Probably should split the two, but here goes. Buying an AOD out of a 91 F150 with a 302. Pickup has 122k, was rolled, been sitting 10+ years. Car makes 180hp now, will be closer to 250 soonish (gt40 heads, mild cam, performer intake, 570 street avenger, and headers) Should i have it fully gone through? I would like to put a lentech valve body in it, with OD on a switch, and lockup in 4th only. Will also get a 2k or 2500 lockup converter. If it doesnt need gone through, is the valve body something i can swap, being that i am mechanically inclined, but completely foreign to automatic transmissions? What are other things i should look at doing? Ive read up on it some, the "A" OD servo seems to be a common suggestion. Does it need a shift kit also, or does the valve body take care of that bit? Will be using the lokar CV cable.

As for the 8.8. Is regearing, rebuilding, and adding a locker / posi something a person can do with typical tools, or does it require special pullers / case spreaders? Also, if someone can confirm that 90-92 Rangers with 8.8 are 56.5" that would be great. Been looking for one with 3.73 or 4.11 with the factory trash lock and having no luck. Theyre either 7.5s, or open diffs. I have confidence in getting the pattern correct, just havent been into a "dana style" differential. I have a lead on a 91 8.8" with they think, a 4.11 open diff for $50. Havent looked into what traction aids are available for the 8.8 as that wasnt in my original plan. Plan was replace the 8" with a narrower, stronger, suitably geared 8.8 with trash lock for round abouts $200, and rebuild the trash lok to tighten it up. That said, if i can get the axle for $50, wouldnt mind putting that towards a better locker. I dont know if you can get the power-lok? for these. If i remember right, thats the clutch type, that puts more pressure on the clutches with more input torque. Which i believe would be my best option, as it is a 70/30 street strip car, trutrac is another with good reviews. Im open to suggestions on differentials. I do not want any clanking or banging, random jerks, unpredictable locking when leaving stoplights and turning. Equally so, i do not want to be spinning a tire off the line. I understand there is some getting used to with even "smooth" lockers, but ive heard some described as having pretty loud clanks and bangs, and erratic locking when turning.

My apologies for the long mixed post.

 

You're buying a 26 year old transmission with 122k miles that's been sitting for 10 years (read: no lubricating fluid circulating to keep the internal rubber seals wet)...

• Should you have it gone through? Yes.
• Should you have someone else do this work? Maybe, but it will be cheaper to do it yourself and you might learn something too.
• Should you install a shift kit? Probably. These kits often fix some of the common transmission issues resulting in premature failure
• Will the valve body upgrade take care of the shift kit issues? Maybe. Read the specs of the valve body and what issues it is intended to fix.

As for the rear-end stuff, I don't know. Never worked on that stuff.

 

Any of the Detroit "locker" type differentials will clunk when going around turns; they have spring loaded teeth that have to be forced apart by the two sides rotating at different speeds when going around turns, and they will be jerky.

The smoothest type of traction aid is probably the worm gear/worm wheel type like Torsen, or the similar spiral gear type like Tru-Trac. But they are technically "open" type differentials that multiply available torque of the slippery side to the tracking side. If the slippery side has no traction at all, like on ice, you're still stuck.

You can add both these types of aftermarket differentials to your stock open differential.

If you want the stock clutch-type locking differential, it's easiest to find one in the used market and install it with the gears you want into the housing that works for you. This type has a preload spring that transfers SOME torque to the non-slippery side even when there is zero traction on the slippery side.

 

As you say, i figured i should. I could probably do it, but i dont have a suitable place for doing it. As far as shift kits, i guess ill have to call them, as i dont know what issues should be fixed, or need fixed.

So youre saying that something like a true-trac or a torsen will still allow 1 tire to spin? If that is the case, im not sure i understand the point of one. Id prefer not to run a clutch style, just due to the nature of them wearing. What i thought sounded great was the true-trac, but now you have me second guessing whether i actually understand how they work or not.

 

Like any open diff, if you get one tire stuck on a completely slick surface, the Torsen and Tru-Trac will spin. They need SOME traction in order to multiply the torque to the other side. Of course, if you get both tires on a completely slick surface, no amount of differential locking will help. But even if you were driving on ice, there is a little bit of traction as the tires melt into the ice surface due to the weight of the car.

The clutch type differential can be made to work well, and they're rebuildable, unlike any of the other types. If you wear out the clutches, you replace them for about $100 in parts, and you don't even need to pull out the diff. If you wear out the locker, or the Torsen or Tru-trac diffs, you replace them, and you have to reset the gears.

I've rebuilt the clutch packs in a couple of 8.8" diffs, and it took me less than a couple of hours in my garage each time. You can't do that with the other types. I've set up the clutch packs to provide better bite than stock, and they've worked quite well.

