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Since the new throttle cable wouldn't operate the kick down switch I've been mulling alternatives. In the end I went with this K052 Vacuum switch. Dead simple to install. Hook it up to a vacuum source and attach the existing kick down wires. Comes pre-set at 1.5" but I tweaked it a bit lower....but my vacuum gauge lacks graduations lower than 5" so I can't say what the final setting is precisely. Kick down now operates reliably...but not too aggressively.
I think I'll wire-in a a/c compressor cut-out as well, to free up a bit of horsepower when the kick down is engaged.
Seems to me that this switch could be used to replace a faulty enrichment switch, if needed. Or....any number of other clever applications.
So you have done some analysis and determined that at near full throttle you have around only 1.5" in vacuum?
Thus the switch will close the circuit and down shift. What happens when the vacuum builds back up, the trans will function "normally" and shift on its own back into 3rd? My throttle cable kickdown is not functioning either, so thanks for this post. Tell us how it works out.
be carefull with a vacuum switch, i had one that with a lockup converter, and when at full throttle and top speed , coming up to top end vacuum would be down around 1"(like no vacuum and convertor clutch was disengaged), all of a sudden clutch would slam locked up, because vacuum was coming back in,(even at full throttle,maybe too small carby) and blew the front transmission seal out the pump housing, and also blew the trans. also!.
acceleration was much better with clutch disengaged , and cruising was great locked up, but it didnt like top end runs, i finally disconnected the switch, converter stayed unlocked !
fuel MPG ,whats that , no such thing with a BBC 467" 7.6L .
ron
be carefull with a vacuum switch, i had one that with a lockup converter, and when at full throttle and top speed , coming up to top end vacuum would be down around 1"(like no vacuum and convertor clutch was disengaged), all of a sudden clutch slam lock up
I was wondering about that. Why not go with the later switch under the gas pedal? Can't find a P/N for it but my 92 has one.
So you have done some analysis and determined that at near full throttle you have around only 1.5" in vacuum?
Thus the switch will close the circuit and down shift. What happens when the vacuum builds back up, the trans will function "normally" and shift on its own back into 3rd? My throttle cable kickdown is not functioning either, so thanks for this post. Tell us how it works out.
So far, so good. it's really just a matter of operating the kick down according to engine load versus mechanical switch.
When vacuum increases (such as easing-up on the throttle) the switch opens and the kick down disengages, just as it would with the cable-operated switch.
If I hold WOT, the transmission shifts at +/- 5500 RPM just as it would with the cable operated switch.
I was wondering about that. Why not go with the later switch under the gas pedal? Can't find a P/N for it but my 92 has one.
Consider that, even bought the switch. Too large/long to conveniently mount under the pedal. With some effort, and modifying of the floorboard and/or pedal arm, I'm sure it can be done, though.
Also considered simply adding another switch to the throttle capstan....just like the enrichment switch. Even bought a bracket. But, the capstan would have to be modified to actuate the switch. Again, I'm sure it's doable, but this vacuum switch was much easier.
be carefull with a vacuum switch, i had one that with a lockup converter, and when at full throttle and top speed , coming up to top end vacuum would be down around 1"(like no vacuum and convertor clutch was disengaged), all of a sudden clutch would slam locked up, because vacuum was coming back in,(even at full throttle,maybe too small carby) and blew the front transmission seal out the pump housing, and also blew the trans. also!.
Kick down and torque converter clutch are two different things!
i only use it for the converter clutch, i use the cable for kickdown, both work fine untill hi rpm/load!
may understand better ,, driving very fast with acceleration, the clutch tries/does engage in and out actually cycling on /off at full throttle, jerks like crazy!
my assumption is at that point engine has no vacuum clutch is open ,then engine starts to get some vacuum, maybe a slight lift of throttle, clutch engages hard!
we have to remember that engine rpm changes between clutch engaged, and clutch disengaged, so vacuum could change with it at that narrow point?
so i disconnect vacuum switch wire, works fine!
that car i used it that way for years , till i sold it!, never any problem! of course a rebuilt transmission,DUH!
ron
on my V12 , with 700R4 , only use a light smaller custom converter, NO clutch, much better engine response , but internal design has very little slip after 2600 rpm, nothing at 3000 up rpm!
something i recommend, if you get the chance to drive one of GM/FORD new 10 speed transmissions , they are AMAZING, i'm like most here,who needs 10 speeds,?
ron
01-29-2019, 09:58 PM
Vacuum switch for V12 kick down and other uses?
