Thread: C4 Transmission

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I plan to put a C4 tranny in my 66 Ford soon and was wondering about some things. A guy told my dad that there are 2 different kinds of C4's (which I never knew since I am all new to all this Ford stuff). He said there is a regular one and then one with overdrive. If this will be a everyday driver and also have some good power still under it (It's got a 302 under the hood so nothing major) then what one is better?
Any info on this tranny would be great, I looked around and people keep telling me (and sites too) that they both are good but I would like some more OPPINIONS.
Thanks a lot!

Shawn-

One is C4, other is AOD.Similar in size, either will fit your truck ok. I have a C4 in my 46 Ford, AOD in my 53 F100. I just had another AOD rebuilt to use in the 46. I can't imagine another driver without overdrive.

Well, what was told to your dad was half right. There are 2 variations of the C4. Neither one is an OD unit. The ford OD is normally referred to as an AOD (automatic Over Drive).

There is the standard C4 normally found in a majority of passenger cars which can be identified by the dip stick tube going into the transmission case.

There is also the other unit which is often referred to as... large case... step case...or truck because that's where the majority though not all are found. This C4 can be identified by the dip stick tube going into the tranny pan and being held on with a large compression fitting which must be removed to drop the pan. The larger case tranny is purported to be slightly stronger than the standard tranny.

The two tranny use a different flex plate with the large case taking a bigger unit.

Just in case you happen to run into it there is also one other variation of the standard C4 and that is the one found in the 75-8 V8 Mustang IIs. The tranny is the same, but the IIs used a smaller bellhousing, torque converter and flex plate which is unique to the IIs.

The other thing you need to watch out for is getting the flex plate to match both the tranny your using and the engine. 68 thru 82 (?) 302 used a 28 oz imbalance and 83 up used a 50 oz. Using the incorrect flexplate will result in severe engine imbalance.

MIke forgot to mention that the Mustang II bellhousing costs 1 arm and 1 leg. Go with any other bellhousing if it'll fit.

The AOD's work great and should handle the horsepower you have real good, Shawn. With gas as high as it is and probably going higher, the overdrive is definitely the way to go.

Thanks a lot guys! I still have to go back and read all this and try to get it stuck in my head more but right now I just learned heaps more. The OD sounds good. One day I would like to get about 350 HP out of this thing or maybe 400 but right now I will stick to the 350 because that is a lot to try and get out of a little 302 I am guessing. Anyways, the 302 I have is from a 77 LTD so what kind of AOD tranny should I look for (if there's a certain kind) and what kind of vehicle can I find it out of? Will I have to change my flex plate or will this original one on here still work?
Thanks a ton guys!

Shawn-

Bump!
Ok guys, I have a guy looking for a nice overdrive tranny. The guy I asked is a Master Tech, etc and knows his stuff. He said he is going to find me a good one. My dad talked to him and just said to find me a good tranny that will take a good lot of HP and have overdrive. Do you guys still think a AOD will be good? I would like to put some kind of shift kit in it so it will have nice firm shift points and shift pretty darn hard if possible.
Remember, I am still young, I don't care much for comfort but in a way need a little hahaha.

Alright... ANOTHER update. I wen't to this guy's house and he found me a AOD tranny and said that this guy he found that rebuilds them and all said it would be 500 for a rebuilt AOD and then about 500 in labor to have to make certain brackets, do the wiring, mount it, put in new tranny mount, etc. So I came to thinking. I can do some of the stuff myself but with the things about hooking it up and making it fit with a lot of fab work I think my best and cheapest bet would be to go with a C4 tranny. What do you guy's think? The tranny I have now is alright, not too bad but it's a straight drive and a pain to drive for an everyday driver driving in stop and go almost everyday and will be doing a ton more of that this summer. Also the clutch probably isn't going to hold much longer (probably till the end of summer) so thought maybe a C4. Any suggestions here? Would a C4 be easier to hook up then if all I need to do is change the tranny mounts?

Thanks guys!

A C-4 would be a snap to put in, Shawn. Probably nothing more than a new trans mount and maybe repositioning the crossmember it bolts to. You should be able to find a decent one for cheap, use it till you get the bucks together for an AOD. Do some studying and research in the meantime, the AOD installation shouldn't be rocket science, and somewhere there's bound to be instructions for the electrical hook up. A C-4 would do you well in the mean time.

Thanks Dave. I really want a tranny that I can just keep for ever in this truck now until one day (not anytime soon, I am talking about years) I change the engine, etc. Right now I want a tranny that will hold around 400 hp or so even though I don't have that much hp but plan to get that much out of it one day in about 2 years or so. The way you said that made it sound like a C4 is a OK tranny for NOW. Do you think I should go with something else? I just want a good rebuilt tranny with a nice shift kit in it that I can keep for a long time. I hear a C6 may be a bit too much for a little 302. What do you think?

