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Technical Ford AOD question

Discussion in 'The Hokey Ass Message Board' started by strangepanel, Feb 10, 2015.

  1. Hello Gentlemen,

    I'm hoping someone on this board might be able to provide a little advice on an issue with an AOD. I have a 38 ford panel with an AOD transmission that was just pu on the vehicle. It upshifts fine and it shifts into OD without a problem, but the coasting is very clunky and it has kind of a rhythmic dragging to it when coasting from highway speeds to a stop. Anyone have any ideas? I would think if it was the tv cable that it wouldn't upshift and shift into OD properly, but I admit I've never had an AOD transmission before. Appreciate any help or insight from any AOD experts out there!

    Cheers,
    Christopher
     
  2. You have to set the Throttle Valve pressure at 35psi,
    They are a bit fiddly
    I suggest you look on you tube under AOD setting the TV.
     
    Clay Belt likes this.
  3. rdemilt
    Joined: Jan 12, 2009
    Posts: 135

    rdemilt
    Member
    from so florida

    What rear end gear is in the truck ? I have 2 AOD's, both vehicles had 325 gears or less & were very choppy / clunky feeling which I think is because the engine was running at such low RPMS. I switched the car to 389's and there was a tremendous improvement, the truck is getting a set of 370's sometime this week. I also have a GM 200-4r in my ford with a small cubic inch motor and 373 gears, it seems to be more forgiving, easier on adjustability and much smoother.

    I've never been a big GM person but I do like the 200-4R over Fords AOD.
     
  4. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    You need to be sure the TV is correct, you can destroy an AOD in a very short time if it is off. I rebuild AODs and run them in several high performance mustangs and I have no idea what you are talking about on the "choppy/clunky feeling". They are very smooth transmissions and I have never had that type of issue with one. I'm guessing that because in both of these cases they are transplanted into a different environment that something is not set up correctly. Need to figure out what is up with the issue before it becomes a bigger issue.
     

  5. Thank you all for the suggestions. The rear end is a 3.55. I admit the idle rpm is around 600, so maybe that is causing an issue? This car does have a big cam so the idle isn't exactly the smoothest: cam specs are: .510/.512 lift, 224/230 duration @.050 with 110* lobe separation angle. I had switched from a C6 to the AOD because I wanted a little better highway mileage, but I also switched to bigger back tires. That moved my highway rpms to around 1500, which has been great for gas mileage. Almost a 40% gain, since the C6 with a small tire was averaging a bit over 3000 rpms at highway speed.

    I've been getting the feeling that there is something off in the way the transmission is coasting, but I'm not sure what it is. I don't have a lift, so I admit to having someone install this for me. It is just difficult to describe since it feels as if the transmission is almost engaging and disengaging at coast, causing that rhythmic breaking feeling. I'm reasonably sure the pressure is set correctly, but I guess I really need to check myself. I'll also give a look at the tv cable to make sure it appears to be set correctly.

    Any other suggestions are greatly appreciated!
     
  6. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    The cable setting and pressure are one in the same thing. The cable setting is what determines the pressure. That is way to low an idle for an engine with any kinda cam! Your issue on curise may also have to do with low RPMs, not sure on that one, but 1500 is fairly low for a cammed engine. Any thing over stock is going to shift the HP/Torque curve up the RPM scale. Looks to me like you may be trying to do things that are moving in opposite directions. If you are wanting to cruise along at 1500 RPM you need a stock cam in there! Why move all you power up the RPM scale and then make the motor try to pull at a low RPM, that just does not make sense. Up the RPM or get the engine set up to run in the RPM range you are wanting to use. I'm guess you may have an engine overload issue as much as a transmission issue.

    What engine are you running?
     
    Last edited: Feb 10, 2015
    Hnstray likes this.
  7. It's a 351 windsor stroker built by blueprint engines. I'll double check the tv cable next time I get a chance, just to be sure. The car shifts up without any issue, it is just the coast with my foot off the gas pedal that produces that rhythmic dragging feeling. I'm definitely trying to find a balance between that engine and gas mileage. I guess in a way I should have tried one thing at a time instead of switching both the back tires to larger ones and the transmission. The car is smooth accelerating and cruising at speed. I also have a lokar kick down kit on the transmission, I'm not sure if that could contribute to the rough coast to stop in any way?
     
  8. flyboy89
    Joined: Oct 6, 2010
    Posts: 417

    flyboy89
    Member
    from So. Cal.

