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well maybe its the instructions i have. in your picture you show 3 holes and in the transgo there are only 2
The two holes are normal . That 3rd hole I know Transgo don't drill it . Other kits do. What that is is a restriction feed at the 2-3 backout valve . Transgo keep that operational with the white spring.
Drilling that extra hole does away with the restriction and usually use a ball or machined plug to block all movement of the 2-3 Backout .
 

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Oh Dacron ... Hmmm yes I have used them on one C6 , it was ok . I prefer not to .

A mate used a unknowingly used Dacron in a Turbo 400 and it made all sorts weird noises too. I got him the brass gauze type cured it.

I wonder???? It that may account for the lower pressure ?

Funny though most new transmissions use Dacron but no problems
 

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Discussion Starter #43
well thank for your responses and just on the dacron filter alone i am not convinced, well i wasn't until i read a post on a mopar forum looking for a brass filter which described similar sounds from early 904's when a single hole filter instead of the 2 hole was used because it has 2 pumps and the rear one would be starved of trans fluid. So i believe i may have found the issue with your help and will know tomorrow when i get a c4 filter.
thanks again for your help guys and if it works i will post back so fingers crossed.I can't wait to find out i'm pulling it apart tonight!
 

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I'm not totally convinced either but I have seen issues as I mentioned .. But what throws that out is the late model cars use a lot of Dacron..

But then something is keeping the pressure down somewhat lower than what I've seen that setup run at , a restriction can cause that , I wonder ?

But still hard to pin point what the noise is exactly.
 

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Discussion Starter #45
Hello guys, after changing from the dacron to a screen i dont have much to tell you because it still squeals, has a small improvement in shift firmness (you can feel it now) and pressure rises more with rpm in neutral otherwise its the same.
Have either of you used the b&m deep pan with the filter extension and greg which filter do use?
please keep the suggestions coming, they are all very much appreciated
 

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Discussion Starter #47
Greg that's good to know, because i bought the second one with the round tube with the 904 screen. do you think the pickup tube in the b&m filter extension is to small and coupled with the dacron filter reduced pressure because i found the dacron filter had sucked in? also my wife said to me if that hole is to small then it could cause the sound like air passing at pressure through a small hole! i am going to try the ford filter and find out so please let me know what you think.
 

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You know it could be . I've never used that filter extension in a C4 , although have used quite a few of the C6 ones that are similar

Is the extension tube bigger than the valvebody passage that feeds the pump? Just thinking though the hole in the filter is fairly small?

FXF-45020 is the part no. for that 1st filter from ATP Motospecs

Motospecs - Contact
 

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That tube type filter extension...

Is it possible it is too close to the inside bottom of the pan?

That would cause a fluid starvation issue.

The C6 tube filter extensions I have seen,
all have little legs that prevent the tube from coming too close to the pan.

The one in the picture above worries me that this could happen.
 

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Discussion Starter #50
Hello again, and although i don't have great news i do have some. removed the b&m filter extension with 904 screen filter and installed a 4x4 filter with round hole and a short extension in it the same size as the hole without the rubber grommet and shifts the same as 904 screen and better than the dacron.

hello Greg, thank you for that info and the b&m tube is about half that of the pump inlet and the filter has the same size of the tube.

Hello Gallaxiex, i am using the filter extension in the picture below and my concern was with the tube, it is 14mm - 9/16 inside diameter where the inlet to the pump is about double that which would flow more than double the fluid.

Greg, if i drill the 110" hole to 125" as in your picture what will this do?

do you guys know of any reason why the line pressure is so low 125 in 3rd, 150 psi in 1st and 2nd gears when 300 at idle in reverse with modulator connected and working? [see transgo line pressure spec in pic below]

in step number 4 of these instructions i used the pink spring as directed, is this wrong?

should i try the omitted spring in step 4 instead?

the (optional spring not used on all models) is not installed in the 2-3 backout valve, should it be?

and thank you again, all of your help is very much appreciated.
 

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Yikes!
That filter extension with the 9/16" hole looks tiny!
I would not use that.
Happy to hear you changed it.

The shift valve springs should not affect the pressure, only the shift timing.

Shift valves are "snap action" valves.
They are either full open or full closed.
They do not regulate pressure.

I'll let Greg comment on the rest. :)

Edit to add...

The 2-3 back out valve function is to prevent a harsh 2-3 upshift when the trans is in second gear at low speed,
and the driver suddenly "backs out" of the throttle.

During this time the shift to 3rd can come in with a bang (tie-up) as the band has not released yet.

It's also called 2-3 shift timing valve.

Also edit.... duh!

It's a manual -3 kit so no automatic shifts.

As an experiment...

I would try blocking the cutback valve so there is no cutback of mainline pressure at speed.
Basically put a really stiff spring in place of the orange one, to jam the valve against the end plate.
Or block it with a check ball or other small bit of metal so the valve cannot stroke.
 

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got it, cutback spring is to soft, would this loss of pressure continue while in 3rd?
I'm going to say "probably"...

The cut back valve is stroked by governor pressure, so it depends on vehicle speed.
Governor pressure rises in proportion to vehicle speed.

The motion of the cutback valve is prevented (resisted) by TV (modulator) pressure...

IOW

Governor pressure pushes on the end plate, end of the valve.

Modulator pressure pushes on the spring end.

Theoretically...
if modulator pressure is high (full throttle @ low vacuum),
the combination of modulator pressure plus the spring would keep the CB valve against the plate.
Thereby keeping line pressure high.

BUT, if governor pressure were able to overcome the modulator and spring pressure,
the cut back valve would stroke or stay stroked, and decrease line pressure.

