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Old 04-08-2012, 09:44 AM
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Quote:
we're supposed to be talking car talk here
Agreed.

BTW ... I'm *reasonably sure* that the vacuum switch that I posted earlier would also work for a TH350C application. You may have to either make your own wiring harness of modify one of the Painless ones.

This theory *may* be reinforced here.
http://67-72chevytrucks.com/vboard/s...d.php?t=335802

Scroll down to the last post in that thread for another (related) link.
http://www.73-87.com/7387garage/drivetrain/lockup.htm

Last edited by 66GMC; 04-08-2012 at 09:49 AM.
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Old 04-08-2012, 12:13 PM
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66gmc...Amen...I did see that thread late last night with the parts listed and finally felt some relief. Now I'm trying to figure out what my car already has as far as those parts go....he was retrofitting the trans to his old 30's vintage truck while I am just trying to use my original trans here. This morning I replaced the second oil sending unit ,,this one down by the filter and now have normal pressure readings at the gage...the pegged gage was giving me some worries. High oil pressure, I am told, usually is caused by spun bearings. At any rate, I unhooked the connections to the trans and personally could not tell any difference in a test drive. Now I;m wondering if it ever worked. Any way to tell that you know of? So it appears as tho the engine swap with the edelbrock carb can be done and the act of getting the lockup to work can be done at my leisure. I am trying to trace the parts on my car already but it is difficult not knowing what all the things are under there....I do see a vacuum switch of types with some wiring to it...i think it might be it...it's mounted on the intake to the right rear of the engine. Now to trace the wiring and lines. Three wires on the trans but engine compt so crowded with hoses and crap..it is hard to track them. It's going to be so much cleaner in there without the air pump and other non-essential items. I can see that I will have to fabricate some standoffs to use with the headers to allow the AC to be retained. In the course of all this investigation I have uncovered many issues, one being the valve covers leaking....I thought that I had snugged them up before but it must have been some other car because these felt like finger tight. Maybe the oil will stop running down he sides of the engine now...I didn't realize how bad it was till I got under there again. It didn't seem to dripping that much but the engine and trans is a mess with it. The other link was for the overdrive trans which is not applicable to the 350..no internal wiring or switches.

Thanks again for the input. It looks as though I have it just about licked.
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Old 04-09-2012, 09:52 AM
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I had to chuckle at myself just a little, when I dicovered the exact same (word for word) post from Houston54 right here on hotrodders.com.

Now I might be wrong ... but the TH350C has to be using some sort of electric solenoid valve to control the TC lockup, just like the overdrive units. Houston54's post seems to confirm this, and hints that a solenoid out of a 200-4R may even work instead.

Quote:
The solenoid switch the rebuilder put in my trans only has one pole on it as the original is difficult to impossible to find. The replacement switch is from a later model GM lockup trans. It may be the 200R4 switch but not sure. If I get by the rebuilders shop again I will ask.
But "difficult to impossible to find?"

NAPA Echlin # TCS536
is what is listed for an 83 El Camino "with 3 speed A/T"

Something else that seems to be confusing me just a little is if that transmission of yours is original to the vehicle ... wouldn't the converter lockup system already be there?

Perhaps somebody simply removed or disconnected that vacuum switch?

To my understanding, there are two (or more) things that will disengage the lock-up converter.
1.) The brake switch ... for obvious reasons.
2.) The vacuum switch. This is for when you are pulling up a hill for example. The reduced manifold vacuum "tells" the transmission that the engine is working hard, and could use that little extra RPM before having to force a downshift to 2nd gear. I'm sure it's also there to protect the converter lockup clutch.

My ex-son-in-law had an 88 Chevy C1500 with a 350 / 700R4 pulling a U-Haul trailer through the Rocky Mountains ... and the lockup function was pretty obvious to me. The RPM would pick up just a few hundred RPM going up a gentle slope, then settle back down on the flat. When a steeper, or longer slope was encountered ... you would note the lockup disengaging first ... followed by a downshift (or downshifts) later.

In other words ... if you're cruising at 1800 RPM in OD, you will see / hear / feel the RPM's pick up to about 2100 when the converter un-locks. Whereas an actual downshift will take the tach into the 3000 + range. (Numbers are approximated)
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Old 04-09-2012, 07:15 PM
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hey guy I think we are getting on he same wavelength...you are making the same deductions I am...I am pretty sure that this car is almost all stock from the day it was built only has 51,000 miles....the distributor was like rusted in place when i tried to bump up the timing last night,,,and what a difference that made. i just cranked it up with no light and waited to hear for any rattling which there is none...I haven't driven it far but it really woke that 305 up. maybe it will overheat,,we'll see. What a b****h it was to get to that dist clamp bolt, so much crap on that engine there isn't room to slip in a piece of paper. I removed and bent some stuff...stupid designers. Or maybe they wanted that way to prevent tampering...like the rolls royces of some years that locked their hoods shut because they didn't want the owners fooling around under there. i think you are probably;y correct about that 400 switch but like you i'm thinking I should have almost everything there already. I found some stuff that maybe be the vacuum switch on the manifold and there is a couple switches activated on the brake pedal arm... I doubt there is room for any more there. Anywho...i disconnected the trans form any wiring and could not tell the difference at all. No tach to tell rpms...Maybe the thing never worked to begin with. I will attempt to get it to operate eventually but I have a warm fuzzy feeling now that I know that it will still work almost the same without it. Time will tell...I hooked it back up for now...my driving is stop and go with speeds up to 60 or so on pretty much flat roads, I will try to be more sensitive to the effect and if it is engaging...I also have a old 92 lincoln continental winter bomb that has an overdrive and I can definitely tell when that one is operating..sometimes right around 42mph it bogs it right out if you try to drive that speed with it in overdrive. I think my system is all there and is complete...working?? I don't' know...but it apparently has more to it than just the three switches listed in that thread...the distributor has some relationship as does the carb itself so there will obviously be more sorting out of the items later.

I consulted one of my many motor manuals and found some reference but it really doesn't show the same setup at all..once I start stripping out all the old systems I will be able to better identify what goes to what. I am making a note of that part and will have it on hand when the time comes. Thanks.
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