I have a 58 ford f100 custom cab with a 312 v8. I wanted to know what year of a ford 9inch rear end can i put in...? I have the original granny w/ a 4 speed manual tranny the gearing (SUCKS) bad on the freeway.... I want something more friendly. Any ideas... Thanks....

 

Your truck should already have a nine inch unless someone changed it. It might be easier to change the ring gear and pinion to a more friendly ratio than change the differential. Something in the low 3's like 3:25 might be what you want...

 

What is your gear ratio, and what about it suck on the freeway? Unless you spend a lot of time in first gear, it shouldn't be that bad, and the granny low gear shouldn't even be a factor.

 

(@ 52 Merc)- I take off in second i dont even go near granny low..lol When im on the freeway it screams at around 65-70 mph... and i mean SCREAMS.. realy realy loud! At (@ GREAT NORTH WOODS)- im still new to things like gearing and stuff so what you mean by ratio is the gears in the pumpkin just change them out completely..? Thanks guys..

 

How can i tell what kind of rear end this babys got in it..?? who knows what people have done or changed in this truck since 58...lol

 

I have a question... A guy told me that my original 312 v8 needs to have an lead additive put in it when i refuel or it will mess up my valves... True or False...???

 

Can you post a picture of the reared?

 

A picture of the rear end should tell us what it is. It is unlikely that anyone would have removed the nine inch and put something else less desirable in its place but stranger things have happened. If it's screaming at 65-70 you probably have a rear end ratio in the mid or upper 4's. That's why I suggested something in the 3's would probably help. There are a lot of rear end ratios available for the nine inch and changing the ring gear and pinion just might solve your problem. First, however, we need to verify that the rear end you have under there now is a nine inch.

Does it look like the one in this picture?

 

What size tires are you running? That affects RPM too. Do you have a tach you can put in it? Even with 4.11 gears, and say 27" tall tires (fairly small), you would only be turning 3325 RPM at 65 mph. I wouldn't do that all day, but it won't kill it if done occassionally. A 3.50 gear ratio would drop that to 2830; with 29" tires and a 3.50, you'd be at 2630 RPM.

No "lead additive" needed or even desirable. It is illegal to sell real lead additives, what is sold is just snake oil.

 

Awsome... Your feedback has been great... I will check out the rear end and get back to you guys.. Thanks again...

 

Here is a pic hopefully this helps... Oh and my tires are 31/10.5/15..

https://www.ford-trucks.com/forums/a...ictureid=75534

 

I can only down load the first pic my computer is giving me problems..

 

That certainly looks like a 9 inch to me. Looks like you need a pinion seal too...

 

Thanks... i was wondering if i change out the gears in the rear end will that granny low tranny have issues...?

 

here's the other 2 pics