 

I rebuilt the trac loc in my 10.5. The problem is, i rebuilt it about 20k ago and then it was pretty awesome (except on slick roads) today its not half what it used to be. I didnt add the addative because it didnt chatter, and i wanted more "posi", maybe thats why its wearing fast. That said, it seems most sources call for a rebuild of a clutch type after 20-50k. Ive not found any instances of lockers, or helical posi's wearing out, im sure you can break them, but they should last as long as the gears / bearings. I found a video that described the true trac and torsen quite well, and i understand better how they work, not how i thought at first, but im thinking thats the way to go if i cant find a trash loc with 3.73s. Its going in a street rod after all, which wont see winter conditions, or mud, but im not sure i like the idea of a tight clutch in the rain with wide tires. Also, the torsen style seems like it should have less binding and gear / tire wear under normal driving than a clutch type.

 

High torque motor in a street rod on wet surfaces is a bad combo, no matter what diff is used. For most conditions, the Torsen or Tru-Trac is probably the best choice for smooth engagement. They will outlast the clutch type diffs, but they will wear out like anything else. All the wear and tear occur in turns, especially under load.

BTW, "Posi" is a trade name of Eaton corp, which built them for GM cars.

 

Regarding the converter and lockup function ...


As far as I know, there is no way to get lock up in 4th and no lockup in 3rd. In the aftermarket there are two types of converters, ones that retain the lockup feature, and ones that don't ... at least the last time I checked. With the dual input shaft arrangement on the AOD, and the fact that the input for 3rd gear is split between the two shafts, I don't think there is a way to eliminate the lockup feature in 3rd that won't also eliminate it in 4th.


If you can live without lockup, then you may consider changing the input shaft to a one piece shaft from the AODE, rather than just buy a converter without the lockup feature. The benefit is getting rid of the smaller input shaft for an increase in durability on the input side. "they" say, that in stock form an AOD can handle somewhere around the 400 hp mark before the input shaft becomes a limiting factor. by changing to a one piece shaft, "they" say it can handle closer to 600 hp, at which point the rest of the trans becomes a limiting factor. Personally, I think those numbers are a little optimistic. the real numbers might be more around the 300 and 400 hp mark if you really want it to be durable.


you depending on your tire size, with the 4.11:1 gears, you might be able to get a 2500 rpm stall converter to work in OD without frying the trans, but something in the 2200 rpm range might be better.


the below is the rpm's you could expect with an AOD and 4.11:1 gears with 235/75r15 tires. This assumes no slip in the converter, so at any speed below the rated stall speed of your converter, you could assume several hundred rpm higher than the table. Below the stall speed one should be aware of the heat you are going to generate and get a good cooler so you don't fry it.







on that note, back in high school I had a B&M Holeshot 2400 converter in an AOD in my otherwise completely stock LTD Crown Vic. The converter did make the car a lot of fun to drive, but looking back, it would have been scary to see what the temps where running! I also had a ATP Shift Improver kit installed and it was awesome. The transmission shifted perfectly with that kit.


I might also look at a constant pressure valve body. they may not shift as nice, but they provide enough line pressure so that you don't fry it with a poorly adjusted cable. and if the cable is poorly adjusted, you WILL fry it in fairly short order ... ask me how I know..... looking back, a constant pressure valve body would have been a good investment. This way, the TV cable just adjusts your shift timing, not line pressure for shift feel.


good luck with your endeavor!
I'm not an Expert on transmissions or AOD's, but there are some on here who are (James, where 'ya at?) ... so with that in mind, if they say something that contradicts what I've said -- they are right, and I am wrong -- and we can all learn something.

 

I appreciate the informative post. Lentech makes a valve body (I assume its in the valve body) That converts the the AOD shift pattern from 1,D,OD into 1,2,OD. Then they use a solenoid to lockout OD. The downfall with this setup, is there is no "real" way to keep the trans from going into OD, besides some sort of switch. After reading up on stuff for the A518 swap in the girlfriends duster, i think i can use a vacuum switch off of ported vacuum to control the OD function more or less automatically, at least keep it from going into OD too soon. With this setup, you have the dependability of a C4 (minus the small input shaft), but still the great economy of lockup overdrive, which is to be used for cruising only. The lentech kit also addresses line pressure, and makes it alot less finicky. To the point that the CV cable is more or less only used to fine tune shift points and harshness. If i have issues with the input shaft, i will convert to the 1 piece with 4R70W geartrain. I doubt that will be a problem, as this is just going to be a mild street 302, unless i decide to build the clevland. Long term (very long im sure) is a 5.0 coyote / 4R70W. Would love to have the wide gearset in my AOD, but I don't think it allows for the 2 piece shaft for lockup.


