Ford Mustang Forum banner

351 Windsor crankshaft and AOD transmission

11K views 10 replies 5 participants last post by  larryc94 
#1 · (Edited)
351 Windsor and 4r70w transmission

Hello all

I building a 351W and AOD combination.. But my research has run aground.

Simple question. Do I need to do anything special to the end of the crank to accommodate an AOD transmission?

Engine is from a 78 Ranchero, (automatic)

It's my understanding the AOD has "direct connection to the crankshaft" and that has caused some anxiety on my part.

The engine is going in for rebuild next week, and I want to tell the builder what to do.. if anything.

I haven't acquired the AOD yet.


Thanks in advance,

ranger90
 
See less See more
#2 ·
The AOD does NOT connect 'directly' to the crankshaft.

It bolts up to a torque converter and flexplate, same as any other automatic for Ford smallblocks. You need to be sure and use the right imbalance with your flexplate for a 351. Should be 28.5 oz imbalance I think? Most AOD flexplates would bolt up, but they'll be balanced for a 5.0 HO, so they'll be 50 oz, and that won't work. The number of teeth should be based on your bellhousing for the AOD, so just look at the number of teeth on the one that it comes with. Probably 164, I think, but make sure.

The stock AOD torque converter is a heavy beast. It does a lot of things though, including lockup. All aftermarket converters for the AOD I've seen are much lighter, but not all of them have full functionality, so before upgrading that, best decide what you want to use your car for. Going to a non-lockup converter may require additional internal changes to the AOD also, I believe.

Anyway, if you haven't already bought the AOD, you might seriously consider going with a 4r70W transmission, because of better durability, shift quality (and ability to customize how and when it shifts easily), and a simplified installation. You will have to buy a controller, but there's no messing with TV cables and calibration - just make sure the shifter linkage is hooked up and hits the basic detents, plug in the controller, set it, and TADA!

Stock AOD's always felt mushy and sad to me. Sort of a 'shift by committee' experience, and when you're really on it, it gets kind of confused after 2nd gear. It's even worse if you are varying the throttle from mid to full and back. Aftermarket parts can improve that, but they still don't do well making full-throttle 3-4 shifts, without major mods. 4R70W transmissions are much tougher, and generally easy to find in non-abused condition, usually behind v6 Mustangs (up to 2002 is good, so you can still use your stock speedo cable)

Anyway, if you want to nerd out and really get some hard facts about the two transmissions, you can read about it here

Good luck with your car!
 
#3 ·
Hmm. AOD converters are actually pretty light. Because they DO NOT HAVE A LOCKUP CLUTCH IN THEM. Like the very much heavier AODE/4R70W converters do. Simple enough to check a vendors site that sells both and check out the shipping weights if you wish verification.
AOD's achieve "lockup" in third and fourth gears by way of an internal shaft that connects those internal parts directly the to the converter. Although some folks refer to this as a direct connection there are still clutch packs and a friction band in play. All internal stuff. A 4R70W achieves the direct connection by way of a single friction clutch inside the converter itself. Two approaches to the same end. AOD behavior is more suited to a simple setup where you and you right foot control the transmission and 4R70W's are much better suited to when you want or need a computer involved (like for emission control).
I like AOD's and the way they shift in a non-racing vehicle suits me. Or does after I tweak it a bit. I have one in a Mustang that I converted to and AOD. I also have two 4R70W's that came factory in daily driver trucks and like them too.

All of which is way more than ranger90 wanted to know. But there was some misinformation happening.
The AOD bolts up like any other automatic, nothing special to be done. You need to use a flexplate for a 351W engine with an AOD or an FMX. If your Ranchero had an FMX (very likely) grab that flexplate and the metal spacer plate on the back of the engine. If the Ranchero had a C6 transmission in it DO NOT use that flexplate, it has the wrong offset. Any parts store will sell you one "for" a 1991 Ford Crown Victoria with the 351W (5.8) engine which will be the correct one. It's also the same plate on some older Fords with FMX transmissions but I can't remember all those and so I ask for the 1991 police car one like I said. National Parts Depot sells the same 164 tooth, 28 ounce imbalance a little cheaper than chain parts stores if you prefer to shop mail order. All flexplates for use with an AOD have 164 teeth. The ones for 1982 and newer 5.0 engines have a different imbalance of 50 ounces and you do NOT want one of those for your 351W. All 351W engines need a 28 ounce imbalance flexplate/flywheel.
 
