TH400 shifting problem - JeepForum.com
 
LinkBack Thread Tools
post #1 of 13 Old 05-02-2013, 05:58 AM Thread Starter
2Xtreme
Web Wheeler
 
2Xtreme's Avatar
1979 CJ7 
 
Join Date: Dec 2003
Location: Schenectady
Posts: 1,417
Garage
TH400 shifting problem

Last night I took the CJ out for a ride and noticed some weird shifting issues. Note, I was driving in town with moderate traffic (up to 30-35 mph), so I have no idea how this would have continued at higher speeds:

In D, the vehicle will take off and accelerate as would seem normal. To a point. But it wont upshift. The RPM's just keep climbing until I back off. Then I can press and let off the accelerator with no affect on speed. The RPM's fluctuate, but vehicle doesn't move any faster.

If I drive it in 2, it seems to act normal.

Starting to feel very defeated with this thing.
Every time I fix one thing, something else crops up.....

2Xtreme is offline  
Sponsored Links
Advertisement
 
post #2 of 13 Old 05-02-2013, 07:08 AM
VooDoo2
Registered User
1978 CJ7 
 
Join Date: Jun 2010
Location: Brisbane
Posts: 693
Easy fix = Shift solenoids. Around $15-20 plus a filter kit and gasket

If its not the solenoids its the clutch bands which means a rebuild BUT id put money on dirty fliud, stuffed shift solinoids and a service required.
VooDoo2 is offline  
post #3 of 13 Old 05-02-2013, 07:14 AM Thread Starter
2Xtreme
Web Wheeler
 
2Xtreme's Avatar
1979 CJ7 
 
Join Date: Dec 2003
Location: Schenectady
Posts: 1,417
Garage
Thank Gawd!

I was planning to attempt a rebuild in the near future, but not just yet....
Hopefully this will do the trick.
2Xtreme is offline  
post #4 of 13 Old 05-02-2013, 08:48 AM Thread Starter
2Xtreme
Web Wheeler
 
2Xtreme's Avatar
1979 CJ7 
 
Join Date: Dec 2003
Location: Schenectady
Posts: 1,417
Garage
Haven't had a chance to do any research yet.

Is this something that can be done with the trans in the Jeep??
2Xtreme is offline  
post #5 of 13 Old 05-02-2013, 11:02 AM
Jon In Tucson
Senior Member
 
Jon In Tucson's Avatar
1983 CJ5 
 
Join Date: Aug 2008
Location: Tucson
Posts: 900
Quote:
Originally Posted by 2Xtreme View Post
Haven't had a chance to do any research yet.

Is this something that can be done with the trans in the Jeep??
Most of those services can be performed in frame. I respectfully disagree with VD2 as to solenoids on a th400. I think those are servos that engage the bands via the valve body hydraulic pressure and the vacuum controlled modulator. Never the less, it is a relative inexpensive fix. A comprehensive fluid and filter change will cure a lot of gremlins of those transmissions. Don't forget to make sure the transmission pan is good and flat before putting back on with the new gasket. God bless.
Jon In Tucson

Jeremiah 17:7 "But blessed is the man who trusts in the Lord, whose confidence in Him."

"The secret to a Jeep, especially a CJ, is you can't
panic." - Mike

"I may not be a smart man, Jenny, but I do know grounds."
Jon In Tucson is online now  
post #6 of 13 Old 05-02-2013, 11:21 AM Thread Starter
2Xtreme
Web Wheeler
 
2Xtreme's Avatar
1979 CJ7 
 
Join Date: Dec 2003
Location: Schenectady
Posts: 1,417
Garage
Quote:
Originally Posted by Jon In Tucson View Post
....I think those are servos that engage the bands via the valve body hydraulic pressure and the vacuum controlled modulator.....
Oh boy... the confusion starts to set in.
2Xtreme is offline  
post #7 of 13 Old 05-02-2013, 11:47 AM
Dngrs1
Registered User
1979 CJ7 
 
Join Date: May 2009
Location: Mohave Valley,AZ
Posts: 866
Quote:
Originally Posted by 2Xtreme View Post
Oh boy... the confusion starts to set in.
Start with a fluid and filter change and go from there. K.I.S.S.

