Anyone on the forum running 2.78 stock gears and AOD trans? I may need to replace my trans, currently C4 and considering the sw/ to AOD. I have slight wine in the trans or converter; I don't know which - but plan to have it resolved b4 nx road season. This is my first C4 and don't know whether this is normal; If I had to bet I wud say no. Also, it won't shift into 3rd until the engine temp abt 130 to 140. After it shifts into 3rd the first time im gud the rest of the day. I have owned the car 6 months; I recently had the differental rebuilt and rear trans seal. Everyone seems to overfill w/ fluid and it leaks from somewhere. I run abt 2500 at 65mph. I figure to loose abt 500rpm if I go AOD. I only plan on driving the car. No racing.
You already have highway gears now. The switch to the aod aren't going to be good for you. I am going with the AOD but will have 3.80 gears, for a calculated 70 mph rpm of around 2200.
It will be fine.ford had no problem putting them in front of 2.73's.i ran mine in front of the stock 2.79's but didnt use od untill 65-70 i just recently went with 3.80 to try to gain a few extra mpg
HI car-nut, Thanks for response. I wud change gear eventually but for now spent my momey on differental rebuild. I did'nt know the whine was in the trans also. I think I cud get by w/ the 2.78 for awhile. I may just redo the C4 I don't plan on any cross country rides - just a few hundred miles at most...
Thanks Joe. I recall u telling me B4 u have AOD. I don't know which way I am going. I wud like the AOD. I don't know what engine and flex combo I have 157/164 or what. I will let the trans folks figure that out and give me the cost factor. I am going to have the work done whichever way I go. I don't have the facilities and too old to be struggling under a car w/ the heavy stuff. How long u use the 2.78 and AOD b4 sw/ to 3.80? Did u gain in mpg w/ the switch?
2600 miles with the stock gear. Havent put maybe 30 miles on the 3.80 so no mpg number yet to compare with
AOD And 2.78 U think the whine might be in the trans and/or converter? I guess when u buy old car w/o any maintance receipts u have to assume everthing needs rebuilding.
Mojo, You will experience a 30% drop in RPM with the AOD - about 850 rpm, and with the locking converter it will actually be closer to 1000 rpm. At that point you are running your engine in the rpm range that is one of the richest ratios there is - "off idle". Every time you press slightly on the accelerator the power circuit is going to dump even more fuel into the engine causing a dramatic LOSS in fuel economy. You already have a good combination of low rpm at cruise and the carb is staying in the cruise range so the mileage is near peak. Financially it will be cheaper to rebuild or buy a new C4 than it will be to buy a core AOD and rebuild it. There are number of mods that may be required to fit the AOD into your car. New cross-member, shortened drive-line, linkage for the AOD throttle valve and the possibility of a new yoke. Now most of these depend on the AOD that you get but some will be needed with any AOD. The use of Mercon V fluid (the recommended oil) is another higher cost at over twice the price of type F in the C4. The AOD has some practical advantages for those who use 3.70 or higher (numerically) gears and is a very worthwhile upgrade for those who use 4.10 and higher (numerically) gears for drag racing but also drive their cars on the street. As an over-view the AOD is about three times the cost of the C4. The initial adjustment to the throttle valve can mean the difference between an AOD that will run for a long time and one that is junk after a week. You can rebuild the C4 (complete) with about $150 in parts. I paid that much for the tooling required to rebuild the AOD. Both transmission can be built to take upwards of 1000 HP but the cost difference to do so is still at least double for the AOD over the C4. I build both for street use and competition so there is no real reason for any prejudice on my part other than fitting the right transmission to the right application. In your application the C4 is an ideal and inexpensive choice. I do not ship transmissions - I build only for local folks
Aod - 2.78 highway gear Hi Paul, Thanks for sharing ur expertise w/ me. I have been thinking along the lines u just mentioned. I never even thought abt some of the other things u mentioned. I knew I wud have to make alterations to crossmember, maybe flexplate, stater and driveline. I just spent ate grand having my differental rebuilt including axlle bearings; my allowance is gone for the hobby car this season. I plan on using the same trans until it starts to slip or some other noticable problem arises. I don't plan on racing or trips over 5 hrs, the C4 is staying.
