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C6 Shifting Problem

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Angelo Voltura

C6 Shifting Problem

Having an issue, can't seem to figure out what the issue is.

So, here's the low-down. My C6 has a B&M ratchet shifter, B&M Stage 2 shift kit and a stock converter (needs a 2500 stall).

Drives absolutely beautifully, in drive, cruising around. Very crisp and firm shifting, mash the pedal and it will make you bash your head off the back window.

First problem. When in manual mode, it will not physically shift down into first, only 2nd. Believe this is due to a stretched cable. I can only start in second gear. In drive this is no issue.

Second issue is if I mash the go pedal, be it in 3rd or from a stop, wide open, this thing will go and rev to the moon and WILL NOT upshift unless I back off a little bit. Then it will firmly shift and I can put it to the wood again. Occasionally I won't have to pedal it, but this is very rare and the transmission has to be very hot for this to happen. Sometimes, when I let up and put my foot back into it, you'll hear the motor pop and putter a little bit/be boggy and then take off like a rocket when it goes up a little bit in the RPMs.

I dont beleive this is due to the kicmdown linkage as it happens from 0mph or at 60mph.

The vacuum modulator was replaced before I bought it and has good vacuum at the modulator itself. I am stumped and not sure where to go from here. I don't believe it is governor related.

What I am thinking however, is that the converter may be too low a stall speed and cannot take the load/torque from the engine until a certain rpm, which is why it gets boggy. But, I find that hard to beleive since the engine in front of it is making 300hp and 425+ for torque which, if I am correct, is well under the limit for a stock C6 let alone one such as mine.

Any ideas fellas?

1978 F150 351W
1979 F150 "410M"
1979 F100 302
1979 F250 400
1987 F150 300
1990 F150 302
1991 F150 300
1995 F150 (1985 clip swapped) 300
1997 F250 351W

Gary Lewis

Re: C6 Shifting Problem

Administrator

Angelo - I know very little about the C6, but I'll suggest a few things.

First, I agree that either you have a stretched cable or one that is out of adjustment. I say that because if the linkage only pulls the tranny down into 2nd it'll start out in 2nd.

Second, the lack of upshift at WOT may well be due to the kickdown linkage. If you have it adjusted too far it might keep it from shifting until very high RPM. I don't know that, but it would be an easy try to either back off the linkage or take it of entirely to test the theory.

As for the converter not being able to take the load, while they did use different converters behind different engines, the more powerful engines actually had a lower stall speed. But, if you are over-powering the torque converter all that will happen is that your stall speed will go up - and you'll heat things up very rapidly.

I think the pop and sputter/bog is due to the air/fuel mix being off, and probably lean. The accelerator pump is supposed to cover the difference in mass of the air vs fuel, so when you hit the throttle hard the lighter air rushes in sooner than the heavier fuel, thereby leaning the mix. Perhaps your accelerator pump isn't covering that gap and you need to adjust it.

Your signature doesn't say anything about your engine or the carb, so I can't suggest how to adjust the pump, but most carbs have that ability.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

Angelo Voltura

Re: C6 Shifting Problem

I can try to run it without the linkage in the spring when I get it out too see if that makes a difference. That would make sense but I was under the impression it only effected downshifting under load. Regardless, as I said the engine will rev out until it floats the valves/rev limiter kicks in before it shifts which by then is out of its useable power band.

It is possible about the mix, I am wondering if it has more to do with pedaling it. Otherwise it acts beautifully. This is a cammed 400ci engine with a 1406 carburetor. I am a Holley man, but I think next step is going to be fuel injection.

1978 F150 351W
1979 F150 "410M"
1979 F100 302
1979 F250 400
1987 F150 300
1990 F150 302
1991 F150 300
1995 F150 (1985 clip swapped) 300
1997 F250 351W

Gary Lewis

Re: C6 Shifting Problem

Administrator

Be careful w/a 600 CFM carb on a hot 400. Tim Meyer said he's seen that sized carb be enough restriction in the intake for the vacuum to come up enough to pull in the vacuum advance, causing detonation. He urged me to go to a bigger carb than a 600.

