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 > 47 - Current classic GM Trucks > The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board > The 1973 - 1991 Blazers, Jimmys, and Suburbans Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 03-31-2011, 04:22 PM   #1
kikkegek
Registered User
 
kikkegek's Avatar
 
Join Date: Aug 2010
Location: Netherlands, The Hague
Posts: 1,518
TH400 - when is it supposed to shift gears

hi there,

My car seems to be running just fine. You can allmost not even feel it shift gears, thats how smooth the ride is. Only when I open up the throttle a lot you can feel it shift from 2nd to 3rd gear.

Now usually it will change from 1st to 2nd pretty fast...anywhere between 6 to 12 mph....and then it will change from 2nd to 3rd at about 20 to 25 mph.

is this normal for a TH400 with 1:4.1 gear ratio?

I recently connected a TACH and it shows about 3000rpm at 55 mph...

also I have never ever been able to let the tranny downshift when I hit the throttle hard.
kikkegek is offline   Reply With Quote
Old 04-02-2011, 06:48 AM   #2
motornut
78K & 79C Jimmys
 
motornut's Avatar
 
Join Date: Nov 2009
Location: Ottawa Ont CANADA
Posts: 7,901
Re: TH400 - when is it supposed to shift gears

Hi
1st to 2nd is a quick shift to get you going
not sure on the shift points but the carb has a tab on the side of it to keep the 4 barrels from kicking in before it warmed up.this is a first mod when i get one(bend out of the way)
the kick down cable controls the downshifting.....need a pic or two the pass side of the carb and from the throttle cable drivers side to the back
Attached Images
  
__________________
John
1978 GMCJimmy4X4-350/203
1979 GMCJimmy4X2-305/350
motornut is offline   Reply With Quote
Old 04-02-2011, 03:32 PM   #3
kikkegek
Registered User
 
kikkegek's Avatar
 
Join Date: Aug 2010
Location: Netherlands, The Hague
Posts: 1,518
Re: TH400 - when is it supposed to shift gears

he John,
what does the first thing do? can it be adjusted?

and I think my downshift is not connected:
kikkegek is offline   Reply With Quote
Old 04-02-2011, 09:59 PM   #4
motornut
78K & 79C Jimmys
 
motornut's Avatar
 
Join Date: Nov 2009
Location: Ottawa Ont CANADA
Posts: 7,901
Re: TH400 - when is it supposed to shift gears

1st pic (not mine)the first thing keeps the secondarys from kicking in while the carb/engine is cold
they last longer lol
the other cable i don't usally see it with the pull chain?
can i see the other end
normally i've seen the cable type i have
it just normally runs straight threw under the throttle not off to the side like my Holley makes it
(i have the bracket to fix it now)
and i have a little extra extention shiney bit you don't need
i have two rochesters it the garage the that mount is different on both
the idea is wide open moves the chain ,moves the cable,downshifts
so see if the cable reaches the end at wide open /if the cable moves along
may need to unhook it to see how far it can go,to feel the shift
__________________
John
1978 GMCJimmy4X4-350/203
1979 GMCJimmy4X2-305/350
motornut is offline   Reply With Quote
Old 04-05-2011, 08:24 AM   #5
kikkegek
Registered User
 
kikkegek's Avatar
 
Join Date: Aug 2010
Location: Netherlands, The Hague
Posts: 1,518
Re: TH400 - when is it supposed to shift gears

I did some research last night.

little throttle:
1-2: 10 mph
2-3: 20 mph

half throttle:
1-2: 15 mph
2-3: 25 mph

full throttle
1-2: 20 mph
2-3: 30 mph

is that OK?

it does seem that the amount of throttle is influencing the shiftpoint...

@John: the cable you are referring to is connected to my cruise control...not any kickdown device

Last edited by kikkegek; 04-05-2011 at 08:25 AM.
kikkegek is offline   Reply With Quote
Old 04-05-2011, 10:54 AM   #6
BLE 'BURBAN
In the Forgotten far North.
 
BLE 'BURBAN's Avatar
 
Join Date: Jul 2007
Location: Anchorage, Alaska
Posts: 2,627
Re: TH400 - when is it supposed to shift gears

TH400 does not have a kick down cable. It's electrically activated. There is an electric terminal on the drivers side of the tranny with a wire connected to it that runs up through the fire wall to a kick down switch mounted on the throttle bracket. then the wire goes over to your fuse block for power.
__________________
1987 R3500 CREW CAB DUALLY (BIG RED)Acquired 06/12/2015
1990 chevy suburban V2500 5.7L
My cluster Mods-Nov 2007
overhead console Stereo install Round 2 Aug 2009
Heated/turn signal mirror upgrade
BLE 'BURBAN is offline   Reply With Quote
Old 04-05-2011, 12:10 PM   #7
motornut
78K & 79C Jimmys
 
motornut's Avatar
 
Join Date: Nov 2009
Location: Ottawa Ont CANADA
Posts: 7,901
Re: TH400 - when is it supposed to shift gears

that explains that cable replaced with a pull chain
the cruises i have are rod driven not chain does it work?
after the chain is it a rubber diaphram?
and i duno about the shift points
__________________
John
1978 GMCJimmy4X4-350/203
1979 GMCJimmy4X2-305/350
motornut is offline   Reply With Quote
Old 04-05-2011, 01:15 PM   #8
kikkegek
Registered User
 
kikkegek's Avatar
 
Join Date: Aug 2010
Location: Netherlands, The Hague
Posts: 1,518
Re: TH400 - when is it supposed to shift gears

Quote:
Originally Posted by motornut View Post
that explains that cable replaced with a pull chain
the cruises i have are rod driven not chain does it work?
after the chain is it a rubber diaphram?
and i duno about the shift points
yes, it goes to a diaphram..and it does not work. I think electrical issue, but havent found it yet!
kikkegek 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 11:05 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com