Having my C-6 rebuilt, what to watch for?

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My 73 Coupe has a 429 and C6 transmission out of a 1970 Torino in it, has not been out of the car since 1987 has work really well untill the last couple of years now it's not downshifting on its own, I have to do it manually and when the transmission gets hot say I've been running a curvy Road hard I start to get a shutter like something slipping inside the transmission, going to have it rebuilt, found a local guy here in Franklin North Carolina that's highly recommended. What should I request or look out for it's got pretty good horsepower and torque pushing it. A friend of my dads rebuilt it in 87, and all I remember is that he said he built it stout. He sure did as I ran it hard for years.

 

Bentworker

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Sonnax brand parts are excellent.  Other than that I don’t have much to offer you.  There is a fair amount of secret sauce when it comes to building a transmission.  

 

giantpune

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I'd go with a reputable shop who's been around a while and offers a warranty.  Around my area, its about $1k for a shop that's licensed, bonded, and insured to pull the transmission, rebuild it, reinstall it, and warranty it for 2yr/24k miles or something around there.  If you want, they'll install a shift kit in it during the rebuild and it'll hit harder when it shifts.

 
I was quoted $900 by a shop with excellent recommendations. Including new torque converter and built to handle the car and driving style. I will be pulling the c6 and motor at home and taking them the tranny. Not leaving my car there.

 
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timachone

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900 is a good quote including a torque converter (TMI?)  But it is important they now their stuff and use not the cheapest brands. And rebuild everything - not just the gaskets. Just my 50 cents... 

 

Fabrice

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900+ torque converter is dirt cheap.
If the converter is of decent quality, which it should to handle the 429 torque, it would cost at least 250 and likely more. 
650 in labour is basically saying, they put it apart, most goes in wash machine and they change the frictions plates, o-rings.

I rebuild mine last year, also for a 429. Not all C6's are the same despite the common assumptions, the planets for instance, for a 429, they can have 5 rollers, 4 is fine and enough and likely what you have coming from a 70 Torino. 

But there are must haves for a 429. The forward and direct clutches should have at least 4 frictions/steels. Some HP version even have 5. but a very large portions of the C6's are coming with 3. So I'd say, ask them to put 4 if there is 3, because behind a 429, that's 10k miles vs 100k if your right foot is on the heavy side.
They need to lathe 2 pressure plates to do this. The trick shops often do is to use another bottom plate and flip it. Nothing wrong on itself, but as I've seen and measured myself, you end up on the high side of specs, too loose (more wear and heat real quick). So ask them either to install thinner plates or better  that they turn yours to end up with the optimal end play. If you have a true 70 trans, you might very well have the great larger drum that would allow 5 plates even if it came with 4. If thats the case, you should really ask that they push 5 in there. You'd have then a scj spec trans ;)

I would also buy a shift kit, the C6 valve body is not that complex, and installing the shift kit in practice, is only to use the kit provided springs and replace the one valve that is under the body plate. One tiny hole in that plate is also required. An additional 2 minutes work for a pro. So there should be near zero extra cost for installing this shift kit aside the kit itself ofc, which is I believe 40ish.

Another additional detail if you have no lift at home:  buy a new pan with a drain plug or weld a bung. The original messy way to drain oil is really unfriendly when you have your nose close to the pan bolts. Its a detail, but if your linkage would leak (common on cars that stay still often) and you need to replace that little seal, you will thank yourself for having that plug in!

Brands, raybestos, sonnax.. a full overhaul quality set is what you should ask for. They include servo, external regulator, clip rings for the governor and pump stator too.

EDIT: I would also make sure the converter they give you has a stall speed bits higher than the original. And make sure the crank pilot is the correct one. 9 out of 10 converters for c6's have the smaller pilot.

EDIT2: Check on your original converter, but I'm 99.99% sure crank pilot must be 1.850 in. While most C6 converters use a 1.375. Double check that one!

 
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giantpune

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Another additional detail if you have no lift at home:  buy a new pan with a drain plug or weld a bung. The original messy way to drain oil is really unfriendly when you have your nose close to the pan bolts. Its a detail, but if your linkage would leak (common on cars that stay still often) and you need to replace that little seal, you will thank yourself for having that plug in!
One life changing tool for the DIYer is a vacuum fluid extractor.  The one at harbor freight even does great.  You can drain your engine oil and transmission fluid out through their dipstick tubes.  

 

Fabrice

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@giantpune got one of these, but use it only for rear end fluid. I find unscrewing a bolt for trans and motor oil changes much more easy ;)

 
900+ torque converter is dirt cheap.
If the converter is of decent quality, which it should to handle the 429 torque, it would cost at least 250 and likely more. 
650 in labour is basically saying, they put it apart, most goes in wash machine and they change the frictions plates, o-rings.