But, a 1406 has an adjustment on the accelerator pump, and I'd suggest you adjust it according to the instructions on Page 8 in the Owners Manual.

And, I do think it has to do with "pedaling it". As said, air rushes in where fuel fears to go. (Wait! Is that it?

) So you have to supply a shot of fuel with the accelerator pump as you come back in rapidly with the throttle - as described on Page 5 in that manual.

As for the kick-down linkage, the '81 FSM says "The carburetor full-throttle stop must be contacted by the throttle linkage and there must be a slight amount of movement left in the downshift linkage."

But, back to the Eddy 1406, there is a note in the FSM to test the shift points of the transmission with both 18" of vacuum, simulating part throttle, and 0-2" of vacuum, simulating WOT, on the diaphragm. That suggests that the tranny is expecting WOT to have less than 2" of vacuum. I don't know what the tranny will do with more than that on it, but it might be something to check.

Gary, AKA "Gary fellow": Profile

85lebaront2

Re: C6 Shifting Problem

Administrator

In reply to this post by Angelo Voltura

Angelo, I had a C6 in my 1977 F150 that I put a 1976 Camper Special 390 in. When I first installed it and went to pass someone, I had the same issue, damn thing wound up so far it floated the valves. Turned out the governor was for a high performance car. I can't remember right now, nor do I have all of my Ford manuals here. If there is a governor pressure test port on a C6. It probably needs a heavier governor weight to increase the pressure.

Bill AKA "LOBO" Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 2009 Flex Limited with factory tow package Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

Angelo Voltura

Re: C6 Shifting Problem

This post was updated on .

Thanks for the advice guys. I'll get a proper response out to you guys later.

On the quick, the 600 is definitely too small and needs at least a 670. I can tell the motor has much more in it and is undercarbureted.

It is is possible the trans is out of a car. The engine is definitely out of a car and not sure if the trans came with it. The rear end is out of a Bronco.

This motor and trans is currently in my 1979 but I figured it would apply to our trucks as well.

Here is a good exactly of having to peddle it and it bog and sputter.

https://youtu.be/NWqQ6rkrpmY

This video is a good example of how it runs as a whole. I have 3.89s not 3.73s if I mentioned that in the video.

https://youtu.be/pffD5Jnhz50

1978 F150 351W
1979 F150 "410M"
1979 F100 302
1979 F250 400
1987 F150 300
1990 F150 302
1991 F150 300
1995 F150 (1985 clip swapped) 300
1997 F250 351W

Gary Lewis

Re: C6 Shifting Problem

Administrator

Wow! That thing sounds wicked!

But I did hear the spitting/bogging when you shifted it, and it doesn't sound like accelerator pump. If you had accelerator pump problems then when you first hit it the engine would have bogged - and it didn't. And the bog when you shifted it was much too long to be due to the accelerator pump.

But I don't know what it is. Perhaps the secondaries are coming open too quickly? Maybe Bill has an idea?

Gary, AKA "Gary fellow": Profile

Angelo Voltura

Re: C6 Shifting Problem

Thanks Gary! This engine restored my faith in the modified engines. It runs like a raped ape!

Its possible the secondaries are coming open too quickly...but on vacuum secondaries is that possible that quickly?

Now that shift was me pedaling it to get it to shift. If I didnt it would just rev to the moon.

1978 F150 351W
1979 F150 "410M"
1979 F100 302
1979 F250 400
1987 F150 300
1990 F150 302
1991 F150 300
1995 F150 (1985 clip swapped) 300
1997 F250 351W

85lebaront2

Re: C6 Shifting Problem

Administrator

This post was updated on .

Just went and realized you have a Carter not Holley on it, mechanical secondaries can be interesting on automatics, we used to recommend manual secondaries for manual transmissions and vacuum for automatics. Logic being, automatic you stomp it and keep it wide open while shifting, manual normally, you let off each shift. The bog upon dropping the throttle to force an upshift, means the Carter weighted air valve on the secondaries closes and has to reopen, during this there is a transition circuit in some AFBs that feeds additional fuel as the air valve tips open. If the 1406 has these it may be causing a momentary over-rich condition during the transition.

