C6 hesitates going to drive when cold

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C6 hesitates going to drive when cold Empty C6 hesitates going to drive when cold

Post  Calypso on March 13th 2014, 8:15 am

I have this c6 issue, that I need to let the engine idle about minute or two before the tranny agrees to engage into drive. It's only a once a day first start issue. Works well and shifts crisp rest of the day. Any thoughts what it could be?

edit: fluid level is in check.

Thanks,
Janne

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Post  Curt on March 13th 2014, 9:52 am

Calypso wrote:I have this c6 issue, that I need to let the engine idle about minute or two before the tranny agrees to engage into drive. It's only a once a day first start issue. Works well and shifts crisp rest of the day. Any thoughts what it could be?

edit: fluid level is in check.

Thanks,
Janne

Sounds like an internal clearance issue. Is it worn out, or rebuilt?
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Post  aquartlow on March 13th 2014, 1:45 pm

I had a similar problem in a C6 years ago, a transmission rebuilder told me "probably the lip seals are getting hard due to age or heat cycles". He explained that when the trans is cold, like in the morning, "the old lip seals aren't as pliable and cause the shift into gear issue". "Once the trans starts to get warm the seals work as they should due to the heat". Not sure if this is accurate info, but I have heard it from more than one rebuilder.
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Post  Calypso on March 13th 2014, 3:29 pm

Curt wrote:
Sounds like an internal clearance issue. Is it worn out, or rebuilt?

Can't really say, I've only had the truck for awhile. Seems like I get to practise transmission rebuilding...

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Post  supervel45 on March 13th 2014, 6:50 pm

aquartlow wrote: I had a similar problem in a C6 years ago, a transmission rebuilder told me "probably the lip seals are getting hard due to age or heat cycles". He explained that when the trans is cold, like in the morning,  "the old lip seals aren't as pliable and cause the shift into gear issue". "Once the trans starts to get warm the seals work as they should due to the heat". Not sure if this is accurate info, but I have heard it from more than one rebuilder.
The older C-6's did not even have lip seals. Ford brought them out later as an improvement on the C-6. I would pull the pan and see what is in the bottom. If it looks good, you may want to pull the valve body, and check for any sticking valves. I believe there is a convertor drain back check valve, and if it does not work properly, the fluid can drain back into the case and cause this problem also.

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Post  rmcomprandy on March 13th 2014, 7:58 pm

Calypso wrote:
Curt wrote:
Sounds like an internal clearance issue. Is it worn out, or rebuilt?

Can't really say, I've only had the truck for awhile. Seems like I get to practise transmission rebuilding...

Time for at least a filter and fluid change tune-up.
With the pan off in front of you, a better evaluation can be made.

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Post  69F100 on March 13th 2014, 8:33 pm

I agree with Randy

I never had a c6 to do that but have had a few old FMX to do it had one in the winter I would go out and fire up my truck and go back inside the truck be warm and would go into gear then in summer it wouldnt take as long if I just went out and fired it and try to pull off it would even think about going in gear. Drove it for about a year doing that until I put a SBF c6 in it.
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Post  crittersf1 on March 14th 2014, 8:04 am

I had a sticky convertor drain back valve years ago that caused this.
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Post  Calypso on March 14th 2014, 11:08 am

Thanks for all the feedback.

Fluids and filter are fresh.

Did a little more investigating:
-Goes into reverse immediately when started cold.
-Engine off cold, tranny fluid level is about 1.5" higher than engine off warm (when it agrees to engage drive).

-Janne

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Post  manofmerc on March 18th 2014, 6:49 am

Since your trans. engages without slipage going into reverse this tells me it is your forward clutch drum seals .This is fairly comon with c6s .The input shaft engages the forward clutch drum and carries heat to the forward clutch drum .It isnt a lip seal it is an o ring .The lip seal would be on the outer perimeter of the clutch drum pressure plate .The o ring hardens with age from the heat and wear and tear .The fluid bypasses the o ring instead of applying pressure to the pressure plate .Just let it warm up a bit until it doesnt slip .With warmer weather coming it shouldnt be an issue but a rebuild should be in your future .Most overhaul kits come with an improved o ring for this very issue .I believe transtar kits had a special green o ring in their kits .But any overhaul kit would have the correct material on ther o ring .The lip seal is an improvement that came about in the mid 70s .It helps to have a lip seal tool to install those .Gregaust on the forum has a good picture of this tool.For your information whenever you shift into reverse you are using the low reverse and direct (or third gear ) clutchs .Kinda told your own story on the forward clutchs good job!!Doug

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Post  Calypso on March 18th 2014, 12:35 pm

Thanks Doug,

Sounds like I need to learn some new ropes. Smile

-Janne

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Post  supervel45 on March 19th 2014, 12:13 am

BBF (385) C-6 cores used to be pretty cheap. I think you will be OK also when it warms up in the summer. This would be a good time to pick up a core, and gather parts for rebuilding and beefing up a spare transmission. When I raced, I could get cores for $20 dollars, and kept two rebuilt spares on hand, since they where cheap and easy to rebuild, and my core guy would give me heavy duty drums, ect. dirt cheap. I would look for 3/4-1 ton truck and police/ambulance cores, for the best starting point. If you get one of the old HD forward drums, be sure and get a 30-30 input shaft with it. It is alot better if you are going to try and rebuild it, when the vechicle is running, then when it is down, and you are pressed for time. You will be able to get all your parts together, and build plan sorted out, and tools rounded up, or made, along with a ATSG manual, and a shift kit/valvebody if you chose. We made our own drum spring compressors out of cut pipe, allthread, and steel strap, with a nut, and a oxy/acc welder. It took about an hour, but it was almost free. Buy your lip tools, they are not that costly, and you will be glad you did. Don't foget long snap ring pliers, to get the pain in the ass C-Clip out, and get a spare C-Clip if you can. The second backup trans is good to have when it all goes Fubar, as you can rob parts from it, or in worst case scenairios. It can and does happen with Hot Rods/Race Cars and Mud trucks.

