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11/29/2017 8:24 AM  #1


C-4 Transmission

I'm preparing to change the filter and gasket on my C-4 transmission. How much transmission fluid will I need to fill it up? Thanks for any assistance. 

 

11/29/2017 9:19 AM  #2


Re: C-4 Transmission

I don't have a C4, but google says 5.5 quarts... but I would suspect that figure probably doesn't take filter capacity into account.

 

11/29/2017 9:54 AM  #3


Re: C-4 Transmission

Can't comment of refill volume, but I will say this: has the transmission ever been rebuilt?  The reason I ask is because when they are rebuilt the new clutches they use do not need the F-type fluid.  An original trans must use the F-type fluid.  A rebuilt can just use regular Mercon/Dextron III or IV (but not V or any of the synthetic or semi-synthetic fluids).  Running F-type in a rebuilt trans will result in harsh, banging shifts.  If the trans has a shift kit in it the problem is even worse. 

 

11/29/2017 10:04 AM  #4


Re: C-4 Transmission

I don't believe a C4, C6 or FMX filter takes extra fluid as an engine does with its external filter. The trans filter location in the pan doesn't require additional fluid.

I use type F in my rebuilt fmx and don't experience harsh banging shifts.


Bob. 69 Mach 1, 393W, SMOD Toploader, Armstrong  steering, factory AC.
 

11/29/2017 10:29 AM  #5


Re: C-4 Transmission

Possibly it depends on which clutches were used.  I know mine was nothing fancy; a typical trans shop rebuild.  It always shifted WAY harsh.  Seemed to hold gears for longer than it should, and then bang into the next one.  I read about the clutch situation and decided to try the Mercon/Dextron fluid.  Problem solved.

I also cannot comment of the differences between the FMX and the C4.  Some autos are finicky about which clutches they like.  With GM 700R4s for example a lot of guys had problems using the Alto Red/Koleen clutch/steel combo that so many use in TH350s.  On advice from a guy who really knows the 700R4 I decided against the Alto Red/Koleen combo and instead went with the Borg/Warner High Energy clutches/steels and the trans shifts amazingly.  Long story short, what's good for the goose isn't always good for the gander.  Or as they also say, your mileage may vary. 

 

11/29/2017 8:40 PM  #6


Re: C-4 Transmission

Wonder IF........you could mix the fluid 50/50 (type F & Dextron IV)and get a firm butt-knot harsh shift?!! Kinda like B & M Trick shift fluid.
6sal6


Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
 

11/30/2017 8:02 AM  #7


Re: C-4 Transmission

Depending on which model C4 you have, you can tune out the harsh and delayed upshifts by either adjusting the vacuum modulator (the small screw inside the vacuum hose connection) or putting in a shim between the modulator and the trans case.  You can turn the small screw outwards, counter-clockwise, up to 2 turns and reduce line pressure which reduces the harshness of upshifts.  If you put in a 1/16" shim or double gasket the original one on the modulator, you accomplish the same thing.  For what its worth, the two different types are the push-in held with a clamp, and a screw in model.
Also, if you do want firmer shifts, turn the screw inwards up to 1 turn.  This was a common procedure I used when I was rebuilding the C-4 and C-6 in the 70's and 80's.  We used Type "F" in all transmissions, including Chrysler and GM products (this was back then if it makes any difference).

Last edited by 66 coupe (11/30/2017 8:03 AM)

 

11/30/2017 8:21 AM  #8


Re: C-4 Transmission

Back when they used to call type F fluid a poor man's shift kit? 

Ah type F fluid: Ford's attempt to screw the oil companies.  Apparently it worked so well that many years later they developed Mercon SP, which is still only available from a Ford dealership at $6/quart.  I keep hoping that the oil companies will create a generic fluid that meets the SP spec, but 11 years later I'm still waiting. 

 

11/30/2017 10:35 AM  #9


Re: C-4 Transmission

Thanks for the responses. The transmission uses Type F. It has not been rebuilt in the 20 years I've owned it although I did have it checked out by a competent tranny guy several years ago. I'm having some leakage from the gasket area so I decided to change the gasket and filter. 5.5 quarts seems like a lot. I think I'll put in a few quarts and then gradually top it up until it shows full. 

     Thread Starter
 

11/30/2017 12:23 PM  #10


Re: C-4 Transmission

The pan will hold a couple of quarts but when you drop it, the torque converter will also tend to drain a bit.  A total fluid fill is somewhere in the 8 to 10 quart range.  I wouldnt be surprised if it held close to 4, maybe a bit more.  Check for leaks at the modulator, the shifter and kickdown shaft seals, the speedo adapter o-ring, and the dipstick o-ring, they are all very common leak points, often mistaken for front seal leaks.

 

11/30/2017 4:20 PM  #11


Re: C-4 Transmission

Speaking about new seals, on high mileage c-4's, the hole in the case where the shifter shaft exits wears out and even a new seal will not stop oil leaks.
 When I had a c-4 in m 68 I had to ream out that hole and put a bushing in it , I wonder any bushing kits exists for that fix?


Good work ain't cheap, Cheap work ain't good!   Simple Man
 

Board footera


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