C4 squeals on gear change and burns clutches - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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post #1 of 68 (permalink) Old 03-07-2019, 01:57 AM Thread Starter
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C4 squeals on gear change and burns clutches

Hello to all, i would appreciate some guidance with a perplexing problem i have had for quite some time but before i get to it i will give you a rundown on some stats first
full weight xd falcon street car
stroker cleveland with 2v heads and north of 400hp with no dyno testing
c4 4200 stall converter from tce
oil mods are, cooler line spring ball delete in pump stator, cooler return line opened up and #9 thrust lube circuit as has the c5 and pump gear lube in pump housing.
this c4 has had all thrusts replaced with roller thrusts except for # 1 and 2 and i think 6 [the back side of the sun shell]
i have installed a 300m input shaft, a 4 pinion billet planet and a PA billet servo
first gear clutch has 6 friction kit from broader while high gear has 5 and both use raybestos reds
standard low reverse band with a solid second gear band from broader
transgo 40-3 full manual shift kit
and now to the issues which i may have several i just do not know.
this gear box has been together 3 times with minor changes to the problems which are burning forward clutch pack the 1st and 2nd time, burnt high gear clutch pack and also the low reverse band the 3rd build all while there is an audible squeal with gear change at 4000 rpm and above.
the first and second builds had the squeal occur from 1st to 2nd change while the 3 build had it on the 2nd to 3rd change.
any advice at this stage will be very much appreciated as i have to pull the box again this coming weekend for a balance issue and will dive into it with your suggestions.
Thank you in advance
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post #2 of 68 (permalink) Old 03-07-2019, 10:16 AM
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Re: C4 squeals on gear change and burns clutches

"I" think your problem is in the valve body. I suggest an aftermarket , dedicated design, manual valve body . My early 24 spline C4 has far fewer modifications and north of 500 hp with over 1,000 runs on it and is trouble free. I use a Winters brand reverse pattern valve body. The only downside for you might be the lack of low gear band apply , so it "freewheels" when you let off the gas in low gear.
Hopefully Gregaust will give his expert opinion too.
Randy

Experimental Ford parts collector.

Last edited by GT350HR; 03-08-2019 at 12:12 PM.
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post #3 of 68 (permalink) Old 03-07-2019, 02:15 PM Thread Starter
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Re: C4 squeals on gear change and burns clutches

thank you for your response, gt350 i did a line pressure test this morning and i believe you are correct. i did the test in reverse and it was 250 and didnt move then in first manual and it was 150 and went to 170 which is the same for 2nd however 3rd started at 150 and dropped to 125 and it squealed on the shift and will stay if i dont back off the accelerator. i have never built an automatic trans before this one and have a friend helping me with it and he hasnt gone to the same level with a c4 and he is also stumped. putting a dedicated manual vb in has been my thought from the start and havent because i hoped i could keep the auto shift which i installed as a test in the last build. as for greg i hope so too he helped me many years ago to get a better understanding of what i needed for my build although i took it further for a fun excercise and thank you again gt350 for your response
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post #4 of 68 (permalink) Old 03-07-2019, 02:46 PM Thread Starter
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Re: C4 squeals on gear change and burns clutches

well after talking to my friend he suggested to pressure test without the modulator so i did and the pressures dont change. reverse is over 300 and all gears are 150 and the sound is still there, oh and i did forget to let you all know it is a late model C4
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post #5 of 68 (permalink) Old 03-08-2019, 01:43 AM
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Re: C4 squeals on gear change and burns clutches

That is a weird issue , particularly if the "squeal" moves on different gearshifts .
That 40-3 kit can work ok. What colour is the pressure spring? If it is the green that 150psi is low . Usually green spring will give 200 psi with low vacuum.
For the pressure not to increase without vacuum , something is wrong..
That kit is unique in that even though it is a manual shift , it does need the modulator to control line pressures.

Now there is no way the forward clutch should burn up.. Even 5 clutches in there with good line pressure take a lot of power .

I have used that 40-3 kit , but in all honesty not a huge fan of it . In reality as the 40-2 kit is much better and works well with auto shifts

Last edited by gregaust; 03-08-2019 at 11:03 PM.
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post #6 of 68 (permalink) Old 03-08-2019, 02:43 AM Thread Starter
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Re: C4 squeals on gear change and burns clutches

hello Greg, its good to hear your thoughts and no one has understood the issue when i ask them until now. the spring is the green one and i had the 40-2 kit in previously with both the yellow and green spring and no noticeable difference even with line pressure and its great news that i could keep the auto shift if i can solve this
the line pressure didnt change when i disconnected the modulator but did when it was connected although it lost pressure in high gear. what is puzzling my friend is that it made over 300psi in reverse yet only 170 in forward gears.
we both do not understand the problem and i have taken the pump and both clutch packs to an auto repairer near me and he air checked them as i had done and told me they were good.
i have just remembered with the last build it got worse when the trans fluid got hot.
any help to find a fix will be much appreciated
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post #7 of 68 (permalink) Old 03-08-2019, 11:06 PM
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Re: C4 squeals on gear change and burns clutches

With no line rise with modulator disconnected there is either an issue with the modulator valve or valvebody.
Disconnecting vacuum should give you instant full pressure. Also the same when driving as load increase (vacuum drops) the pressure should rise.

The Green spring with no vacuum you should see around 200 or a bit over
The yellow should be around 170ish from memory

If the clutch packs are tested and not losing any pressure it comes back to the valvebody. All the valves must be free to move under their own weight.

You prob know this but there are different gaskets whether you use the -2 or -3 part of the kit. That is all correct I take it ?