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Post  supervel45 on March 19th 2014, 12:38 am

http://www.fourwheeler.com/how-to/ford-c6-automatic-transmission-rebuild/ Here is a little taste of what your getting in for. It is not that bad if you have a good work area, take a few pictures as you go, have a diagram, and keep your parts organized. When you start to modify a stock overhaul, is when it gets more complicated. Some HP parts can drop in OK, others not so much.

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Post  supervel45 on March 19th 2014, 12:55 am

I noticed he was polishing the valve body bores with a drill. I would be real careful about that. If the bore gets to big valves can tilt and more dirt can get between them and stick the valve. If the valve body gets refried to many times, it can be a problem, and on an old 70's transmission, it likely has been. If a valve moves freely, leave it alone, is my policy. Also check the input shaft end play, and log it, on your core before teardown. The link I posted was more for the pictures, not a end all be all guide to C-6's by a long shot.

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Post  manofmerc on March 19th 2014, 7:13 am

Janne you are already learning with your diagnosis of no slippage in reverse .Supervel is giving some good advise too an extra trans. would give you something to work with and learn on .The best simple available book on c6s is one haynes puts out .It has pictures and specs .The part# for this manual is 10355.That atsg manual Supervel mentioned is a good one but has illustrations no pictures .It doesnt hurt to have them both .But for now your transmisson isnt going to fail anytime soon just let it warm up before driving And if you plan on building it yourself get yourself a spare c6 a manual and tools .If you have a libary nearby go and look up an old motor manual it will have good info .You do need a homemade tool to compress the low reverse and direct (third gear) clutch packs .And some retaining ring pliers .If installing a shift kit in sounds intimidating you can buy one or find a trustworthy trans shop to install for you .Broader performance Has a website and lots of c6 parts available .Good luck and feel free to ask more questions .This is what forums are about .Doug Cool 

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Post  supervel45 on March 19th 2014, 8:30 am

The bad thing about building automatic transmisions is that you may get good at it, and enjoy the challenage. Then your friends will find out and want you to build theirs. Then you may end up moonlighting. I would look at LKQ for cores if their is one in your area. That is where the big problems start, when you let someone else install them, or a build goes wrong. Find someone into Fords or hotrods that works their and send them some business, if you can. They can hook you up on the Police/Ambulance C6's when they come through and other HD units. May get lucky and find a CJ C6 with the aluminum servo piston, but not likely. They can also tip you off to any other speed parts, that they don't grab for themselves, if you are lucky. Seen quite a bit of HP stuff come through my area LKQ. I would read everthing you can find on C-6 including what has been mentioned here, before you start. Alot of tricks to the trade, and some bad info out their also. I was fortuniate enough to have some expert builder's in my area teach me, and I will admit there is a learning curve, if you get my drift. I also don't claim to be a pro builder either, but do all my own stuff and a few freinds.

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Post  Calypso on March 20th 2014, 12:46 pm

Thank you all for your help and encouragement! I agree, it would be a good idea to find a core, rebuild and swap. They are a bit rare here, but do come up occasionally. Are there many lengths of these trannies? Mine is in a 75 F250 with 460, but I'm not sure if tranny is original. It's a column shift auto, so it might be. Will need to do a little crawling with a tape measure, and trying to read casting marks. Very Happy

BTW. We've had some temp variations, and it's very noticeable that warm air helps the situation.

F-series may be the most sold car over there, but you would not believe the stares here, when I've been driving it in the middle of the winter with a 500lbs steel plate on the bed. Yes, 2wd. No, it does not help MPG! LOL!

Cheers,
Janne

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Post  supervel45 on March 20th 2014, 3:37 pm

Get you tape measure and start crawling, and get the tail shaft housing lenght, just to be safe. There are at least 3 C6 tailshaft lenghts. Two wheel drive Trucks are usually the middle lenght, but sometimes people change stuff on these old vechicles, esp. if they are second hand. If you get a different lenght core, they can be converted with a new output shaft and tail housing. Try to get a core with a ribbed case, as they where the HD BBF units, and usually have better drums. I would think for $100 dollars you can find a C6 core, as not many people run them any more. Ask the transmission shops around your area where they get cores from, and maybe they will be nice enough to help you. If not go to the nearest big city and start hunting. Then order parts online or over the phone that you need, or want to upgrade. Do not be concerned about shift levers, as you can use the ones on the old unit in your new build. They are easy to swap over. If you go at automatic transmission building, don't do it halfassed or cut corners, you will be sorry and get burned almost every time. When you build, do a unit at a time, as they are modular in a sense. Start with the oil pump and work you way back. If you do your homework and take your time, and maybe get some help if you need any, they are not as bad as most people seem to think. Watch a few video's of builds first, and take note's they can be handy.

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