TH 350 swap - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



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

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 06-18-2007, 07:13 PM
Registered User
 
Join Date: Jun 2007
Location: Ontario
Posts: 7
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
TH 350 swap

Hi all,
I have a '78 TH350 that is gone and I now have a '83 TH350 from a Pontiac, they are identical side by side but the only difference is, on the '78 tranny the neutral start, back-up lite switch is mounted by 2 bolts on the side of the tranny with 4 wires leading to a plug, the '83 tranny has a square blue plug-in with 4 holes, only one wire is used and it goes to a coil and then to a sensor. Is this the neutral start/back-up lites switch? Can I use this tranny with my 305 in my '76 Chevy Van? Is there a way to mod this to work. What would happen if I left it unplugged?
Thanks for your help
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 06-18-2007, 08:48 PM
Crosley's Avatar
Hotrodders.com Moderator
 
Last wiki edit: T-350 rebuild tech
Last journal entry: Bar under the dash
Last photo:
Join Date: Nov 2002
Location: ... USA
Posts: 7,982
Wiki Edits: 1659

Thanks: 257
Thanked 86 Times in 83 Posts
Quote:
Originally Posted by habfan72
Hi all,
I have a '78 TH350 that is gone and I now have a '83 TH350 from a Pontiac, they are identical side by side but the only difference is, on the '78 tranny the neutral start, back-up lite switch is mounted by 2 bolts on the side of the tranny with 4 wires leading to a plug, the '83 tranny has a square blue plug-in with 4 holes, only one wire is used and it goes to a coil and then to a sensor. Is this the neutral start/back-up lites switch? Can I use this tranny with my 305 in my '76 Chevy Van? Is there a way to mod this to work. What would happen if I left it unplugged?
Thanks for your help

the trannys are very different... the 83 unit is a t-350C or a t-250C trans.. these are lock up converter type trannys. The wires are for lock up on the converter , not neutral switch

A t-250C is ID'd by looking near the cooler line fittings on the passenger side of tranny.. Is there a threaded stud with nut protruding from the case near this area? If there is , it is a t-250C tranny

the 78 tranny will be a non lock up trans .

Physical size wise they are very close IF the tail housing is the same length... they will interchange with each other when the matching torque converter is used.

The lock up converter does not need to be hooked up if you so desire... trans will not over heat if done so with converter not locked up.

..

__________________
Some people are like Slinkies... Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 06-19-2007, 02:10 PM
Registered User
 
Join Date: Jun 2007
Location: Ontario
Posts: 7
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Th250C swap

Thanks Crosley for your quick reply, it is a th250C tranny, has the stud where you said it was. Both have a 6" tailstock so it will fit to my 305 block. I'll have to make up a bracket to hold my old neutral start/back-up lites and swap over a few parts from the old tranny.
I have a heavy duty th350-th400 torque converter, new for this tranny, a bit bigger and beefier than the original one, 1600 stall speed they say, have to change my flexplate (153t) to a 168t one to fit the converter.
Bottom line I guess is will this set-up work with my th250C tranny and no damage will be done by not using the lock-up connection.
The tranny is going in a Custom '76 Chevy Van, never see's winter, used as an R/V, and will be towing a 20ft tent trailer or 18ft boat, maybe see's 2500 miles a year and well taken care of
Thanks again
Jim
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 06-19-2007, 07:32 PM
Crosley's Avatar
Hotrodders.com Moderator
 
Last wiki edit: T-350 rebuild tech
Last journal entry: Bar under the dash
Last photo:
Join Date: Nov 2002
Location: ... USA
Posts: 7,982
Wiki Edits: 1659

Thanks: 257
Thanked 86 Times in 83 Posts
A t-250C tranny is for a low horse power situation / vehicle...

__________________
Some people are like Slinkies... Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 06-20-2007, 03:15 PM
Registered User
 
Join Date: Jun 2007
Location: Ontario
Posts: 7
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Th 250C tranny

Quote:
Originally Posted by Crosley
A t-250C tranny is for a low horse power situation / vehicle...

Thanks Crosley, understood, make due with what I have for now, p/u this tranny, rebuilt, for pocket change.
I'll get a th350 or 400 later for a project, be happy if this one lasts the summer.
Thanks for your help

Jim
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 06-28-2007, 04:54 PM
Registered User
 
Join Date: Jun 2007
Location: Ontario
Posts: 7
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Th 250C tranny udate

Swap successfull, runs fine, no vibrations, etc. somehow got it right!
Thanks for the info/help Crosley.
Here's what I put it in,
'76 Chevy 10 1/2 ton van, 1,362,422 orig miles, 5 engines and 6 trannys
Jim
Reply With Quote Quick reply to this message

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:
If you do not want to register, fill this field only and the name will be used as user name for your post.
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:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




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
Buick 350 auto to manual swap, need info SkylarkCustom71 Transmission - Rearend 7 04-27-2006 07:29 PM
HELP: Olds 350 swap in a 85 Regal Torx Engine 3 04-12-2006 03:55 AM
350 to 305 swap 78Z Engine 10 02-06-2005 01:42 AM
1978 grand prix chevy 350 swap threesand9s Engine 5 06-28-2004 02:31 PM
400 to a 350 engine swap any tips?? sparks55918 Hotrodding Basics 8 11-15-2003 04:27 PM


All times are GMT -6. The time now is 07:08 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.