First thing I would do is figure out the shifting issue, maybe a heavier governor weight, maybe Gary's parts lists might give the PNs for the governors. On stall speed, where is your torque peak? a built 400 should be fairly low in the rpm band due to the 3.98" stroke, you don't really want a high stall speed for a torquey engine, high stall speeds are for high revving engines, like a 302. Gary is correct on the higher stall speed = more heat, E4ODs have a higher stall speed than a C6, but they also have a lockup converter. One of the tricks on them is to use the engine's torque and stay in lockup to avoid overheating the transmission fluid.

Bill AKA "LOBO" Profile

Angelo Voltura

Re: C6 Shifting Problem

As I mentioned, this is an Edelbrock 1406, basically an AFB. I want to go with a Holley. I do beleive 600cfm is a bit too small, as far as I know this Eddy is completely stock but tuned for the engine.

It's been a while since I've played with it.

Where would I begin as far as adjusting shift points? I mean as you can see it seems fine other wise, only WOT runs are really affected on the upshift.

Correct me if I am wrong, I'm not a trans guy at all, but isnt the governor in the tail shaft and requires dissassembly to change?

1978 F150 351W
1979 F150 "410M"
1979 F100 302
1979 F250 400
1987 F150 300
1990 F150 302
1991 F150 300
1995 F150 (1985 clip swapped) 300
1997 F250 351W

Angelo Voltura

Re: C6 Shifting Problem

Just saw your update. This carb is vacuum secondaries.

I believe it is a 1800rpm stall. I didnt put the trans together so I am unsure but pretty firm on that. The engine has an EXTREMELY strong midrange, I would say its putting down a good 425 ft lbs around 4500rpm, she starts to Peter out around 5200. By 5500 its done.

The overrich condition does make a lot of sense to me, it doesnt do that at all when it actually does shift properly wide open which is rare but has happened. And when it does it is far quicker.

1978 F150 351W
1979 F150 "410M"
1979 F100 302
1979 F250 400
1987 F150 300
1990 F150 302
1991 F150 300
1995 F150 (1985 clip swapped) 300
1997 F250 351W

85lebaront2

Re: C6 Shifting Problem

Administrator

I have only seen a very few Carter AFBs with vacuum secondaries, 1957 T-Bird 312, some 1958 Lincoln 430s, they are extremely rare.

On the governor, extension housing comes off, it unbolts from the park lock gear and slides off the shaft. Mine was a pain because of the exhaust system, the left pipe passed under the extension housing so both pipes went down the right side to clear the fuel tank.

Bill AKA "LOBO" Profile

Gary Lewis

Re: C6 Shifting Problem

Administrator

I think it is a terminology issue. The AFB/1406 isn't truly vacuum but velocity. As Bill knows, the adjustment on them is a pain - pull the carb all apart and grind weight off of the lever arm or add weight to it. An AVS/Thunder series is MUCH better - turn a screw to adjust.

Anyway, I think it is an issue when the secondaries close and then open again. Not sure how to fix it w/o getting another carb that can be adjusted for opening point. But first I'd get the tranny shifting correctly and the carb problem will probably go away.

Gary, AKA "Gary fellow": Profile

Angelo Voltura

Re: C6 Shifting Problem

In reply to this post by 85lebaront2

Fortunately if it comes down to that, I have nothing for an exhaust system on it (straight headers and about 4 feet of pipe off each collector) so that wont be in the way.

Either way I want to get rid of that carb completely but that will be after I replace the camshaft since I took a lobe out.

Gary what should I do to get it shifting correctly? I'm beyond stumped. Like I said I dont know transmissions too well.

1978 F150 351W
1979 F150 "410M"
1979 F100 302
1979 F250 400
1987 F150 300
1990 F150 302
1991 F150 300
1995 F150 (1985 clip swapped) 300
1997 F250 351W

85lebaront2

Re: C6 Shifting Problem

Administrator

Bad cam lobe can cause some of the running issues depending on whether it is exhaust or intake. Bad exhaust lobe can make the affected cylinder backfire on sudden throttle opening.