Also, if the cut back valve were sticky in its bore, it's possible it could "hang up" in the low pressure position.

Thus I proposed the experiment to block the cut back valve, to make sure it is not responsible for the low pressure in 3rd. :)

The other thing to look at is the boost valve on the main pressure regulator valve.

It's the aluminum sleeve with the small steel valve inside.
They have been known to wear the inside of the aluminum sleeve, and cause leaks in the boost circuit.
 

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Discussion Starter #54
great info Galaxiex, i will give anything a try, although this is my 3rd valve body i need to find the problem.
you mentioned the governor which i haven't replaced although we have checked it several times could this be the problem/
 

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Ok , those holes drilled are for the 2-3 shift feed

The cutback valve in a normal trans is supposed to drop line pressure as road speed increases . The cutback sees governor pressure as road speed increase. That spring (orange) should work as a blocker and basically disable that function. By blocker I mean with the spring installed it is basically coil bound so the valve cant really move enough to have any effect. I often use a 1/4" steel checkball. Usually needs a slight grind on the valve to allow it sit sit in flush so the end cover fits right.

I have done the same with the 2-3 backout with a steel ball to block its movement . The white spring is stiffer than original so to a point does similar

The 2nd hole I show drilled is a restriction that meters oil for the apply of 2-3 shift depending on teh position of the 2-3 backout valve . Drilling the extra hole and blocking the valve gives kind of like a direct apply regardless . I have done a few and not really noticed any excess harshness .

I agree that filter extension is too small. That tube in mine has clearance to the pan bottom.

I think from memory that pink spring is pretty heavy? Both that and that gold splitter in the 1-2 shift valve i think puts both those valves in a position that allows oil flow right through from the manual valve for the shifts
With the governor pressure blocked off anyway the shift valves don't need to move
It's hard to pinpoint where the pressure loss is . With that kit still using modulated line pressure the pressure reg valve and the boost valve are still active. Could be some wear there somewhere .

It's been a few years since I studied up all the circuits , testing my memory now lol
 

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Discussion Starter #56
wow that's pretty in depth, so steel ball it is, although probably not necessary?
filter extension is gone for good
i will drill the second hole this time and the extra next time
i cannot understand with the little knowledge i have why there is such a difference in line pressure between rev and forward, this doesn't make sense
you guys are excellent, i read a post a few years ago where a guy wrote how he had an issue and before it could be sorted he put in a manual valve body and declared all fixed now and i like most wanted to see a reason and a solution. that has not changed because i think it might mask a more serious problem.
keep up the good work
 

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wow that's pretty in depth, so steel ball it is, although probably not necessary?
filter extension is gone for good
i will drill the second hole this time and the extra next time
i cannot understand with the little knowledge i have why there is such a difference in line pressure between rev and forward, this doesn't make sense
you guys are excellent, i read a post a few years ago where a guy wrote how he had an issue and before it could be sorted he put in a manual valve body and declared all fixed now and i like most wanted to see a reason and a solution. that has not changed because i think it might mask a more serious problem.
keep up the good work
Reverse line is higher because line pressure is sent to the boost valve when the manual valve is in the reverse position.

Pretty much all automatics have boosted reverse pressure because of the nature of the gearing.

If reverse pressure was not boosted, the trans would slip in reverse.

In the picture below, the red lines are mainline pressure. (sorry for the poor scan)

Notice the small black arrow at the bottom at the manual valve, showing that the valve is in the reverse position.

Now the big black arrow on the left is pointing at the line pressure going to the boost valve.
This give a big boost in pressure, in reverse only.

That oil going to the boost valve is ONLY there in reverse.

When the manual valve is in any other position, that boost oil is not there.

If you trace out the circuit you will see it. :)
 

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Discussion Starter #58
thank you Galaxiex, that explains a lot and now i understand how that works, (the question i have was not worded properly and i apologise for that) so, what could cause the vast differences between the pressures i have and the transgo instructions?
my pressure's are 280 -320 in reverse and 150 in 1st and 2nd with 125 in 3rd and don't really climb or fall from idle to wot yet the pressures in the transgo instructions are drive idle 55-65 wot 150-185 and rev idle 60-110 wot 240-270, why is this so?
thank you Galaxiex for your help and i have a link for you with the pictures out of an original training manual so you don't have to photocopy them lol, and before i forget is there much difference in the circuits themselves from the 65-67 to 71-81 gearboxes as i have the late valve body?

1971 Ford C4 Automatic Transmission Technician Reference Manual page 1 of 1
 

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OIC, sorry I did not pick up on what you meant. (embarrassed)

Thanks for the link to that manual, very nice!

I used the early oil circuit from my book because it's the only one in color,
the later diagrams in my book are B/W and hard to trace.

There are some differences, but for the purpose of what I described above, they are essentially the same.

Sorry I don't have an answer for your specific issue with the pressure discrepancy.

The only thing I can think of is there may be an internal leak somewhere, somehow, pressure is bleeding off.

As you already know, the trick will be to find it.

I'll keep looking....
 

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Discussion Starter #60
all good, i felt embarrassed also. i'm glad you liked that link as i did when i found it, and although i have read through it i still don't understand what i have going on. could it be a spring is wrong or in the wrong position? i only ask because i am aware of the importance of the springs and there positions and have been as careful as possible when dismantling and reassembling the valve bodies (1st vb has been rebuilt 5 times and i have rebuilt 2 other valve bodies twice each) and still cannot find anything to answer the question of line pressure.
all of your efforts, and gregs to resolve this is very much appreciated
 
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