    Do you think maybe the driveline angle is not correct? Might be worth checking.
     
  9. I guess anything is possible, but a drive shaft angle issue should show up in acceleration and deceleration. I also have a lock-up torque converter. Can those fail in a way that it would not properly unlock and stay unlocked during coasting?
     
  10. FrozenMerc
    Joined: Sep 4, 2009
    Posts: 2,734

    FrozenMerc
    Member

    What are your torque convertor specs??? Factory AOD's do NOT use a lock up torque convertor for 3rd gear and OD, like other OEM overdrive autos. Lock-Up is done internally in the trans and normally around 17-1800 rpms for highway cruising, bypassing the torque converter entirely in OD. If you have a lock-up style convertor, that may be causing the problem by affecting fluid flow during coasting, especially at such low idle and cruise rpms. Are you running high fluid temps as well??? That could also point to a converter problem. Shudder will often be felt when the converter is slipping against the lockup feature due to bad fluid (overheated) or the wrong converter type.
     
    Last edited: Feb 11, 2015
  11. OLDSMAN
    Joined: Jul 20, 2006
    Posts: 2,422

    OLDSMAN
    BANNED

    A TV cable adjustment should not cause this problem, however it a clutch pack was not releasing properly you could get this kind of a feel. There have been several threads on setting TV pressure lately, I would recheck the pressure to make sure, but I don't think this is the issue
     
  12. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    Not sure why you would use a lock-up converter with an AOD, as stated the AOD has it's own lock-up. Seems like there is a lot of issues with this setup. I still think a big one is the RPMs you are trying to force this combination to run at. Fuel economy is one thing, but in a lot of ways high performance and drastic economy modifications don't mix. As FrozenMerc said the AOD locks-up "normally around 17-1800 rpms for highway cruising, bypassing the torque converter entirely in OD." Trying to run way below that in high gear cruising is going to cause an issue. Who knows what is going on if the normal AOD lock-up is attempting to work with a lock-up converter. How about putting smaller diameter tires on it and just see what changes.
     
  13. Hmm. Now I'm even more confused. TCI makes a lock-up torque converter for the AOD transmission.

    http://www.americanmuscle.com/tciauto-converter-8093.html

    The truck cruises at 55 just fine. It's quiet and smooth. Yeah, rpms are in the 1600 range, but she jumps into the 2-3000 during acceleration without any issues. I've a small gauge, so it may even be a touch higher. Sounds as if you can't use just anything as a lock-up torque converter on an AOD. I have to look at the spec on my torque converter now, since maybe that is causing an issue. The guy that did the transmission for me selected the torque converter, so I thought it would be right. I'll report back if I make any progress. I can't believe switching tires would make a difference, but this torque converter issue might just be it. fingers crossed. Thanks to everyone for the assistance so far.
     
  14. OLDSMAN
    Joined: Jul 20, 2006
    Posts: 2,422

    OLDSMAN
    BANNED

    An AOD transmission doesn't have a lock up convertor as normally thought of. When it does into overdrivd the dorect clutch is applied, and there is a shaft splined into the direct clutch hub, and splined into the convertor itself. That is why you feel it go into ovderdrive so hard, it is a complete mechanical lockup. I does not have linings like lockup convertors have
     
  15. rails32
    Joined: Oct 29, 2008
    Posts: 110

    rails32
    Member

    use to work for ford when the aod came out. had problems with them new. ford called it trailer
    hitching. problem was to low rpm in od, recomended not putting car in od around town or under 35 mph


    -
     
  16. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    The tire comment was to get the RPMs up!!!! Seems like an easy check to see if increasing the RPMs into a more normal range helps any?
     
    Last edited: Feb 11, 2015
  17. If I understand you, it is possible that the issue is due to the transmission staying in overdrive even though I've coasted below 35 mph? Perhaps it isn't a complete automatic after all, I just need to manually shift when I come out of overdrive. :) I'll try driving it in drive and see if it acts differently,. The transmission usually shifts a bit over 45 mph and over 2400 rpm into overdrive at the moment. Still looking into a few other things, but the lock-up torque converter installed is supposedly built for the AOD style transmission.

    Oldsman, thanks for the lesson in AOD design! Maybe it is just staying in overdrive when I go into coast and the low engine rpms are causing an issue. I'll have to try a little more experimenting. As I've said, no hard shift into overdrive. She shifts in very smoothly, I just see the rpms drop and barely even feel the actual shift. My 1988 mazda shifted way harder.
     
