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KEN!! Mayday!

BigRed

Well-known member
Joined
May 23, 2001
Messages
948
Location
Edmonton
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1985 Bright Red Rocket
KEN!!OR LEN!! Mayday! (4+3 Switch)

Ken I need to know more about the DN 4+3 switch removal procedure. I saw your site but im unclear as to what your trying to say..

Can I remove the plug off the harness and simply tie the wires together?

Or is it the little part on the Tranny itself that I have to bridge? If so do I remove the switch then jumper? If you remove the harness won't it eliminate the power and rendure the switch usless?

Can you please spell this out for me ABC's my mechanic and I looked at it today on the hoist and we decided to wait till I got more information from you.

Thanks Bro.
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
BigRed said:
Can I remove the plug off the harness and simply tie the wires together?

Bear in mind that I personally have never performed this operation, although Len (nyernga) has and he has reported good results. If I'm correct, you don't have to remove any plug from the harness, but those are the wires that get jumpered together.

If you remove the harness won't it eliminate the power and rendure the switch usless?

That's the idea. ;)

I hope this helps you man.

_ken :w
 

BigRed

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Joined
May 23, 2001
Messages
948
Location
Edmonton
Corvette
1985 Bright Red Rocket
I see so by removing the wires the switch on the tranny loses power, then with the wires crossed this will fool the computer into thinking that its permanently engauged giving me complete control at the stick with the switch ON the stick.

Reason why I said to chop the plug off (And save it of course) was because doing a wire splice with soder and heat shrink seemed like a ideal soultion compared to making a jumper (We can't find them darn connectors for the life of us). And If I ever sell the car (God forbid) I can simply reconnect the plug I cut off.

Ok now where the thing actually is..

Theres like 3 wires going to my transmission.

1.) furthest to the rear, it has only one wire and is a rubbery cone shape going onto the tranny

2.) Looks like its around the access panel to the manual gear box
(This is the one I thought it was)

3.) more toward the front. (I think this ones the reverse indicator)

Thanks Ken
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
One thing that is going to remain a sore spot for me in regards the 4+3, and that is the fact that the relay for the overdrive unit could be the culprit leading to the overdrive not staying engaged, yet the "technicians" never found it, and the books I have don't actually have any direct referrence to it (with a location that is).

I fought that problem for years, not to mention spending a needlessly exorbitant amount of money, before I discovered the relay. I only found it when pursuing another problem! :mad

Just an FYI for you guys to keep in mind. ;)

_ken :w
 

Top

Well-known member
Joined
Mar 20, 2002
Messages
161
Location
Las Vegas, Nv
Corvette
1986 Convertible Dark Red Metallic
Ken, I hear ya. I wanted to 'jump' my 4+3 but it's an 86, no wire to jump. After you talked about the relay, I replaced it and all is well, but I was on the rebuild road until I found your info. I 'owe' you a cold one someday :beer
 

Ken

Gone but not forgotten
Joined
Jan 30, 2001
Messages
8,236
Location
Hermosa Beach, CA
Corvette
1987 Z51 Silver Coupe
I'm glad I'm able to give something back, in this life. ;)

_ken :w
 
Joined
Oct 30, 2001
Messages
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Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Relay... hmm.. Could this be why occasionally the car will jump into and then out of OD when shifting from first to second? It almost seems like the computer thinks I'm giving it more gas than I am, though, because when I get to 4th it drops back into OD by itself.
[RICHR]
 
J

Jedi86

Guest
I hate my 4+3, its been in the shop for almost three weeks now. Its summer and I can't even drive it! I am really irritated with GM right now. Its really starting to **** me off where I am at a point where I want to throw an auto in there. :mad
 

BigRed

Well-known member
Joined
May 23, 2001
Messages
948
Location
Edmonton
Corvette
1985 Bright Red Rocket
WHOA!

I have an 85 I think I see the place where Im supposed to cut but Im not sure as to which wire to cut..

1.) furthest to the rear, it has only one wire and is a rubbery cone shape going onto the tranny

2.) Looks like its around the access panel to the manual gear box
(This is the one I thought it was)

3.) more toward the front. (I think this ones the reverse indicator)

Do I even have this switch to mod? I should according to articles Ive read but why doesn't the 86' have this.
 
Joined
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1986 Bright Red Coupe
Well, Ken has a chart on his 4+3 info page (which seems to be down?) that lists the changes between the various years of 4+3's. For 86, it says that there are only two connections into the transmission (reverse and temp sensor? I can't find the chart right now). All other years (lucky me) have the third connection.
[RICHR]
 
Joined
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Messages
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Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Doh! Thanks... would have hated to lose that reference.

Anyway, this is the passage I was referring to:
" Many questions are always asked about what features and characteristics of the overdrive are normal or not. Problems always arise since people will compare the operation of different years and think something is wrong. This chart was designed to help you see these variations. There were also changes in the amount of side cover switches on the 4 speed section. All 1984 cars had 3 switches (1st, 2nd, and 4th ). 1985 , 1987, and 1988 cars had a 1st gear switch and 1986 cars had NONE."

