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    aod or c4 question

    Hey guys. As some of you know i have a really old aod that needs replacing at some point and thought about replacing the trouble some aod with a c4. My buddy has a used c4 trans that came out of his cougar and wanted to ask you guys some questions. I know that the c4 will bolt up and the cross member has the be moved back to the second slot and i will be able to reuse my drive shaft but how will the shifting linkage work. The trans will be for the 84 cfi and she has the kickdown rod on the throttle body so will my kickdown work with the c4. Will the c4 get worse or better mileage as the merc has just the 3.08 gears and is this in general a good idea or should i just stick with what i got and get another aod. Thanks matt
    1984 mercury grand marquis ls rebuilt 306 flat top pistons with factory cfi and lincoln headers with single glasspack dual snorkle air cleaner. Gloss black paint with slick top coversion.
    1986 mercury grand marquis colony park 5.0 sefi dual exhuast thrush turbos with h pipe and turbines

    #2
    Talk to Dan at Silverfox Transmissions for a true expert's analysis,
    but when I was reading about AOD engineering to modify my AOD in minor ways, there were some mentions of the C4.

    What I gleaned was this; for the serious racer, at one point in time, a C4 was either more durable, or at least, more cheaply modifiable to make more durable, to handle extremes of torque and horsepower.
    The AOD has since come a long way, with parts from later generations able to be installed into your 1984 or 1986, and is just fine.
    What I've read is that an AOD will last a healthy 100,000 miles before probably the overdrive band goes out first: and this is inline with both of my colony parks, one which needed an trans at 105k (due to the tv grommet, actually), and the other which is going strong at 90k still.

    So I feel that just getting a rebuilt AOD that bolts right in, no modifying necessary, will be just fine. I love modifications, but every time I try, it seems I open up a bag of worms that costs twice and much and takes 3x as long to make it work properly, for negligible gains. Just drop in an AOD.

    For years, supposedly 1989+ has superior tailshaft lubrication and a superior valve body, that eliminates a problematic 2-3 accumulator that has leaked on some people. You can also get a stock rebuilt valve body with the 1989+ features from silverfox for about $100, maybe with some minor improvements; this is what I did, and I'm happy with it; there's also a 4-seal 3-4 accumulator upgrade for $15 from dirtydog transmissions that you can install for cheap peace of mind.

    You can also get a 2" OD band, but that opens up a small bag of worms that I (and others) can walk you through: it ends up adding about $200+ in parts though, and when I bought the A++ overdrive servo upgrade, I had to very carefully modify it to work correctly (the clearance gauge provided, resulted in a slipping overdrive, and I had to make up my own clearance: it is entirely possible that the 2" overdrive band needed a different custom clearance, however, and that the gauge provided was for a stock band).

    Comment


      #3
      I'm starting to ramble.
      Short of it: stock 1989 or newer AOD rebuild will do great.

      Further durability modifications can be discussed/looked into if you like.

      Comment


        #4
        This is just advice from very recent experience. I thought c4's were stronger so I put on in my car with a very mild 351w. It has a 2400 stall, manual reverse valve body, and other tci goodies. It is an outstanding transmission and has never failed me once for the last 5k miles of beating it to death. It also amazed people at the drag strip whenever I chirped 2nd every time and pulled a 9.65 in the 1/8th. However, this car is my daily driver and sucks down the gas, whether I'm on it or not. So I have called silverfox for their awesome AOD and am waiting to get it. I would never recommend a c4 to anyone that is using the application in a daily driver or doesn't have the funds for gas. As a strip only car, the c4 does wonders, but hopefully the AOD will do even better. And with the AOD, it's just a drop right back in deal.
        85' Crown Vic 2dr. Small tire stock block grudge car.
        09’ CTS-V family car making over 700whp with ease.
        79’ f350 427 ls7 swapped with th400. Prerunner setup
        64’ c30 dually. Slammed and turbo 5.3 with 4l80e

