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-   -   Forward Drum Diaphram fail (https://www.fordmuscleforums.com/c4-transmissions/652523-forward-drum-diaphram-fail.html)

Spud408 01-16-2019 02:00 AM

Forward Drum Diaphram fail
 
I have a C4 with Broader full manual VB, 6 clutches per pack. Oil Dex 2
behind a nitroused 408C, car weighs 3700 with me in it.

Trans has done about 300 street miles and 10 passes,

Last Friday I finally started to get some decent traction and was wheelstanding out to the 60" lights (1.37 60' time).

On the 4th pass took off flashed to 5K then shuddered and engine revved freely like in nuetral, I lost all forward gears.

Pulled trans apart and the forward clutches are fried. the Diaphram spring has flipped and bent all the fingers up.


Transbuilder is suggesting we machine the hub to accept 2 Diaphram Springs.
Any Pro's and Cons of doing this?
Any other suggestions?

Spud408 01-16-2019 03:23 AM

Re: Forward Drum Diaphram fail
 
1 Attachment(s)
Here is apic of the flipped Belville washer with bent finger.

galaxiex 01-16-2019 07:53 PM

Re: Forward Drum Diaphram fail
 
The real question is...

Did the clutch burn first and cause the piston and spring to over travel and that caused the bent spring?

OR, did the spring bend from excessive pressure, and then the clutch burnt?

If pressure is excessive it can bend the spring.

Need to put a trans line pressure gauge on it (at least 300psi gauge) and see where it's at with regards to pressure when making a pass.

Machining the drum to add a spring risks weakening the drum.

Spud408 01-16-2019 09:50 PM

Re: Forward Drum Diaphram fail
 
I have heard aftermarket Belville Springs bending, we used a factory one as they are supposed to be better.

I take your point about excessive pressure bending the fingers, as to me thats what looks like happened. On the previous pass I badly overrevved it, so that spike could have caused a high pressure spike in the trans?
I will definetly be checking line pressure when back together.

Thanks for your input.
Have you heard of 2 springs being used, Im thinking the pressure required to force teh 2 springs up will take clamping force away from the clutch pack.
Spud

galaxiex 01-16-2019 10:37 PM

Re: Forward Drum Diaphram fail
 
Quote:

Originally Posted by Spud408 (Post 1629575817)
I have heard aftermarket Belville Springs bending, we used a factory one as they are supposed to be better.

I take your point about excessive pressure bending the fingers, as to me thats what looks like happened. On the previous pass I badly overrevved it, so that spike could have caused a high pressure spike in the trans?
I will definetly be checking line pressure when back together.

Thanks for your input.
Have you heard of 2 springs being used, Im thinking the pressure required to force teh 2 springs up will take clamping force away from the clutch pack.
Spud

Over-rev might have caused a pressure spike, maybe...
Usually by 3000 rpm pressure is maxed anyway.

I have seen 2 springs used as installed by the factory on some Benz and ZF transmissions, so it's not a completely out there idea, but those were very thin.

I've just never seen it used on a C4 as a modification, and would still be concerned about weakening the drum with the machining.

Good point about the extra force that might take away clamping force from the clutches.
I was going to mention that too.
I'm not sure there would be all that much extra pressure/force needed with 2 springs.
Consider that the spring acts as a lever on the clutch pack anyway.

I suppose you could put the springs in an arbor press and measure/compare how much force to compress 1 and then 2 stacked.

Spud408 01-16-2019 11:37 PM

Re: Forward Drum Diaphram fail
 
What about the potential to loose pressure when dong an extended wheel stand? and the pick up sucking in air, aerating the fluid and lowering pressere therfore lowering clamping force on the clutches causing them to slip and wear increasing the clearance and then over stroking the piston and flipping the Belville inside out?

I have a large Aluminum pan on it but there is no baffling in there,
I believe the biggest B&M pan is baffled?

Spud

gregaust 01-17-2019 01:09 AM

Re: Forward Drum Diaphram fail
 
What was the line pressure? . I have seen a belleville running a bit 300 PSI and still looked ok. Another pegged my guage past 360psi and smashed itself (That was two bad valvebodies was the cause)

Also what clutch pack clearance ?
With a deep pan like that , assuming it has a filter with an extension to the bottom and not a stock filter , the car would near have to be standing on end to uncover the pickup.

The two belleville idea i have seen done and does work . That was in a trans that was specifically set for 295psi line pressure .

With a valvebody around 200-220 psi and all set up right in the drum the single belleville should suffice

Spud408 01-17-2019 04:59 AM

Re: Forward Drum Diaphram fail
 
Thanks Greg for your response. Im down in Geelong, Vic, Trans is in a full weight XY 408C with nitrous.

It has the large deeper filter but but dont think it has an extension to near teh bottom of the deep pan, I will have to asker the builder.

The Broader full manual VB is supposed to be 220 - 230 psi, we did not check running PSi I will do that this time.


The 6 disc clutch pack was set up at 0.030" clearance, but was a lot more than that after failing.


Do you see any negatives of running the 2 Belvilles?


Spud

galaxiex 01-17-2019 05:21 PM

Re: Forward Drum Diaphram fail
 
Quote:

Originally Posted by Spud408 (Post 1629575821)
What about the potential to loose pressure when dong an extended wheel stand? and the pick up sucking in air, aerating the fluid and lowering pressere therfore lowering clamping force on the clutches causing them to slip and wear increasing the clearance and then over stroking the piston and flipping the Belville inside out?

I have a large Aluminum pan on it but there is no baffling in there,
I believe the biggest B&M pan is baffled?

Spud

I see greg answered this already, but I'll just throw in that if it lost pressure during a wheel stand....

... I'm thinking the front would come down rather fast and hard and you'd know it.

gregaust 01-18-2019 01:03 AM

Re: Forward Drum Diaphram fail
 
Quote:

Originally Posted by Spud408 (Post 1629575825)
Thanks Greg for your response. Im down in Geelong, Vic, Trans is in a full weight XY 408C with nitrous.

It has the large deeper filter but but dont think it has an extension to near teh bottom of the deep pan, I will have to asker the builder.

The Broader full manual VB is supposed to be 220 - 230 psi, we did not check running PSi I will do that this time.


The 6 disc clutch pack was set up at 0.030" clearance, but was a lot more than that after failing.


Do you see any negatives of running the 2 Belvilles?


Spud

Sounds reasonable . Was the Belleville new to start with? I replace on every build , they are cheap.
No negatives to the two bellevilles that I can see . As I say a guy up here I helped did that on his , was a turbo 6 cortina and he was at 295 PSI.

The broader valvebodies are very good , pressure i'd say would be spot on with his setup. Still check as could be a sticky P.R valve.

I've used the deep pan filters with the rectangular bottom hole , usually they are fine even though not right to the bottom they are well down in the oil. I like to use the filters from the U.S that have the rubber grommet , then make the tube to suit.

Also just a thought. Need to ensure that you actually have a C4 forward drum and not a C5. Each type has a specific lower step plate . A c4 lower plate in a c5 drum leaves a gap between lower step plate and the belleville . Theres about .050"-.060" diffence in thickness in the two plates

I'd have to double check but from memory a c4 has the lower snap ring groove that retains the bellevile is .087", a C5 uses a unique wave snap ring and lower groove is around .0135"


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