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foothilltom

C4 tranny year compatibility with 69 coupe

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Hello my brethren.  Damn, it's been a long time since I posted here.  I hope you're all alive and happy.

My question is regarding "fitment" and compatibility of a 2nd generation C4 (1972 to be precise) with a 1969 coupe.  Filling in some details...

  • original 302 swapped out for a 351W, shorty headers some years ago
  • original 1969 C4 stayed in car, was never super awesome, recently slipping bad, fluid smells burnt, etc. 
  • original C4 absolutely needs a rebuild

For logistical reasons (son uses this as his daily), I decided to buy a tranny that aledgedly runs good with the plan to quickly swap out the ailing original C4, put this one in, and then buy some breathing room for me to rebuild the original C4.  Hence my question about compatibility and fitment.

Ideally, it won't require drive shaft alterations, but I do wonder if the different bell-housing, dipstick into pan type tranny may pose fit issues with shorty headers, for example.

In summary, does anybody have any direct experience with this, knowledge of physical dimensions being mostly the same (or not) between the 1st and 2nd generation C4?

Thanks very much in advance.  My son and I restored this coupe when he was 14.  He's 29 now and it's his daily driver.  I'm 59 now and still learning.

Tommy D

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Pretty sure they all bolt up, as long as it's a 6 bolt. In the future, I would look into getting a C5, it has better oiling. Look for an H or R servo.

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The C-4s went to a larger diameter 26 spline input shaft in either '69 or '70, so you need a later model torque converter.  If the trans is a "pan fill" then it will have a 164 tooth flexplate.  If it is a "case fill" it could have a 164 or 157 tooth flexplate.  The good news is that they are both 28oz imbalance.  A C-5 is much better, I think they may be 50 oz imbalance, maybe RPM knows.  The C5s also have a lock up torque converter.

Hope this helps.  I think the answer is that the '72 will work, but you will need to use the 26 spline torque converter.

 

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40+ years ago I put a C4 from a 71 full size into a 69 Mustang with a 5.0. Only problem was the bell housing hit the tunnel. My recollection was the converter was a larger diameter.

Took a few hits from a 3# sludge hammer to add more clearance.

Tire would chirp when manually shifting up through the gears. Not sure if this was just due to the difference in the converter diameter or a good rebuild.

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Hey guys, thanks for the responses.  Like anything, you learn as you go and I just learned that buying what I thought would be a "straight up, bolt-up, replacement" to buy some time was probably not well thought out on my part.  This C4 came with a torque converter, so at least I'm covered in terms of the spline difference in this generation C4.

I was concerned about going with a C5 for fear of needing to do a lot of modifications, but it sounds like (from dcm0123's memory) I'll need to be doing some ahem, modifications to the tunnel to make the larger bell-housing fit.   Maybe that'll go easy, but anytime the sledge is coming out, it's probably a sign of some bad planning.

I understood the C5's have the lock-up converter, but I've also read that the early C5's had issues with the lock-up?   Anyway, I got tunnel vision trying to get a straight swap to buy time for me to do a careful rebuild of the original tranny, but should have stopped long enough to think about all the improvements that have come

Maybe I'll just unload this 1971 vintage C4 and start poking around for a C5 or open up the whole spectrum of AOD, etc.

Thanks again.

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1 hour ago, RPM said:

By the time you upgrade the aod to 4R70W specs the cost is a wash. 

Yes u are correct.  I got  a 4R from a thunderbird and used for internals and Dan (Silverfox) helped me out with the valve body. He told me the tricks to do to it to make it shift properly. Then sold me the springs and governor parts for hardly nothing. It worked good I just never liked the nature of the AOD. 

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50 minutes ago, EastYorkStang said:

What mods can be done to the AOD to better it ?

 

Already have the AOD.

First I would not do it, but if u go that route u need to look at the casting number. If it is not an E9 casting I would not waste my money.

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The only thing I can add is. If you go with the C5 make sure who every is going to rebuild it they know what they are doing. My transmission guy said. The C4 & c5 look a lot alike. I was told if they use C4 stuff you will burn it up on the first drive. I’m not a transmission guy just passing on what I was told. Good luck 

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Hey guys, just for "closure" (as often there is none in these threads), I chose to sell the 2nd gen C4 I had bought as a stop-gap (per my original description).  Son limped the car up from LA and I set about re-building his original C4 first gen tranny over a 3 week period.  Never had done that before, so I was quite uneasy.  Took my time, took a zillion photos, and found at least 3 significant issues that would have explained the bad behavior.

Anyway, C4 is back in, new servo, o-rings, bands, clutches, steel, thrust washers, bushings, seals, etc. and the Stang is back on the road.  Only set us back the price of the master rebuild kit so I'm going to call it good for now.  I'm sort of trivializing a rebuild that my hair standing on end at times, but it all worke dout.

Thanks again for all your input.  

Tom

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