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Old 05-07-2008, 04:41 PM
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high line pressure, 700r4

hey there, new to this forum, found it in a search for a solution to my problem.

so here it is, i got a freshly rebuilt 700-r4 hooked up to a 350 SBC. im having a problem with high line pressure in the trans. it constantly reads anywhere from 120-150psi no matter what gear its in. the tv cable does nothing to the pressure but is hooked up correctly. i also just put a new valve body in it.

does anybody have any guidance on how to normalize the line pressure?

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Old 05-09-2008, 08:57 AM
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Quote:
Originally Posted by TCI
200-4R/700-R4 Pressure Test

Forward Pattern - P R N OD D 2 1
Park
Min 90-110 Max 190-230
Reverse
Min 95-120 Max 200-300
Neutral
Min 90-110 Max 190-230
Overdrive
Min 90-110 Max 190-230
Drive
Min 90-110 Max 190-230
Second
Min 185-230 Max 185-230
Low
Min 185-230 Max 185-230

I know this is hard to read but I can't create a table with out HTML.

So whats the problem?
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Old 05-09-2008, 10:59 AM
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well it was from my understanding that at idle the pressure for P,R,N,OD,D was to be 65-85psi and at WOT it is supposed to be 165-210psi but my pressure isnt changing at all from idle to WOT in any gear. this is causing the transmission to shift extreemly late. it didnt shift to 4th until 75mph. it was shifting solid, but just late.
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Old 05-09-2008, 02:29 PM
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Line pressure doesn't effect shift position. your governor and mod valve does that.
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Old 05-09-2008, 05:14 PM
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What kind of valvebody did you install? Stock or TCI constant pressure VB? The TCI VB does away with the TV cable.
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Old 05-09-2008, 05:22 PM
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refurbished stock
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Old 05-09-2008, 06:35 PM
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couple of things;

There is no mod valve on the 700r4 trans... IF you are referring to a vacuum modulator.

The TV cable moves the inner TV valve which will raise line pressure. Since you have high line full time and late shifts... this tells me the inner TV valve is stuck in a high position or the trans is in "fail safe " mode IF the fail safe check ball was installed.

A few items can cause the "fail safe" mode... TV cable Minimum setting incorrect. The check ball seats and puts the trans into fail safe.

A worn out inner TV valve bore can cause a false fail safe by internal leakage in the worn valve bore.

I hope the correct replacement valve body was installed... there are differences in design and years , check ball counts.

Help this helps some , not confuse.

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Last edited by Crosley; 05-10-2008 at 07:25 AM. Reason: clarity -- speeling
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Old 05-10-2008, 01:33 AM
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it was a direct replacement valve body for an 85 700r4, we had the safety check ball installed after it was doing the same thing and caused the trans to blow 3rd and 4th.

the inner TV valve isnt stuck either, we've checked it while outside the transmission when we were installing the new valve body; and we also made certain that it worked properly with someone in the car while on the lift, depressing the pedal to WOT and making sure the TV valve was acting as it was supposed to.

and as for a worn valve bore, we used two different valve bodies, it would be improbable that both of them would be in bad condition, although i guess not terribly unlikely since they were both used
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Old 05-10-2008, 07:32 AM
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IF the main pressure remains high and does not modulate with the TV cable pull... the trans is in fail safe mode or a false fail safe ......

OR there is a problem in the boost valve - PR circuit. PR= pressure regulator.

Boost valves installed incorrectly?

I've seen many valve bores worn out on the TV circuit. A common wear area.

Since your post indicates the trans shifts late like the throttle is wide open , this indicates a TV problem along with the high main line pressure .....

OR you have two problems. A PR circuit problem and a sticking governor.

post back when you can.

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