700R4 1-2 shift issue, please help!

1987 GMC Jimmy said:

And that Transgo full kit is a fantastic upgrade. You’ll be cooking with fish grease after that.

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When I get this sorted Ill start working on the lumberyard skiff I need.

Also need a new case connector pigtail...



Starting to get expensive..
Ordered case connector
Connector pigtail
New solenoid

The only thing I can't find is an individual two prong pressure switch / that doesn't come in kit with stuff I don't need!

Before I removed the valve body, I'd watch throttle valve movement while a friend opens and closes the throttle linkage. And make sure that fast idle (choke on) is not set! Then manually move the TV lever to make sure the cable is moving the valve fully open, and that the spring is fully closing it.

I recently worked on a 700R4 where the bottom of the inner cable end was getting hung up inside the brand new OE-type cable housing. So when we felt resistance and thought the valve was fully open, it wasn't! Don't know the symptoms because the car hadn't been on the road yet. Ended up using a PTFE-lined Lokar cable which was expensive, but light years better.

What you want is the smallest bit of off-idle throttle movement to start pulling on the cable. In fact, a little preload won't hurt at all. And if you ever re-adjust idle speed, re-check TV cable adjustment.

Great idea, I will then drain the fluid, remove the pan and check the tv cable, plunger and valve cycling, or lack of, before taking it down.

Now Im waiting for parts to arrive in one or two weeks.

Going back to the lockup topic... I read somewhere that the one prong pressure switch is for grounding to the case itself and completing the solenoid circuit with 12v constant to the solenoid.

Since my VB has both one and two prong pressure switches and I only want 4th circuit lockup, I could use either of the pressure switches on the 4th circuit.

One prong - use it as a ground switch and wire 12v directly to the solenoid.

or

Two prong - for 12v switching of the solenoid and the ground just directly taken from any bolt inside the case with a ring terminal.

Any issues with either idea?

Update:
Considering … the task it is to remove the TC and transmission and work on that beast in my limited shop space; I have decided to remove the valve body only and work on it on my small shop table without having all the extra parts around cluttering my space.

Matt69olds said:

Why would you need to remove the transmission to remove the valve body?

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If things get complicated when I do rewove the valve body then I'll consider removing the TC and transmission.

I received the separator plate, transgo SK700 kit and case connector pigtail (exterior plug). Waiting on the case connector itself, TCC solenoid, filter and pan gasket.

Should start the ATF draining, pan removal, TV plunger and valve action/movement verification, VB disassembly this weekend.

There are a lot of springs and balls in the transgo kit .

Get the valve body out, the longer it drains now, the cleaner reassembly will be later.

I received the skift kit, case connector, case pigtail plug, separator plate, tcc solenoid, filter and gasket.

Last weekend I took the VB down and completely rebuilt it with all new springs in all circuits and a new TV valve assembly.

I had used rtv and the gasket on the pan and it was a chore to remove, wont glue it down again!

See first photo and notice the new valve on top and the old valve below. The new valve has an additional spring, a stronger cone spring, spacer, shim and new plunger spring.

Used brake cleaner and then PB blaster to get the VB clean before rebuilding each circuit.
It was hard to tell if the TV valve was sticking (plunger itself was not sticking) but with the stronger and additional valve springs... valve and plunger are definitely reacting faster.

I did have one circuit valve fully stuck and had to get the valve housing/bushing in the oven to free it, cleaned and reassembled. It was one of the step 7 bushings/valve, I think 3-4 TV valve and bushing shown in C step.

Now Im waiting to receive the Sonnax 1-2 and 3-4 pinless accumulators. The original ones has some wear in the pin hole, so I decided to do this now.

And Im trying to figure out the best check ball setup. Many sites and many videos show different ideas that apparently all work great.

I do have photos of all the VB and case check ball locations of when I disassembled my VB. I think I have 8 in total, (4 in case and 4 in VB) two larger ones in those 8.

Its a 1984 700R4 4x4 non auxiliary transmission.

Some sites and videos leave out check balls that are "not needed".

Does anyone have a proven check ball location diagram that I can go by for my reassembly?

AlexK10 said:

Yeap Last night a read through a few ideas to wire the lockup,

1. 4th and 4-3 circuits
2. 4th only
3. vacuum activated
4. break pedal opening switch
5. interior or exterior case pressure switches
6. temperature based
7. Simplest of all - no pressure or temp or vacuum switches and manually switching direct to the TCC solenoid with a dash mounted toggle switch (lock up any time at any gear on driver demand)
8. and combinations of all of the above.

Looking at my VB I think it originally had/have a 4th and 4-3 pressure switch system.

The simplest automatic lockup I've found was to ground the TCC internally to one of the VB (valve body) bolts and only run a single 12v from the TCC solenoid through a two prong 4th pressure switch and out the case via the case plug to a fused and dash switched 12v.

That way I eliminate the 4-3 switch, npt plug it or leave it disconnected, which I think is what later models had, only a 4th circuit pressure switch.

Usually the ground is the one being interrupted by the pressure switch not the powered 12v.

Anything wrong with switching this and grounding to the case and running the 12v through the 4th circuit pressure switch?

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I would recommend
using a brake switch to disconnect lock up on braking
using a vacuum switch it disconnects lock up on acceleration ( basically 4th lock up to 4th kickdown)
if you have the 4/3 switch use it its only 1 more wire ,it was to disconnect the lock up on 4/3 downshift , and wasn't eliminated until computers took control of the lock up.
if you wire it this way its all automatic no dash switch to mess with and forget.

Follow the instructions for check ball locations. You can get into trouble deleting them, some are designed to unseat only on clutch release. In other words, hydraulic pressure seats a check ball, which forces fluid thru the small apply hole allowing a smooth clutch/band apply. When the clutch releases, the ball unseats, and then fluid can exhaust thru the orifice and the large check ball hole. You can get into a bind up or flare during a shift if the check balls aren’t used to control the shift timing.


Follow the instructions, if you decide the transmission shifts to soft, you can always make the feed holes bigger. In my experience, TransGo is pretty conservative on shift feel. I don’t like girlie-man soft shifts, at the minimum I want a solid “thud”. Just enough that you can definitely tell the trans shifted. I set them up with the feed holes drilled on the bigger calibration, I have yet to have someone complain about one shifting too hard.

Not sure about the 2nd piston casting code for holes A and C. If this is inside the VB bushings/valves, I am not about to take the VB circuits apart again to find this code.

Please guide me to finding this 2nd piston code; or should I drill them anyways?

These two openings I have in the original plate but not on the new Transgo plate:

And this one I have in the new Transgo plate but not the original...

The holes above are for the auxiliary system which mine does not have, a plate goes over this area with the gaskets, an also covers this square hole that Im pointing at, when compared to the previous post photos of the original plate.

Matt69olds said:

Follow the instructions, if you decide the transmission shifts to soft, you can always make the feed holes bigger.

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I found this on the Sonnax site. My 2nd and 3rd feeder holes are .093 and Transgo suggests drilling to .110 (see Transgo plate instructions on previous post photo) which is 50% according to the Sonnax guide from .095 which is the closest to .093 (see photos on this post).

However, Sonnax recommends a 20% increase in hole size which would be .104".

Sonnax also shows 2nd 3rd and 4th feeder holes to be drilled and Transgo only holes A and C which are for 2nd and 3rd.

This is a lot to follow.

Should I drill any, all or none and to what size?

Your going to have to pull the servo out to get the casting number.