Auto Tranny problems

[rjpohl]

Finally got the 73 mach 1 engine running good enough to take it out for a test drive.  Tranny seems ok in first and 2nd gear but as soon as it shifts into 3rd the engine just races and tranny doesn't pull.  I checked fluid and it is to top of full.  I had noticed over the winter that there was always a large leaking of trans fluid.  That seems to have quit.  I'm not sure what tranny I have or how to identify.  Any suggestions on fix? 

Thanks

Bob

I did a search on google and I believe I have the AOD (FIOD) 4 speed with overdrive. My floor shift does have a "D" and "OD" label. The tanny oil pan does say METRIC.

 

[Pegleg]

First thing to check is your vacuum line. After re-instaalling my auto i didnt put vacuum line in correctly and it wouldnt go past second, For the sake of a few dollars you may consider a new vacuum line. Then make sure your oil is hot and you check oil level while its idling.

 

[Hemikiller]

First thing to check is your vacuum line. After re-installing my auto i didnt put vacuum line in correctly and it wouldnt go past second, For the sake of a few dollars you may consider a new vacuum line. Then make sure your oil is hot and you check oil level while its idling.

He has an AOD - which has a throttle valve (TV) cable, no vacuum modulator

Finally got the 73 mach 1 engine running good enough to take it out for a test drive.  Tranny seems ok in first and 2nd gear but as soon as it shifts into 3rd the engine just races and tranny doesn't pull.  I checked fluid and it is to top of full.  I had noticed over the winter that there was always a large leaking of trans fluid.  That seems to have quit.  I'm not sure what tranny I have or how to identify.  Any suggestions on fix? 

Thanks

Bob

I did a search on google and I believe I have the AOD (FIOD)  4 speed with overdrive.  My floor shift does have a "D" and "OD" label.  The tanny oil pan does say METRIC.

TV cable adjustment is critical on an AOD. Driving with it off or misadjusted will burn up the transmission in short order. Google "AOD TV cable adjustment", follow the procedure and let us know what the results are.

 

[rjpohl]

First thing to check is your vacuum line. After re-installing my auto i didnt put vacuum line in correctly and it wouldnt go past second, For the sake of a few dollars you may consider a new vacuum line. Then make sure your oil is hot and you check oil level while its idling.

He has an AOD - which has a throttle valve (TV) cable, no vacuum modulator

Finally got the 73 mach 1 engine running good enough to take it out for a test drive.  Tranny seems ok in first and 2nd gear but as soon as it shifts into 3rd the engine just races and tranny doesn't pull.  I checked fluid and it is to top of full.  I had noticed over the winter that there was always a large leaking of trans fluid.  That seems to have quit.  I'm not sure what tranny I have or how to identify.  Any suggestions on fix? 

Thanks

Bob

I did a search on google and I believe I have the AOD (FIOD)  4 speed with overdrive.  My floor shift does have a "D" and "OD" label.  The tanny oil pan does say METRIC.

TV cable adjustment is critical on an AOD. Driving with it off or misadjusted will burn up the transmission in short order. Google "AOD TV cable adjustment", follow the procedure and let us know what the results are.

Just had guy look at it and he said it is burnt up, this guy use to own a transmission shop but is retired now.  Fluid has a burnt smell, he said he happens quickly.   He also said it looked like the cable/linkage was incorrect too.  Yesterday was the first time I had ever driven it fast enough to get into 3rd gear.  I called another shop and guy said jt would cost approx $1350 to pull/rebuild/re-install.

 

[Bill73Ragtop]

AOD's have an inherent issue with (as you found out) failing if correct pressure is not set properly. TV Pressure is typically set by cable tension.

https://static.summitracing.com/global/images/instructions/tci-431000.pdf

Since you are already into a rebuild, best thing at this stage would be to install a new throttle body with the pressure already controlled.

https://www.speedwaymotors.com/TCI-436020-80-93-AOD-Constant-Pressure-Valve-Body,333622.html

You'll never have an issue with pressure and the throttle cable now only sets the shift points.

