Who is the "authority" on C6s?

[cammerfe]

Originally, C6 transmissions as factory designed, had a lot of extra drag inside, due to 'solid' thrust washers. When assembled with the latest rollerizing, including the proper clearances, they do much better. A C4 will do better yet since the parts are smaller and, therefore, have less mass to move internally. It's said that the upper limit for a C4 is somewhere in the range of 1K HP---or actually the torque that is what you get that goes with the 1000 HP.

Years ago, I was involved in the weekly rebuilding of the C4s Doug Nash used in his 'Bronco Buster' fuel funny car. It had an aluminum chassis and body, so it weighed practically nothing, and ran a small block on 'pop'. The transmissions were ready for rebuild after only a couple passes at most. He usually expected to change out the trans about three or four times during a weekend's racing. Better parts and other improvements would probably mean that today you'd get, perhaps, half-a-dozen passes before needing to change under the same conditions.

KS

KS

[RustyCrankshaft]

I've had a couple of FE C6 cases that were cracked.  Its something to look for when buying one.  Saw one that had been "pre-welded" by the re-builder.

Depending on how/where they're cracked I've stitched them up before to save the case. I have done the same on a TON of Allison cases, most I can save. It can be a tedious process however. I have had way better results stitching transmission cases than I have welding them.

Personally I think weight has as much to do with HP. If it's a truck/heavy car, etc. a C6 will hold up better, but you do pay a penalty for it. As was mentioned, a full rollerized build does a LOT to reduce friction and drag losses. I like C6's for non-competition use - I'll trade a little bit of HP loss to gain longevity. If it isn't a race car I want to build it once and drive the wheels off it. If I'm racing it I've already accepted I'll have to refresh stuff and it's coming apart on a "regular" basis.

[thatdarncat]

Just a thought, is your current C6 the original one for your Mach 1? If it is, it should have the partial VIN stamped on it to match your car. I understand your desire to get a replacement to get your car back running, but you might want to hang on to original to keep with the vehicle for the future. If it’s already been replaced then you can ignore this, but I just wanted to mention it because not everyone realizes about the VIN stamping.

[66FAIRLANE]

Anyone measured how many HP rollerization frees up? If not, educated guesses?

[jmlay]

I found this interesting reading:

https://www.fordforumsonline.com/threads/1966-ltd-resto-mod-thread.14264/page-2#post-77070

https://www.fordmuscleforums.com/threads/1966-c6-build-rollerization-part-2-modification.610433/

https://www.fordmuscleforums.com/threads/1966-c6-build-rollerization-part-3-assembly.610465

https://www.460ford.com/threads/roller-c6-is-it-worth-it.105633/

[RustyCrankshaft]

Anyone measured how many HP rollerization frees up? If not, educated guesses?

Not apples to apples because I've never done a back to back test with a C6. I did with another model of transmission from the "other brand" when I was rebuilding the trans dyno at a friends place some years ago. I was trying to see what I could get the repeatable resolution down to. Back to back test with the same trans, just a swap from thrust washers to torrington's showed about a 15hp difference at 350hp (dyno was powered by a 350hp 8v71TA and I swapped the hydraulic absorber for a Telma retarder). I would expect a C6 to be in the ball park.

This was more about messing around with building the dyno rather than a specific test of the trans so results may vary. However, it was a repeatable and noticeable difference and verified with a LOT of pulls over several weeks. But again, this may not be the average results of rollerizing and that isn't what I set out to discover so take it all with a grain of interwebs salt.

Only thing I couldn't do was run it long enough for sustained load testing. At full load the engine would get hot after about 20 minutes-had a bad block which is why it ended up on the dyno in the first place. But worked fine for that application.

[gt350hr]

  I have a rollerized C4 ( PA parts) that I built. No change in ET that I could prove, Also just finished building myself a wide ratio full roller C6. YES the effort to turn it went way down!
   Randy

[CV355]

Just a thought, is your current C6 the original one for your Mach 1? If it is, it should have the partial VIN stamped on it to match your car. I understand your desire to get a replacement to get your car back running, but you might want to hang on to original to keep with the vehicle for the future. If it’s already been replaced then you can ignore this, but I just wanted to mention it because not everyone realizes about the VIN stamping.

I can check.  I have not scrapped anything at all, and I plan to keep all of the take-off parts in storage just in case I get the itch to do a concourse restore someday, or if I have to part with the car for some unforeseen reason and a future buyer wants original parts.

