Unibody62F100

I am trying to figure out how to raise my gear ratio in my "chunk". I currently am still running the original differential. And to call it a three speed is not really true in today's world. It blows the tranny gasket if I run 50 mph in it. it doesnt like to get above 45. i have to be able to run it on the road but i keep getting different stories from my truck guys. one says it needs a 3.08 the other says a 3.50 or a 3.70. Help! Its a cruiseomatic tranny. I need to order parts and get this done but cant. Please post some input for me. Thanks guys!

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Lovin' my classic truck

F'funundred

I presume you are running a 9" diff... What motor?
I have a 74F100. At the mo, its running a 300ci 6, with a Ford AOD 4Sp Auto & a 4.11 LSD, 15" rims with 10.5 American Kelly road Tyres. At 2000rpm in top gear, I'm cruising at 110k's.

I frigged around with different diff ratios. Initially my truck was a 4 speed manual with 3.55 Diff. I replaced that with a C4, it went got along pretty well. I thought I might try to get a bit more top end speed so went for a 3.33 diff. That was ok, on the flat, or down hill or with the wind. But uphill or against the wind, dissapointing...

I then put the reco'd AOD & a lock up torque converter in. After 2 more Diff Ratio changes (3.55, then 4.11) I am pretty happy. It tows really well as well as good cruise speed.

I can't say to you what to do but, if you can save some money from my experience, excellent. If I had listened to 1 guy who knew who his stuff, I could've saved at least $2000.

I'm currently building a 351C to drop in. I'm taking my time & listening to experts who can speak from experience.

If you want to know about the AOD, just ask, I'll be glad to help...

Cheers...

Unibody62F100

Thanks for the reply!
It has its original 292 engine in it. nearly everything is original in the truck. including the muffler. it was a farm truck in calif so it only has 88k miles on it for real. i had it carried to GA so as not to add additional mileage to it.
the tranny i had rebuilt because the yahoo that drove it to the pick up point didnt check it for fluid or know not to run it over 45 mph. so it nearly burnt it up. but i had original parts to replace it.
but the differential in it is just too low for todays world. it isnt on the farm anymore.
i guess that its a 9" in there, this is my learning truck. i grew up around this stuff but didnt pay attention. so i have a guy that is trying to help me but he is into the much older fords and doesnt have alot of time for me.
but i LOVE my truck. it rides so smooth on the road.(at 40 mph) i love to take it up town and drive around and watch folks stop and look. it looks good.
not showroom, but good.

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Lovin' my classic truck