Poor line pressure readings

[gusszgs]

I've been suspicious of my transmission for some time now due to it's annoying 1-2 2-3 flare as most would call it. Well I finally got my butt in gear and decided to perform a line pressure check today.
The readings I got were not impressive to say the least. The trans to the best of my knowledge stock BRF 2OO4r with the original D5. Approx 120 miles. The only mod is a deep Hughes pan.

These are the readings I got after taking the car out for a good drive and warmed up.

No TV rpm approx 1200 Full TV rpm approx 1200
Park - 68 psi Park - 155
R - 135 R - 200
N - 68 N - 155
D4 - 75 D4 - 175
D3 -75 D3 - 175
D2 -140 D2 - 140
D1 -140 D1 - 140

The transmission shifts flawless when driving in a civil manner. But, like I stated has that horrible flare from 1-2 and seems about the same going from 2-3. Fluid is nice and pink and I've never found any serious trash in the pan.

Thoughts on these readings would be appreciated

 

[bison]

Those don't look like stock BR calibration pressures.


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[gusszgs]

anyone?
As stated this is a confirmed BR transmission. I believe original to the car.
When I checked the pressures in 1st and 2nd the gauge didn't move off of 140 when I pulled the TV to max.
Could there be a broken spring? Or a stuck valve maybe?
According to my CK manual I should be seeing pressures of 300psi in 1-2, so I understand the values I've posted don't jive. Overall it seems that all the pressures are too low.
Any help on possible causes would be much appreciated

 

[bison]

anyone?
As stated this is a confirmed BR transmission. I believe original to the car.
When I checked the pressures in 1st and 2nd the gauge didn't move off of 140 when I pulled the TV to max.
Could there be a broken spring? Or a stuck valve maybe?
According to my CK manual I should be seeing pressures of 300psi in 1-2, so I understand the values I've posted don't jive. Overall it seems that all the pressures are too low.
Any help on possible causes would be much appreciated

You should be seeing about 225 psi with a .471" boost valve. It's possible you have other pressure regulator components in there. Now that you know the pressures are inadequate you would pull the pressure regulator assembly and measure the boost valves and post pics of the spring and valve here


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[larry33kc]

How do you do this test?

 

[gusszgs]

You should be seeing about 225 psi with a .471" boost valve. It's possible you have other pressure regulator components in there. Now that you know the pressures are inadequate you would pull the pressure regulator assembly and measure the boost valves and post pics of the spring and valve here


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Thanks, is this something that can be done by just dropping the pan?

 

[gusszgs]

How do you do this test?

There is a 1/8 npt port above the shift linkage on the transmission. Remove the plug and install a high pressure gauge

 

[bison]

Thanks, is this something that can be done by just dropping the pan?

Yes


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[larry33kc]

Do you drive the car?

 

[gusszgs]

Do you drive the car?

well sorta, while on axle stands or hoist

 

[larry33kc]

Ok thanks.

 

[gusszgs]

You should be seeing about 225 psi with a .471" boost valve. It's possible you have other pressure regulator components in there. Now that you know the pressures are inadequate you would pull the pressure regulator assembly and measure the boost valves and post pics of the spring and valve here


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Hi Bison, I finally got around to removing the PR assembly and boost valves. I measured the boost valves at where I believe one would measure them. The larger one measured just under 1/2" and the smaller one was a tad less than 3/8". Sorry, I don't have a digital caliper, The spring is very dark grey or black, hard to tell.
Also, when I removed the C-clip everything seemed to come out fine but the pressure reg valve hung up a bit, as it did not fall out on it's own. I looked up in there with a good light and can see some dark debris in there.

