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Discussion Starter #1
Hi,
I could really use some good advice. I have just fitted a rebuilt Th700R4.
To ensure the correct TV setting and pressures I have connected a gauge.The pressures in P,R,N,O/D,3 and 2 are all good and well within the ranges. But when 1st is selected the pressure drops to about 59 psi and when I pull on the TV cable it rises to about 150 psi but is very erratic. When driven ( short test drive ) all gears work well, but when Manual 1st is selected it upshifs to 2nd at 2500 rpm,I cannot get it to hold 1st.
The Low/rev valve has been changed but its still the same.
Help please,
Warmest regards,
Dave
 

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Dave Brown said:
Hi,
I could really use some good advice. I have just fitted a rebuilt Th700R4.
To ensure the correct TV setting and pressures I have connected a gauge.The pressures in P,R,N,O/D,3 and 2 are all good and well within the ranges. But when 1st is selected the pressure drops to about 59 psi and when I pull on the TV cable it rises to about 150 psi but is very erratic. When driven ( short test drive ) all gears work well, but when Manual 1st is selected it upshifs to 2nd at 2500 rpm,I cannot get it to hold 1st.
The Low/rev valve has been changed but its still the same.
Help please,
Warmest regards,
Dave
What low/rev valve are you changing? What is still the same? pressure or upshift point in manual low gear?

Low PSI in manual low gear sounds like you left out a check ball or cut the square cut seals on the low reverse piston in the back of the case.
 

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Discussion Starter #4
Dear Crosley,
Thank you very much for your reply, I am right out of my depth with this one.
It was at the Builders suggestion that the Low/Rev Boost valve was changed.
There is no improvement in either the Low (59 psi ) pressure or the Upshift at 2500 rpm in Manual Low.
I REALLY appreciate any help.
Thanks again,
Dave
 

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Dave Brown said:
Dear Crosley,
Thank you very much for your reply, I am right out of my depth with this one.
It was at the Builders suggestion that the Low/Rev Boost valve was changed.
There is no improvement in either the Low (59 psi ) pressure or the Upshift at 2500 rpm in Manual Low.
I REALLY appreciate any help.
Thanks again,
Dave
With a larger low/reverse boost valve an early 700/4L60 ( pre-1987) non - aux valve body tranny will hold 1st gear longer.

If the boost l/r valve is installed backwards there will be low PSI too
 

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Discussion Starter #6
Crosley
Thank you for all your help,Looks like I need to take it to a Tranny Shop, I live in Scotland so shipping it back to the builders who sold me it would cost $500.
Local guys here don't have much experience with TH700s. have you any advice I can pass to them as to where to start looking.
So far I've got:- If the boost l/r valve is installed backwards there will be low PSI,
Check Ball missing and Square seal.
Again many many thanks
Dave
 
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