The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > General Truck Forums > Engine & Drivetrain

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 03-07-2018, 03:09 PM   #1
65chevysub
Senior Member
 
65chevysub's Avatar
 
Join Date: Feb 2013
Location: Cottonwood, Arizona
Posts: 1,139
TH350 harsh shifting

My TH350 is shifting hard, and I'd like to know what I can do to "smooth" it out? Its almost a neck snapper when shifting into 2nd and 3rd. Fluid is full, and the vacuum modulator is about a year old. The number on the pan indicates its a 1978, hooked to a 283.
Thanks
65chevysub is offline   Reply With Quote
Old 03-07-2018, 08:25 PM   #2
YoungPup1977
Registered User
 
Join Date: Jun 2015
Location: North Carolina
Posts: 446
Re: TH350 harsh shifting

T350 Harsh upshifts ?
Most likely its something common to both upshifts 1st to 2nd and 2nd to 3rd...

simple items to check first:
Check vac at the modulator, if vac is OK, remove modulator and check modulator valve inside the case, use a needle nose pliers to grip onto the end of the modulator valve and move the valve in and out of the bore, sticky ?

If the modulator checks out OK, the gov would be next to check out......

Remove gov cover and pull the gov out of the case....hold the gov upright with gear pointing towards the sky, squeeze the weights towards the center of gov....you should see the gov valve move inside the gov. or grip the weights in one hand and shake back and forth, you should feel the gov valve move.... Check the colors of the gov springs...

Detent cable connected correctly ?

Please provide some history of this trans, been rebuilt ? Did it just start upshifting harshly...any engine work lately ?

check these items and we can go on from here....good luck.

Last edited by YoungPup1977; 03-07-2018 at 08:32 PM.
YoungPup1977 is offline   Reply With Quote
Old 03-07-2018, 08:45 PM   #3
GASoline71
"I ain't nobody, dork."
 
GASoline71's Avatar
 
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,294
Re: TH350 harsh shifting

Possibly has a "shift kit" in it and the check balls in the valve body have been removed as well.

Gary
__________________
'cuz chicks dig scars...

My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread.

The Rebuild of Creeping Death after the wreck

Quote:
Originally Posted by LONGHAIR View Post
I would never rebuild a 305.
Quote:
Originally Posted by prostreetC-10 View Post
I love using vacuum gauges as part of the carb tuning process. I hook the gauge to the inside of my garbage can and leave it there.
Quote:
Originally Posted by Marv D View Post
Remember Murphys 2nd law of mechanical relationships... "OPPOSING COMPONENTS ATTEMPTING TO OCCUPY THE SAME SPACE, AT THE SAME TIME, GENERALLY END UP OCCUPYING ADJOINING SPACE AT THE BOTTOM OF THE OIL PAN"
GASoline71 is offline   Reply With Quote
Old 03-07-2018, 09:22 PM   #4
YoungPup1977
Registered User
 
Join Date: Jun 2015
Location: North Carolina
Posts: 446
Re: TH350 harsh shifting

As I re-read the OP, it indicated the modulator was replaced a year ago, so its not a fresh build and if it had a "SHIFT KIT" installed, the vehicle has been driven awhile with some harsh shifting.... Another suggestion is to pull the cover off the accumulator and see it the spring is broke.... this is on the passenger side of the trans (cooler lines/dipstick side).... remove the snap ring with a small punch that fits into the hole where the snap ring sits....pull snap ring and cover...cover has an o-ring, spring is next....
YoungPup1977 is offline   Reply With Quote
Old 03-07-2018, 10:11 PM   #5
65chevysub
Senior Member
 
65chevysub's Avatar
 
Join Date: Feb 2013
Location: Cottonwood, Arizona
Posts: 1,139
Re: TH350 harsh shifting

Thanks for the replies. As far as history of the trans: I had it put in in 1999, replacing the Power glide my Suburban came with. I'm not sure if it was rebuilt, or just freshened up. It:s been shifting hard for awhile now. I'm just concerned the hard shifts will affect my U-Joints. I have 3 new ones, just finding time to replace them as it's my only vehicle so can't take it down right now. The fluid looks pretty good. Red)clear and not burnt. Kickdown cable is hooked up as it's supposed to be. I will check the other items as mentioned and get back to you all. It may be awhile as my days off are Weds and Sat and I'm having issues with my post op knee.
65chevysub is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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

Forum Jump


All times are GMT -4. The time now is 04:36 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Copyright 1997-2013 67-72chevytrucks.com