I have a 1987 F-150 300 (4.9L) straight six and C6 transmission with over 260,000 miles on it.

I got it in 1993 with little over 100,000 miles. Back then I put in a B&M tow transpack and it ran great. However, here lately the passing gear/down shift has a problem. It won’t stay down long enough or it will flip between 2nd and 3rd back and forth until I stomp on it to stay in 2nd or let off so it will stay in 3rd.

I’ve adjusted the band throughout the years and thought it must be time again, but this time it didn’t seem to help. Fluid and level is good.
The high mileage, driving (and sometimes hauling my belongings) across the U.S. 5 times, and last year I hauled two full, and I mean scrapping the axle full, 8’ bed of dirt, it might be time to replace it.

So I thinking of two routes:
1. Replace the current C6 with an aftermarket C6 with a tow/towing converter package
2. Replace the current C6 with an AOD aftermarket with a tow/towing converter package

There is a possible 3rd route, rebuild the current transmission, but I’m not sure if I have the time or the equipment needed. I’ve rebuilt trannys in the past, but I am so meticulous it would take a mouth or two before I was done and I don’t have my clutch pack tools any more. A swap might be better.

I like the idea of the over drive gear, better gas mileage, and it runs great in my 86 Grand Marquis. I’m not sure if it’s worth the trouble of modifying the cross member, drive shaft, and other items associated with upgrading to the AOD (like getting the TV cable just right).

What say you? Pros…? Cons…?

 

Keep c6, bullet proof, had 5 aod's none of them stood up to what i threw at them (2 stock ones, 3 built ones) if you want that extra gear id go standard. but i would never trust an aod again, if budget permits you could run an e40d, they are pretty solid as well (c6 internals)

 

Keep the c6 or get an e4od. There is a reason ford didn't trust the aod behind anything but a little 302. The torque of a 300 would not be kind to it

 

It's not worth the trouble or benifits of doing an upgrade. Good to know, because I plan on hauling and towing with the truck.

You're right about the torque of the 300, seems like if I can hook up to it, I can move it!

So I'm reading through the forums and it seems like there are no special tools required for rebuilding the C6. When I did a GM turbo 350, I needed a special tool for 1st and reverse clutch pack in the bottom of the transmission.

If I rebuild the old tranny, I know it would fit without worring about small things like linkage, tail shaft, and speedometer gears are right.

Have either of you rebuilt a C6? Is it as easy as I'm reading?

 

Rebuilding a c6 isn't hard at all, I did it using regular tools, the only tool I had to buy was a good snap ring plier set, thought I would cheap out the first time, you get what you pay for in the end, while you have it apart, may as well upgrade a few things, rollerize it, put more clutches in it, shift kit, and a heavy'er duty band

 

I have name brand snap ring tools large and small. I understand everything you said, but "rollerize it." What might that be? The #9 thrust washer?

 

If you're going to haul or tow with it than stick to a C6. If you really want an OD I'd swap in a ZF5 or a built E4od if you really want an auto.

 

Ok guys I need to say something here.
I did this swap and it was the best thing to do.
My 94 f150 4x4 came with a 300 cid 5 speed .
Only thing I noticed was that the C6 auto had a little better take off than the AOD and this is not a big problem and I had 33' tires and I plow snow with it.
The trans has been in my truck for the last 5 years with no issues at all not to mention I went from 9 mpg to 24 after the AOD swap on the highway.
With 33' tires and 3.55 gears at 70 mpg my tach reads 1550rpm in overdrive where with the C6 I was AT 3400.
The trans was rebuilt before it was put in my truck and the detent cable is set correct on the throttle body.
Now the flywheel/flexplate you will need to use is a 87 302 flywheel and it will bolt up to the engine but you MUST remove the ballance weight off of it or you will have a vibration.
This is the only flywheel/flexplate you can use because Ford never put the AOD behind the 300 straight 6.
You said something about modifying the cross member, drive shaft.
Same crossmember and the driveshaft fit fine.
As far as putting in a e40d good luck because your truck does not have the wiring harness or the computer for it and is not worth the hassle for me.
As far as a AOD being strong ? I have not had a issue
After 5 years mine still squalls the tires with posi rear end hitting 2nd gear and has no slipage.

