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c4 help!!!

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11K views 68 replies 19 participants last post by  PUNKIN  
J
#1 ·
since changing gear ratios. i have melted 4 transmissions in 50 passes. i am going back to my old gear and fixing my transmission one more time before going to a glide....

i want to know any secret and what clearances are "perfect" i want it to be as good as it gets cuz this is the last time im doing this.
 
E
#2 ·
How much power and how much weight? What it run?60ft? I been fighting one with a BBF runs 6.0s in 1/8 1.30 60ft and mainly been just breaking forward drum. I suppose you are burning high gear up and seem like 200+ psi and and 5 to 6 clutches. Some were burning high clutches up because of high rpms making fluid behind high piston applly from centrifical force and made a big differance putting a bleed whole in drum behind piston. I was showing some heat with 35 passes and just now did the bleed hole. Alto clutches seem to do better if there is a flare and not burn as fast i read. More Info please.
 
J
#5 ·
its slow as christmas. idk what the problem is. 6.50's @3080lbs

idk what the clearances were. . . thats what i want to do is just start fresh.

it just starts to slip and blow completely through any gear but reverse, " i can baby it back on the trailer"

i had one transmission that lasted 2 years and the trst haven't lasted 2 races
 
E
#7 ·
I bet your loosen pressure some where. I suggest after you get er done putting a gauge on it and make sure you dont have a cracked case or something. Did you air pressure the trannies?? Thats a good ideal every time. I think most will say 5 thousands pere clutch on forward drum and no more then 10 per clutch i high. Do the bleed hole, cant hurt, If you got reverse and not low then its got to be valve body pressure valve. Reverse has a boost valve and i suspect it helps it work with pressure problems.
 
B
#8 ·
How much pressure at the port? How many clutches?

Some people run clearances as tight as .005" per clutch and others as much as .010" per clutch. Mine are around .007" which is on the tight side IMO. I don't think that clearances are that critical on the forward which you seem to have trouble with. I would want 5 clutches in both drums. Line pressure should be up around 220psi.
 
J
#10 ·
no. i dont know the system pressure.
yes. it is forward clutches every time
and i have 2 completely different transmissions.
i really dont remember which vb they have.


what controls system pressure? is it controled by the vb or a valve in the pump?


sorry for not knowing exactly what im talkin about. my paw builds the trans and i just stand there. lol.

he has built them for years but isn't exactly a "performance" builder. so all the stuff involves in a stock rebuild is covered.

and yes. all packs are always air tested
 
E
#11 ·
I suppose the are manual valvebodies? I suspect even then most will need the spring shimmed to get 200+ psi. It looking like you have a stuck pressure releif in the valve body. Everytime you tear one up, the trash plays havic on the valves. First gear is the strongest gear especially in a c4. It has all the gear in it that saves it and its already applied so know slipping trying to engage. No tranny will live with pressure problems. Goodluck
 
J
#13 ·
ok guys. i got my facts straight now. the forward drum burns up after the spring breaks or flips inside out. clearances on the pack has been .024-.030 every time.

why is it fliping inside out and breaking? i thought it was too loose and he insisted that it had less that .030 every time
 
E
#15 · (Edited)
I were out one will fail sooner or too much fliud pressure, like sticking releif valve. Some cut a grove in drum and install a snap ring for it to stop against, I now someone makes a drum that uses one big spring in middle like direct drum. Most builders replase the bellevidere spring when freshening up. A sticky releif valve would cause this to flip also. Also you need atleast 40 thousanths in high or it will drag in 1st and second and cause extra heat on the high clutches. I run atleast 50-60 clearance in high.
 
G
#20 · (Edited)
Those belleville springs take a lot . I fixed a C4 for a guy that had a dodgy V.B was running around 350psi when i checked it and the belleville spring looked not too bad. I always fit new ones . ALWAYS use teflon rings in any trans that runs a constant line pressure ..
Those test forward drums without the belleville spring and 1 large spring from what i've seen don't really work. Without the extra multiplied force that the belleville spring gives they weren't overly successful even with added line pressure .

Shout yourself a pressure gauge and check every time . If the pressure is there and clearances right , good chance it will live
 
B
#21 ·
Anyone use Broaders modified drum? http://www.broaderperformance.com/product.php?id_product=44 I put one in mine and his TB also.

Description
This is a complete and ready to install forward drum assembly. Includes welded jelly bean holes and is loaded with 6 red frictions. The disc spring has been modified to provide a 1.75:1 ratio mechanical advantage. No more flipped disc springs or forward clutch failure due to high line pressure required for high horsepower, transbrake and manual valve bodies. Clutch clearance is much more stable. Allows you to run higher line pressures required for increased direct clutch life. A must for any true high performance C4. A great problem solver developed in our shop! We use this drum exclusively in our Racing/Big Block C4 transmission. 200PSI minimum line pressure is recommended with this drum.
 
#25 ·
I've seen it the other way around, the cast rings will wear into the drums etc. If the teflons were jacked I'll bet money on an improper install. The cast rings will seal better on an "air test", but you get some fluid pressure on the teflons and they just seal better..............and wont eat into the drums.

If cast is so good why has all most of the oem gone to teflon?
 
#30 ·
Well you can get mad and cuss me' doesnt realy matter...Didnt use any harsh words to or at you...I know for a fact 100% thats what causes all the clutches to burn in c4's with people running nylon seals...Had one tci trans also that kept burning clutches & i replaced them with cast rings & trans has been running flawless since...Im not a chevy/trans expert and dont offer no advice at all...But i do know c4's and think i do a pretty good job at building them and making them last....:cool:
 
#32 ·
See thats what im sayin right there....You have to go to a glide cause you can't make or have a c4 built that will hold up to the power for you...But thats the differance between me and others....I been running c4's for years and always will....I dont have to switch to something else cause i dont know how to build a trans...I KNOW C4'S!!! Thats my story and im sticking to it....
:rock:
 
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