Here is the calculator ive been using to figure out gear spacing, and final gear ratio. http://www.grimmjeeper.com/gears.html It has all sorts of trans data already entered, provisions for t-case / aux OD and a ton of variables that are fun to play with. As per typical, 4.11 is about perfect for my power level and engine combination (not going much over 5k due to stock rod bolts). However, I live 160 miles from the track, and want to be able to enjoy the car, not just at the track. Granted, even 4.11s with OD will still cruise slightly lower than I do now with the 2.60 gears. Even so, im leaning more toward 3.73s, but it depends on what I can find. The first narrow ranger axle I can find with a trac-loc I will pickup assuming its not shot. Not sure what the options were in them, but 3.73 and 4.11 appear to be the most common. If I cannot find a trac-loc axle, then I will pony up the money for a true-trac I suppose.

 

If you haven't stumbled upon these yet, loads of info about building a strong AOD
clickclickracing.com and TCCoA.com

I'm in the middle of building a 300/ 4R70W combo to go into my '85. Current plan is to keep my LS 3.08 rear. It's only going to be a fun grocery getter, so we'll see.

 

Little update, I found an 8.8 out of a 93 ranger. No discernible wear on the gears, and the carrier bearings feel good. Its 58.5" from drum to drum, has the larger brakes, and is 3.73 geared with trac-lock. I didn't have the tools to pull the companion flange, and I didn't want to pay $42 for an otherwise useless driveshaft. Im assuming they were 1310 u-joints anyway. It also has a composite diff cover. Its in good shape, but should I swap this for a steel cover, or are the plastic ones good pieces?

Now, onto the transmission. While looking for a rear end, I found out I can get an AOD out of an 87-91 town car for $150 already pulled. Naturally, $150 loaded, is a lot better than $250 and I have to pull it out of a pickup that has no wheels on it, so I bought it. Question is, will it work? I am ignorant of what to look for to be honest. It DOES have dual input shafts, so I assume it is in fact, an AOD, but there are a lot of wires on this thing. It is apparently electronically shifted, and I don't see where the TV cable is supposed to go. It looks like there may be a standard shift lever underneath the electronic shifting unit. It is from an 89 Town Car with 126k miles.

 

A 1989 Town Car would have an AOD, shifted by internal governor and TV cable transmitting engine load info to trans. In other words, a regular AOD. Wires? There would be the output speed pickup to run to the speedometer, and I don't remember where the neutral safety switch/back up lamp function is.

 

Im working on getting a pic. Its either been dark or snowing. It has a sensor in the rear of the case on the right side, same as an AODE / 4R70 with 4 or 5 pins, as well as another on the left side toward the front I want to say with 2 or 3 pins. It has the electric sender plugged into the mechanical speedometer worm gear. They all come together into a pigtail that lead towards the engine, with im guessing 8-10 pins. I just haven't been able to source any reliable info on the Lincoln trans specifically, and most pics of AOD's don't show the other connections I have, nor the electronic shifting mechanism. I was "sure" I was right in thinking it will work, but your words give me confidence. Will get pics this afternoon.


As it was already pulled, its only trans, converter, and wiring harness. Im hoping my C4 slip yoke will work, as well as the block plate. Im planning on using the lokar TV cable. Should be about all I need right, minus some fresh atf and filter?

 

Here they are, sorry for the poor quality, dark in the shop. I only expected to see one or two, three wire plugs for reverse, and neutral / park safety switch.

 

Whoa, I think you have the wrong trans!

Look at that trans range switch/MLPS on the driver side of the trans, all those wires! Right behind the range switch, there is a part # on the main case... looks like a "F7" number to me, right? F7 would be 1997.

On passenger side, bigger plug goes downwards into case just above the pan rim... looks like a trans shift solenoid connector.

Also, the orange label on the side of the pan says TSB 97-17. That is a 1997 factory sticker put on select tran's at the factory, alerting dealerships that if that particular trans comes in for service within a certain max interval from sold new, they are to follow a particular procedure. Basically minor stuff OK to do, more major, the trans gets pulled and shipped back to Ford, fact guys send out brand new trans to use instead. The trans factory dissects the marked trans. That happened on my 1997 f-150 when OD disappeared completely, free-wheeling, shortly after I got it.

So I think you have an AOD-E or 4R70. I think the AOD, AOD-E, and the 4R70 all have the same shape pan and #of bolts, so pan is not a good ID factor like in other automatics.

Check your source for that trans! Something went wrong! Far from a 1989 AOD! The AOD is all-mechanical.