Reverse is different , it gets an extra boost to raise line pressure

You can still use it as a auto shift. All that kit does is takes way the governor signal to prevent auto shifting.

Last edited by gregaust; 03-08-2019 at 11:08 PM.
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post #8 of 68 (permalink) Old 03-10-2019, 12:14 AM Thread Starter
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Re: C4 squeals on gear change and burns clutches

thank you, this is with a new modulator that has 3 turns in and a longer rod giving approx 2mm preload and the valve slides in easily and no full 200 plus psi with green spring. Valve body may have an issue however this is the third one (1st and 2nd had 40-2, 2nd and 3rd had 40-3) with no differences which is down right annoying.the gaskets i used are described and when i opened the box too find several i made sure to double check during installation. Now what possibilities are there for the lack of pressure, could it be some holes need to be enlarged in the valve body or added as some other vendors require for there kits? After talking with my mate he suggested the sprag for the noise so is this getting close? Greg your help is invaluable and i appreciate that very much
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post #9 of 68 (permalink) Old 03-10-2019, 10:10 AM
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Re: C4 squeals on gear change and burns clutches

On valve bodys that are modified for higher pressure, we used to leave out the gasket(s).

The gasket can blow out between the suction and pressure passages. Not good.

This was especially common on the C6.

Not having a gasket in there won't matter at all.
Of course you should make sure the mating surfaces are nice and flat.

Chrysler valve bodys (727 and 904) never used any gaskets from day one.
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post #10 of 68 (permalink) Old 03-11-2019, 01:51 AM
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Re: C4 squeals on gear change and burns clutches

Using that Transgo kit you MUST use the gasket. Either with the 40-2 or -3 version must have the gaskets as there are bleeds built into them .
On the 40-2 there are holes that bridge across channels to create a bleed as such to give the manual control of the 2-1 shift at any speed .

On the 40-3 kits there is a bleed for the governor pressures to give the manual shifts

You only need to drill the holes as per transgo instructions , no extras

The usual rule for gaskets are just ensure that no holes are covered on the separator plate

I don't see how the sprag / rear roller clutch would cause the noise . It is only holding in first gear and then over runs on the shift to 2nd.

The mystery is why the noise moves at different times on the 1-2 or the 2-3.

If you've used different valvebodies and the pressures haven't moved either , that then leaves either the pump or a leak off of main pressure somewhere . As I mentioned a burn't forward clutch is very unusual.

Were any parts substituted between transmissions ? There are differences in C4 + C5 forward drums than are not interchangeable . All parts must match each drum. Just thinking out loud now trying to think of what else can cause these issues.

The squeal noise is definitely from the trans???
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post #11 of 68 (permalink) Old 03-11-2019, 02:33 PM Thread Starter
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Re: C4 squeals on gear change and burns clutches

ok thats great guys, so valve body mods as per instructions with the correct gasket installed ( i double checked after your last post greg ) and used drill bit supplied. the sprag has new rollers and springs with broaders roller conversion and machined centre, so ruling that out is nice to know. the pump has been changed because it had no wear in it and the other one had some wear on the crescent from the gear set, not bad, just slight wear. the low reverse drum was changed in the last build, again with jays roller conversion unit.
could the low rev band adjustment be a little loose causing the sound as the last time i pulled it apart the drum had a lot of hot spotting that wasnt there when pulled down previously and i am confident the sound is gear box related as it is only on the shift under power.
i will have the box out and disassembled today and will let you know what i find
thanks again this has kicked my rear for so long and i have not been able to drive it because the gearbox is always in pieces
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post #12 of 68 (permalink) Old 03-12-2019, 02:41 AM
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Re: C4 squeals on gear change and burns clutches

Band adjustments , Snug at 50 inlbs , I do low/reverse 2 to 2-1/4 turns out , Intermediate @ 1-1/8 out . The hot spotting is not good , could be a source of the noise ? Hard to say
Just thinking out loud if there was a tie up on the shifts between bands releasing and clutches apply might cause ? Just throws you out since it happens at two different shifts

What intermediate servo you using ?
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post #13 of 68 (permalink) Old 03-13-2019, 04:22 PM Thread Starter
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Re: C4 squeals on gear change and burns clutches

thanks greg, that sounds highly likely because i used the adjustments in the transgo instructions which are not as tight by far which would also explain why it doesnt pull as hard as other cars ive been. the servo is a pa item with no modifications which come to think of it i remembered reading about some aftermarket servos needed machining although that was a while ago and it wasnt the pa brand so i wasnt concerned. what are your thoughts about the pa servo and do you know the release and apply? thanks again Greg, i feel we are getting close to curing this problem.
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post #14 of 68 (permalink) Old 03-14-2019, 12:51 AM
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Re: C4 squeals on gear change and burns clutches

The P.A servo's are based on a "H" servo 'H'=2.960"apply+ 3.785" release

A servo having to be machined you're either thinking of a C6 Sonnax servo or else that silly TCI mod that hacks up the apply section of the C4 servo.

Using your servo unmodified is good.
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post #15 of 68 (permalink) Old 03-14-2019, 05:30 PM Thread Starter
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Re: C4 squeals on gear change and burns clutches

thank you Greg, i could not remember the circumstances behind the mods and started to worry which is now a relief. this c4 had an R in it, would that be better for this build?
anyhow the box came apart without any issues, nothing burnt or discoloured and no damage so the pump housing has been changed with new seal, c6 converter bush, stator support bushes and gears, installed teflon rings and put it back together. only need to set band adjustment and check the valve body and install it.
your band settings sound like they are on the money however are the intermediate band adjustment different between a flex band and a solid (broader solid flex band)?
thank you again, Greg you know your stuff
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