C4 transmission - shift linkage and shift points

[1987cp]

As some of you know, I'm acquiring an '81 LTD "tudor" and as part of the project of eliminating the allegedly anemic 255ci motor, I'm planning to drop in my 5.0L/C4 combo I've been running in the '79 wagon that's going byebye. I know the C4 doesn't have overdrive (duh), but this particular unit is about two years old and has been used pretty gently, plus I spent $550 on it and want to get use out of it in addition to having a solid, reliable transmission in the new car. Some of this stuff has come up before, but I'd really like to get it answered in a single thread.

Question number one: What, if anything, will I need to modify in the shift linkage to make the thing work? I've got the C4 driveshaft, so that's a nonissue if lengths, etc. don't match up, but the shift linkage looks like much more of a pain to harvest and I'm wasting a lot of my time getting the door wiring out intact (I'm no good at interiors). I ask this particularly because ads for aftermarket shifters always say they're for a C4 or C6 only and need a special kit in order to use them with an AOD.

Question number two: Is it possible to increase the automatic shift points to 5000 rpm without changing the torque converter? I've been told it doesn't use a governor to monitor shift points, and I know that the kickdown rod should have nothing to do with WOT upshifts. I know about the adjustable vacuum modulator (and yes, the one supplied with the rebuilt tranny is indeed adjustable), but I *think* that's only for raising or lowering shift points very slightly. I want to raise them by 1000 rpm, as this transmission has always shifted with the engine at 4000 rpm (stock reman 12" converter) but the E7 headed, Explorer-cammed 302 should definitely have usable power above this point (simulated HP peak falls around 4500). Is there a simple upgrade I could get from my local speed shop that would allow it to shift at ~4800rpm or higher?

[mrltd]

1. no idea
2. The torque converter has NOTHING to do with shift points. The kickdown rod does however! The vacuum modulator should adjust the points. it's been awhile since I messed with a C4.

[Nathan in MI]

Couldn't you compare the shift linkage between the '79 and the '87 and see what the differences are?

[1987cp]

Mercracer responded to a post on CVN and said that TransGo makes kits that include a selection of governor springs, and also that modification to the shift linkage is not necessary as long as I make sure the lever on the tranny is the same length as what came out of the car. I will try to give TransGo a call tomorrow to verify the info about governor springs. Based on limited information, it appears that Pinto governors will allow WOT shifts at 5800, but that's probably higher than I need (unless I could tweak it back down somewhat with lower modulator pressure or whatever).

Didn't mean to sound like an idiot with the torque converter reference, I was meaning to take into account the fact that with a looser converter, even though everything internal to the transmission is happening exactly the same, the actual observed engine RPM is higher. Not the same thing, I know; I was being imprecise.

[Archangel]

1. Quit your bitchin and swap the linkage, it ain't like you know that no matter what you do it ain't gonna fit right (the bull I had to go through, having the tranny like 2" further back than where it should be). As far as aftermarket shifters go, the C4 and C6 levers just side over the stocker and clamp on top of it, whereas the AOD lever gets in the way of a potential aftermarket unit and so needs swapped entirely.

2. Have the same issue with the C6, still need to fuck with modulator first tho.

[1987cp]

Update: Today I picked up a TransGo PN 40-2 "reprogramming" kit. In addition to the springs and junk for valvebody mods, this kit includes two different length plunger rods for the vacuum modulator, as well as a spacer grommet. The instructions say that for higher shift points, install the longer rod without the spacer, the shorter rod for lower shift points, and the shorter rod plus the spacer for even lower shift points. It also said something about two different push-in-style modulators, one for cars with EGR and one for cars without. I guess I'll have to try to figure out which modulator I have.

The guy at the transmission shop where I bought the kit did mention that it's possible to tune a governor by removing material from the weights. I've not had a governor apart personally, but the guy led me to assume that Ford governors have only one set of weights, unlike the two sets of weights in a GM transmission - though of course I might well be mistaken here. So I'm thinking that perhaps sometime soon I'll pull the governor and open it up, and see if I can make sense of this tip. It'd be interesting to know approximately how much material to remove in order to adjust the shift points by a particular amount ......

