No wiring to my 700R4. I would like to get it to lockup to make sure it works, then commence wiring the brake light switch etc.. I believe it to be an '83 diesel trans. Here is a photo of the inside of the pan. 3 wires run to the connector. Can anyone tell me which wires get 12v and ground? Does it only lock in overdrive? TIA
CK5
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700r4 Lockup help
- Thread starter PaulZ
- Start date
If the lockup doesn't work, don't use 4th gear!
There are several variants of wiring for the 700's. In general, there are 2 "hot" wires to the transmission.
There are several variants of wiring for the 700's. In general, there are 2 "hot" wires to the transmission.
- One is routed only through the brake switch. If you aren't on the brake pedal, it should be hot. This ensures lockup in 4th gear.
- The other is routed through the brake switch, the 4WD relay (triggered by the transfer case) and the vacuum switch (located near the brake booster). This gives you lockup in 3rd and 4th gear, given the hydraulic conditions are right (based on vehicle speed and TV pressure).
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Blue85, thanks for replying, sorry I'm late getting back to you, been doing some investigating. I do have the normally closed 3/4 switch as shown in you schematic. Why though do I have a wire running to position D on the connector also as shown but no external wire?
Anyway do I really want 3rd gear lockup? I have fairly low gears and it seldom stays in 3rd unless I leave it there. Didn't they eliminate the 3rd gear lockup later on?
I have nothing wired to the transfer case, what is the purpose of that?
Anyway do I really want 3rd gear lockup? I have fairly low gears and it seldom stays in 3rd unless I leave it there. Didn't they eliminate the 3rd gear lockup later on?
I have nothing wired to the transfer case, what is the purpose of that?
You may be set up like this. Like I said, there are many variations, but basically:
- A is the main power input.
- B is the 4th clutch switch. Typically this is used as an output - either so the ECM knows you're in 4th gear or for some other emissions purpose on carb trucks (like enabling EGR or evap purge).
- C is an output from some other switch
- D is ground for the solenoid, but many units have the solenoid grounded inside with a ring terminal to one of the solenoid mounting bolts. D is mostly used with ECM.
Thanks again! This diagram is exactly how mine is wired inside the pan. So with power to A and D grounded (two wire solenoid) it should work, then just a matter of adding brake/toggle/vacuum switches as desired? I leave B open?
Can't wait to get this thing back together, blocking my driveway.
Can't wait to get this thing back together, blocking my driveway.
Are you sure it's locking all the time in 2 and 3? Many years had hydraulics that would provide the lockup pressure (see M in the diagram below), so it was only available above a certain speed (governor pressure) and certain loads (TV pressure). So without those being met, you could supply power to the solenoid and still not have lockup. Maybe yours isn't set up that way. The TBI trans could lock even in 1st gear.
You can test by keeping your foot on the gas while cutting power to the trans (typically by tapping the brake pedal, but in your case maybe just removing a clip from a battery?) to see if the engine speed changes.
It's preferred to be unlocked while shifting. The trans is set by default to unlock during the downshift out of overdrive.
You can test by keeping your foot on the gas while cutting power to the trans (typically by tapping the brake pedal, but in your case maybe just removing a clip from a battery?) to see if the engine speed changes.
It's preferred to be unlocked while shifting. The trans is set by default to unlock during the downshift out of overdrive.
I have A wired through the brake switch and a toggle now. It locks up at slow speed and stays locked up even if I floor it unless I flip the toggle.
The 3/4 presure switch says it opens between that shift but nothing about 2-3. I'm thinking about disconnecting that circuit and just using the 4th gear pressure switch for ground. That should give me 4th lockup only, safely, correct?
The 3/4 presure switch says it opens between that shift but nothing about 2-3. I'm thinking about disconnecting that circuit and just using the 4th gear pressure switch for ground. That should give me 4th lockup only, safely, correct?
Do you have the vacuum switch underhood? When that's routed to a ported vacuum source it turns off the lockup when you're at idle/decel and at heavy throttle. It could be good enough to solve your problem. You could wire the the vacuum switch as a ground source to pin B.
If you can't get that to work, locking in 4th only is probably better than always locking.
If you can't get that to work, locking in 4th only is probably better than always locking.
I would wire it up for 4th only lockup, lockup is possible in 2nd , 3rd and 4th gears.
After running around with the 2 3 4 lockup I think I would prefer just 4th. So far no luck. Originally I had power to A (420) and D (422) grounded. That got me the 2 3 4 lockup. Today I tried connecting B to D and ungrounding, which should have given me lockup when the 4th gear switch grounded but it did not. Perhaps I have a bad 4th gear switch.
Just run the brake switch to A and leave the rest disconnected. If the diagram above is what you have, the ground will come through the chassis and you'll have lockup only in 4th - unless it's downshifting or you're pushing the brake pedal or the tranny is cold.
It seems as if yours is like both of my old trucks.
I believe that you would need a vacuum switch and some sort of speed disconnect to keep it to just 3 and 4.
I believe that you would need a vacuum switch and some sort of speed disconnect to keep it to just 3 and 4.
More testing yesterday. With it wired as shown here, I should have a complete circuit when the 4th gear switch closes, but it's not locking up, even at freeway speed and warm. The only way I have been able to get it to lock is by grounding 422 (D), but then it locks in 2,3,4. Next move will be to pull the pan again and test the 4th gear switch.