From this, I read that there is no switch on the transmission that can be bypassed. Of course, I could be (and would love to be, in this case) wrong.

[RICHR]
 

BigRed

Well-known member
Joined
May 23, 2001
Messages
948
Location
Edmonton
Corvette
1985 Bright Red Rocket
Ouch..But Good news for me LOL

So all I have to do it figure out with one to cut and join.

Im assuming the one with the single wire is temp right?

So now Im down to two, any Ideas?
 
Joined
Oct 30, 2001
Messages
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Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
Another quote from the same page (if you haven't browsed the whole page yet, WHY THE &*(&^#(*^&$( NOT????):

" What we did was fool the computer into thinking that I'm always in second gear or higher. This switch is on the left side of the transmission, and can be seen easily if you have the car on a lift. This switch moved around a little during the years, but it was always the switch toward the rear. Remove the wiring harness from the switch and hook it out of the way with a tie-wrap. You won't be using this harness. Now make a little jumper wire that fits into the two terminals. You can actually remove the switch from the transmission and make the jumper wire on your workbench. It shouldn't take more than 15 minutes."

Just on the off chance that I do in fact have that switch, next time I have the car in for service somewhere with a lift, I may try playing with whatever plug is at the rear of the transmission (there is something there; no idea what, though).
[RICHR]
 
Joined
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Messages
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Location
Glen Burnie, MD, USA
Corvette
1986 Bright Red Coupe
tidbits from the service manual for 1986:
"the output shaft from the manual unit is linked to a 40-tooth input sun gear in the overdrive unit. This, in turn, is meshed with four double planet gears (24 and 30 tooth), which mesh with the 34-tooth output shaft gear. The planet gears are mounted in a carrier to which two sets of clutch plates are also attached. The outer plates, when engaged, lock the carrier in place with the transmission housing. the inner clutch plates, when engaged, lock the output shaft to the carrier. These two clutch packs are arranged so that if one is engaged, the other is disengaged."
"The operation of these clutch packs is controlled by a hydraulic circuit which causes the movement of the main finger plate via a piston and accumulator assembly. When the piston is forced down against a series of springs applying approximately 1350 pounds of thruts, the outer (carrier to housing) clutch plates are compressed while the inner plates are released. When the piston is allowed to return to the initial position, the outer plates are released while the inner set is compressed. A sprag clutch is used to avoid a neutral position for the brief periods when both clutch packs are disengaged. The accumulator is used to regulate the speed at which the piston moves, and thus, the speed of the complete shift from direct to overdrive or vice versa. This accumulator is essentially a "cusion" attached to the piston whose firmness is controlled by fluid pressure, and a series of springs by which it is held to the piston."
"The hydraulic circuit consists mainly of a gerotor pump on the overdrive units output shaft and a shift valve and solenoid, and accumulator valve, and a pressure relief valve all located in the valve body assembly. In the normal (direct drive) mode fluid circulates from the pump through the 115-125 PSI pressure relief valve and through the cooler lines then back to the pan or sump area. A small amount is also circulated through the shift valve and solenoid. When the overdrive switch is closed by the ECM, the solenoid plunger is activated. This causes the shift valve to provide an open channel for flow into the piston. With a new path by which fluid can flow, the relief valve lines experience a drop in pressure causing the valve to close, and subsequently, routing nearly all flow to the piston. A similar valve in the cooler lines also closes if pressure drops below 70 PSI. The piston then moves against its springs and activates the overdrive mode. When the piston stroke is complete, pressure returns to the cooler lines and reopens the pressure relief valve. Flow to the piston ceases, but the 115-125 PSI pressure maintains position as long as the shift solenoid is energised. When the solenoid de0energises, the shift valve returns to the original position. Fluid is forced from the piston as the springs move it back to the direct drive position. The speed at which this downshift occurs is regulated by an orifice in the shift valve exhaust line and by an orifice in the accumulator lines. When low speed upshifts occur, the valve maintains a low accumulator pressure. The accumulator slides forward as pressure builds on the piston. in this way the complete piston stroke is slowed allowing more slipping of the clutch plates, and thus, a smooth shift to the overdrive mode. When high speed shifts occur, pressure to the accumulator is high. The accumulator and piston move completely together. This causes a much faster piston stroke and subsequent shift to overdrive which is desirable at high speeds."
 
Joined
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Messages
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Location
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1986 Bright Red Coupe
More stuff: you can adjust the linkages from INSIDE the car, without raising it on a lift, by removing the driver's seat and the whole left side of the center console (plus shift knob). I assume you adjust the linkages if you're having trouble getting into gear?
There's a list of about 12 things to check if overdrive is inoperable. Any interest?
Nothing, though, on any overdrive select switch.
[RICHR]
 

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