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  Topic Review (Newest First)
04-22-2019 05:51 AM
lenoaust
Re: C4 squeals on gear change and burns clutches

hello again, that is good to know so how much do you think will be enough shim thickness to see a difference?
i found my dads vacuum gauge and did a vac test 9inm at idle 1000 rpm and 18 at 3000 rpm with a corresponding drop in line pressure which seems normal to me, what do you think?
thanks again Greg much appreciated
04-21-2019 11:57 PM
gregaust
Re: C4 squeals on gear change and burns clutches

You know , at this stage it really can't hurt . My only concern would be you don't really want reverse any higher .

I'm still trying to figure what the noise is , very unusual for something internal to make a noise like that .
04-21-2019 02:17 AM
lenoaust
Re: C4 squeals on gear change and burns clutches

thank you Greg for confirming that idea. i took a look at the reverse circuit and i get that (well sort of) pressure, and noticed it bypasses the throttle pressure valve altogether where the forward gears are run past it to bleed off pressure. do you think line pressure would rise considerably if i shimmed it with a couple of washers?
04-20-2019 12:28 AM
gregaust
Re: C4 squeals on gear change and burns clutches

Quote:
Originally Posted by lenoaust View Post
i chose transgo as recommended to me due to there quality and accuracy however i have never used them before.
you are correct, i do have air and know how to air check and to make sure i was doing it correctly i took the stator support and clutch drums too a transmission specialist to verify my work and it checked out perfectly.
when i assembled the box before installing the vb i again air checked the drums and bands for correct operation and yes there is a slight amount of air getting through whilst the items are functioning properly, i put this down to air is thinner than oil. maybe i am wrong, will have to check that!
i am going to have a look at the circuits to better understand.
this is great thank you guys
Transgo is good stuff .. You are correct , air checking is different to oil flow when the trans is running . The oil would seal better . You always hear some minor ring leakage .
04-18-2019 03:30 PM
lenoaust
Re: C4 squeals on gear change and burns clutches

Hello Galaxiex, after taking your advice, i looked at the schematic of the reverse circuit and understand how that works.
the rev circuit bypasses all other's so how is it's pressure regulated?
how are the forward's pressure regulated?
where would be a loss in pressure in the 3rd gear circuit? (PA intermediate servo installed)
looking at those circuits are producing more questions (and a headache) than i expected, certainly no smoking gun i could see.
thanks again, i appreciate your help
04-16-2019 03:52 PM
lenoaust
Re: C4 squeals on gear change and burns clutches

hello Galaxiex, well i have no idea, any of my ideas went out the window long ago.
with the vb's, i have laid the items out in there positions on my table relative to the vb so i cannot mess it up then clean inspect replace
i chose transgo as recommended to me due to there quality and accuracy however i have never used them before.
you are correct, i do have air and know how to air check and to make sure i was doing it correctly i took the stator support and clutch drums too a transmission specialist to verify my work and it checked out perfectly.
when i assembled the box before installing the vb i again air checked the drums and bands for correct operation and yes there is a slight amount of air getting through whilst the items are functioning properly, i put this down to air is thinner than oil. maybe i am wrong, will have to check that!
i am going to have a look at the circuits to better understand.
this is great thank you guys
04-16-2019 06:16 AM
galaxiex
Re: C4 squeals on gear change and burns clutches

Well I am starting to think the problem may not be the valve body,
unless you are making the same mistake on every one (unlikely),
or there is something wrong with the Shift Kit. (also unlikely)

I assume you have compressed air and know how to air check the clutch packs with the valve body off?

Possible leak in the high clutch circuit?

The video below shows air checks,
but I would use a rubber tipped blow gun to get a really good seal on the passages, not just a piece of hose.

You want to pressure up the circuit and try and hold pressure and listen for excessive leakage.
There will be a small amount of air leak but it should not be excessive.

Don't forget that the front servo release passage is also in the high clutch circuit.
(have a look at the oil circuit diagram when the trans is in high gear)
Wear at the servo pin in the case can cause issues.

That's all I got for now....

04-16-2019 04:17 AM
lenoaust
Re: C4 squeals on gear change and burns clutches

hello greg, thank you for confirming the differences in valve bodies as i have read they are not interchangeable i didn't know why.
items changed between valve bodies are only those found in the shift kits as i move from one vb to another.
i agree with you as i have 3 different vb's and 2 different separator plates all of which have been kept together for use later if need be.
i have noticed differences in the galleries within the vb halves and also the different hole positions and sizes.
yes the gaskets are correct for the 40-3 and all holes are clear (not blocked) as per the visual light test and are not standard.
i will try the cutback spring for bind and install steel ball just in case.
now for the boost regulator,

does the boost regulator work identically in all forward gears if so what could cause a different pressure between them?

what do i look for with its condition?
i know that i have at least 2 different boost regs as the spool valves do not fit the other sleeves.

how can i diagnose boost valve problems?

wow thanks this is getting deep, also i was driving it and at low rpm it would change harder if i held the rpm at say 3000 for a couple seconds then got on it and changed. it sort of felt as if it had to build pressure which didn't show up on the gauge.
what happens when the modulator valve is stuck all the way in so it doesn't move?
thanks again
04-16-2019 02:22 AM
gregaust
Re: C4 squeals on gear change and burns clutches

I'm at a bit of a loss with the pressure .
Reverse IMO is actually high , and Forward gears low .
I can't help thinking something odd in the pressure reg boost valve area .

The circuitry is very similar between early and late styles .. The ports in the cases are different so they shouldn't be interchanged anyway . I know that's not what you've done just answering the question.

Now have any parts components been switched between valvebodies ?

Reason I ask , In the late 70 on valvebodies , there are actual few different castings , I'll say 3 I know for sure in some comparisons i've done , maybe more.

There are 3 different size 1-2 shift valves , and 2 different seperator plates . The plates are close to same looking but a couple holes slightly different .

The gaskets in the kits usually have the holes to suit both plates ..

You do have the correct gasket for the 40-3 kit ???? It is different to a standard gasket .
The cutback valve can have a ball fitted , but just to prove it check that orange spring , I think you'll find it wont allow the cutback to move enough to actually function to drop pressure.
04-16-2019 12:43 AM
lenoaust
Re: C4 squeals on gear change and burns clutches

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
04-15-2019 06:15 PM
galaxiex
Re: C4 squeals on gear change and burns clutches

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....
04-15-2019 04:45 PM
lenoaust
Re: C4 squeals on gear change and burns clutches

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
04-15-2019 08:43 AM
galaxiex
Re: C4 squeals on gear change and burns clutches

Quote:
Originally Posted by lenoaust View Post
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.
04-15-2019 02:56 AM
lenoaust
Re: C4 squeals on gear change and burns clutches

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
04-15-2019 02:02 AM
gregaust
Re: C4 squeals on gear change and burns clutches

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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