Automatic Transmission 2-Speed thru 10-Speed GM Autos | Converters | Shift Kits
Sponsored by:
Sponsored by:

TH400 Question - Early Shifting

Thread Tools
 
Search this Thread
 
Old Jul 15, 2008 | 01:48 PM
  #1  
Dirty 30's Avatar
Thread Starter
TECH Fanatic
20 Year Member
Photogenic
Photoriffic
Shutterbug
iTrader: (96)
 
Joined: Apr 2002
Posts: 1,840
Likes: 1
From: Dallas, Tejas
Default TH400 Question - Early Shifting

I have a TH400 on my 03 Silverado. As far as i know, it is completely stock. I have the modulator hooked up to the vacuum directly to my intake. The problem is that when I manually shift the tranny, from 1st to 2nd it will still shift on its own. It usually shifts at around 4,800-5,200 RPM. From 2nd to 3rd, It will hold the shift up to when I shift it (about 6,200). I dont have the kickdown solenoid hooked up cause that only made it worse at WOT. I do have a 4,500 stall on it tho.
Is there a way to get it to shift when I want it to without having to get it built w/a manual valve body?
Reply
Old Jul 15, 2008 | 01:56 PM
  #2  
Firechikn's Avatar
TECH Enthusiast
iTrader: (15)
 
Joined: Jul 2005
Posts: 678
Likes: 0
Default

I have a manual/automatic vb in my old school. You can leave in drive to let it shift its self or manually shift it and it will hold any gear until you shift. You can buy the complete vb for cheap if you look around. Look for Manual/Automatic vb. Just have to swap it out with the stocker.
Reply
Old Jul 15, 2008 | 02:06 PM
  #3  
Dirty 30's Avatar
Thread Starter
TECH Fanatic
20 Year Member
Photogenic
Photoriffic
Shutterbug
iTrader: (96)
 
Joined: Apr 2002
Posts: 1,840
Likes: 1
From: Dallas, Tejas
Default

I see, so with this manual/auto VB does the tranny have to be built? I dont want a transbrake or RMVB. If i leave my stock one to shift on its own (3rd) it shifts fine accordingly to my speed.
Reply
Old Jul 15, 2008 | 03:23 PM
  #4  
9000th01ss's Avatar
Banned
iTrader: (10)
 
Joined: Feb 2008
Posts: 3,235
Likes: 2
Default

Not my picture.

You can take the 1-2 shift valve out and grind two flats in it and plug the hole in the VB to prevent it from shifting 1-2 on it's own.
All shift kits have a modified 1-2 valve.
Reply
Old Jul 15, 2008 | 05:30 PM
  #5  
Omega Doom's Avatar
TECH Fanatic
15 Year Member
Photogenic
Photoriffic
Shutterbug
iTrader: (2)
 
Joined: Dec 2006
Posts: 1,532
Likes: 18
From: DFW,TX
Default

Originally Posted by Dirty 30
I have a TH400 on my 03 Silverado. As far as i know, it is completely stock. I have the modulator hooked up to the vacuum directly to my intake. The problem is that when I manually shift the tranny, from 1st to 2nd it will still shift on its own. It usually shifts at around 4,800-5,200 RPM. From 2nd to 3rd, It will hold the shift up to when I shift it (about 6,200). I dont have the kickdown solenoid hooked up cause that only made it worse at WOT. I do have a 4,500 stall on it tho.
Is there a way to get it to shift when I want it to without having to get it built w/a manual valve body?
no wonder that truck moves out quickly!
Reply
Old Jul 15, 2008 | 08:07 PM
  #6  
b00sted's Avatar
TECH Fanatic
20 Year Member
iTrader: (7)
 
Joined: Jun 2005
Posts: 1,109
Likes: 0
From: Chicago
Default

The governor needs to be adjusted. Gearing, vehicle weight, etc, throws it off.
Reply
Old Jul 16, 2008 | 01:23 AM
  #7  
9000th01ss's Avatar
Banned
iTrader: (10)
 
Joined: Feb 2008
Posts: 3,235
Likes: 2
Default

Originally Posted by b00sted
The governor needs to be adjusted. Gearing, vehicle weight, etc, throws it off.
True but a stock 1-2 shift valve will always make it shift earlier.
Reply
Old Jul 16, 2008 | 11:53 AM
  #8  
jakeshoe's Avatar
TECH Resident
20 Year Member
Liked
Loved
iTrader: (14)
 
Joined: Sep 2005
Posts: 821
Likes: 114
From: North Texas
Default

The picture above (mine), shows how to mod the VB to hold manual low gear.

The trans will not shift once this mod is done until you move the lever to 2nd gear. It will also shift to low gear if you pull it to low, no matter what the road speed or engine rpm.

For early shifts, you will have to modify the governor weights. I have an articel that describes how to do this using a package of nails from the hardware store for less than $1.
Or you can buy a kit to do it for about $30-40.
Reply
LS1 Tech Stories

The Best V8 Stories One Small Block at Time

story-0

Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

 Verdad Gallardo
story-1

6 Common C5 Corvette Failures and What's Involved In Repairing Them

 Pouria Savadkouei
story-2

Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

 Verdad Gallardo
story-3

Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

 Pouria Savadkouei
story-4

Top 10 Most Powerful Chevy Trucks Ever Made!

 
story-5

Hennessey's New Supercharged Silverado ZR2 Has 700 HP

 Verdad Gallardo
story-6

Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

 Verdad Gallardo
story-7

Awesome K5 Blazer Restomod Comes With C7 Corvette Power

 Verdad Gallardo
story-8

10 Camaros You Should Never Buy

 
story-9

10 LS Engine Myths That Refuse to Die

 Verdad Gallardo




All times are GMT -5. The time now is 07:29 AM.

story-0
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

Slideshow: This heavily modified 1971 Camaro mixes classic muscle car styling with a fifth-generation Camaro interior and modern LS3 power.

By Verdad Gallardo | 2026-05-12 18:06:42


VIEW MORE
story-1
6 Common C5 Corvette Failures and What's Involved In Repairing Them

Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.

By Pouria Savadkouei | 2026-05-07 18:44:57


VIEW MORE
story-2
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-3
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-4
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE
story-5
Hennessey's New Supercharged Silverado ZR2 Has 700 HP

Slideshow: Hennessey has turned the Silverado ZR2 into a 700-hp off-road monster with supercharged V8 power and a limited production run.

By Verdad Gallardo | 2026-03-24 18:57:52


VIEW MORE
story-6
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.

By Verdad Gallardo | 2026-03-23 18:53:41


VIEW MORE
story-7
Awesome K5 Blazer Restomod Comes With C7 Corvette Power

Slideshow: A heavily reworked 1972 K5 Blazer swaps its off-road roots for a low-slung street-focused build with modern V8 power.

By Verdad Gallardo | 2026-03-09 18:08:45


VIEW MORE
story-8
10 Camaros You Should Never Buy

Slideshow: There are thousands of used Camaros on the market but we think you should avoid these 10

By | 2026-02-17 17:09:30


VIEW MORE
story-9
10 LS Engine Myths That Refuse to Die

Slideshows: Which one of these myths do you believe?

By Verdad Gallardo | 2026-01-28 18:10:11


VIEW MORE