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Auto Tranny problems - Printable Version

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Auto Tranny problems - rjpohl - 04-02-2019

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.


RE: Auto Tranny problems - Pegleg - 04-02-2019

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.


RE: Auto Tranny problems - Hemikiller - 04-02-2019

(04-02-2019, 12:50 PM)Pegleg Wrote: 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

rjpohl Wrote: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.


RE: Auto Tranny problems - rjpohl - 04-02-2019

(04-02-2019, 01:53 PM)Hemikiller Wrote:
(04-02-2019, 12:50 PM)Pegleg Wrote: 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

rjpohl Wrote: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.


RE: Auto Tranny problems - Bill73Ragtop - 04-03-2019

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.


RE: Auto Tranny problems - rjpohl - 04-03-2019

(04-03-2019, 06:40 AM)Bill73Ragtop Wrote: 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.


RE: Auto Tranny problems - 73pony - 04-03-2019

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


RE: Auto Tranny problems - mustang7173 - 04-03-2019

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


RE: Auto Tranny problems - rjpohl - 04-04-2019

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


RE: Auto Tranny problems - Bill73Ragtop - 04-04-2019

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.