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Transmission and rear end recommendations for a 91 mustang 5.0

3K views 8 replies 2 participants last post by  jkeckss 
#1 ·
Hi guys,
I am just finishing up building a 5.0 liter from a 1991 mustang, it has been converted to a carb set up and according to my local engine shop the combo I am running should have round 400 hp. I am putting this engine in a 1930 ford model A build.

I trying to decide on a transmission and rear end combo to run. I have a 1986 Cougar parts car with an AOD and what I think is a 7.5" trac loc. I am sure this wont hold up too long with that engine depending how nice I drive :mwink: haha. I found a guy selling an older C4(with 2pc drive-shaft) and a C6 for $100 each and he also has a large assortment of 9" rear ends and 2 8.8" (3.08 and 3.55open according to him I thought all 8.8 were posi from the factory :confused: ) rear ends also $100 each.

I was wondering what combo would work best? keep the AOD and run a new rear end? or is the C4 a better idea? And what rear end would be best?

Thanks in advance for your help!
 
#2 ·
What do you want it to do? Stop light to light toy with no open highway? The C4/3.55 would do nice. Stoplight toy with good highway manners? AOD with a few mods (Baumann being 1 on medium settings) and 3.55 or 3.73 as a nicer option. A screamer would call for a lightly modded AOD, Baumann on firm (with converter below), 4.11, 9.5" 3400ish non-lockup converter (call the converter company to tune this for your setup). Go the latter and you'll thank me later! 4.11 behind an AOD is sweet provided the valve body is properly setup to retain the shift points. 3.73 is nice for mileage but kinda boring in overdrive. Add the Transgo hi rev setup to the Baumann kit (minus the crappy governor, throw it away as they break) and the trans will really wake up.
 
#3 ·
I intend to use it as much as possible (daily fairweather driver) when I am finished, so I am thinking that overdrive would be a good idea (it will be stored at the farm so it will see a fair amount of highway). I definitely dont want to have to worry about breaking anything if I step on it though. But of course we dont do that in town haha :p

It wont see a drag strip or slicks or anything either. I am trying to build on a budget though too, how much do AOD mods cost? and where would I find them?

Also I would really like a posi rear end, and I have heard that 9" are stronger than 8.8" so I am not sure what to get, I suppose I could always upgrade the diff itself later on.

Thanks for the input!
 
#4 ·
9" is a bit stronger, 8.8 is a bit quicker in the quarter due to lower resistance - I dare you to break an 8.8 with 400 hp! A Tracloc is a must!

Around 83 and up for the AOD will be good. Mustangs had higher speed governors. Crown Vics are popular with lower shift points. Any of them with the proper shift kit will do great. You can go all out with 4R70 internals which gives a wider OD band along with wide ratio gearing but the shift points are screwed since the valve body is setup for stock gearing. I bring this up because you'll run across it - just be aware if upgrading this direction. Also, don't confuse the AODE for an AOD. The E is electronic and will need a computer to shift it.

The most needed and most basic mod is the Baumann shift kit which is $60. It looks cheap outta the bag, but you're paying for technology along with the hardware store looking items - and the smile it'll put on your face will have you understanding! Transgo HP kits are around $100. You'll feel better opening the package but once it's installed and you're wondering "Is there more?" you'll be disappointed. If you go this direction, drop me a note and I'll fill you in on how to ad $25 for a Transgo Hi Rev kit you can combine with the Baumann and REALLY turn this thing on!

Next is the Lokar cable setup, the Sonnex throttle corrector depending on the carb you use, and a few other trinkets. There's another $100 of needed parts.

Many suggest expensive mods inside the AOD, but at 400hp and down, it will live unless you abuse it daily. The most often OVER sold item is an A servo for overdrive and/or wide OD band arrangement. It's good and all, but unless you abuse OD, the 16% extra clamping force it offers over the common B servo is useless. Now, if you get an AOD with a C servo, upgrade it! The servos are clearly marked.

There are tons of other mods ranging from free to $$$. You need to decide which way you're going before getting into too much detail. clickclickracing is a good source of reading on all Ford autos.
 
#5 ·
Ok well if this guy has a 9" posi and the 8.8s are open I'll get the posi I guess, which would be easier to change the ratio in or replace the diff in if it is worn out? I hear the 9" is because it has a removable carrier?

I already have an AOD from that 1986 cougar so I will probably use that, I am definitely interested in those upgrades you mentioned (Bauman kit and High rev kit), how bulky are they? I am in Canada so shipping costs can get ridiculous. Also how hard is it to install this stuff? any more than quick bolt on with a transmission and I am pretty much useless.

And I know for sure the car isnt going to get abused often, when you build it yourself you baby the car that much more.. that said, i am not giving it that much power to not enjoy it every now and then, but occasionally punching it isnt gonna abuse it much.

I keep hearing about needing lokar stuff to run an AOD with a carbed engine, i really know next to nothing about transmissions though so any more info would be awesome.

Thanks again!
 
#6 ·
Between the 9 and 8.8, you can't go wrong either way. Get the closest to suit your needs.

Both shift kits are light. Just springs and paperwork with a few extra small parts. They DO require removing the valve body but this is one of the easiest to remove out there.

Do some searching/reading on Sonnex AS2-02K and Lokar AOD cable. Poke around the Transgo website and you'll find their video on installing the Transgo HP kit which I don't like, but the vid will give you a generic idea of details in any shift kit.

The 86 model you have will have a 3-4 accumulator in the case with a matching valve body. If a later valve body is used the case will have an empty hole in it or the hole can be left empty.
 
#7 · (Edited)
Have you heard much about Lentech? I read an article about the guy that started that company it seemed to suggest that lentech was the way to go for an AOD. They do lots with AOD transmissions but it seems like they replace the valve bodies first and foremost to increase the transmissions power handling. Would that be worthwhile for me or is that Baumann kit by itself (along with the lokar and sonnax kits) enough?

Also can I run the stock converter from the cougar? I had heard that the 302 HO mustangs ran a different one than the Cougar would have. Or is it a good idea to get a new one like you suggested earlier ( quote: 9.5" 3400ish non-lockup converter )? Or something different than that?

Sorry for all the questions, but I want this all done right the first time.

Thanks!
 
#8 ·
Shift kits are the cheaper/hands on way to go. Lentech is top notch for those with the money and less skill. If it's in your budget, go for it! Call with your needs.

For converter, a stock one will drive like the AOD was intended - great for groceries. I have an Edge Racing converter waiting for me to get off my *** and install with a review as asked about a while back (100 degrees weather doesn't help). I plan to install it in a few days. I currently have a 2500 behind about 350-370 horsepower in a 65 Mustang attached to an AOD. Simply put - the holeshot sux. I planned to get it right the first time as well and I have a shop full of lightly used parts to prove it! Have a chat with Andre at Edge Racing with your setup and expectations. Ya'll may decide to go stock but I doubt it. I can't speak first hand about his (yet) but will in a few days. I dare you to find a disgruntled customer! I tried long enough plus he was the MOST informative, so he got my money.
 
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