I rebuild mine last year, also for a 429. Not all C6's are the same despite the common assumptions, the planets for instance, for a 429, they can have 5 rollers, 4 is fine and enough and likely what you have coming from a 70 Torino. 

But there are must haves for a 429. The forward and direct clutches should have at least 4 frictions/steels. Some HP version even have 5. but a very large portions of the C6's are coming with 3. So I'd say, ask them to put 4 if there is 3, because behind a 429, that's 10k miles vs 100k if your right foot is on the heavy side.
They need to lathe 2 pressure plates to do this. The trick shops often do is to use another bottom plate and flip it. Nothing wrong on itself, but as I've seen and measured myself, you end up on the high side of specs, too loose (more wear and heat real quick). So ask them either to install thinner plates or better  that they turn yours to end up with the optimal end play. If you have a true 70 trans, you might very well have the great larger drum that would allow 5 plates even if it came with 4. If thats the case, you should really ask that they push 5 in there. You'd have then a scj spec trans ;)

I would also buy a shift kit, the C6 valve body is not that complex, and installing the shift kit in practice, is only to use the kit provided springs and replace the one valve that is under the body plate. One tiny hole in that plate is also required. An additional 2 minutes work for a pro. So there should be near zero extra cost for installing this shift kit aside the kit itself ofc, which is I believe 40ish.

Another additional detail if you have no lift at home:  buy a new pan with a drain plug or weld a bung. The original messy way to drain oil is really unfriendly when you have your nose close to the pan bolts. Its a detail, but if your linkage would leak (common on cars that stay still often) and you need to replace that little seal, you will thank yourself for having that plug in!

Brands, raybestos, sonnax.. a full overhaul quality set is what you should ask for. They include servo, external regulator, clip rings for the governor and pump stator too.

EDIT: I would also make sure the converter they give you has a stall speed bits higher than the original. And make sure the crank pilot is the correct one. 9 out of 10 converters for c6's have the smaller pilot.

EDIT2: Check on your original converter, but I'm 99.99% sure crank pilot must be 1.850 in. While most C6 converters use a 1.375. Double check that one!
Now that's alot of good info, thank you very much. Transmissions are Greek to me, it does have a slightly deeper pan with a plug already. 

I would not mind driving a ways to deliver and pick this one up if anybody knows of a really good place within 100 miles of Bryson City NC.  

 
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Fabrice

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No need to look for a far away top notch specialist, any serious shop can do the rebuild of that trans, you simply need to tell them what you want. If they receive the transmission and you just say rebuild it please, they know most people ask for the cheapest, so you get the cheapest. If there are 3 plates inside you will get it back with 3 new plates and they will simply change the parts that wear most. For the price they ask, you can't expect them to spend ages on that trans. That doesn't say they can't.
For this specific engine you really need at least 4 friction plates. It's a must. If you tell them that, they will do it and that will cost you more but not much more. If the donor Torino was a cobra, it might already be "loaded" too.
Read a bit on the diffs in C6's and as you will speak "Greek" a little, they'll be aware you're a client that knows his sh.t., something that always comes handy if you need to discuss costs ;)

For the converter, aside the crank pilot dimensions ask them the details/brand, a cheapo one with plastic parts inside that will balloon up your pump can become an expensive free gift!

 

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good info has been shared...   steel planetaries, roller thrust bearings, more clutch disks/plates, etc...

Most good stuff is from the E4OD transmission...

Depending on what you want/have for rear gearing, many replace the C6 first & second gears from the E4OD  2.71, 1.54 verses C6 2.47, 1.46 ... more gettty up out of the hole w/o a big rear gearing allowing a nicer cruise in 3rd/highway

the best torque converter Ford ever offered came in the 429 SCJ [believe you had to order the drag pack] , it had eight stud TC and flex plate, rated 3,000-3300.  That sounds hight but a 429 SCJ made a lot of torque lowering the actual stall ... 2,500???   

That converter was available after market  F33A P1A 10-1/2" had a thick backing ring to fit a standard four hole flex plate

here's a video ...   funny good old boy talking about C6 rebuild good info




IMG_0427.jpeg

 
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I have not had to have one rebuilt in years. One of two times I took my car to have work done. The guy at the Ford dealership in Hendersonville did my C-6 in Econoline van and was great. He has long since retired.
I would suggest that you take the fluid lines off and flush very good. Then put on a stand alone transmission cooler. Sometimes trash is in the old radiator cooler.
Here are pics of one I put on my 73 but it has a C-4. Return line is cool going back to radiator. Use the fuel injection hose clamps. I made the brackets to use existing Ford holes and fasteners.
 We need to meet up sometime. I was in Highlands today to meet a friend there.
Keeping transmission cool is key to long oil life.

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