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06-13-2004, 05:06 AM
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#1 |
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Registered User
Join Date: Apr 2004
Location: Commerce City, CO
Posts: 66
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HELP! th400
passed emissions... new problem.
if I accelerate at an easy rate, like city driving, the truck won't **** until it hits about 3,200 rpm, as if I had it wide open.... when i punched it before the problem that is when it would shift into second followed by third at the same rpm. so that means when I leave a stop light the shift to second is hard and won't happen until around 3,200 rpm (with a chirp of the tires) and when I hit 45-50 mph (speed limit) I'm running around 3 grand in second. if I go up to 55 to get it to shift and then back it down to 45-50 mph it'll stay in third. fluid is full. HELP ME PLEASE! 
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'71 C10 swb 350sb/700r4 |
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06-13-2004, 05:09 AM
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#2 |
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Registered User
Join Date: Apr 2004
Location: Commerce City, CO
Posts: 66
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Ha! I left out the "f" in shift in my first post.
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'71 C10 swb 350sb/700r4 |
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06-13-2004, 07:21 AM
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#3 |
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Registered User
Join Date: Jun 2002
Location: central pa
Posts: 1,525
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Did you check the kick down switch to see if it is miss adjusted? Also check the Vaccum line to the modulator on the passenger side. The modulator could do the same thing. The vaccum on it should run through a metal tube from trans to intake vaccum Tee on the manifold behind the carb. let us know?
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72 longhorn c30 502BB/th400/fact air/4.11rear/ custom camper 72 bug(the better half's) under reconstruction 2009 HHR aqua blue 71 GMC k20 350/sm465 2009 Chevy hd3500 6.6 Victory Red crew cab dually Dave & Jeanne |
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06-13-2004, 12:36 PM
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#4 |
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Registered User
Join Date: Jul 2003
Location: north of Phx AZ about 30 miles
Posts: 698
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Sounds like a vacuum modulator problem to me. I'd check the line first, then replace the can second.
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Andy,Phx AZ '67 C-10 (Ahhh, done at last. Well there is that disk front end I want to put in and...) "23 C-Cab-sold '48 Ford 8N tractor(still working) '67 Scout(Now on the road) '70 MG B.-sold |
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06-13-2004, 01:26 PM
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#5 |
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Senior Member
 Join Date: Mar 2003
Location: Colfax-California
Posts: 8,487
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Vacuum line first-- In rare case I have seen the rear output shaft bushing in the case walk out towards the rear and destroy the plastic governor drive gear.
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06-13-2004, 01:58 PM
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#6 |
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huh?
Join Date: May 2000
Location: Washington, Illinois
Posts: 5,692
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Definitely check the vacuum line first. If that doesn't work, check your kickdown switch...if that's ok, replace the modulator. It's most likely a vacuum problem....best of luck.
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Someday when I'm lonely, Wishing you weren't so far away, Then I will remember Things we said today. RIP El Jay |
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06-13-2004, 02:39 PM
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#7 |
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Registered User
Join Date: Apr 2004
Location: Commerce City, CO
Posts: 66
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the vacuum line is rubber not metal, but I don't see that being a problem for vacuum. and another thing what is a kick down switch and where is it located? this is all new stuff to me.
The only previous experience is getting an old suzuki 250 bike running.
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'71 C10 swb 350sb/700r4 |
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06-13-2004, 02:43 PM
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#8 |
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Registered User
Join Date: Feb 2003
Location: sw
Posts: 341
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My rubber line got weak over the years & started collapsing under vacuum causing the same problem !
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06-13-2004, 04:00 PM
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#9 |
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Registered User
Join Date: Apr 2004
Location: Commerce City, CO
Posts: 66
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ok replaced the line and regulator... shifted great for about two miles, then when it warmed up the same problem.
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'71 C10 swb 350sb/700r4 |
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06-13-2004, 10:09 PM
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#10 |
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Registered User
Join Date: Jun 2002
Location: central pa
Posts: 1,525
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Kick down selinoid is on the driverside of the trans, an orange wire runs up to either the passenger side of carb to a switch activated when you go WOT or a switch under the dash attached to the gas peddle.
I have a 72 BB/th400 and the switch is on the gas peddle. I also have a metal tube with about 3inches of rubber tubing on the ends for the vaccum modulator to manifold. It must be a BB 72 thing. I would check the rubber tubing and make sure it didn't get burnt or pinched.
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72 longhorn c30 502BB/th400/fact air/4.11rear/ custom camper 72 bug(the better half's) under reconstruction 2009 HHR aqua blue 71 GMC k20 350/sm465 2009 Chevy hd3500 6.6 Victory Red crew cab dually Dave & Jeanne |
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06-14-2004, 05:20 PM
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#11 |
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Registered User
Join Date: Apr 2004
Location: Commerce City, CO
Posts: 66
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ok now I have metal lines to the vacuum mod. time to check the kickdown.
Thanx dwaite72lnghrn, I was looking all over the carb, my cable is connected to the gas peddal.
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'71 C10 swb 350sb/700r4 |
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06-14-2004, 05:55 PM
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#12 |
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Registered User
Join Date: Jun 2002
Location: central pa
Posts: 1,525
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If you disconnect the wire from the trans it will eliminate the switch for now. It just won't kick down when you floor it. I think in normal mode there is no voltage to the switchon the trans.
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72 longhorn c30 502BB/th400/fact air/4.11rear/ custom camper 72 bug(the better half's) under reconstruction 2009 HHR aqua blue 71 GMC k20 350/sm465 2009 Chevy hd3500 6.6 Victory Red crew cab dually Dave & Jeanne |
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