Th400 pressure too high?
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From: Seattle
Th400 pressure too high? Good Morning,
So I recently rebuilt my th400 for my turbo LM7 swapped Cutlass.
- built with Jake's stage 2 setup
- 3500 stall converter
- 1-2 valve was modded for no upshift
- 2-3 accumulator was disabled
- dual fed internally
- converter feed was restricted to .157.
- Stock automatic valve body otherwise
- Sonnax pressure booster valve and spring setup.
My pressures are as follows with a fairly cold trans:
When I manual select 1 or 2 the pressure fluctuates a bit which is why there is a range, but is rock solid in other gears.
The question is why is my manual 1st and 2nd so high and is it an issue?
Thanks in advance for the help.
So I recently rebuilt my th400 for my turbo LM7 swapped Cutlass.
- built with Jake's stage 2 setup
- 3500 stall converter
- 1-2 valve was modded for no upshift
- 2-3 accumulator was disabled
- dual fed internally
- converter feed was restricted to .157.
- Stock automatic valve body otherwise
- Sonnax pressure booster valve and spring setup.
My pressures are as follows with a fairly cold trans:
When I manual select 1 or 2 the pressure fluctuates a bit which is why there is a range, but is rock solid in other gears.
The question is why is my manual 1st and 2nd so high and is it an issue?
Thanks in advance for the help.
Thread Starter
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From: Seattle
Also of note is that the car seems to drive and shift just fine. My only real concern is the fluctuation of pressure and how high it goes. I am willing to bet that it gets up to 250 or better when I floor it but have been having a hard time keeping an eye on that gauge while flooring it 
Thread Starter
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From: Seattle
@jake: I will get those numbers for you when I get home.
My recollection was with modulator disconnected that they are about the same in Manual 1 and 2 but quite a bit higher for all the others. I know for sure reverse was way up in the 200 PSI range and believe park, neutral and drive were all 150 or so.
My recollection was with modulator disconnected that they are about the same in Manual 1 and 2 but quite a bit higher for all the others. I know for sure reverse was way up in the 200 PSI range and believe park, neutral and drive were all 150 or so.
That all sounds good.
Wild fluctuation is often due to low fluid.
Be sure it's full.
3rd is usually lower on auto VB.
Reverse will be 50% higher. 300 psi plus with modulator unhooked is normal.
Wild fluctuation is often due to low fluid.
Be sure it's full.
3rd is usually lower on auto VB.
Reverse will be 50% higher. 300 psi plus with modulator unhooked is normal.
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From: Seattle
ok So I took the readings you asked for this time the trans was warm:
**edit** pay no attention to this I am a dummy. Real pressures below.
The fluctuation didnt seem as bad today and in retrospect it may have been a product of a surging motor. Tonight when I double checked it the fluctuation was about 5 psi and I think part of that might be the gauge. I finished dialing in the vacuum modulator and the car is running pretty good.
Thanks again for your input
**edit** pay no attention to this I am a dummy. Real pressures below.
The fluctuation didnt seem as bad today and in retrospect it may have been a product of a surging motor. Tonight when I double checked it the fluctuation was about 5 psi and I think part of that might be the gauge. I finished dialing in the vacuum modulator and the car is running pretty good.
Thanks again for your input
Last edited by jtotheizzo; Sep 17, 2015 at 11:08 AM.
5-10 psi is normal fluctuation caused by the PR valve shuttling to adjust the pressure.
50 psi is an odd fluctuation.
Pressures look good except the R is low, and neutral is high. Are you sure you didn't confuse those two?
50 psi is an odd fluctuation.
Pressures look good except the R is low, and neutral is high. Are you sure you didn't confuse those two?
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Thread Starter
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Joined: Jul 2011
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From: Seattle
I have corrected it so as not to confuse the kids following along at home:
I would have been concerned if neutral was that high and reverse was that low.
So you dont think 225 is too much pressure? I was concerned because all the literature and reading I have done says not to exceed 200 PSI.
If you think this is all good then we will give it a go.
My last question is what is your recommended burn out procedure for this setup? I cant seem to find consensus from anyone. Since these are your parts I will ask the man
Last edited by jtotheizzo; Sep 17, 2015 at 11:08 AM.
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Verdad Gallardo 225 is a bit high but not really a problem.
You could put a slightly lighter pressure regulator spring to lower the pressure.
Light throttle in 1st to get the tires spinning, shift to 2nd at part throttle with decent wheelspeed, then WOT and shift to 3rd to finish burnout.
You could put a slightly lighter pressure regulator spring to lower the pressure.
Light throttle in 1st to get the tires spinning, shift to 2nd at part throttle with decent wheelspeed, then WOT and shift to 3rd to finish burnout.
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From: Seattle
I am curious about this as most people say it is not a big deal to leave it disconnected. Would this raise my line pressure in auto third? it certainly wouldnt be a big deal to connect it I just thought it wasnt worth the trouble.
27% is a lot. Stay off the limiter. If it going to over rev because of the slip just let off. Dyno numbers are just numbers. Better for comparison when you make changes IMHO. Get it to leave and it'll run.