C6 Shifting Problem

[Angelo Voltura]

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?

 

[Gary Lewis]

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.

 

[Angelo Voltura]

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.

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.

[Gary Lewis]

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.

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.

[85lebaront2]

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.

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.

[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.

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.

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.

 

[Gary Lewis]

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.

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.

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?

[Angelo Voltura]

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?

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.

[85lebaront2]

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.

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.

[Angelo Voltura]

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.

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?