[Blaze86Vic]

There is a floating cylinder in the governor, that is the weight that he is referring to.

[gadget73]

Some governers you adjust the weight, some you change the spring. I guess it probably has the same net effect though.

[Pirate]

Update: Today I picked up a TransGo PN 40-2 "reprogramming" kit. In addition to the springs and junk for valvebody mods, this kit includes two different length plunger rods for the vacuum modulator, as well as a spacer grommet. The instructions say that for higher shift points, install the longer rod without the spacer, the shorter rod for lower shift points, and the shorter rod plus the spacer for even lower shift points. It also said something about two different push-in-style modulators, one for cars with EGR and one for cars without. I guess I'll have to try to figure out which modulator I have.

The guy at the transmission shop where I bought the kit did mention that it's possible to tune a governor by removing material from the weights. I've not had a governor apart personally, but the guy led me to assume that Ford governors have only one set of weights, unlike the two sets of weights in a GM transmission - though of course I might well be mistaken here. So I'm thinking that perhaps sometime soon I'll pull the governor and open it up, and see if I can make sense of this tip. It'd be interesting to know approximately how much material to remove in order to adjust the shift points by a particular amount ......

Before you get too carried away, I have a few notes concerning the C4 ( I have built a couple, including the one in the old yellow banana 79 Ford f150)....

1. Before you do anything with the shift kit, you might need to replace the shift servo (it's the round servo cover with the big letter in the middle, on the right side) with at least an "H" code servo, maybe even get an oversized billet servo replacement. Like the O/D servos in AOD's, there are different-sized servos, and the factory "H" codes are my favorite. If it already has the "H", a "C", or an "R", you are in good shape (the "H" being the strongest).
Personally, I would just get the PA billet servo, and be done with it.

2. Want to have some fun for a change? Get the billet servo, and set the shift kit up for "Kill". When I built the Yellow Banana C4, I used the H servo, and installed the same kit, along with using the 'race' setting everywhere I could, and the resulting 1-2 and 2-3 shifts would shift so hard, that it would launch your head into the back window, if you didn't brace for impact. In fact, my brother lost a girlfriend after he did this deliberately after an argument (he did this several times to her, to get a laugh); she got out and walked home afterward.

3. Yes, definitely install a lighter governor weight. The vacuum modulator can alter shifts, but I don't recall being able to go up or down 1000 rpm.

[1987cp]

I'm gonna see about maybe getting that thing removed and apart sometime today ... I'm getting real interested to see what the inside of my governor actually looks like. And heck, if I get this figured out, maybe I can perform the same mod(s) on one of my AOD governors and safe a few pennies on buying another one.

Before you get too carried away, I have a few notes concerning the C4 ( I have built a couple, including the one in the old yellow banana 79 Ford f150)....

1. Before you do anything with the shift kit, you might need to replace the shift servo (it's the round servo cover with the big letter in the middle, on the right side) with at least an "H" code servo, maybe even get an oversized billet servo replacement. Like the O/D servos in AOD's, there are different-sized servos, and the factory "H" codes are my favorite. If it already has the "H", a "C", or an "R", you are in good shape (the "H" being the strongest).
Personally, I would just get the PA billet servo, and be done with it.

3. Yes, definitely install a lighter governor weight. The vacuum modulator can alter shifts, but I don't recall being able to go up or down 1000 rpm.

Will do. If the servo is located where I'm thinking, that should be easy to check. Out of curiosity, would the thing have previously exhibited fairly weak shifts if a non-desirable servo were present?

P-mang, do you happen to know of a source for different governor weights? I'm finding a complete lack of information on C4 governors for the most part, and the tranny shop guy said TransGo said that "90% of the adjustment is done with the modulator", whatever that means. I share your skepticism that modulator changes can make more than a few hundred RPM difference in shift points under the best of circumstances - and like I mentioned before, the only specific info I've found on a different factory governor assembly was about that ~6-grand-shifting '78 Pinto unit that still wouldn't be what I need even if I can find one.

