Originally Posted by 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!
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...