  18. I see. I've somewhat heard someone else say that the roughness of the motor can translate back into an AOD. Still if I'm coasting from 30 down to 25, the motor has never shifted into overdrive, so would it still be an issue? rpms are going to be well into the 1500 range at 25 mph. Unless the transmission is shifting in and out of overdrive and that is the drag I'm feeling. Good food for thought, thank you. I think I'd get some idea by simply putting the car in drive instead of overdrive and seeing if the coast feels different.

    Does anyone else have the problem with an AOD that it stays in OD and you get a shudder or rhythmic braking feeling? I would have thought if the answer were that easy there would be more people talking about it, I can't be the only person putting these two engines together. Wouldn't some of the mustangs have had an AOD and a similar engine?

    Again very appreciative of all your insights! I've not had an older ford setup like this before.
     
  19. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    The AOD has no idea what speed you are driving. I'm sure the 35 mph is some average for stock autos at the time, different gearing and/or tire size will change the number around, but the concept remains the same. But remember the transmission is seeing rpm, not mph.
    The AODs I work on are in mustangs but the gearing is in the 3:73 to 4:11 range (where I think they belong LOL!) and they run great. That's what the OD is for to make up for the low gearing. Same concept with the T5s, I have a few of them as well. Have kids that love mustangs (and manage to tear them up at a good rate!).
     
    Last edited: Feb 11, 2015
    Clay Belt likes this.
  20. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    Ok, a story. This is not an AOD but you might find it interesting. My fairly new 2005 mustang was developing a rear end whine. Ford decided to replace the ring and pinion. I though as long as they were at it why not drop the ratio. One of the Ford mechanics raced 4.6 mustangs and suggested a 4:10 gear. I was concerned about the gas mileage and wanted to only go to 3:73. He told me that was a mistake as the engine liked a 4:10 gear. I went with the 3:73 as I do a lot of highway driving and did not want to drop the gas mileage that much. Well got the mustang back and went on a trip, to my surprise the mileage with up with the 3:73 gear!! Not much, but maybe 1/4 to 1/2 mpg. Then I noticed that the stop and go mpg went up about 2 mpg. So, the guy was correct, I should have went with the 4:10. The point is mpg depends on a balance of a lot of factors and IMHO overloading the hell out of the engine is not one of them. The engine needs to be running in the RPM range that it is setup for (cam etc.).
     
  21. I get you. I was using mph and trying to equate it into the rpms for different gears. I'm hoping not to tear this one up, but worse to worse I could switch the back end to a 3.72 from the 3.55 to get a similar increase in rpms. I just got the larger tires on the back and the truck looks so muck better with them that I hate to switch back. :) I know looks shouldn't be everything.

    I find it interesting that this transmission may be so sensitive to the lower rpms of the engine. I still have the suspicion that there is something not right somewhere and it is more than rpms, but even just staying in drive instead of OD should show some difference for high speed coasting in terms of raising the rpms. Coasting in drive at 45 mph will result in rpms over 2400, so if it is still shudderng at that higher rpm there is another issue going on. Still, isn't the whole idea of this transmission to lower the rpms of the engine to get better gas mileage anyway? I definitely have a lot more reading to do!

    For such a large car the fuel tank is pretty small (15 gallons with no room for anything much bigger than that, original tank was a 10 gallon on some of these 38's), so I'd prefer not to drive gas station to gas station. Which is what I was doing when I was getting about 10 mpg highway. The AOD with those tires moved me up close to 15 mpg highway. A 50% increase almost in range. A big difference when your driving up the coast.
     
  22. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    "A 50% increase almost in range. A big difference when your driving up the coast." I hear you! I was thinking a temporary tire change just to see if it helped figure out want was going on, not a permanent change. I think a good guide would be what the OEM cars were running RPM wise in the AOD years. But, remember on top of that you have messed with the RPM range on the engine, not directly related to the RPMs the AOD see, but very much related to the RPM the engine wants to run at. Big question: why does the engine have that cam in it if you are than concerned about the mileage? It makes no sense whatever to put a big cam in an engine that totally kills the lower RPM torque/power and then try to drive it with a high rearend gear at low RPM. I really don't understand that.
     