        Comment


          #5
          Thanks for the great infos guys. I talked to my buddy with the trans and he said its been rebuilt 10k ago had has no modifications as he ripped the c4 out to do a t5 swap. I was really hoping that if i used the c4 that the mpgs wouldnt be affected but my aod has a solid 245k and is still going but has its small issues. Ill look up silverfox and see what they have. I just want a good reliable trans that will last and just thought of using a c4 instead of an aod because of the horror storys ive heard on the site. Thanks matt
          1984 mercury grand marquis ls rebuilt 306 flat top pistons with factory cfi and lincoln headers with single glasspack dual snorkle air cleaner. Gloss black paint with slick top coversion.
          1986 mercury grand marquis colony park 5.0 sefi dual exhuast thrush turbos with h pipe and turbines

          Comment


            #6
            My AOD lasted forever and I did every little cheap thing I could do to it in order for faster/firmer shifts. But the c4 seemed the ideal way to go. I was getting 22-24mpg before with a 302/AOD. I switched to 351/c4 and am getting 14mpg maybe when going easy on it, and it's a torquy engine that should struggle much less than the 302. So I'm hoping for about 18-22mpg with the new AOD. And I also have 3.08 gears, which I will probably keep if I finish up with a turbo; or the alternative route would be 3.55 gears with my new nitrous setup.

            -Blane
            85' Crown Vic 2dr. Small tire stock block grudge car.
            09’ CTS-V family car making over 700whp with ease.
            79’ f350 427 ls7 swapped with th400. Prerunner setup
            64’ c30 dually. Slammed and turbo 5.3 with 4l80e

            Comment


              #7
              I thought automatics basically only lost fuel economy in the torque converter.
              Once gears are locked in place, there are no losses in the drivetrain, past the torque converter.

              Was it the 2400 stall that did it? (high stall definitely hurts fuel economy; you're churning fluid around just making heat until lockup)
              Or does the C4 have different, steeper, gear ratios that forced engine rpms higher, burning more fuel?
              Just not sure why a C4 would have poorer fuel economy: if there is a good reason why it would, now I'm curious to know
              might just be the 351?

              I've got an AOD and I'm getting like 15mpg, but I did put a higher stall (like 2000rpm) converter in, non-locking, and I have a short commute, and 3.55 gears now, and I drive routinely at 80mph, while evidence does show that 55mph is a golden number for fuel economy.
              I'm going to be taking a very long highway trip in 3 weeks, something I have never done, as we just never end up using my car for any long trips with friends; and I'm hoping to see better: hoping it's just the short trips that kill my fuel economy.

              245,000 miles is probably your small issues A stock rebuild may be just fine. What problems do you have?

              Comment


                #8
                yea 245k is alot for it. I finally got the slow down shift out of 4th fixed but overall it just old. Real slow shifts and a hard shift going into overdrive. Knock on wood she isnt slipping but just needs a good overhaul. Im just a little short on cash and thought maybe the c4 would be a good reliable fix but your right about modifying stuff and how it usually ends up costing more then just slapping in a new or used aod and doing it the right way as she is my 75 mile a day daily driver. thanks matt
                1984 mercury grand marquis ls rebuilt 306 flat top pistons with factory cfi and lincoln headers with single glasspack dual snorkle air cleaner. Gloss black paint with slick top coversion.
                1986 mercury grand marquis colony park 5.0 sefi dual exhuast thrush turbos with h pipe and turbines

                Comment


                  #9
                  I believe the fuel economy loss was due to the overdrive in the AOD, and the c4 only being a three speed. The gear ratios are only different in first and second and by a minimal difference, not enough to notice unless that is the final piece of a 1000+hp combo. That makes a big difference when all highways around me are 65-70mph zones. And I drive 72 mile round trip most days to college and work and back. I am also running a non-lockup converter which doesn't help at all. You should be getting more than 15mpg, but maybe that is also the converter and the taller gears. Driving at 80 doesn't help either.

                  -Blane
                  85' Crown Vic 2dr. Small tire stock block grudge car.
                  09’ CTS-V family car making over 700whp with ease.
                  79’ f350 427 ls7 swapped with th400. Prerunner setup
                  64’ c30 dually. Slammed and turbo 5.3 with 4l80e

                  Comment


                    #10
                    OH-- OK. I don't know the C4, and wasn't thinking about the lack of overdrive. That'd do it!

