not shifting gears with new carb and manifold!

nohn · 07-11-2007, 01:12 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 · 07-11-2007, 05:22 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 · 07-11-2007, 10:10 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 · 07-22-2007, 10:57 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?

07-11-2007, 01:12 AM	#1 (permalink)
nohn Member Join Date: Oct 2006 Location: Naples, Italy Posts: 51	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?

07-11-2007, 05:22 AM	#2 (permalink)
Oldsguy Administrator Join Date: May 2004 Location: Lees Summit MO Posts: 2,859	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 '46 2 door

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07-22-2007, 10:57 AM	#4 (permalink)
nohn Member Join Date: Oct 2006 Location: Naples, Italy Posts: 51	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?