I have a 75 F-100 with the 300 I6 and a C4 3 speed trans. I want to know if anyone has and how hard it would be to swap it for a 4 speed Overdrive transmission. Because I dont haul anything most the time and i do a lot of highway driving and would like to improve my mpg doing 60+.

 

A 4 speed automatic OD?

Your best bet is the AOD. It may be a bolt in. Or it could be driveshaft and cross member.

Here are some sites, they may have emails and can tell you exactly what you need. Some sell the cross members or mounts. Also vital to an AOD install is the linkage to the throttle so it will shift up and down correctly.

Some sell the trans too.

http://www.transmissioncenter.net/AOD.htm

http://www.baumannengineering.com/aodcat.htm

http://ckperformance.com/ford_aod.html

http://www.tciauto.com/Products/Ford/ford_aod.asp

OK, the first question we should ask is what rear gear do you have? If you don't haul much and when you do it isn't heavy and you're not in the mountains, you and your wallet might be happier with just a higher rear diff ratio.

Your truck has "The Poor Man's Quick Change" rear axle, the Ford 9 inch.

If you have 3.25s or 3.50s you could swap down to 3.0 or 2.79 for far less than the OD swap, and be done with the job in about 2 hours.

I bought a rebuilt 9" for my van for about $450. You can probably do better than that. I'd just buy one and keep the old carrier as a back up or if you decide your new gears are too tall for some jobs or if gas goes back to 28.9 cents/gal, you'll have it.

Heck, buy several and swap gears like you change socks.....

You will still be ahead of the cost of the OD>

Now if you are talking manual trans, there is a Ford 4 speed OD. You are looking at the basic auto to clutch conversion, and a floor shifter. This means under the dash work, new flywheel and bell, and probably a hydraulic clutch set up. All of which you can find at the local scrappy if he has a truck with this set up sitting there ready for you to swipe the parts off.

This is cheaper than the automatic, but more work.

Did I mention changing rear end gears and being done in two hours? (24 if beer is involved)

 

See I live in Louisiana so all my driving is flat the biggest climb will be going on a bridge and the most I will haul is a few 2x4's or some trash to the dump. The reson i wanted to know if the AOD would be a pain to swap was I have a rebuilt AOD that was in my 80 LTD that was totaled when a tree fell on it during Katrina. I do have the 9 inch axle with 3.5 gears but I dont want to wast that rebuilt AOD.

 

m5od 5 speed manual trannys came stock behind later 80's 300's. So that's another option. Otherwise what post #2 said. I have a C6 behind my 300, and I know what you mean at 60 mph+. I plan on swapping after this winter, too. I hope to find a zf5-speed though.

 

Heres a tech article from somewhere else on this website:

https://www.ford-trucks.com/article/...rd_Bronco.html

Not exactly like your set up - but similar in that it's an AOD retrofit in a vehicle that never came with one from the factory. Maybe it will help you some, or at least give you a vague idea.

 

Yes you can swap the AOD into your truck. I put an 85 AOD in my 75 van with 300 six. The only thing I needed was the flex plate from a later model
300ci six that had the AOD. I didn't have to change anything. The crossmember worked without any mods and the drive shaft also fit.

My swap was from a three speed stick. It was really easy, as a matter of fact I once put a three speed auto in a 75 Dodge van, same deal, went from three speed stick to automatic without changeing anything exept the radiator. Not all swaps are so easy but these two were.

Good luck,
Cranky

PS: The adjustment of the TV linkage is critical if you don't get it right you will burn up the clutches real quick, that's the only tricky part.

 

I concour with the recommendations on the AOD - it features 100% lock up in top gear (4th) so your mileage will be the same as a manual without all of the work of shifting.

David

 

Thanks Cranky for assureing me that its not that hard. I have been taking mesurements and it dose look like it fit I just wanted to be sure it would work. I'm going to swap the trans as soon as i can get 2 days off in a row lol