Doesn't this [earlier] Motorcraft 2150 with an AOD throttle shaft fit what you are saying can't be done? This style uses a return spring on the TV lever:




I don't see how the AOD could be hurt if the kickdown (or TV) return spring breaks and the TV rod drops to WOT position, like in the picture above. Wouldn't the weight of the TV rod push down on the TV lever, which would give the AOD full TV pressure, and *save* the transmission? (One of the advantages of the TV rod setup compared to a TV cable).

With a TV cable, if the cable breaks off or is pulled out of adjustment, the TV pressure would drop to zero, and *that* will destroy the AOD in a hurry.

Right?

 

No I did not say the above could not be done . What can be done is to have 3 axial return springs on the throttle shaft which is what would be needed for how the AOD carb was done later. That set up is basically EXACTLY the same as the Trans kick down.



The TV thinks it is WOT if that spring breaks or comes off and the rod fall down to WOT, you then get full WOT pressure , right from idle. running like this will in rather short order fracture the original early cast iron clutch drum rendering the trans scrap and non rebuildable for all practical purposes.. This is why the above set up never lasted. That style of carb TV lever was only used from 80-82 then changed to the more complicated and expensive to manufacture later style with the pump overtravel for the noted reasons ( no car company voluntarily increases the cost of manufacture of parts) . The clutch drum was also upgraded in 83 with a stronger cast iron piece.. Finally the cast iron drum was replaced all together in 91 with a steel piece and that solved the issues of fractured clutch drums once and for all. For use with Type F fluid the trans did not need as high clutch pressures to keep the clutches from slipping and the cast drum was more than adequate, but with the more sipperly Dexron clutch pressures had to be increased substantially and this can fracture the cast drum (especially the early ones) if the TV goes full WOT.

The AOD seen many revisions throughout it's life the early units 80-81 were the worst. In 82 revisions to line pressures were made and they were marginally better . 83 seen several internal upgrades and this when the AOD started to become a somewhat reliable trans. There were incremental upgrades basically every year the trans was in use till about 91. The a last few years 91-93 were the best of the lot. 80-82 should be avoided altogether as a basis for a build , as pretty much everything in the trans will need to be swapped out. The ones to look for a build basis are the 91-93 units

 

Okay, so why didn't Ford simply use their existing Motorcraft 2150 carburetors with the Ford kickdown linkage with the AOD? I mean, surely it would have been MUCH cheaper for them to simply design the TV lever on the transmission end to match the longer arc of the Ford kickdown linkage. Right?

Quote:

Originally Posted by matthewq4b

That style of carb TV lever was only used from 80-82 then changed to the more complicated and expensive to manufacture later style with the pump overtravel for the noted reasons ( no car company voluntarily increases the cost of manufacture of parts) .

Doesn't the carburetor in the picture above have the pump overtravel?

 

As for Ford not making the TV rod arc radius the same as the kick down or even using the auto kick down lever, no idea why they did not do that there certainly was nothing stopping them from doing it. It may have simply been an idiot proofing measure for tech's and the DIYer, given the similarity to a kickdown rod. This was still in the era when many people still did a lot of the basic maintenance on their vehicles themselves. And not like today where basically nobody does. Back in that era everyone I knew and all of my relatives older than myself did their own basic maintenance, the house hold that did not do basic stuff was an exception ... Now a days the exception is the ones that do , do it themselves... So who really knows why Ford did it the way they did. But I suspect it had something to do with idiot proofing. Cause even today some people think the TV rod does the same thing as a kick down rod... We have even seen that on this forum in from more than one newbie ....

No idea if the carb in the pic has an over travel or not and I can not recall if the early style AOD carbs had them or not, it has been over 30 years since I handled one. As the early AOD's could not really handle any increases in power at all.
But just because it has the deep accel pump cover does not automatically make it an over travel accel pump as Ford used this style of cover in some non over travel applications just with a longer plunger rod on the accel pump.
In the later AOD carbs the Accel pump and the TV rod were on the same lever so that lever had to full stroke with the throttle and that was too much movement for the old style accel pumps so an over travel was needed. They also used the over travel pumps in some non AOD applications where the accel pump lever was fixed to the throttle shaft since the accel pump lever full stroked like the AOD's it also needed an over travel accel pump.
See below pic of an over travel accel pump diaphragm. There is a another piece not shown the cup/sleeve that sits over the pump rod and in to the cup the retains the spring and it acted upon buy the pump lever... When the pump diaphragm bottoms out the rest of the travel/stroke is taken up in the spring as the sleeve moves down the pump rod. So the accel pump rod over travels the movement of the pump diaphragm.
There are so many variations of the 2150 carb especially in the early 80's it is mind boggling. and I'm sure you could find any variation you can think of if you looked long enough.