not shifting gears with new carb and manifold!

nohn · July 11th, 2007, 02:12 AM

I am at a loss here. I installed and new 4bb Edelbrock carb and preformer manifold starts without a problem and sounds good. The problem is when I took it for a drive it didn't switch gears. I tried to pick up speed to see if it would shift but nothing changed. I did put it into low gear and then back to drive and it felt like it changed into 2nd gear. Does anyone have any ideas or is it possible I may have missed hooking something up?

Oldsguy · July 11th, 2007, 06:22 AM

The TH400 requires a vacuum signal to operate the kickdown mechanism, the TH350 uses a mechanical linkage from the carb. Did you miss either (don't know which you have).

joe_padavano · July 11th, 2007, 11:10 AM

Quote:

Originally Posted by Oldsguy

The TH400 requires a vacuum signal to operate the kickdown mechanism, the TH350 uses a mechanical linkage from the carb. Did you miss either (don't know which you have).

Not quite. The TH400 uses an electric solenoid valve for kickdown, the TH350 uses a cable. Both transmissions, however, use a vacuum modulator as a way to sense throttle position and load. Failing to reconnect the vacuum modulator line will cause the trans to only upshift at wide open throttle. That's not a problem for ME, but normal drivers may not like this...

nohn · July 22nd, 2007, 11:57 AM

Thanks for the feed back. I finally had a chance to look over my reinstallation of my carb and manifold and found I had the transmission hose in the wrong port. For the most part everything is good. I did notice when I accelerated on the highway it doesn't down shift. Also when I was testing the acceleration I seemed that I couldn't go faster the 95 miles per hour. Any idea what could be causing this to happen?

July 11th, 2007, 02:12 AM	#1 (permalink)
nohn Registered User Join Date: Oct 2006 Location: Naples, Italy Posts: 77	not shifting gears with new carb and manifold! I am at a loss here. I installed and new 4bb Edelbrock carb and preformer manifold starts without a problem and sounds good. The problem is when I took it for a drive it didn't switch gears. I tried to pick up speed to see if it would shift but nothing changed. I did put it into low gear and then back to drive and it felt like it changed into 2nd gear. Does anyone have any ideas or is it possible I may have missed hooking something up?

July 11th, 2007, 06:22 AM	#2 (permalink)
Oldsguy Hot Rodder at heart Administrator Join Date: May 2004 Location: Lees Summit MO Posts: 5,360	The TH400 requires a vacuum signal to operate the kickdown mechanism, the TH350 uses a mechanical linkage from the carb. Did you miss either (don't know which you have). __________________ Dan '77 Cutlass Supreme '46 2 door "The rocket 455.....it's a sledgehammer approach to a thumbtack world" LuxBlue of HAMB.

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July 22nd, 2007, 11:57 AM	#4 (permalink)
nohn Registered User Join Date: Oct 2006 Location: Naples, Italy Posts: 77	Thanks for the feed back. I finally had a chance to look over my reinstallation of my carb and manifold and found I had the transmission hose in the wrong port. For the most part everything is good. I did notice when I accelerated on the highway it doesn't down shift. Also when I was testing the acceleration I seemed that I couldn't go faster the 95 miles per hour. Any idea what could be causing this to happen?