    Last edited: Feb 11, 2015
  23. OLDSMAN
    Joined: Jul 20, 2006
    Posts: 2,422

    OLDSMAN
    BANNED

    Rails32 is right on that one. Trailer hitching was a big problem early on with the AOD transmission. Keeping it out of overdrive helped the problem
     
  24. rdemilt
    Joined: Jan 12, 2009
    Posts: 135

    rdemilt
    Member
    from so florida

    I did some driving yesterday with my truck, making some quick notes of how the truck reacts under several driving situations. As I posted earlier the truck has a stock 302 / AOD and a 325 gear. Maybe ill get my butt in gear and swap to 370's today, I have everything ready just lacking the ambition. I'll report back as to how things change. My previous experience is that if the set up is correct the lower gearing resolved everything else.
     
    Last edited: Feb 12, 2015
  25. jseery. I can explain how that cam got in there. I took over custodianship of this project just recently. So, the engine and cam choice was the previous owners. I just haven't had the heart to change it. The engine runs like a clock, and when you step on the gas the truck really moves. The engine is rated at 425 hp right now. Not sure where the rpm/torque curve come out on it. I'm sure I'm way below it in general, but she picks up into the 3000 rpm range during heavy acceleration, which is not far from the c6 that was in it before. As I read more I'm starting to get convinced that it may be a tv cable adjustment after all. I found someone with a jeep that had a very similar issue that just tightened the tv cable and he reported that the issue almost completely went away. His was only showing up when coasting down hill. Hopefully I can get out there this weekend and give that a try. I'll report back if there is any change.
     
  26. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    That will be interesting to follow. Just a note: going from 3:25 to 3:70 is referred to as going to "lower" gears. The higher the number ratio the lower the gearing, and the lower the number ratio the higher the gearing. So, a 3:00 would be a high gear ratio and say a 4:11 would be a low gear ratio.
     
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  27. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    Only torque/horsepower curve I can find is for a 302, somewhat similar cam. The chart starts at 2500 RPM, but you can see where the torque is headed. Basically what a high performance camshaft does is shift the torque/horsepower curve to the right and up on a graph. I'm a Hot Rodder! I love performance! So, I see this as all good. BUT, the gearing and such in the vehicle have to be matched to the performance for everything to work together.
     

    Attached Files:

    Clay Belt likes this.
  28. Yeah, I'm not a hot rodder. I probably gave that away. I did want a 30's truck and this one was very attractive and met all of my criteria. I even liked the idea of the hot rod characteristics. Never really owned a performance car before. My 76 olds cutlass with the tiny 260 V8 sure didn't cut it and my swap to a 350 in that car was a total failure. For the truck, I just wanted to increase mpg for my use since I plan on driving this thing a bit more than the previous owner. The build was in 2008 and I have about 1700 miles on it. About 700 of that was from me, so it was barely broken in when I got it. Thank you for posting that curve. According to what I've read on blueprint's site I should actually have a torque/HP curve for my specific engine. The previous owner kept very good records. Blueprint shows a flatter HP curve than your example in the one curve on its site. My engine is based upon a 351W block, but it is bored to a 408 (425 and 455 ft pound). They have been great in helping me with the change over to the AOD, so I also decided to put the situation past them for their opinion. Here is the curve for a slightly smaller engine than mine:
    upload_2015-2-12_13-26-38.png
    I'll post mine if I can find it.
     
    Last edited: Feb 12, 2015
  29. jseery
    Joined: Sep 4, 2013
    Posts: 743

    jseery
    Member
    from Wichita KS

    Not much difference in the graphs. Check out the scaling. The first one tops out (the graph) about 400hp and the second one 500hp, on the same scale it would be at least an inch taller (it is true that as cubic inches increases the torque curves tend to flatten). Also notice on the first graph the torque starts to drop below 3000rpm, and the second one starts at 2700rpm. Now what range are you trying to force the engine to run in? 1500rpm? Lights come on anywhere?
    If your that interested you could re-plot both graphs on top of each other and see what it looks like.
     
  30. Apologies for the size. Unfortunately the curve also ends above 3000. Jseery, I wouldn't say I was trying to force the engine to run at that low rpm, but that was the result of the change. I'm way out of the power band when cruising, but the engine builders didn't appear to have any issue with that. They did suggest that being below the torque converter stall speed while coasting in those conditions may contribute to it locking and unlocking. I was reading somewhere else that a bottle of friction modifier added to the transmission fluid might solve the problem. Anyone ever use it? I see Ford makes some that comes in a 4 oz. bottle. They also said that there are kits to stop a torque converter from locking? Have to look into that if none of the other fixes work. It's too cold to be out working on the car this weekend, but I'll try the tv cable adjust first and then move on to the other things.

    torquehorsepower.jpg
     

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