#4 ·
I went to the salvage yard Saturday and procured both a 351W (from 1978 Ranchero) and a 4r70w transmission (1998 F150 2WD, originally with 4.2 V6).

After much reading, and then more reading, I decided with the masses, the 4R70W is the better choice, even if it does need a controller.

I dropped the engine off to be rebuilt today. I think I'll tackle the tranny rebuild myself.

Ebay has been my friend. I found a 28oz, 164 tooth flexplate from Summit racing... as well as other bits and bobs.

A quick question. I remember flexplates in the past needing an extra stiffening plate before bolting onto the crank. I went out to fordparts.com, and looked. I didn't see that extra stiffening plate in their diagrams.

Do I need the reinforcement plate on the flexplate?

Thanks in advance,

ranger90
 
#5 ·
Gypsy, the stock AOD torque converters usually weigh in at about 33-34 lbs, vs. the old C4 (no lockup stuff) type converters which usually weigh about 25 lbs stock. So yeah, that seems heavy to me! As far as I know, that extra weight is in part due to the construction of said converter which uses the concentric shaft stuff that lets AOD transmissions manually lock the stator inside the converter.

The AOD-E and 4r70W converters are heavier yet; I was just trying to say that some of the aftermarket converters are much lighter for AOD's using a solid shaft (without the concentrics and with no lockup). Sorry for the confusion.

All irrelevant now, I guess, since he's got his transmission bought! And no, there's no 'reinforcement plate' needed for your flexplate, Ranger. Use it just as it is. The crank has a flange, the flexplate bolts to that, and then the torque converter bolts to the flexplate, once you have the engine and transmission bolted together. Easy peasy lemon squeezy!

The important bit here is making sure you get the torque converter seated properly to the transmission, and that all the shafts are engaged before you start bolting the transmission to the engine. If you're not sure about this, it really isn't complicated but maybe watch a video.

If it is not fully seated, when you bolt things up it can break parts inside the transmission, or ruin your torque converter very easily. Again, it is not really a difficult thing to do, just an easy thing to get very wrong, causing you to say and learn new words that aren't fit for polite company.
 
#6 ·
The stock 11" pattern V8 application C4 converters that I ship weigh out at 32 pounds. AOD converters 33 pounds. C6 converters 35 pounds. Hence I don't see an AOD converter as a "heavy beast". Might say that about the 4R70W's though since they weigh in at more like 45 pounds. Ten pounds more than than a C6. Aftermarket converters don't count as they tend to be smaller diameter and different weights. All irrelevant now though indeed.

No, Ranger90, you don't need that extra plate with your application.
 
#7 ·
New question.

I'm about to tear into the transmission. Can somebody verify what transmission I have?

I'm told it's a 4r70w from a 1998 F-150, with a 4.2 V6. Here's the tag. Can somebody confirm?

I've search the web, and found examples of trans tags being explained. But not the actual method/key of doing so.

One of my concerns, is while looking for an overhaul kit, I see a different kit for a 97 trans, compared to a 98.

Who knows.. it might be a 97 model trans left over and put in a 98 truck. I just want to make sure one way or the other.



Thank-you.

ranger90
 

Attachments

#9 ·
From some research looks like Ford used 3 different pilot depths .560 up to '82, .680 from '83-'97 and the in '97 went .760 because the were having thrust failures with electronic OD's. The latter were 351's. The info was from the Engine Data source.

The spec for the pilot depth actually was .760-.810, they recommend to bring it to the .810 and you will be safe.

It would be wise while your have the machine work done that you have the clearance for the convertor, it can't bottom out in the back of the crank, it has to have room to move. If not it will ruin the thrust bearing.

Your crank is .560 which will definitely a problem

Larry
 
#11 ·
I just put this info up because I thought the question ranger90 was asking wasn't addressed. I could be wrong.
Gypsy's setup has .120" more depth than yours, that's almost 1/8". It maybe more economical to have the depth on your crank taken care while it's out of the block. More difficult once the block is assembled

Larry
 
#10 ·
PKF-BC means it's a 1998 F150 4.2 automatic. That's the code the transmission parts suppliers/rebuilders go by, ignore the rest.
4R70W's weren't put behind 351W's from the factory, I think that pilot depth "thrust failure" thing may refer to E4OD/4R100 converters and has nothing to do with a 4R70W and a 351W. You'd certainly want to check and be sure though. I'd be very surprised if there was an issue though. I haven't heard of Ford going to a different crank spec the very last two years of the 351W's 29 year production run, I might look into that. The 5.8 I have a 4r70w behind right now is a 1996.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top