Topic: C6 Transmission Engagement Lag: Looking for advice

[Angela]

Concerning the 390 FE & C6 drivetrain in my '67, I am looking for some advice. After 12 yrs of restoration I finally got the front end aligned, which made me feel a bit better about trying to test drive the car up and down my driveway. I don't like what I observed.

With the engine OFF, cycling through the gear selector provides you with at least some amount of feedback, meaning that you can kind of feel and hear the "detents" in the shift bucket and transmission. The shift indicator light lines up with the correct "P", "D", "1", etc markings in the console indicator.

With the engine running, however, there's *almost* no feedback to tell you when you move the shift lever into drive that you are actually in drive. You pull the shift lever back into drive, but you have to watch the indicator light to know you're in drive....... i.e. there isn't any mechanical feedback that you can "feel" you've found the drive gear position. There then appears to be a several second delay between when the indicator light shows you're in drive, and when you feel the transmission engage. The car will move forward. The same thing happens in any gear..... very "mushy" feel to the shift mechanism and a several second delay before you feel the transmission choose to engage.

I'm wondering what to look for. Is the transmission low on fluid? Too much fluid? She's still royally temperamental and it takes a good 15 minutes of feathering the throttle before she'll idle. I believe I need the engine idling in park in order to check the fluid level, yet I'd like some feedback and advice before I fire it up again.

[Smokey 15]

 First, check the fluid level, with the transmission hot. Don't overfill it.  With the car safely on jackstands (very safely), unhook the linage. Put the transmission in Drive. See if the reaction is the same you are getting with the shifter. With the transmission still in Drive, have a helper put the shifter in Driver, with the linkage still unhooked. See if the linkage will slip on the transmission without moving either. If not, adjust the linkage to fit. Do NOT move the arm from the trans, just the linkage. Having Drive engaged first is most important. Now, with the linkage hooked up, have the helper slowly check each gear. If they don't fully engage, there is something wrong with the linkage that needs to be dealt with. If all this is correct, then the problem may be in the valve body. I always add a can of Lube Guard to the trans, being careful not to overfill. Try it before any disassembly. It won't repair broken parts, but it works to improve shift quality.

[suskeenwiske]

There are many things that could cause the Transmission to perform poorly. I could write a book here on this subject but you may want to seek the advice from Ken with Bad Shoe Productions. You can Google Bad Shoe or he can also be found on Facebook.

Good luck

Ray

[67gtasanjose]

There are many things that could cause the Transmission to perform poorly. I could write a book here on this subject but you may want to seek the advice ...

Good luck

Ray

+1

FIRST question I have, what is the history of this transmission? Has it been rebuilt? I assume it IS NOT THE SAME ONE out of the car with the frozen engine you discussed in another thread, right?

Assuming it is NOT that transmission, I completely agree with Ray. After checking the basics, and once being certain those are OK (Fluid level and basic adjustments including any external band adjustment), it would be time to have a transmission specialist look at it.
These C6 transmissions are like the easiest, most basic and most durable transmissions on the planet. They were used for so very many years, I imagine EVERY transmission specialist has worked on one or learned "HOW to rebuild" transmissions using the C6 as a lab rat.

My thoughts, if externals are all OK then you have an internal problem. Most serious possibilities will require transmission removal for repair. I hope (and pray) that isn't the case for you.

Good luck, but DO NOT jump to conclusions without first double checking all the basics. FLUID, must be checked, double checked and triple checked. I think these hold up to 12 quarts from dead-empty. Be absolutely sure you have the correct dipstick and the correct dipstick tube for your application or it could be reading incorrectly. Dead-empty is meant to read as a fully drained converter and a fully empty transmission that has been disassembled for overhaul, still having all of the fluid passages empty including the valve body. . 

Hope this helps and I hope all you need is another quart or three to get it right. Most of the time, that is all it is. (just a few quarts low)

BTW, true that you do not wish to overfill it. But if you find you have, it is far worse to be a bit UNDER full than to be OVER full. Any excess fluid can be removed using a large syringe-type extractor with a hose down into the dipstick tube. A temporary overfill would likely result ONLY in a fluid leak at the vent tube on top of trans case when it was hot (makes a mess) Having it overfilled for extended time can be harmful though...That is why they say "DO NOT OVERFILL"

[WT8095]

I'll echo the advice everyone else has given - go through the basics first: fluid level, linkage, etc. Unfortunately I think you're going to find that it's an internal problem. Most likely a worn or hardened seal on the forward clutch. Google "C6 transmission morning sickness" and you'll find plenty of references.