 

The 302 has more torque then a 300.

A properly build AOD would be your ticket, BUT I can only speculate that it would be quite abit more costly to get one built right.

 

The 302 has more torque then a 300?? Really?
I have driven trucks with both engines quite a bit, and would take the inline 6 over the 302 any time.
Sorry but i think it's funny because I had a 88 f350 rollback car hauler with a 300 inline and my friend has one and mine would always take off better than his loaded down same exact truck he went threw 3 different 302's and mine still had the original with 366k miles when i sold it.
my plow truck has the same 300 cid

 

An overdrive gear will not add 15mpg and make a 2k rpm difference in engine cruising speed. As to the guy that thinks that the 302 has more torque then the 300, have you ever driven trucks with both engines? I have owned trucks with both power plants and I can say from personal experience that the 302 has much less torque then the 300. Like I said, there was a reason ford never installed the aod behind anything but the 302.

 

I think the AOD unfairly gets a bad rap around here way too often. Now, I agree that if you plan to do a lot of very heavy towing the C6 is a simpler and stronger transmission in stock form, but the AOD isn't anywhere near as bad as some of you make it out to be. The main thing to remember with an AOD is this:

DO NOT TOW IN THE OVERDRIVE GEAR!

Ford clearly states this in the owner's manual!

What usually happens when you use overdrive for towing is that the transmission will hunt back and forth between 4th and 3rd gear, and that will produce excess heat and wear out the overdrive band and ultimately, the transmission itself. Auxiliary transmission coolers were installed with the AOD that had the towing package, and I personally feel that every AOD should have an auxiliary cooler. Heat is what kills any automatic transmission.

The AOD is actually a pretty decent transmission, as long as the owner understands how it is meant to be used and understands its limitations. The Ford AOD was the very first Automatic Overdrive transmission around. It was designed in the early 1980s for those times, which primarily demanded better fuel economy.

The much lower RPMs that occurs as a result of the 0.67:1 overdrive gear is awesome for highway cruising, which makes the AOD return MUCH better fuel economy than the C6. But the overdrive gear is not suitable for towing or hill climbing because it is such a high gear. In stop-and-go traffic, I usually leave mine in "D," or the OVERDRIVE LOCKOUT position. Otherwise, excessive shifting or "hunting" between third and fourth can sometimes occur, and that produces excess heat which will wear out the overdrive band prematurely and shorten the life of the transmission.

If you are towing or climbing hills, it is best to go ahead and manually put the gear selector in "D", or OVERDRIVE LOCKOUT until you get on a long stretch of level ground again. Doing this will essentially make the AOD a C6, as third gear is a 1:1 ratio. This will not only give you better towing ability and performance because your truck will be in a better power band in 3rd gear, and it will keep your AOD from overheating and extend the life of the transmission.

Good luck with your decision.

 

I don't recall the exact numbers of the 302 and the 300 but the EFI versions were within 5hp and the same torque I believe or it was so close they might as well have been the same. HOWEVER the 300 makes it's peak torque about 500rpm lower than the 302 giving it a more desirable powerband for a truck and the feeling of more torque.

Adding overdrive will not improve mileage by 15 mpg everything else being equal and I doubt 24 mpg is even possible with one of these trucks normally.

Also make sure you have adequate cooling for the transmission. Heat kills auto trannys so a large cooler and a temp gauge can help ensure you get the most life from your tans.

 

I do not believe any factory power numbers published, especially on the older power plants. They have been proven many times to be innacurate.

 

No, its pure and simple, the aod is not meant for a truck... Period much less one that's towing or one that's racing. In a car? Sure, I've heard good things if you throw a good savings account at it. Ford did have the e40d behind lots of 4.9's, I'm driving one right now. 302 have always had the weakest trans, even when the c6 was behind it. And don't get me started on the t-5's.