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NaymzJaymz
User
Jun 23, 2013, 10:05 AM
Post #1 of 2
(1376 views)
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Ford Bronco transmission
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Hello, I once again have a question about my 1991 Ford Bronco with AOD transmission, 5.0L engine, and mileage of 209K. Yesterday I threw a major tuneup on it and found that it ran excellent after sitting for about 2 years. Today, however, I notice that when I put the vehicle in reverse, there is a hesitation of one second and then a noticable "clunk" as the tranny goes into reverse. After that it backs up just fine. In "drive" it shifts very smoothly going down the road. I realize that the mileage is high, and this is definately the point that a transmission could go bad, but is that what it is? I carefully checked and filled the fluid to the correct point before it was driven(it leaks). Several weeks ago I started the rig and briefly attempted to reverse it but it wouldn't roll, but after adding the correct fluid it reversed fine with no "clunk". Could it be the U joints? I wouldn't be surprised if they've never been changed, just as the ignition parts I replaced yesterday may have been original. Again, I realize that at this mileage level anything could go wrong. Is it probably a bad transmission? If so, why does it shift so well out on the road? I greatly appreciate the help I recieve on this forum and always try to follow the advice. Thank you.
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Discretesignals
Ultimate Carjunky
/ Moderator
Jun 23, 2013, 11:56 AM
Post #2 of 2
(1360 views)
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Re: Ford Bronco transmission
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Does it have engine braking in manual low?
It is also important to be sure the throttle valve cable is functional and adjusted properly. Too little throttle pressure and it will burn up the clutches and too much will cause harsh/delayed shifts.
Low fluid level will cause delay in reverse, so you should fix your leak.
The AOD transmission is all mechanical, so it can't be an electrical issue. If drive engages fine and the fluid level is good, but there is a delay in reverse, you have a pressure leak in the reverse circuit somewhere or an end play issue. The clunk is a timing problem between the input member (front clutch) and the holding member (reverse band) probably due from the delayed engagement.
With the mileage and age the transmission seals get hard and leak, valves leak or stick, check balls or ball holes wear out, friction components burn up from pressure leaks or end play problems, and etc. If you do find out it is time for a rebuild, they have updates that can be performed during the rebuild to correct known problems or to increase reliability and performance.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Jun 23, 2013, 12:20 PM)
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