[e philpott]

I have rollerized mine but have no data to support any conclusion , C6's have a heavy drum that spins up in first gear but has to stop for second gear , to make third gear the band has lets go of the drum and the direct clutch has to spin the drum back up to speed for third gear . At some point you might need the strength of a C6 or if you're not chasing every ounce of ET a C6 is a good choice , but the shear weight of the C6 Drum and having to stop all that weight just to turn around to spin it back up I just can't see a C6 keeping pace with a C4 despite the C6 being rollerized

[thatdarncat]

Just a thought, is your current C6 the original one for your Mach 1? If it is, it should have the partial VIN stamped on it to match your car. I understand your desire to get a replacement to get your car back running, but you might want to hang on to original to keep with the vehicle for the future. If it’s already been replaced then you can ignore this, but I just wanted to mention it because not everyone realizes about the VIN stamping.

I can check.  I have not scrapped anything at all, and I plan to keep all of the take-off parts in storage just in case I get the itch to do a concourse restore someday, or if I have to part with the car for some unforeseen reason and a future buyer wants original parts.

Here’s a few examples. Usually stamped on the flat pad near the tailshaft. Sometimes distinct, sometimes faint. In general it applies to 1968 model years & later cars in our FE era.

[Gaugster]

I don't know who does C-6s, but I'd like to suggest that you switch to a C-4 instead.  You will pick up quite a bit of power at the rear wheels with that swap, because the C-4 takes a lot less power to run than a C-6.  When I replace the C-6 in my Mach 1 with a C-4, it felt like somebody had released the emergency brake.  Big, big difference.  Performance Automatics makes a good C-4 and the adapter bellhousing for the FE.

This is good to know. The C6 in my Cougar is acting funny and I had planned on a rebuild or replace with a more stout C-6. It was previously fitted with a steeper 1st gear ratio. So a C-4 can be made just as strong and more efficient? Did any of the transmission gear ratios change as a result of the swap to the C-4? I'm guessing the C-4 is overall less weight too?

[thatdarncat]

Both the C4 & the C6 have the same stock gear ratios - 2.46:1 / 1.46:1 / 1.00:1. The aftermarket makes “wide ratio” gear kits for both transmissions, I’m not sure off hand if they are the same ratio or not, but they’re probably close. I have couple C6’s with the Ford Motorsports wide ratio kits, they are 2.72:1 / 1.54:1 / 1.00:1 ratio. I don’t have the actual transmission weight on hand, but yes, the C4 will be considerably lighter. The main thing for making the swap to a C4 for a FE is you need to buy the adapter bellhousing, and they’re not cheap. I think you have three choices for adapter bellhousings, Performance Automatic makes one, Quick Time makes one, they are both SFI certified, which is good if you’re racing at a quick enough ET that you need the SFI certification. JPT used to make an adapter bellhousing too, but I think he may have retired. Used JPT bellhousings turn up for sale occasionally. I think JPT might have been the first to make a commercially available FE to C4 bellhousing. And of course the C4 is shorter, so you will need a new driveshaft too if you are changing from a C6. The C4 uses a smaller input & output shaft. They make stronger C4 input shafts, they are probably a good idea for a healthy FE. I have a friend who snapped a stock C4 input shaft last summer with a 700hp Windsor in his race car, I would think by at least 600hp a person should be looking at the stronger aftermarket C4 input shaft.

[winr1]

Weighed a C4 an C6 .. no fluid, no convertor .. C6 was 30 lbs heavier

12" C6 convertor would add a bit of weight

JPT C4 to FE bell is for pan fill C4 only.... Jim sold the last bunch to Jessie Holmes IIRC

I have one I bought through the forum but not directly, it has been welded an machined to accept an FE 184 tooth auto flywheel



Ricky.

[Dr Mabuse]

For what it's worth (of course, your results may vary), over the years, I have had six C6's fail on me.

The 4R70W  in my 2003 Marauder has lasted well over 100K miles, and the 4R75W in my 2009 Crown Victoria also has (probably - bought it used) 100K+ miles on it. The 4R75W in my 2000 Crown Vic PI was rebuilt just before I bought it, has 165K on the chassis, but the prior owner had supercharged it with 17 lbs of boost and over 600 rwhp (before the 4R70W trans failed).

I like Jay's recommendation of using a C4. Broader says their C4 can handle ~800 hp, and Performance Automatic claim 1,000 hp capacity, with a lifetime warranty and rebuilding program.

[Val406]

Over on the other forum (fordfe.com), there is currently one listed for sale. Looks new and a great price. Not mine.

https://www.fordfe.com/pa-fe-bellhousing-t163917.html