Pontiac_SE

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Re: Evil TH350 leak and dipstick issue
« Reply #10 on: September 16, 2018, 01:10:36 AM »
I did also had a leak and it was the shifter shaft that leaked, just a thought.
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Re: Evil TH350 leak and dipstick issue
« Reply #10 on: September 16, 2018, 01:10:36 AM »
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