C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette
Sponsored by:
Sponsored by:

th350

Thread Tools
 
Search this Thread
 
Old Aug 30, 2016 | 11:16 AM
  #1  
manfroni's Avatar
manfroni
Thread Starter
Instructor
10 Year Member
 
Joined: Jun 2010
Posts: 165
Likes: 0
From: concord ohio
Default th350

The TH350 in my '78 did something very strange. Put the car in drive last night and nothing happened. After a few seconds it engaged and was fine. Drove about 20 miles no issues. Went back out to drive home and a smaller lag time of engagement. Just about home (on my street) and smelled some smoke. There was quite a bit of trans fluid leaking on the exhaust very near the starter. Parked it in the drive and it leaked fluid the size of a basketball. Checked the dipstick and there was no fluid on it. Never leaked before and I have never had an issue with this transmission. Any ideas?
Reply
Old Aug 30, 2016 | 11:48 AM
  #2  
REELAV8R's Avatar
REELAV8R
Le Mans Master
10 Year Member
Liked
Loved
Community Favorite
 
Joined: Apr 2011
Posts: 6,284
Likes: 1,170
From: Hermosa
Default

Sounds like the front seal on the trans let go. Just behind the torque converter.
You'll have to drop the trans to get at it and replace the seal. Removing the rock guard around the torque converter between the motor and trans may give you a better idea of where it's coming from.
Reply
Old Aug 30, 2016 | 03:31 PM
  #3  
domenic tallarita's Avatar
domenic tallarita
Burning Brakes
10 Year Member
 
Joined: Aug 2013
Posts: 1,063
Likes: 319
From: palm springs ca
Default

Previous post had good suggestion on problem but it is possible that you were very low on trans fluid and it heated up and came out of the vent tube on the top of the trans. I would invest in enough fluid to get a good reading on the dip stick and see what happens. If it is leaking out of the front seal it will come out of the hole on the bottom of the dust guard while at idle in your driveway.
The flywheel will sling oil in severe cases and it will show up between the bell housing and block.
If the oil is dark it also is a indication that the oil was low and got hot. I am almost sure that your trans has the tube on the top.

Dom
Reply
Old Aug 30, 2016 | 03:53 PM
  #4  
jim in oregon's Avatar
jim in oregon
Burning Brakes
 
Joined: Oct 2015
Posts: 781
Likes: 113
Default

Originally Posted by manfroni
The TH350 in my '78 did something very strange. Put the car in drive last night and nothing happened. After a few seconds it engaged and was fine. Drove about 20 miles no issues. Went back out to drive home and a smaller lag time of engagement. Just about home (on my street) and smelled some smoke. There was quite a bit of trans fluid leaking on the exhaust very near the starter. Parked it in the drive and it leaked fluid the size of a basketball. Checked the dipstick and there was no fluid on it. Never leaked before and I have never had an issue with this transmission. Any ideas?
Quick question..WHEN was the last time the THM350 was serviced, fluid & filter changed by a competent technician??

AS others have said above..possibly it was low on fluid.and simply overheated..during your drive..
AS note to yourself..WHENEVER the transmission isn't acting right..STOP and check for leaks(obvious) and CHECK THE ATF fluid..Best checked when at operating temp..hot..not cold of course..Good luck..hope no permanent damage was done..and it's a simple fix..Jim
Reply
Old Aug 31, 2016 | 07:00 AM
  #5  
manfroni's Avatar
manfroni
Thread Starter
Instructor
10 Year Member
 
Joined: Jun 2010
Posts: 165
Likes: 0
From: concord ohio
Default

The transmission was serviced about 3,000 miles ago (4 years). It is leaking at the speedo cable. And the cooling line. Will add fluid and let you know how it acts.
Reply
Old Sep 6, 2016 | 03:14 PM
  #6  
manfroni's Avatar
manfroni
Thread Starter
Instructor
10 Year Member
 
Joined: Jun 2010
Posts: 165
Likes: 0
From: concord ohio
Default

Jim in Oregon was 100% correct. The trans had no fluid on the stick. Added 3 quarts and it worked perfectly. It does have a leak at the speedo cable that I will get fixed (and check the fluid far more often) Thanks for the help.
Reply

Get notified of new replies

To th350





All times are GMT -4. The time now is 08:39 AM.

story-0
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)

Slideshow: Every Corvette Grand Sport explained

By Joe Kucinski | 2026-03-26 07:13:44


VIEW MORE
story-1
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!

Slideshow: Breaking down the 2027 Grand Sport, Grand Sport X, Stingray, and LS6 V8.

By Michael S. Palmer | 2026-03-26 13:48:45


VIEW MORE
story-2
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!

Slideshow: 5 reasons bad drivers crash sports cars & 5 ways to avoid a costly shame!

By Joe Kucinski | 2026-03-25 16:32:55


VIEW MORE
story-3
7 Bolt-On Upgrades From Extreme Online Store to Level Up Your C6 Corvette

Slideshow: Check out these easy-to-install upgrades from Extreme Online Store that reshape the look and feel of the C6 Corvette.

By Pouria Savadkouei | 2026-03-23 17:00:27


VIEW MORE
story-4
How Likely Are These Five 2027 Corvette Rumors to Be True?

There may be some big changes on the horizon.

By Brett Foote | 2026-03-18 06:55:42


VIEW MORE
story-5
9 Best Corvettes You Can Buy for Half Price (& 1 You Should NEVER Buy!)

Slideshow: 9 best Corvettes you can buy for half price (and 1 you shouldn't!)

By Joe Kucinski | 2026-03-17 10:20:26


VIEW MORE
story-6
8 Very Best Corvettes of Amelia Island 2026

Slideshow: 8 best Corvette of Amelia Island 2026

By Joe Kucinski | 2026-03-11 09:28:52


VIEW MORE
story-7
Top 10 WORST Corvette Engineering Failures of All Time!

Slideshow: Top 10 worst Corvette engineering failures

By Joe Kucinski | 2026-03-10 17:38:03


VIEW MORE
story-8
10 Records the C8 Corvette Generation Has SMASHED (& 1 Glaring Failure)

Slideshow: 10 records the C8 Corvette generation has SMASHED (& 1 glaring failure).

By Joe Kucinski | 2026-03-02 11:16:36


VIEW MORE
story-9
7 Wildest Corvette Concepts Ever Made

Out of the many Corvette concepts that exist, these are by far the wildest of the bunch.

By Brett Foote | 2026-03-02 11:03:54


VIEW MORE