C6 Shifting Problem

[Angelo Voltura]

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?

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.

[85lebaront2]

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.

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.

[Gary Lewis]

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.

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.

[Angelo Voltura]

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.

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.

[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.

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.

[Angelo Voltura]

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.

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.

[Gary Lewis]

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.

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

[85lebaront2]

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

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.

[Gary Lewis]

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.

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 Lewis]

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......

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.