C6 tranny issues. Won't engage. ( Any Help?)

[Filthy67]

I just bought my truck about a month ago. When I purchased the truck, the previous owner stated that there were some issues with the tranny. So, I used that to my advantage on negotiating the price. I am 100% happy with the truck, but would now like some opinions on what the underlying issue might be.

1967 f100- Tranny is a c6, with a fairly new B&M shift kit.

When the truck is cold, the tranny will not engage. Upon start up, I can put the truck in gear, and nothing.Doesn't matter, whether it's forward or reverse.....NOTHING. It usually takes about 3-5 minutes of idle, for the tranny to finally engage. Once warmed up, it engages, and shifts great. No slippage, or other issues of any kind. It shifts hard, and drives right. But, without fail...if the truck has been sitting for any more than 6-8 hours, it needs this "warm up" time to engage. But in normal everyday driving, once it's warmed up, it doesnt give me any problems, no matter how many times I turn off the truck, or restart it.

One more issue that I have discovered, is that the incline or decline in which the truck is parked, has a big part in this. My driveway is somewhat steep. If I park normally, with the nose of the truck higher than the rear, than it takes forever for it
to engage...(sometimes never at all, even after idling for 10+ minutes) But, I can then push the truck out into the street on flat ground, and get it to engage pretty quickly. So, I now park the truck in the driveway backwards, so that the nose of the truck is pointed down. This seems to help the issue. However, any time the truck sits for extended periods of time, and the nose is higher than the rear, than it is almost impossible to get the tranny to engage.

So, that is my issue. With the incline/decline being a definate part of the equation, my thought is that it has something to do with the fluid, and where it is traveling inside the tranny. It hasn't been a major concern, because it is not something, that has hampered me driving the truck, and has never left me stranded. Once, warmed up, it runs, drives, and shifts just fine. Any suggestions, or thoughts would be greatly appreciated.

[caseyj10]

im no an expert on trannys at all, but i would say check your trans fluid level, and if that doesnt work replace the filter and fluid.

[Filthy67]

Yes, the fluid level was one of my first thoughts. Previous owner, stated that it didnt matter how much fluid was in it, that it was still having the issue. Sure enough, I have topped off fluid, and issue is still there.

[caseyj10]

Maybe the guy drilled a wrong hole?

[70_F100]

Forward clutch seal.

[72BahamaBlue]

Or a failing pump?

[Donnie]

Your torque converter is draining the fluid back to the pan...There are several reasons to cause this condition........A work front pump bushing is the most common cause....Also some shift programs have you drill the valve body passage "line to lube"...this will cause drainback, but help keep the pressure up & things lubed on a long haul...Like WOT pulling a trailer up a mountain..
I don't know if B&M has you do this drilling or not as I don't use their kits..They do not allow the accumulators (these offer to take some of the fluid away from the drums or bands, whichever is in play) on soft throttle driveaway conditions.. Maybe some one on here has the B&M instructions and can qualify my concern...Not allowing accumulation will give you FIRM shifts under all throttle positions. Which you said that you have.
The best way to qualify the drain back condition is to park the truck on level ground overnight & in the AM , before starting the engine, pull the dipstick & see if the fluid level is way up the stick.....If it is , your converter has lost it's charge...Make this test & repost..
You said that it won't move foreward or reverse..And your description leads me to the above diagnosis....The foreward inner clutch seal is known to fail on this trans, but you would still have reverse..................Donnie

[Filthy67]

Donnie,

I appreciate you taking the time to type all of that out. I am going to set the truck out in the street overnight, and check the fluid levels tomorrow.

[dirtwrench]

What you are dealing with is what folks in my area always called "C6 morning sickness" It has to do with the seal letting fluid out of the converter as posted by several above, usually. It doesn't matter if the trans is full of fluid or not if the converter drains back. Also it is worse in cold weather. One thing you may want to try if a rebuild/reseal is not an option right now- K&W Trans X. aka "snake oil" or "overhaul in a can" It may help you get by for a few months as it will soften & swell seals.

And yes, I have had 3 transmissions affected by this morning sickness. Two were "fixed" by the snake oil, 1 had to be rebuilt.

[Donnie]

Just read the last post on this condition........I'd like to add a word of caution before adding
ANY "Tranny Man in A Can" to your trans. There are many different "let's call them rubber
compounds" used in the seals in any automatic trans.
Nitrile or Buna is cheap to mfg & are used in apps. where they will hold up..max temp about 200 degrees
Poly has replaced Buna in many applications..a bit more costly, but wears better in the clutch drums and is a bit more reluctant to take a flat set ( the O ring is more willing to stay round.)
Viton is used where there is a concern for heat...The newer kits now use Viton for the inner seal in the foreward clutch drum in the C6 as the shaft coming from the converter carries heat directly into the center of this drum...Those of you that have had the inner seal snap like a pretzel know what I mean....Viton is costly & used sparingly...It is good to about 400 degrees & is used for all seal's in the lock up torque industry...
Where I am going with this is back to the Tranny Man in the Can..........
A lot of the compounds used in the make up of the internal seals in the trans will not tolerate any CHLORINE which is used in many additives.. If you are going to go this route
READ YOUR LABEL'S ......................there is a mechanical fix for some drain back problems.......& NO , don't use brake fluid either..........Donnie