[drummingrocks]

There are many things that could cause the Transmission to perform poorly. I could write a book here on this subject but you may want to seek the advice from Ken with Bad Shoe Productions. You can Google Bad Shoe or he can also be found on Facebook.

I'll second this.  Ken has a whole series of how-to DVDs covering everything from rebuilding transmissions, rearends, etc.  And he's super helpful if you run into a problem you can't overcome or need professional advice about something.  I have pretty much all of his available DVDs.  I bought one, and immediately knew I needed to buy the others too.

[69GT350H]

I'll second this.  Ken has a whole series of how-to DVDs covering everything from rebuilding transmissions, rearends, etc.  And he's super helpful if you run into a problem you can't overcome or need professional advice about something.  I have pretty much all of his available DVDs.  I bought one, and immediately knew I needed to buy the others too.

Ken and his DVD's are great. I ordered the set for the FMX and rebuilt mine using them and his input from his Facebook Group. He has some sample videos you can watch on his WEB site if you want to get an idea what they are like.

[Angela]

I'm gearing up to re-check external transmission connections before I fire it up again and try to see if the fluid level is low. Per the shop manual,\

I first need to adjust the kick-down cable length, then
Adjust the gear selector linkage

 I have not been able to find a clear picture indicating if and where there are supposed to be washers, rubber or plastic bushings etc at either end of the kick-down cable, so that step is slowing me up. I know there should be a clevis at the accelerator linkage end and that a clip is used at the transmission end. However, I don't know where there are supposed to be washers (metal, plastic or rubber). Neither my shop manual or my assembly manuals have good pictures of this.

NO, this is not the same car or trans which I posted a few months ago concerning a stuck engine/transmission.

This particular '67 C6 was professionally rebuilt by a Ford technician of 30+ years. I should probably call him, but he's probably just going to tell me it's nothing he did, so first I'll readjust the kickdown and linkage, then fire it up to check the fluid level.

The shop manual discusses adjusting the bands through a set screw and lock nut. Does that have anything to do with the symptom I mentioned above?

[suskeenwiske]

Angela,

It could be in the Bands but slippage is more common if they're incorrectly adjusted or worn. Slow engagement is more likely to be a Servo, Front Pump or Valve Body issue, assuming that the fluid level is correct and that it is circulating.

Adjusting the Bands should not be done if you're not familiar with the adjustment procedure and specifications; you're working with 'Inch Pounds' not Foot Pounds when adjusting Bands; it's easy to make a mistake if you're in unfamiliar territory. If you are familiar however, definitely check that the Bands are properly adjusted.

Out of curiosity, how much time passed between the Transmission rebuild and the first time it was engaged? If it sat for a long time, the Clutches and Bands could have dried out to the point that they were damaged on start-up.

Ray

[Angela]

It's been at least 5 yrs since the trans was rebuilt. It may have sat for 6 months to one year before I installed the trans. I start the car once a month, thus I doubt the tranny dried up.

[suskeenwiske]

OK, so it appears that it hasn't sat idle long enough for the Clutches or Bands to dry out. Infrequent operation of the Transmission may have been a factor. Has this been a problem right from the start or did it just show up one day?

Do you live anywhere near Dallas, Texas? If so, I would be more than happy to take a look at the Transmission for you.

Ray

[Angela]

I finally made time to unhook, check and re-adjust the transmission linkage and fire it up so I could check the transmission fluid level. I admittedly only let it run for about 10 minutes, but with it idling in park, there was NO fluid on the dipstick. I pulled the dipstick, wiped it off, re-inserted it into the tube, waiting a few moments and then pulled the stick out to read the level. I repeated this process four times over the period of 3-5 minutes to make sure I was confident with what I was reading.

So, my question is how much fluid should I add, as a starting point? I thought I read somewhere that the "add" line means you're 1/2qt low. If I see no fluid at all, should I add 1qt?

[Smokey 15]

 Yes.  It will probably take more. Add slowly 'til it shows on the dipstick. then you'll have that as a guide to get the level correct. Get it warmed up after you get fluid to the 'add' level. Run it through the gears, then recheck it to see if you need more.

[Angela]

Wait, what?! with the engine off, add fluid until I read the "ADD" level, then start it up again and check it while warm and idling in park? So add 1/4 qt at a time, perhaps, and keep checking it until I reach the "add" line?

[Smokey 15]

 Check and fill with engine running.  Add until it shows on the 'add line'. Run long enough for fluid to get up to temp. Then recheck and add if needed, again, while running.