 

[McHaggis]

One thing I have discovered (in my limited experience) is that there are at least two different PR valves. The biggest difference with them is the location of the spring seat. One is closer to the boost valves and if you have the wrong spring on the wrong valve you either get way low pressure or too much (within reason). This might be the case here? You can shim the spring and while its a bit tricky to get everything back in there it works in a pinch. The limited pressure change in manual 1 & 2 when the TV cable is pulled seems to me to be normal?? BUT you should see a big increase in P,N,D & 3. Roughly this is how the PR works...
The TV valve, moved by the TV cable, increases pressure (as you continue to pull on the cable) to the boost valve (the bigger one that came out first) This "pushes" against the low/rev valve which in turn pushes against the end of the PR valve. This extra push increases line pressure.
In manual 1&2 the extra pressure is achieved by oil pressure flowing into the low/rev boost valve which pushes against the PR valve and this oil pressure also works against the Boost Valve (the bigger one) pushing it away from the PR valve so this is why pulling the TV cable has less/limited/no infulence on the pressure in this case.
Long story short.... More spring pressure, higher pressure. Bigger boost valves more pressure when those valves are acted on by either TV pressure (with is limited to 90psi by the TV Limit valve) or "clutch oil" as in M 1&2. Spring pressure gives you your initial no TV pressure in P,N, D, 3 so this is the place to start.
Therefore you can get the result you're after by changing out these parts to get the pressure where you want them.
I'd get someone to send you a new PR valve with the correct spring then you know you've got the mix correct to start with. This should get your initial pressure up to say 95psi and I'd go from there but be prepared to pull the pan and coulpe more times until you have it "right".

 

[Raeban]

Here are the factory specs on line pressures from the manual.

Here are mine after a local shop freshened it up ;(
4/8/2014 Results
Spec My Min TV My Max TV
P 60 220
R 95 240
N 60 200
4 60 230
3 60 230
2 200 200
1 200 200

And here is some EA values I found sometime ago in my research.
Extreme Automatics
Min TV Max TV
70 225
200 200
70 225
70 225
70 225
225 225
225 225


EA Excellent Results
Min TV Max TV
90 275
230 230
90 275
90 275
90 275
250 250
250 250

 

[gusszgs]

Thanks, I cleaned eveything up and reinstalled. Took the car out yesterday and it shifts nice and crisp 1-2 and 2-3 at half throttle or so. Had a chance to really lay into it from a stop and it shifted quik into 2nd while roasting the hides, but then let off (cars coming the other way)
I'll hook up my pressure gauge again this weekend and see the cleaning made a difference but I doubt it

 

[gusszgs]

Here are the factory specs on line pressures from the manual.
View attachment 228544

Here are mine after a local shop freshened it up ;(
4/8/2014 Results
Spec My Min TV My Max TV
P 60 220
R 95 240
N 60 200
4 60 230
3 60 230
2 200 200
1 200 200

And here is some EA values I found sometime ago in my research.
Extreme Automatics
Min TV Max TV
70 225
200 200
70 225
70 225
70 225
225 225
225 225


EA Excellent Results
Min TV Max TV
90 275
230 230
90 275
90 275
90 275
250 250
250 250

Wow, looks like my pressures are not so bad after all. According to the chart you've posted, all my values are inline with that info except for reverse, where I only seen 200psi. Maybe was debris. Thanks for posting

 

[mikestertwo]

I see someone ground down one of the lands on the pressure regulator valve. I know that is common practice with some builders but that is not a good idea. It increases the charge pressure in the converter forcing it forward putting extra load on the crank thrust bearing. I have seen this cause premature thrust bearing failures. FYI.

 

[gusszgs]

I see someone ground down one of the lands on the pressure regulator valve. I know that is common practice with some builders but that is not a good idea. It increases the charge pressure in the converter forcing it forward putting extra load on the crank thrust bearing. I have seen this cause premature thrust bearing failures. FYI.

Good eye Mike, ya I noticed that part of the valve wasn't of the same texture/smoothness like the rest of it. It didn't occur to me that someone would grind it down on purpose. Thanks for that info, now my anxiety has increased worrying about the thrust bearing.

 

[Steve V]

I see someone ground down one of the lands on the pressure regulator valve. I know that is common practice with some builders but that is not a good idea. It increases the charge pressure in the converter forcing it forward putting extra load on the crank thrust bearing. I have seen this cause premature thrust bearing failures. FYI.

I was taught to grind two flats on the top land of the PR valve not to grind it down, whats your opinion on this? They called it the "full time convertor lube" mod.

 

[TexasT]

It increases the charge pressure in the converter forcing it forward putting extra load on the crank thrust bearing.

Does it increase pressure or volume, or maybe both? How does the converter get lubed otherwise?
I'm guessing as we add extra pressure this makes the problem worse
Sorry to get off track. Thought others might wonder too.

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