The C6s are great trannys but as far as the aftermarket has come with the C4, the C4 ends up being the better unit between the two. The C6 is a little bigger and much heavier than a C4. Personally, I'd go with an AOD, but if cash is an issue, just stuff in a C4 for the time being, like Dave was saying.
When looking for C4s, pay attention to where you're getting it from. You shouldn't have any trouble with the swap as long as you get the flexplate, heat shield, and Tq Converter from the tranny's donor car, it should be a snap. The C4 cam in a few different bellhousing configurations. There was the earlier C4 that used a 157 Tooth flexplate or the later 168 (i believe) flexplate both having the 10.5" converter bolt circle. Earlier C4s refer to the smaller more slanted 65-73 C4 trannys. The later C4s (74-79) and the 80-82 C5s had a slightly larger diameter flexplate and a bellhousing that bulged out more at the back against where the firewall would be. The earlier C4 bellhousing works the best in most streetrod apps and in most cases the bellhousing/TQ converters can be interchanged. There was also a HD C4 that has what's refered to as a "stepped case" where the bellhousing bolts to the case rather than to the front of the pump case like the typical C4s do. These "step case" trannys also typically have the dipstick going into the oil pan rather than into the case. These are commonly found in Pickups and Econoline Vans and such. I'd stay clear of these if you're space limited. This particular C4 has a much larger bellhousing and uses an even larger TQ Converter with an 11.4 bolt pattern (same as an AOD but different tooth count on the flexplate starter ring, I believe)

You mentioned messing with electrical on an AOD... What year was the AOD? I use the 89 and older (or was it 87??) Anyhow, these trannys only require a TV cable and that's it. No electrical garbage to fool with. Just a 3 wire plug for the backup/neutral safety switch. I definately know the carbed cars with an AOD were TV cable opereated. I used one out of an '87 Crown Vic in another rig I had and it worked great.
As far as the balance issue, 81-82 and older was 50oz imbalance and 80 and older was 28oz imbalance. The 351W through all the years was 28oz imbabance. Just use an AOD flexplate from a 351W and it'll work fine on the '77 302. Even a HD C4 flexplate may work as the converter bolt circle is the same, but I never compared the two flexplate to see if the ring gear tooth count was the same or not.

Be advised though, the AOD is considerably wider than a C4 (doubble the width pan compared to a C4) so be cautios of your exhaust routing an other things under the chassis.

Dano78, thanks a ton for the info man! You seem to know your stuff on these trannies. To answer your question, I do not have a clue what the AOD tranny was. The guy just told me he found a rebuilt one but it would be over 500 bucks to have it installed for labor and then 500 for the tranny itself. He said the guy he found it from has a tranny shop or works in one where they rebuild them and that the guy said to bolt up in my 302 that it would take a lot of fabrication work on the carburator, etc. I don't know what he meant by that but he said I would need to make brackets for it, wiring, etc etc so I just said ok that I will pass on it. I don't know anything about trannies so not sure what I am ever getting that is why I held off. Also I am not too sure about getting one from a junk yard not rebuilt. My dad said to probably stay away from that because the last thing I need is a tranny that I have no clue how well it was taken care of no matter the miles on the trip and that I don't have all this money to fix it if it breaks. I may go look and see if I can get a rebuilt one for fairly cheap. I don't want to spend anymore than 600 bucks on a rebuilt tranny and even that is a lot for me but I thought I'd set my price a little higher than 400 like I wanted to spend at first just in case.
Like I may have said before, I want a tranny that will hold around 400 HP, be good for the street and last a long time... I don't need any drag racing or highly modified tranny, etc just a strong and plain built one like anyone else would put in a fast street car or truck. Sorry if I sound like an idiot here but not sure how else to put all that.

Maybe you can answer this question too if you don't mind. Everytime I go to change gears and put the truck in reverse I put the clutch all the way to the floor and go to shift but it want's to grind. I will put the clutch back up and then try again and still wont so what I do is push it forward, until RIGHT when it tries to grind and wait a second and then it will work. It will do it when going to first gear SOMETIMES. Is this a clutch adjustment type of thing or do I need a new clutch or what?
Thanks!

You have a non-synchromesh first gear in that '66 Ford. When going for First or Reverse, put it in Second when you press the clutch. This stops the shafts from turning, then, without letting up the clutch, pull 'er to Low. This becomes instinctive after a while.
I would suggest a T5OD standard trans, or a 4-speed OD from a Torino or a newer half-ton. You'll never get the mileage from an automatic like you will from a stick, and I'm not just talking gas mileage. I have a 62 Unibody with a 351W and four over with 3.78 gears. Works great.

Thanks for the info I will try that tomarrow! I never knew that. Some guy told me the tranny was some like flat top Ford tranny or something similar to that. I have no clue but all I know is I think it's the original 3 speed from the 66. I didn't even know it could hold a 302. I plan to build this 302 up some and not sure how long this tranny will hold it. I really would like to have a automatic though but your right about the stick I guess.
Some people on another forum (forgot which one) told me that a C6 would probably be better under the 302. A few of them said they had C4's and they were nice but didn't hold up as long and as well as the C6.
If I ever get a tranny then it will be at the end of Fall.

Your '66 3spd. is as good a 3spd as you'll ever get, it will handle a 302 for years. An early toploader 4spd will fit the bellhousing, same clutch,etc. Overdrive versions, too. (There are two different bolt patterns, watch out.)
The C4 is a good choice for a 302, but there are several combinations that won't work, different ring gear diameters, starter locations, etc. Get the whole works at once from a donor car, then rebuild it. The main problem with a C4 is inadequate fluid flow to the cooler, limiting its towing ability. If you plan on towing a trailer or anything, go with the C6.