Automatic Transmission 2-Speed thru 10-Speed GM Autos | Converters | Shift Kits
Sponsored by:
Sponsored by:

TH350 3rd gear problems - diagnosis

Thread Tools
 
Search this Thread
 
Old Sep 29, 2005 | 09:47 AM
  #1  
350SS's Avatar
Thread Starter
TECH Fanatic
iTrader: (38)
 
Joined: Feb 2004
Posts: 1,135
Likes: 21
From: Houston, TX
Unhappy TH350 3rd gear problems - diagnosis

My buddy has a 68 chevelle w/ a mild 350/th350 combo. The TH350 came out of my 72 chevelle that I’m doing the LQ9/4L80 swap on and I don‘t know its history or mileage but the fluid looked good when we did the filter/fluid change. The trans was shifting well and working normal until a couple of days ago it happened. The tranny started to have some slipping in 3rd gear. We had just replaced manifold intake gaskets and noticed that the trans vacuum modulator line came undone from the intake vacuum source. We hooked it back up and it seemed to be back to normal. Then the slipping came back and progressed to bad shaking when it shifts into 3rd and is now totally unusable. 1st and 2nd work fine and still shift nice and crisp. Any ideas on diagnosis? I don’t know much about trannys so bear with me. I think that if it sounds doable, I might try to rebuild it if it’s not too expensive. I don’t think we have much to lose at this point and it would be some good experience. Any thoughts on this? I have decent mechanical skills (supercharger installs, engine/trans swaps) but haven’t really got into the guts of an engine or trans yet. Is this something I should consider tackling on my own?
Reply
Old Sep 29, 2005 | 12:03 PM
  #2  
ty_ty13's Avatar
7 Second Club
iTrader: (42)
 
Joined: Jun 2004
Posts: 4,558
Likes: 0
From: paducah, ky
Default

have you been letting it coast (no gas) and then floor it?

this causes damage to the sprag...... you might need to go ahead and replace the sprag and drum...

get the hardend drum and the 34 element sprag.... this is the first thing that usually goes in th350s
Reply
Old Sep 29, 2005 | 02:10 PM
  #3  
350SS's Avatar
Thread Starter
TECH Fanatic
iTrader: (38)
 
Joined: Feb 2004
Posts: 1,135
Likes: 21
From: Houston, TX
Default

that's exactly what was going on before it first started. Does this affect 3rd gear only when it goes out? Thanks for the lead...anyone else?
Reply
Old Sep 29, 2005 | 04:27 PM
  #4  
john kilgore's Avatar
TECH Regular
 
Joined: Feb 2004
Posts: 439
Likes: 1
From: burbank ca
Default slip

does it slip in rev? third and rev. share the same clutch pack. if it does l'm afraid it's dead. good luck
Reply




All times are GMT -5. The time now is 02:04 AM.

story-0
6 Gifts Neither Your Dad Nor Grad Will Shove Into the 'Trinket Drawer'

Don't get dad new socks or a grill brush this year.

By Brett Foote | 2026-06-09 14:55:56


VIEW MORE
story-1
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?

Slideshow: We take a close look at the ONE and Artidiag 800BT2 diagnostic tools from Topdon and the reasons to buy one over the other.

By Pouria Savadkouei | 2026-05-28 11:05:11


VIEW MORE
story-2
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine

Slideshow: The controversial Ferrari F6 swaps its original flat-12 for a Corvette Z06-derived LT4 V8 and sends power to four rear wheels through a custom-built drivetrain.

By Verdad Gallardo | 2026-05-26 18:23:54


VIEW MORE
story-3
7 Most Reliable High-Performance Engines GM Has Ever Built

Slideshow:These GM engines didn't just make huge power, they survived abuse, boost, track days, and six-digit mileage with a reputation for refusing to quit.

By Verdad Gallardo | 2026-05-21 16:45:27


VIEW MORE
story-4
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

Slideshow: This heavily modified 1971 Camaro mixes classic muscle car styling with a fifth-generation Camaro interior and modern LS3 power.

By Verdad Gallardo | 2026-05-12 18:06:42


VIEW MORE
story-5
6 Common C5 Corvette Failures and What's Involved In Repairing Them

Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.

By Pouria Savadkouei | 2026-05-07 18:44:57


VIEW MORE
story-6
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-7
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-8
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE
story-9
Hennessey's New Supercharged Silverado ZR2 Has 700 HP

Slideshow: Hennessey has turned the Silverado ZR2 into a 700-hp off-road monster with supercharged V8 power and a limited production run.

By Verdad Gallardo | 2026-03-24 18:57:52


VIEW MORE