AOD Troubleshooting, need help
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Junior User
Joined: May 2004
Posts: 51
Likes: 0
From: St. Louis, MO
AOD Troubleshooting, need help
My son has a 51' F1. It has a '68 289 with an early model AOD transmission (type with "rod" throttlevalve control).
The problem is that it is slow to shift between 1st and 2nd ... seems like it should shift soon. The same goes for shifting between 2nd and third.
Also, when shifting from 3rd to 2nd and from 2nd to 1st.
The scary part is that the engine rev's very high when it shifts out of one gear and into the other. If you take your foot off the gas it will go into the correct gear pretty quick but if you have a driver who isn't familiar with the problem and leaves their foot on the gas it feels like the transmission is going to explode!
We tuned the engine (new plugs, wires, points, etc.) and adjusted the idle, timing, etc.
Did some transmission pressure tests. On regular driving the transmission pressure stays like it is suposed to, between 55 and 70 psi. High rev's with the brake holding the car from moving will drive the pressure up in the 125 PSI, or more, range. At idle, the pressure is 45psi to 55psi.
One area of concern is at idle, in park or neutral, the pressue will sometimes slip down to 5-15psi for maybe 30 seconds or more and then climb back up to normal.
Lastly, the transmission doesn't lock into park correctly. For example, it park (without the parking brake on) on a slight hill, it will go ahead and roll and the transmission will "click, click, click).
As far as I can tell, the transmission isn't slipping in any gear.
Also, the transmission will downshift if you are cruising at 55mph and floor it.
We bought the two popular manuals and they tell in detail how to do the pressure test but don't really tell you have to troubleshoot or test for specific symptoms. They do tell how to rebuild the transmission but I don't think we are to that point yet (plus, although we are pretty confident amatuer mechanics deep into a truck restoration ... we need to get some confidence to really jump into a transmission rebuild).
Anyway, we would appreciate some advice from a few transmission experts before we take our next step: 1) high rev's between gears, 2) 5 psi trans pressure in neutral, 3) park lock.
Thanks, Richard
The problem is that it is slow to shift between 1st and 2nd ... seems like it should shift soon. The same goes for shifting between 2nd and third.
Also, when shifting from 3rd to 2nd and from 2nd to 1st.
The scary part is that the engine rev's very high when it shifts out of one gear and into the other. If you take your foot off the gas it will go into the correct gear pretty quick but if you have a driver who isn't familiar with the problem and leaves their foot on the gas it feels like the transmission is going to explode!
We tuned the engine (new plugs, wires, points, etc.) and adjusted the idle, timing, etc.
Did some transmission pressure tests. On regular driving the transmission pressure stays like it is suposed to, between 55 and 70 psi. High rev's with the brake holding the car from moving will drive the pressure up in the 125 PSI, or more, range. At idle, the pressure is 45psi to 55psi.
One area of concern is at idle, in park or neutral, the pressue will sometimes slip down to 5-15psi for maybe 30 seconds or more and then climb back up to normal.
Lastly, the transmission doesn't lock into park correctly. For example, it park (without the parking brake on) on a slight hill, it will go ahead and roll and the transmission will "click, click, click).
As far as I can tell, the transmission isn't slipping in any gear.
Also, the transmission will downshift if you are cruising at 55mph and floor it.
We bought the two popular manuals and they tell in detail how to do the pressure test but don't really tell you have to troubleshoot or test for specific symptoms. They do tell how to rebuild the transmission but I don't think we are to that point yet (plus, although we are pretty confident amatuer mechanics deep into a truck restoration ... we need to get some confidence to really jump into a transmission rebuild).
Anyway, we would appreciate some advice from a few transmission experts before we take our next step: 1) high rev's between gears, 2) 5 psi trans pressure in neutral, 3) park lock.
Thanks, Richard
Lead Driver
Joined: Aug 2002
Posts: 6,682
Likes: 12
From: Saskatoon SK Canada
How do you have the TV Rod connected to the carb? If you have the rod not going in the correct arc it may cause this problem. I have a 302 and AOD in my '51 M-3. I also have a TV Rod attached to a Motorcraft 2150 2 barrel and have no problems.
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Junior User
Joined: May 2004
Posts: 51
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From: St. Louis, MO
Dear 51dueller,
Thanks for the feedback.
I have a 4-barrel Motorcraft (by Holley or Carter or someone - I need to write that down!) carb. The top end transmission throttle-rod connection is to a lever on the carb. A little arm on the end of the rod simply pushes through a small rubber bushing in the carb lever. The rubber bushing holds the rod tip into the lever. The rubber bushing does need replaced but it doesn't seem to be bad enough to be causing a problem (do you know where to buy this little rubber part?).
Obviously the AOD wasn't being made when my '68 289 was built but I assume the carb is newer or some adapter was purchased because it does look pretty much like a manufactured part (not home made) and looks like it "should be there."
The adjustment is all at the transmission end. It is very crude with a lock nut in a block on the rod ... and a spring wrapped around the rod. There is about 2" of adjustment possible. That stupid lock nut was hitting/catching on the header flange and acting like a stuck accel. pedal but I think we solved.
Other thoughts?
Richard
PS, The little bracket that the idle screw "hits" at normal idle and is used for adjusting the idle has been bent up a bit and doesn't look normal. I don't know the history of that.
Thanks for the feedback.
I have a 4-barrel Motorcraft (by Holley or Carter or someone - I need to write that down!) carb. The top end transmission throttle-rod connection is to a lever on the carb. A little arm on the end of the rod simply pushes through a small rubber bushing in the carb lever. The rubber bushing holds the rod tip into the lever. The rubber bushing does need replaced but it doesn't seem to be bad enough to be causing a problem (do you know where to buy this little rubber part?).
Obviously the AOD wasn't being made when my '68 289 was built but I assume the carb is newer or some adapter was purchased because it does look pretty much like a manufactured part (not home made) and looks like it "should be there."
The adjustment is all at the transmission end. It is very crude with a lock nut in a block on the rod ... and a spring wrapped around the rod. There is about 2" of adjustment possible. That stupid lock nut was hitting/catching on the header flange and acting like a stuck accel. pedal but I think we solved.
Other thoughts?
Richard
PS, The little bracket that the idle screw "hits" at normal idle and is used for adjusting the idle has been bent up a bit and doesn't look normal. I don't know the history of that.
Posting Guru
Joined: Apr 2003
Posts: 1,153
Likes: 1
From: Venezuela
1° Pressure setting is done in Neutral, tranny and engine at normal temp and Idle, be sure no any Climatic control or Cruise control is in way of throttle, be sure throttle is resting at Carbureter stop, at this point adjust Cable/Rod untill pressure is under 5psi
2° Upgrade to TV cable is easier to setup and calibrate.
3° Your actual setup should provide almost linear moving betwen Carb Throttle and TV lever at tranny
4° If Carb. Throttle is at minimun, TV should be at minimun. If Carb. Throttle is in full, TV should be almost at full
5° There is another factor that control shifting, the Governor weight at output shaft, there are several governors to match different rear axels ratio and tire sizes, first work on previous 4 points then work on governor...
Hope it helps...
2° Upgrade to TV cable is easier to setup and calibrate.
3° Your actual setup should provide almost linear moving betwen Carb Throttle and TV lever at tranny
4° If Carb. Throttle is at minimun, TV should be at minimun. If Carb. Throttle is in full, TV should be almost at full
5° There is another factor that control shifting, the Governor weight at output shaft, there are several governors to match different rear axels ratio and tire sizes, first work on previous 4 points then work on governor...
Hope it helps...
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