[Pirate]

I'm gonna see about maybe getting that thing removed and apart sometime today ... I'm getting real interested to see what the inside of my governor actually looks like. And heck, if I get this figured out, maybe I can perform the same mod(s) on one of my AOD governors and safe a few pennies on buying another one.



Will do. If the servo is located where I'm thinking, that should be easy to check. Out of curiosity, would the thing have previously exhibited fairly weak shifts if a non-desirable servo were present?

P-mang, do you happen to know of a source for different governor weights? I'm finding a complete lack of information on C4 governors for the most part, and the tranny shop guy said TransGo said that "90% of the adjustment is done with the modulator", whatever that means. I share your skepticism that modulator changes can make more than a few hundred RPM difference in shift points under the best of circumstances - and like I mentioned before, the only specific info I've found on a different factory governor assembly was about that ~6-grand-shifting '78 Pinto unit that still wouldn't be what I need even if I can find one.

Considering it's been a couple of years since I had to monkey around with a C4, you might just try adjusting the modular screw in a few rounds to experiment with the shift points.

Weak shifts? Shift kit cures quite a bit of that, and if it's a weak servo, that obviously doesn't help, either, and could be at least a partial explanation for wussy shifting.

One other note? Run synthetic Type FA fluid in this tranny, when you get done with it. Modern type FA is about as effective as running tap water in there, as all modern tranny fluid (except for Mercon V) has about the same lubricating properties as water does, and also breaks down far quicker due to the heat build up of non-locking torque convertors, like a C4 would be running.

[1987cp]

Synthetic FA ... that doesn't ring a bell ... what I'm used to seeing at the parts store are labeled "Type F" and "Mercon/Dextron III". Though, for a zillion dollars a quart I can use Amsoil tranny fluid ......

I was curious about the soft shift thing since my experience with this tranny is that it shifts fairly decently for a near-stock rebuild. Guess I'll just have to see what's actually in it.

[Pirate]

Synthetic FA ... that doesn't ring a bell ... what I'm used to seeing at the parts store are labeled "Type F" and "Mercon/Dextron III". Though, for a zillion dollars a quart I can use Amsoil tranny fluid ......

I was curious about the soft shift thing since my experience with this tranny is that it shifts fairly decently for a near-stock rebuild. Guess I'll just have to see what's actually in it.

Get the 'F' then. Half of the bottles I have seen call it FA and the other half F, and it's all the same stuff.

[1987cp]

Hm.... seems I have an "H" servo (big round thing on the p/s side has an "H" cast into it), and the modulator rod that I just pulled from the transmission is about the same length as the longer of the two rods provided with the reprogramming kit, with no shim installed .... that would seem to mean, shifts are already as firm as they're going to be without further valvebody mods (presumably what would result by installing the kit I just bought, which presumably would supercede the "stage 1" shift kit of unknown origin I had installed when the tranny was built for an extra $50 over the price of the tranny). I also pulled the governor apart and located the two weights and springs. My current head-scratcher is now how to precisely measure the mass of each weight so as to estimate how much material should be removed from each (or else, measure the rate of the springs and attempt to find generic springs of the same size but the desired rate). My wife says she doesn't personally have access to a precise balance at the cyclotron lab, which leaves me with a machine shop as my next most likely option ............

[1987cp]

Ookee ookee, got me a photo album of random views of the troublesome little bugger. Actually, the governor appears to be simple enough, it's info on it that's blasted hard to come by. But having to actually learn about the thing can be the fun part, and thankfully our pal Pirate had some key info to share. The most recent update is that I successfully weighed the governor weight with a cheap mechanical kitchen scale (oddly, a digital one that cost 5x as much refused to give any sort of consistent or reasonable readings). Came in at about 1.7 ounces; Pirate-mang says to try removing about 0.4 oz. to start, so that's what I plan to do.

Oh yeah, linky to photo album: http://picasaweb.google.com/mcwest20...norExperiments