I would rather have a tool I don't need, than need a tool I don't have.
Dngrs1 is offline  
post #8 of 13 Old 05-02-2013, 12:59 PM Thread Starter
2Xtreme
Web Wheeler
 
2Xtreme's Avatar
1979 CJ7 
 
Join Date: Dec 2003
Location: Schenectady
Posts: 1,417
Garage
Quote:
Originally Posted by Dngrs1 View Post
... K.I.S.S.
LOL!

Well, if I am going to be in there already, why not do the solenoids or whatevers instead of dropping the pan and drainging it twice?
2Xtreme is offline  
post #9 of 13 Old 05-02-2013, 01:28 PM
Jon In Tucson
Senior Member
 
Jon In Tucson's Avatar
1983 CJ5 
 
Join Date: Aug 2008
Location: Tucson
Posts: 900
Quote:
Originally Posted by Dngrs1 View Post
Start with a fluid and filter change and go from there. K.I.S.S.
X2

If you haven't done a filter and fluid change, definitely do that first. If you find any large (that is, bigger than your thumbnail) pieces of metal or band material, then it's time to rethink the direction you're going... Chances are the tranny is coming is coming out then anyway. God bless.
Jon In Tucson

Jeremiah 17:7 "But blessed is the man who trusts in the Lord, whose confidence in Him."

"The secret to a Jeep, especially a CJ, is you can't
panic." - Mike

"I may not be a smart man, Jenny, but I do know grounds."
Jon In Tucson is online now  
post #10 of 13 Old 05-02-2013, 04:39 PM
VooDoo2
Registered User
1978 CJ7 
 
Join Date: Jun 2010
Location: Brisbane
Posts: 693
My Mistake (it was late here)

ON the newer gearboxes they are electronically shifted via solenoids and they get blocked and stuff up. i did my 4L60e repair with them.

The old er TH400/700r is mechanically shifted so use the cable and vac controlled servo's. Doing a service on the box can free up the gunk that can collect and get the servo's moving. As it still shifts from 2-3 should mean only the 1-2 shift is the issue. The TH400 is a very simple box. Ebay has a heap of shift kits and service kits available. Drop the pan and all can be done on the car.
VooDoo2 is offline  
post #11 of 13 Old 05-02-2013, 06:15 PM
skizriz
Registered User
1978 CJ7 
 
Join Date: Jun 2011
Location: Scottdale
Posts: 4,936
The most probable things are also the cheapest.

1. Vacuum line to the modulator cracked, broken, or fell off.

2. Vacuum modulator itself went bad.

3. Valve behind the modulator sticking.

4. Parts missing/broke from the elbow of the modulator.

5. Sticky governor.

78 CJ7.. 258.. TH400/Dana18.. SOA/stock YJ springs.. 35" General Grabbers.. Waggy 44s.. 4.88 gears...Spartan/Lockright...Fiberglass front to rear
skizriz is offline  
post #12 of 13 Old 05-03-2013, 02:00 AM
jumbojeepman
Registered User
1976 CJ7 
 
Join Date: Sep 2008
Location: Greenville
Posts: 1,099
I would second checking the vacuum line and modulator parts. I'll add that mine started shifting funky one time, and a fluid and filter change took care of the problem, hasn't come back in years.
jumbojeepman is offline  
post #13 of 13 Old 05-03-2013, 06:18 AM Thread Starter
2Xtreme
Web Wheeler
 
2Xtreme's Avatar
1979 CJ7 
 
Join Date: Dec 2003
Location: Schenectady
Posts: 1,417
Garage
Thanks for all of the info!

Will look into it this weekend.
2Xtreme is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user 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 e-mail address for yourself.



Email Address:
OR

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
Show Printable Version Show Printable Version
Email this Page Email this Page



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 Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome