T-350 wont shift to 3rd - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans Advertise
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Transmission - Rearend
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 04-07-2014, 09:27 PM
Registered User
 
Join Date: Apr 2014
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
T-350 wont shift to 3rd

I have just replaced a th350 in my first car. It is a 1978 Chevy Cheyenne with a L6 250........ So the transmission has less than 200 miles on it and it wont shift to third when the truck is warm. It does it fine when the truck is cold. Also it makes a whistling noise when it shifts to 2nd and when it makes this noise again the truck is warm.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 04-07-2014, 09:47 PM
66GMC's Avatar
Get in, sit down, hang on
 

Last journal entry: Blower & Accessory belt drive
Join Date: May 2005
Location: Olds, Alberta Canada
Age: 62
Posts: 2,784
Wiki Edits: 0

Thanks: 36
Thanked 101 Times in 93 Posts


TH350's used a vacuum shift modulator.
If it's not connected, it does the "late shifting" thing ... even "governor" shifting into 3rd eventually.

It's doing it's job ... holding the trans in 2nd gear when there is low manifold vacuum (ie pulling up a steep hill)

You'll want to make sure that it's connected to straight manifold vacuum, and not a ported vacuum source on the carb.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 04-07-2014, 09:54 PM
Registered User
 
Join Date: Apr 2014
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
What would the manifold vacuum port look like
Reply With Quote Quick reply to this message
 
  #4 (permalink)  
Old 04-07-2014, 10:04 PM
Registered User
 
Join Date: Apr 2014
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
So i found it and the manifold vacuum goes to the egr and then goes to the carb which then splits to the vacuum modulator on the tranny. And the whistle sounds like a vacuum leak is there any way to find it with ease
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 04-07-2014, 10:59 PM
ericnova72's Avatar
More for Less Racer
 
Join Date: Jan 2007
Location: S.W. Lower Michigan
Age: 53
Posts: 17,685
Wiki Edits: 0

Thanks: 274
Thanked 3,215 Times in 2,696 Posts
With the engine running, spray a little carb cleaner around every suspected vacuum leak point, engine rpm will change when you hit the leak with the spray.

You can do the same with an unlit propane torch around every suspected leak point, rpm will go up when the propane is sucked in.

Just remember to shut the torch gas off when you aren't actually using it!!
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 04-07-2014, 11:32 PM
Registered User
 
Join Date: Apr 2014
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
thank you for the help
Reply With Quote Quick reply to this message

Tags
1978, chevy pick up, th350

Recent Transmission - Rearend posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Insurance
Please select your insurance company (Optional)

Log-in



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
700r transmission wont shift to 3rd or 4th gear what could it be bong Transmission - Rearend 2 02-06-2012 09:40 PM
700r4 wont shift into 3rd. dms Transmission - Rearend 3 08-26-2011 09:04 PM
th-350 takes forever to shift into 3rd bigwildgrin Transmission - Rearend 1 01-02-2006 05:46 PM
My th350 wont shift into 3rd Matthewnstuff Transmission - Rearend 10 11-23-2005 06:49 PM
700r4 wont shift into 3rd BIG DIXIE Transmission - Rearend 1 01-12-2005 08:04 PM


All times are GMT -6. The time now is 05:25 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.