Transmission, I repeat GOVERNOR pressure is probably too low. I am trying to see if there is a governor pressure test point on the case, I don't think there is unfortunately. Having been through the exact same issue with a C6, I am quite confident that is the problem unless someone put a shift kit in that would delay the upshifts. The other item, the fact that sometimes it works and other times not, could indicate either a sticking governor (not uncommon) or sticking shift valves. The other, slight possibility is the modulator is set too high, but that would affect part throttle shift timing also.

If Gary has the manuals for either Dad's truck or Big Blue (I'm sure he has both) maybe he could look in there. There are really not too many changes on the C6 from 1966 till it was finally discontinued.

Bill AKA "LOBO" Profile

Angelo Voltura

Re: C6 Shifting Problem

Yeah I put the truck away after I lost a lobe. I'm going to replace that in the spring. That happened months after I took the videos.

It does have one gnarly shift kit in it, but I'm starting to think you are right considering the motor is out of a car I think the trans came with it.

1978 F150 351W
1979 F150 "410M"
1979 F100 302
1979 F250 400
1987 F150 300
1990 F150 302
1991 F150 300
1995 F150 (1985 clip swapped) 300
1997 F250 351W

Gary Lewis

Re: C6 Shifting Problem

Administrator

I’ll pull the C6 pages out of the ‘85 FSM and scan them in this afternoon.

Gary, AKA "Gary fellow": Profile

85lebaront2

Re: C6 Shifting Problem

Administrator

Thanks, that should help. On your parts fiches, some time could you look at them and see if the C6 governors are listed, PNs will show if they are different. Angelo, FWIW, I have rebuilt a number of C6, C4, FMX, AOD, E4OD, 4R70/75W and even an old 2 speed Ford-O-Matic, the light duty aluminum one fitted to Falcon and Comet and even full size Fords 1959-1964.

If my memory is correct (haven't been into a C6 in years) the governor has two weights, a heavy one for low speed shifts and a lighter one for the rest of the speed range. The heavy weight pulls the light one through a spring giving a fairly quick initial pressure rise followed by a slower rise to full pressure. The valve body is essentially a hydraulic computer using road speed and engine load to determine when to shift up or down. the downshift rod is an override to force a downshift for sudden acceleration "passing gear". There are calibrated springs in the valve body that set a zero load upshift speed, the vacuum modulator provides a pressure based on manifold vacuum, low vacuum = high pressure. This pressure is added to the calibrated spring to increase the speed needed to shift up. There is a port that is blocked after shifting up to prevent "hunting". An AOD with the throttle rod or cable set to long or short for the cable will hunt in and out of OD at 45 - 65 mph.

Bill AKA "LOBO" Profile

Gary Lewis

Re: C6 Shifting Problem

Administrator

Check out Driveline/Transmissions/Automatic Transmissions/C6. This doc is from the '85 FSM and is ORC'd so you can search it. And it was scanned at 600 dpi so you should be able to zoom in and see any detail you need. But feedback on that would be helpful.

And I'll check on the question about the governor......

Gary, AKA "Gary fellow": Profile

Gary Lewis

Re: C6 Shifting Problem

Administrator

Bill - I've now added the whole of the parts list from the catalog to the parts list tab. And I added all of the illustrations to the Illustration tab. All three, meaning the illustrations, parts list, and rebuild proc's are OCR'd pdf's, so you can open them in a new tab on your browser using the Full Screen icon in the bottom right and search the document for what you want.

I suspect the governor is 7C063 and you'll see the application of the various ones used. But, there's no info as to the differences between them.

Angelo - If you know what vehicle the tranny is out of I might be able to find it in the catalogs I have.

All - I duplicated the first illustration in order to prove/disprove a theory I have that the first page in a pdf isn't as crisp. So please provide me some feedback on that.

Gary, AKA "Gary fellow": Profile