 

[rjpohl]

AOD's have an inherent issue with (as you found out) failing if correct pressure is not set properly.  TV Pressure is typically set by cable tension.

https://static.summitracing.com/global/images/instructions/tci-431000.pdf

Since you are already into a rebuild, best thing at this stage would be to install a new throttle body with the pressure already controlled.

https://www.speedwaymotors.com/TCI-436020-80-93-AOD-Constant-Pressure-Valve-Body,333622.html

You'll never have an issue with pressure and the throttle cable now only sets the shift points.

Bill, thanks for the info, I believe the guy at the trans shop was also talking about the same things.  

Maybe I'll consider changing to a manual 4 speed.

 

[73pony]

Or a 5 speed. The OD on a 5 speed is nice to have.

 

[mustang7173]

rjpohl,

Hemikiller is spot on. I am with Bill73Ragtop on his recommendation. I purchased the AOD Fixed Line Pressure Valve Body for my AOD. It is worth looking into.

https://www.broaderperformance.com/7-valve-bodies

 

[rjpohl]

I just talked to 2 local transmission shops and neither one was familiar with the Fixed Line Pressure valves. I send each one links to them and I'm waiting to hear back.

thanks

Bob

 

[Bill73Ragtop]

I'm sure we don't have to remind you to pick your shop carefully. The AOD is 25+ years in the past and many general transmission shops probably have not seen or touched one in years - not mention the mechanic may have never worked on one or been trained to rebuild one not to mention even born when they were in use by Ford.

See if you can find a shop the local hot rod / vintage car guys talk up in a positive manner. That may be worth driving the extra miles to get to it for a good rebuild. From your description, the toughest part of your rebuild is the new clutches. The FLP Valve body is a bolt in upgrade. Hope it works out for you.

 

[rjpohl]

The shifter in the car is tall and doesn't look good. I had bought a stock original shifter for a C4. Can I use that shifter with the AOD tranny?

C4 shifter only has D 2nd 1st, the AOD tanny has OD D 2nd 1st.

thanks

 

[Don C]

Did you look at the write-up Luxstang did, and check some of the links he provided, including the Hemmings article?

https://www.7173mustangs.com/thread-fmx-to-aod-swap-complete-report

 

[Bill73Ragtop]

This is a pic of my 69 vert with AOD where I used the stock shifter.  Works fine.  I did get a custom shifter linkage setup so everything matches up.

 

[rjpohl]

Bill, does the face on yours show  all 4 forward gear settings (1, 2, D & OD)?  Did the shifter have to be modified or just the linkage?  Any info on where to get custom parts is appreciated.  Here are pics or the shifter now in car and the cover plate for stock shifter.

Thanks

Bob

 

[Bill73Ragtop]

My shifter plate is similar to the 2nd lower pic of the stock cover -- D - 2 - 1. Shifter itself was the original 69 assembly that was dressed up with a new cover plate. The linkage from the shifter to the AOD transmission was custom made (this was back in 2006). Somebody on the Vintage Mustang forums was making them in his workshop and selling them thru Ebay. I would recommend you get in touch with Ron Morris Performance and see if they can help. I purchased quite a bit from them as part of the changeover from C4 to AOD.

The custom linkage allowed me to adjust it to line up the AOD transmission shift detents to match the P-R-N-D-2-1.

 

[rjpohl]

If I understand than you are actually in OD when indicator shows D? In Drive when indicator shows 2? In 2nd when indicator shows 1? And you can not actually put manually in 1st?

Thanks

 

[Bill73Ragtop]

It's in OD when showing 'D'. Perfectly capable of manually shifting down thru 3rd, 2nd and 1st, but those don't line up perfectly with the cover. 1st is below the '1'.

Neutral, Reverse and Park all line up just fine.

 

[Don C]

AOD transmissions have the same number of detent positions as C4s. AOD selectors have 1 - D - OD. You can manually keep it in first. To keep it in second requires a little finessing, when accelerating to a point that is higher than the downshift (into first) speed, shift into D, transmission will shift into second, to keep it in second shift the lever back into first, it will stay in second unless you slow down to the first downshift speed, and will not shift up into drive (third).

Here are some links that should help you:

http://www.fordsunlimited.com/fords_C4_AODswap.html

https://www.diyford.com/ford-aod-transmission-installation-and-swapping-guide/

The only problem with using your C4 shifter is that the shift lever throw (movement) may not match the throw distance on the shift lever on the transmission. The detents (notches) on the C4 shifter may also be a little different and require modification.