                    Sometimes it's 90-100
                    Also, like I said, all short trips does not help at all, and I have reason to believe my tripmeter (on which I'm calculating my fuel economy) is inaccurate: I've caught it frozen a couple times. I'm looking forward to this 900 mile drive in, gosh, just 3 weeks; to really find out what I'm getting.

                    Comment


                      #11
                      I always thought the C4 was aptly named. C4 is an explosive, and when beat on, the C4 transmission also blows up. They shift like mush, and in stock form don't hold up worth a damn unless you put a big cooler on there. They have no overdrive, and no lockup converter so it makes a lot of heat. As you might infer, I am not a fan. I'll take an AOD any day. I know a guy who knows how to make them work, so they don't bother me. Many places cannot make an AOD shift or hold up worth a damn though, but everyone seems to be able to make a C4 operate.
                      86 Lincoln Town Car (Galactica).
                      5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

                      91 Lincoln Mark VII LSC grandpa spec white and cranberry

                      1984 Lincoln Continental TurboDiesel - rolls coal

                      Originally posted by phayzer5
                      I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

                      Comment


                        #12
                        I've had two bizarre AOD experiences already; my rebuild burnt up the direct clutches in a matter of maybe 100 miles, and I never did find out why. Swapped some parts, seems to work now: but the parts-swapping was really just buckshot in the dark.
                        And then a friend had an AOD, clean as a whistle when installed, and still very clean in the post-mortem exam, that just would not shift past 1st gear. Not the governor, not the valve body. If not those things, then what?
                        Rebuilt a different one for him and didn't waste further time trying to figure it out.

                        Oh well.

                        Speaking of coolers. I've now got a non-locking converter. I added a moderately large external cooler salvaged from a pickup, should I be OK?
                        Or would I really benefit a lot from 3/8" cooler lines and a massive radiator-sized external cooler?

                        Comment


                          #13
                          Originally posted by 84merc951 View Post
                          Hey guys. As some of you know i have a really old aod that needs replacing at some point and thought about replacing the trouble some aod with a c4. My buddy has a used c4 trans that came out of his cougar and wanted to ask you guys some questions. I know that the c4 will bolt up and the cross member has the be moved back to the second slot and i will be able to reuse my drive shaft but how will the shifting linkage work. The trans will be for the 84 cfi and she has the kickdown rod on the throttle body so will my kickdown work with the c4. Will the c4 get worse or better mileage as the merc has just the 3.08 gears and is this in general a good idea or should i just stick with what i got and get another aod. Thanks matt
                          Just a thougtht... you could leave your aod in D for a week and see how it feels not having OD.

                          Comment


                            #14
                            Originally posted by ford man View Post
                            Just a thougtht... you could leave your aod in D for a week and see how it feels not having OD.
                            That's pretty damn smart! Should be fairly close to what the engine will be running at. (a quick Google showed third gear on an AOD and C4 are both 1:1)

                            I drove my 89 MGM for a few months w/o overdrive. Gas was cheap then, but I do remember it sucking it down pretty good.
                            2020 Volvo XC90 T6 Momentum (Ice White / Blonde)
                            2022 Ram 1500 4x4 5.7 Etorque, Built to Serve Edition, (Granite Crystal / Black)
                            Past Panthers
                            1989 Grand Marquis LS (Cabernet/Grey), 1989 Lincoln Town Car SS (White/Blue), 2004 Mercury Grand Marquis Ultimate (White/Black)

                            Originally posted by Lincolnmania
                            if its got tits or tires it's bound to give you trouble

                            Comment


                              #15
                              it'll be slightly worse with a C4 than an AOD in D. No lockup on the C4, though you're talking about maybe 2-300 rpm.

                              Bernini: stories like that are why I feel fortunate to know a guy who can get the AOD to behave properly. I don't know how automatic transmissions work, though I suspect it involves black magic and a dead chicken somehow. I figure the chicken blood is the real reason that ATF is red. All I know is that he knows how to make them work, and I'm happy to pay for his expertise.
                              86 Lincoln Town Car (Galactica).
                              5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

                              91 Lincoln Mark VII LSC grandpa spec white and cranberry

                              1984 Lincoln Continental TurboDiesel - rolls coal

                              Originally posted by phayzer5
                              I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

                              Comment

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