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1991 Convertible w 5.0 V8

Veloce66

New Member
Hello all, thanks for adding me.
My wife's dad just gave her his 1991 Mustang, garage kept, 60k miles. Its a great looking/sounding car. I will now be her mechanic, have been looking thru the 'common problems' data online :). We are in the process of driving it from his house (Michigan) to our house (Boise ID). On our way west out of Denver, driving up the steep hill on I70, the engine began to show high revs at a gear change, I'm assuming one of the gears was slipping in the AOD. We could go no further. We now have it at a transmission shop, they think the tranny needs a rebuild. 60k miles seems early for a worn out transmission, but don't have any reason to doubt them. Do any of you have experience with similar problems on these cars? Do these cars have transmission coolers? I did not look before dropping the car off. (I will have the rear main seal replaced if we do pull he transmission)
Thanks,
Billy
 

broncojunkie

Well-Known Member
Congrats on the new vert! The most common problem with them is incorrect adjustment of the tv cable. It will cause the o/d to go out and trash the transmission. Too bad you had to find out the hard way (if this was the problem). Five minutes under the hood could have saved you some grief and money. Also, the aod transmissions can be found cheap and in perfect working order. Lots of fox guys ditch them for a t5 swap. I would have just picked up a good used one instead of taking it to a shop. It seems like every transmission shop I've been to charges ridiculous prices. Plus, they don't tend to know much more than the average jackleg. Nothing like spending $2500 to have a "professionally rebuilt" transmission go out in a week.

You may have a good shop where you live. If so, consider yourself lucky!
 

Veloce66

New Member
Thanks for the reply. Tranny guy said exactly what you said, TV cable was out of adjustment, caused the tranny to 'burn up'. Before tearing apart the tranny they said rebuilding would be up to 2k, a reman would be 3K or more, the only way to tell exact cost would be to open it up, so I figured at 60K maybe a rebuild would be the cheaper option. I'm stuck in Denver so could not wait to find a used one. Apparently the AOD has a cooler line to the radiator already, so no need for an external cooler (and overheating was not the cause).

How often do you have your TV cable adjusted? Any way to tell when it needs to be adjusted?
 

broncojunkie

Well-Known Member
I really don't know much about the aod, other than looking into one as an option. I do know they are fairly simple to rebuild, but I imagine a good portion of the $2k they're charging you is for r&r.

I finally decided that a 4r70w would be better for my application. They hold more power and you don't have to worry about the tv cable (doesn't have one). They are a dime a dozen from later v6 mustangs and use the same bellhousing pattern. You can perform what is known as a "J Mod" to tighten up the shifts, which basically costs nothing but time. The only downside is that you need an electronic controller to run it. The controller costs almost a grand, but it's a 1-time cost. If your transmission goes out, you find another one for $150 and you're back in business. A manual valve body can be used instead of the controller. In fact, you can buy a kit to convert the stock valve body to manual and I believe it's only a couple hundred bucks. But that's more for racing applications, not very practical for a cruiser.

Sorry to rant. Just passing on some info/options that I came across in my research. I have a (hopefully) 500ish hp 408w stroker motor built and was looking for an auto to use. I ended up stumbling across a nice built c4 with 4500 stall converter, so I'm going with that. I also have a 4r70w and may do the swap some day.
 

Veloce66

New Member
Thanks for the feedback, I’ll sit on this rebuilt unit for a while. Made it home to Boise today, no further problems. When I picked it up at the garage and talked to the mechanic he said the bushing was missing! Is this the bushing? It makes me wonder if the bushing degraded some time ago and under the stress of a long drive w hills the tranny gave in or did the bushing fall out recently thus causing a quick tranny failure? (Ie do I need to carry a spare around)
 

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broncojunkie

Well-Known Member
Wish I could help you with the bushing info. My memory isn't what it used to was lol! Been a while since I owned one (early 90's). But you may be right about its disappearance. Plastic parts get brittle with age.....which reminds me... give your engine bay a once-over for cracked or broken vacuum lines. I believe most or all of them should be over by the passenger side firewall. They tend to get brittle and cause problems.
 

JoeC

New Member
Any one have any thoughts on why after I replaced the grommet between the gas fill pipe to the tank and reassembled I can’t get it to fill with gas pump keeps shutting of like it’s full 91 Gt mustang here. Thanks for any help
 
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