Join Date: Sep 2002
Location: Geelong Australia
Re: Anyone Know Much About AOD Boxes
I put one in an XD wagoon about 10 years ago, very straight forward fit, except mine was a column auto and I kept it that way. I had to make up a lot of new linkage parts and re-engineer some of the existing parts.
I believe they come in various extension housing lengths but mine was exactly the same as the dirty of C4 I replaced so required no tailshaft surgery. The gearbox mount had to go to the rearmost position, and I had to do a little on the exhaust to clear the linkages. The electronic speedo drive just slipped straight in but there was a 13-15% error I found out later...
The really difficult part of the fit was getting the throttle position linkage to work properly. I made up a rod that had a threaded rose joint on one end so I could adjust the length of the rod easily. The next hurdle was getting the right arc of travel, I made up an adjustable arm so I could change the arc and travel without drilling millions of holes. This is extremely important as the AOD doesn’t use mechanical / vacuum kickdown system like C4’s or FMX (I guess).
The throttle position linkage tells the box how fast the throttle is opening and what position the butterflies are. Get it wrong and the auto changes like a dog, get it right and it’s lovely
Another issue is the detents allow for the following modes:
Drive (1, 2, 3 & OD)
Drive 2 (1, 2, 3)
My AOD had an OD ratio of about 0.67:1 which meant that the standard 2.72:1 diff had the old 302 slugging along at 1,450rpm @ 100km/h. Way too low! Also with the speedo error, I only found out that when Mr. Plod gave me an accurate radar measured reading (Speedo 110km/h, Radar 126km/h, later verified with a stopwatch over 10kms…) I ended up putting a 3.23:1 diff centre in that not only brought my revs up to about 1,750rpm @100km/h but also corrected my speedo error to a less than 1% error.
As a tow car, the old girl was great if left in Drive 2, forget about the overdrive, it was just too tall. For performance, it was a slight improvement. For reliability, be careful, one of my not very mechanically sympathetic brother in laws gave the old girl a 6,000rmp enema once and the torque converter disintegrated. It caused so much damage I had to have the transmission rebuilt (Cost the same as buying it!).
But in the end the trannie did well over 100,000 km of varied abuse and torture. I believe it’s still going strong but probably not in the same car…
I did it more to prove I could, than to actually get a benefit out of it, fuel economy was slightly better but not measurably so. Now I’m an older and more wiser car nut, I would think twice about something like that. I’m thinking that a E or A series 5 Litre and 4 speed would be a better option now, especially as the engine management system controls both and you could transplant the loom ECM et al.
Also one last final thing, on the bottom of the sump pan in big and very clear letters is one word: METRIC. if you plan to play with the internals remember what spanners to use!
Have fun, getting it working properly is really the enjoyable part of this conversion!