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08-30-2013, 09:20 PM
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#1 |
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Junior Member
Join Date: Jul 2002
Location: Scottsdale, AZ
Posts: 1,701
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TCI vacuum switch on 700R4
My 700R4 installation works great except the lock-up does not unlock with low vacuum. I also have a brake switch wired in the 12v to trans and if I press the brake pedal it unlocks. The vacuum switch does not seem to be working to interrupt the 12v to trans.
I took out the switch, hooked up my multimeter and switched it to the "audible" zero ohms setting. Attached my hand vacuum pump with inHg dial on it. Set the adjustment screw to 'beep' the meter at about 10 inches. (which is the adjusting screw waaaay out) Installed the switch and when it shifts in 4th it immediately goes to lockup. I can lug it way down below 1000 rpm with my dash vacuum gauge indicating 0 and it will not unlock until it downshifts into 3rd. Any ideas?
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"I was patina when patina wasn't cool." 1973 Cheyenne SWB Sunset Gold / Frost White / Saddle |
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08-31-2013, 02:04 AM
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#2 |
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Registered User
 Join Date: Sep 2012
Location: Factory
Posts: 681
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Re: TCI vacuum switch on 700R4
bump
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08-31-2013, 11:14 AM
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#3 |
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Registered User
Join Date: Oct 2010
Location: Ocean Springs, MS
Posts: 1,746
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Re: TCI vacuum switch on 700R4
Seems to me like it needs something to bleed off the vacuum, as with a vacuum cruise control servo. It has a vacuum dump switch on the brake pedal to instantly release the cruise.
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Gary 1971 Chevrolet C/10 1951 GMC 100 1977 GMC C15 1955 Chevrolet 3100 |
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08-31-2013, 11:23 AM
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#4 |
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Registered User
Join Date: Jan 2000
Location: Wyoming USA
Posts: 2,453
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Re: TCI vacuum switch on 700R4
Do u know how it is wired in the pan?Look on TCI web page for the wire schematic.Seems to me there were a coupla differant ways to wire the solonoids
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2001 Silverado K-1500 2005 FXDWG stage3 69 CHEVY Short/Step 327/4L60 373 posi 63 IMPALA 327/4L60 |
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08-31-2013, 11:48 AM
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#5 |
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Registered User
Join Date: Feb 2012
Location: Ruskin Florida
Posts: 4,567
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Re: TCI vacuum switch on 700R4
You should only have to adjust slightly a hair this way or that but not that much.
Edit. Just checked my vacuum switch and it makes continuity at around 13 and below that shuts down. I guess I cannot remember how this thing works.
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70 swb 4x4 406sbc 700r4 203/205 d60/14blt locker yadda yadda http://67-72chevytrucks.com/vboard/s...88#post6935688 Yeller 72 Blazer 2wd conversion project "No Daggum Money" http://67-72chevytrucks.com/vboard/s...d.php?t=550804 LS1-T56 3.73 LSD super budget build Blanco-2014 Sierra SWB https://67-72chevytrucks.com/vboard/...d.php?t=810350 Last edited by jjzepplin; 08-31-2013 at 12:49 PM. |
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09-10-2013, 02:41 PM
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#6 |
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Junior Member
Join Date: Jul 2002
Location: Scottsdale, AZ
Posts: 1,701
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Re: TCI vacuum switch on 700R4
I had it wired in a separate circuit which is the way my previous trans worked. I put it in series with the brake switch and now it's switching on/off. Now for the 'tuning'. I think I'll get it figured out. thanks for the replies!
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"I was patina when patina wasn't cool." 1973 Cheyenne SWB Sunset Gold / Frost White / Saddle |
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01-29-2014, 11:16 PM
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#7 |
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Junior Member
Join Date: Jul 2002
Location: Scottsdale, AZ
Posts: 1,701
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Re: TCI vacuum switch on 700R4
Never got the vacuum switch to work right. Put a toggle switch under the dash instead. I like it. Flip it on the highway and locked in.
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"I was patina when patina wasn't cool." 1973 Cheyenne SWB Sunset Gold / Frost White / Saddle |
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01-30-2014, 03:06 AM
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#8 |
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Old member
Join Date: Jan 2002
Location: Liberty, & Garden City S.C. , U.S.
Posts: 19,945
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Re: TCI vacuum switch on 700R4
That's how I ran mine for years! If you ever tow a small trailer you can leave it unlocked and pull better to.
 
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1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs. |
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02-01-2014, 11:41 AM
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#9 |
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Registered User
Join Date: Jan 2013
Location: Irving,TX
Posts: 122
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Re: TCI vacuum switch on 700R4
I am having the same problem so I am going to wire up my dash switch today. Did you connect your vacuum line to the carb or the intake?
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02-01-2014, 12:20 PM
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#10 |
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Registered User
Join Date: Feb 2012
Location: Ruskin Florida
Posts: 4,567
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Re: TCI vacuum switch on 700R4
I hooked mine to the carb at first and seemed to work better on the manifold. After a few years it stopped working and I found the vacuum switch had been contaminated. I drilled out the rivets and cleaned it up and re-riveted but haven't got it hooked up yet but tested good with multimeter. Then sealed back up with rtv.
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70 swb 4x4 406sbc 700r4 203/205 d60/14blt locker yadda yadda http://67-72chevytrucks.com/vboard/s...88#post6935688 Yeller 72 Blazer 2wd conversion project "No Daggum Money" http://67-72chevytrucks.com/vboard/s...d.php?t=550804 LS1-T56 3.73 LSD super budget build Blanco-2014 Sierra SWB https://67-72chevytrucks.com/vboard/...d.php?t=810350 |
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02-01-2014, 12:29 PM
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#11 |
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Junior Member
Join Date: Jul 2002
Location: Scottsdale, AZ
Posts: 1,701
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Re: TCI vacuum switch on 700R4
Intake. On the same fitting as my dash vac gauge so I could watch the in hg.
__________________
"I was patina when patina wasn't cool." 1973 Cheyenne SWB Sunset Gold / Frost White / Saddle |
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